4.Main Book (Need Modified page corection)

“A Study of Next Generation Cellular Technology”

Overview of Cellular Network A cellular network is a radio network made up of a number of radio cells (or just cells) each served by at least one fixed-location transceiver known as a cell site or base station. These cells cover different land areas to provide radio coverage over a wider area than the area of one cell, so that a variable number of portable transceivers can be used in any one cell and moved through more than one cell during transmission.

A cellular network is a network of telecommunications links and nodes arranged so that messages may be passed from one part of the network to another over multiple links and through various nodes.

Cellular networks offer a number of advantages over alternative solutions: •

increased capacity

•

reduced power usage

•

larger coverage area

•

reduced interference from other signals

1.2 General characteristics To distinguish signals from several different transmitters, frequency division multiple access (FDMA) and code division multiple access (CDMA) were developed.

With FDMA, the transmitting and receiving frequencies used in each cell are different than the frequencies used in each neighboring cell. In a simple taxi system, the taxi driver manually tuned to a frequency of a chosen cell to obtain a strong signal and to avoid interference from signals from other cells. The principle of CDMA is more complex, but achieves the same result; the distributed transceivers can select one cell and listen to it. Other available methods of multiplexing such as polarization division multiple access (PDMA) and time division multiple access (TDMA) cannot be used to separate signals from one cell to the next since the effects of both vary with position and this would make signal separation practically impossible. Time division multiple access, however, is used

in combination with either FDMA or CDMA in a number of systems to give multiple channels within the coverage area of a single cell.

1.3 Mobile phone networks The most common example of a cellular network is a mobile phone (cell phone) network. A mobile phone is a portable telephone which receives or makes calls through a cell site (base station), or transmitting tower. Radio waves are used to transfer signals to and from the cell phone. Large geographic areas (representing the coverage range of a service provider) may be split into smaller cells to avoid line-of-sight signal loss and the large number of active phones in an area. In cities, each cell site has a range of up to approximately ½ mile, while in rural areas, the range is approximately 5 miles. Many times in clear open areas, a user may receive signals from a cell site 25 miles away. All of the cell sites are connected to cellular telephone exchanges "switches", which connect to a public telephone network or to another switch of the cellular company.

As the phone user moves from one cell area to another cell, the switch automatically commands the handset and a cell site with a stronger signal (reported by each handset) to switch to a new radio channel (frequency). When the handset responds through the new cell site, the exchange switches the connection to the new cell site.

With CDMA, multiple CDMA handsets share a specific radio channel. The signals are separated by using a pseudonoise code (PN code) specific to each phone. As the user moves from one cell to another, the handset sets up radio links with multiple cell sites (or sectors of the same site) simultaneously. This is known as "soft handoff" because, unlike with traditional cellular technology, there is no one defined point where the phone switches to the new cell.

Modern mobile phone networks use cells because radio frequencies are a limited, shared resource. Cell-sites and handsets change frequency under computer control and use low power transmitters so that a limited number of radio frequencies can be simultaneously used by many callers with less interference.

Since almost all mobile phones use cellular technology, including GSM, CDMA, and AMPS (analog), the term "cell phone" is used interchangeably with "mobile phone". However, satellite phones are mobile phones that do not communicate directly with a ground-based cellular tower, but may do so indirectly by way of a satellite.

There are a number of different digital cellular technologies, including: Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), Code Division Multiple Access (CDMA), Evolution-Data Optimized (EV-DO), Enhanced Data Rates for GSM Evolution (EDGE), 3GSM, Digital Enhanced Cordless Telecommunications (DECT), Digital AMPS (IS136/TDMA), and Integrated Digital Enhanced Network (iDEN).

1.4

Evolution Of Cellular Technology

0G Mobile Phone TECHNOLOGY 0G refers to pre-cellphone mobile telephony technology, such as radio telephones that some had in cars before the advent of cellphones.

One such technology is the Auto Radio Puhelin (ARP) launched in 1971 in Finland as the country's first public commercial mobile phone network.

1G Mobile Phone TECHNOLOGY 1G (or 1-G) is short for first-generation wireless telephone technology, cellphones. These are the analog cellphone standards that were introduced in the 80's and continued until being replaced by 2G digital cellphones.

One such standard is NMT (Nordic Mobile Telephone), used in Nordic countries, Eastern Europe and Russia. Another is AMPS (Advanced Mobile Phone System) used in the United States.

Anticedant to 1G technology is the mobile radio telephone, or 0G.

2G Mobile Phone TECHNOLOGY 2G (or 2-G) is short for second-generation wireless telephone technology. It cannot normally transfer data, such as email or software, other than the digital voice call itself, and other basic ancillary data

such as time and date. Nevertheless, SMS messaging is also available as a form of data transmission for some standards.

2G services are frequently referred as Personal Communications Service or PCS in the US. 2G technologies can be divided into TDMA-based and CDMA-based standards depending on the type of multiplexing used. The main 2G standards are:

GSM (TDMA-based), originally from Europe but used worldwide IDEN (TDMA-based), proprietary network used by Nextel in the United States and Telus Mobility in Canada IS-136 aka D-AMPS, (TDMA-based, commonly referred as simply TDMA in the US), used in the Americas IS-95 aka cdmaOne, (CDMA-based, commonly referred as simply CDMA in the US), used in the Americas and parts of Asia PDC (TDMA-based), used exclusively in Japan The GSM operates in the 850Mhz. and 1900Mhz. bands in the US, & 900Mhz. and 1.8Mhz. bands in the rest of the world.

2.5G services are already available in many countries and 3G will be widely available in many countries during 2004. Work on 4G has already started although its scope is not clear yet.

2.5G Mobile Phone TECHNOLOGY2.5G is a stepping stone between 2G and 3G cellular wireless technologies. The term "second and a half generation" is used to describe 2Gsystems that have implemented a packet switched domain in addition to the circuit switched domain. It does not necessarily provide faster services because bundling of timeslots is used for circuit switched data services (HSCSD) as well.

2.5G provides some of the benefits of 3G (e.g. it is packet-switched) and can use some of the existing 2G infrastructure in GSM and CDMA networks. GPRS is a 2.5G technology used by GSM operators. Some protocols, such as EDGE for GSM and CDMA2000 1x-RTT for CDMA, can qualify as "3G" services (because they have a data rate of above 144 kbit/s), but are considered by most to be 2.5G services (or 2.75G which sounds even more sophisticated) because they are several times slower than "true" 3G services.

While the terms "2G" and "3G" are officially defined, "2.5G" is not. It was invented for marketing purposes only.

2G is the current generation of full digital mobile phone systems. It transmits primarily voice but is used for circuit-switched data service and SMS as well.

3G is now the third generation of mobile phone systems. They provide both a packet-switched and a circuit-switched domain from the beginning. It requires a new access network, different from that already available in 2G systems. Due to cost and complexity, rollout of 3G has been somewhat slower than anticipated.

2.5G, which stands for "second and a half generation," is a cellular wireless technology developed in between its predecessor, 2G, and its successor, 3G.

"2.5G" is an informal term, invented solely for marketing purposes, unlike "2G" or "3G" which are officially defined standards based on those defined by the International Telecommunication (ITU). The term "2.5G" usually describes a 2G cellular system combined with General Packet Radio Services (GPRS), or other services not generally found in 2G or 1G networks.

GPRS is a service commonly associated with 2.5G technology. It has data transmission rates of 28 kbps or higher. GPRS came after the development of the Global System for Mobile (GSM) service, which is classified as 2G technology, and it was succeeded by the development of the Universal Mobile Telecommunication Service (UMTS), which is classified as 3G technology.

A 2.5G system may make use of 2G system infrastructure, but it implements a packet-switched network domain in addition to a circuit-switched domain. This does not necessarily give 2.5G an advantage over 2G in terms of network speed, because bundling of timeslots is also used for circuit-switched data services (HSCSD).

2.75G Mobile Phone TECHNOLOGY A 2G mobile phone is a circuit switched digital mobile phone. A 3G mobile is a digital phone with rapid data according to one of the standards being a member of the IMT-2000 family of standards. After those terms were defined, slow packet switched data was added to 2G standards

and called 2.5G. 2.75G is the term which has been decided on for systems which don't meet the 3G requirements but are marketed as if they do (e.g. CDMA-2000 without multi-carrier) or which do, just, meet the requirements but aren't strongly marketed as such. (e.g. EDGE systems).

The term 2.75G has not been officially defined anywhere, but as of 2004 is beginning to be used quite often in media reports.

2.75G is a pretty recent standard, allows for downloading faster. Since mobile devices have become both a TV and a ‘walkman’ or music player, people needed to be able to watch streaming video and download mp3 files faster – that’s precisely what EDGE allows for and that’s for the good news. The bad news is that if EDGE rocks at downloading, it’s protocol is asymmetrical hence making EDGE suck at uploading i.e. broadcasting videos of yours for instance. Still an interesting achievement thanks to which data packets can effectively reach 180kbytes/sec. EDGE is now widely being used.

3G Mobile Phone TECHNOLOGY Introduction A short perusal of the major tech blogs on the internet, like Mobile Magazine, will inevitably result in at least a small handful of entries drooling over 3G mobile phone technology, with everyone drooling over the latest 3G offering coming out of cell phone manufacturers in Korea, Japan, and the rest of the world. But what exactly does 3G mean? 3G technologies are an answer to the International Telecommunications Union's IMT-2000 specification.

In a nutshell, 3G simply refers to the third generation of cellular phone technology.

3G (or 3-G) is short for third-generation mobile telephone technology. The services associated with 3G provide the ability to transfer both voice data (a telephone call) and non-voice data (such as downloading information, exchanging email, and instant messaging.

Current Technology By and large, most of the mobile phones on the market today are a part of the second generation, or "2G". This includes such standards as GSM (Global System for Mobile Communications: like

the services offered by T-Mobile), and iDEN (Integrated Digital Enhanced Network: as developed by Motorola and deployed by Sprint/Nextel).

Several handsets and networks are also capable of higher speed data than standard 2G technology. These are often referred to as part of the 2.5G or 2.75G. The most common 2.5G technology is GPRS, or General Packet Radio Service, which works in tandem with GSM networks. Further along the spectrum are such technologies as CDMA2000 1xRTT (1 times Radio Transmission Technology) and EDGE (Enhanced Data rates for GSM Evolution). Each successive generation has provided faster and faster data transfer rates, in order to keep up with high demand services like picture messaging, ringtone downloading, and mobile web.

So What's the Big Deal with 3G? 3G Mobile Phone Technology is said to be a substantial leap forward in data transfer rates for cellular phones, and as people demand more and fuller content, mobile networks need to keep up and send the data faster than ever.

Video Telephony Video conferencing was said to be the "killer app" for 3G. As such, many 3G handsets feature not one, but two cameras. The "primary" camera is typically on the back of the phone and is a megapixel (or better) picture taker. Finding phones with 2-megapixel cameras or better is no longer out of the ordinary, with some units offering as high as 8 megapixels. The "secondary" camera, however, is usually next to the display and a simple VGA unit. This is meant to be used for video telephony. However, in areas where 3G is more prevalent, like urban regions of Japan, video telephony has not been as popular as previously predicted.

Mobile TV and Web For more on mobile TV, check out the official Mobile TV article here on LoveToKnow Cell Phones. While mobile television is technically a separate issue from 3G mobile phone technology, the two are often discussed in the same breath. Oftentimes, users download short video clips and even streaming movies using 3G technology, especially where "conventional" mobile television -- like T-DMB -- is not available.

Ringtones, Music, and More Where 3G has really begun to shine, even before it has reached widespread deployment in the United States and Canada, is its use in downloading mobile content. Cell Phone Ringtones are incredibly popular, with several services being offering allowing users to customize their mobile phones with unique ringtones, especially since so many handsets are capable of MP3 ringtones these days. Instead of a standard ring, imagine hearing your phone blast out the latest Lil Jon hit, or a classic Frank Sinatra song.

Musicphones, like the Walkman line from Sony Ericsson, are also growing in prevalence. In fact, some have said that by 2010, over-the-air mobile music services -- that is, downloading music onto your cell phone directly on a purely wireless basis, rather than using your home computer as an intermediary -- will have more users than online music stores (read: iTunes). 3G technology (and successive generations) have had, and will continue to have a lot to do with this trend.

3G Standards There are three main 3G standards that have already been deployed in selected regions around the globe.

W-CDMA: Not to be confused with standard CDMA (which is the direct competitor for GSM), W-CDMA is "Wideband" Code Division Multiple Access, and is allied with 2G GSM. Originally, 3G was supposed to be a single, unified, worldwide standard, but in practice, the 3G world has been split into three camps.

UMTS (W-CDMA) UMTS (Universal Mobile Telephone System), based on W-CDMA technology, is the solution generally preferred by countries that used GSM, centered in Europe. UMTS is managed by the 3GPP organization also responsible for GSM, GPRS and EDGE. FOMA, launched by Japan's NTT DoCoMo in 2001, is generally regarded as the world's first commercial 3G service. However, while based on W-CDMA, it is not generally compatible with UMTS (although there are steps currently under way to remedy the situation).

CDMA2000 The other significant 3G standard is CDMA2000, which is an outgrowth of the earlier 2G CDMA standard IS-95. CDMA2000's primary proponents are outside the GSM zone in the Americas, Japan and Korea. CDMA2000 is managed by 3GPP2, which is separate and independent from UMTS's 3GPP. TD-SCDMA A less well known standard is TD-SCDMA which is being developed in the People's Republic of China by the companies Datang and Siemens. They are predicting an operational system for 2005.

There are two main forms: UMTS stands for Universal Mobile Telecommunications System, and is sometimes referred to as 3GSM. UMTS is said to be capable of data transfer rates of up to 1920 kbit/sec.

FOMA stands for Freedom of Mobile Multimedia Access and is the brand name for 3G services offered through NTT DoCoMo of Japan. A pioneer in 3G, FOMA was officially launched way back in 2001. 1xEV-DO, initially designed by Qualcomm, is CDMA's answer to W-CDMA, if that makes any sense. EV-DO stands for Evolution Data Optimized, and is a broadband data standard that has already been adopted by such wireless service providers as Telus Mobility of Canada and Verizon Wireless, the latter of which marketing its EV-DO services as "V CAST".

EV-DO's data transfer rate is right in line with W-CDMA, offering approximately 2Mbit/sec downlinks.

TD-SCDMA is being developed by and for the People's Republic of China. Standing for Time Division-Synchronous Code Division Multiple Access, TD-SCDMA was meant to provide the Chinese people with high speed data that wasn't "dependent on Western technology". TDSCDMA testing is currently underway, with full deployment expected before the end of the year.

What the Future Holds HSDPA: Even before 3G has been fully adopted, cellular phone technology companies have already started working on and testing the next sub-generation of wireless data. As part of the 3.5G, HSDPA

(high-speed downlink packet access) is a new mobile telephony protocol, and it is said to be an extension of WCDMA in much the same way that CDMA2000 was improved upon to become EV-DO.

HSUPA: Whereas HSDPA allowed for "downlinks" (cell phones receiving data), HSUPA allows for "uplinks" (cell phones sending data). In this way, it naturally accompanies HSDPA, and is said to be 3.75G.

List of countries that have deployed 3G: Argentina (CDMA2000 1x)

Australia

(W-CDMA)

(CDMA2000

Austria (W-CDMA)

Azerbaijan

Belarus (CDMA2000 1x)

Bermuda

Brazil (CDMA2000 1x)

Canada

Chile (CDMA2000 1x)

China

Colombia (CDMA2000 1x)

Cyprus

Denmark (W-CDMA)

Dominican

Ecuador (CDMA2000 1x)

Finland

Georgia (CDMA2000 1x)

Germany

Greece (W-CDMA)

Guatemala

Hong Kong (W-CDMA)

India

Indonesia (CDMA2000 1x)

Israel

Italy (W-CDMA)

Jamaica

Japan (W-CDMA, CDMA2000 1x)

Kazakhstan

Kyrgyzstan (CDMA2000 1x)

Mexico

Moldova (CDMA2000 1x)

Netherlands

New Zealand (CDMA2000 1x)

Nicaragua

Nigeria (CDMA2000 1x)

Norway

Pakistan (CDMA2000 1x)

Panama

(CDMA2000

1x)

Peru (CDMA2000 1x)

Poland

(CDMA2000

1x)

Portugal (W-CDMA)

Romania

Russia (CDMA2000 1x)

Singapore

Slovenia (W-CDMA)

South Korea (CDMA2000 1x)

South Africa (W-CDMA in testing)

Spain (W-CDMA),

Sweden (W-CDMA)

Taiwan (CDMA2000 1x)

(CDMA2000 (CDMA2000 (CDMA2000 (CDMA2000

1x)

1x) 1x) 1x) 1x)

(W-CDMA) Republic

(CDMA2000

(W-CDMA) (W-CDMA) (CDMA2000 (CDMA2000

1x) 1x)

(W-CDMA) (CDMA2000 (CDMA2000 (CDMA2000

1x) 1x) 1x)

(W-CDMA) (CDMA2000

1x)

(W-CDMA)

(CDMA2000 (W-CDMA)

1x)

1x)

Thailand (CDMA2000 1x)

United Arab Emirates (W-CDMA)

United Kingdom (W-CDMA),

US (CDMA2000 1x) (W-CDMA in testing)

Uzbekistan (CDMA2000 1x)

Venezuela (CDMA2000 1x)

Vietnam

(CDMA2000

1x)

3.5G Mobile Phone TECHNOLOGY High-Speed Downlink Packet Access or HSDPA is a mobile telephony protocol which is theoretically 6 times faster than UMTS (up to 3.6 Mbytes/sec)!. Also called 3.5G (or "3½G") High Speed Downlink Packet Access (HSDPA) is a packet-based data service in W-CDMA downlink with data transmission up to 8-10 Mbit/s (and 20 Mbit/s for MIMO systems) over a 5MHz bandwidth in WCDMA downlink. HSDPA implementations includes Adaptive Modulation and Coding (AMC), Multiple-Input Multiple-Output (MIMO), Hybrid Automatic Request (HARQ), fast cell search, and advanced receiver design.

HSDPA is beginning to reach deployment status in North America. Cingular has announced that they will begin to deploy UMTS with expansion to HSDPA in 2005.

In 3rd generation partnership project (3GPP) standards, Release 4 specifications provide efficient IP support enabling provision of services through an all-IP core network and Release 5 specifications focus on HSDPA to provide data rates up to approximately 10 Mbit/s to support packet-based multimedia services. MIMO systems are the work item in Release 6 specifications, which will support even higher data transmission rates up to 20 Mbit/s. HSDPA is evolved from and backward compatible with Release 99 WCDMA systems.

Practically speaking, this would mean downloading an mp3 file would take about 30 secs instead of something like 2 minutes. Not bad, uh?

4G Mobile Phone TECHNOLOGY 4G (also known as Beyond 3G), an abbreviation for Fourth-Generation, is a term used to describe the next complete evolution in wireless communications. A 4G system will be a

complete replacement for current networks and be able to provide a comprehensive and secure IP solution where voice, data, and streamed multimedia can be given to users on an "Anytime, Anywhere" basis, and at much higher data rates than previous generations 4G (or 4-G) is short for fourth-generation the successor of 3G and is a wireless access technology. It describes two different but overlapping ideas.

High-speed mobile wireless access with a very high data transmission speed, of the same order of magnitude as a local area network connection (10 Mbits/s and up). It has been used to describe wireless LAN technologies like Wi-Fi, as well as other potential successors of the current 3G mobile telephone standards.

Objectives 4G is being developed to accommodate the quality of service (QoS) and rate requirements set by forthcoming applications like wireless broadband access, Multimedia Messaging Service (MMS), video chat, mobile TV, HDTV content, Digital Video Broadcasting (DVB), minimal service like voice and data, and other streaming services for "anytime-anywhere". The 4G working group has defined the following as objectives of the 4G wireless communication standard: •

A spectrally efficient system (in bits/s/Hz and bits/s/Hz/site),[2]

•

High network capacity: more simultaneous users per cell,[3]

•

A nominal data rate of 100 Mbit/s while the client physically moves at high speeds relative to the station, and 1 Gbit/s while client and station are in relatively fixed positions as defined by the ITU-R,[1]

•

A data rate of at least 100 Mbit/s between any two points in the world,[1]

•

Smooth handoff across heterogeneous networks,[4]

•

Seamless connectivity and global roaming across multiple networks,[5]

•

High quality of service for next generation multimedia support (real time audio, high speed data, HDTV video content, mobile TV, etc)[5]

•

Interoperability with existing wireless standards,[6] and

•

An all IP, packet switched network.[5]

In summary, the 4G system should dynamically share and utilize network resources to meet the minimal requirements of all the 4G enabled users.

1.5 Key Technology of Each Generations We briefly listed all the key technologies and protocols used in each generation of the mobile wireless communications in th following table: 0G refers to pre-cellular mobile telephony technology in 1970s. These 0G

mobile telephones were usually mounted in cars or trucks, though briefcase models were also made.

PTT

Push to talk

MTS

Mobile Telephone System

IMTS

Improved Mobile Telephone Service

AMTS

Advanced Mobile Telephone System

0.5G

0.5G is a group of technologies with improved feature than the basic 0G technologies.

Autotel/PALM Autotel, or PALM (Public Automated Land Mobile) ARP

Autoradiopuhelin, Car Radio Phone

HCMTS

High Capacity Mobile Telephone System 1G (or 1-G) is the first-generation wireless telephone technology,

1G

cellphones. These are the analog cellphone standards that were introduced in the 1980s.

NMT

Nordic Mobile Telephone

AMPS

Advanced Mobile Phone System

TAGS JTAGS

Total Access Communication System (TACS) is the European version of AMPS. Japan Total Access Communication System 2G (or 2-G) is the second-generation wireless telephone, which is based on

2G

digital technologies. 2G networks is basically for voice communications only, except SMS messaging is also available as a form of data transmission for some standards.

GSM

Global System for Mobile Communications

iDEN

Integrated Digital Enhanced Network

D-AMPS

Digital Advanced Mobile Phone System based on TDMA

cdmaOne

Code Division Multiple Access technology defined by IS-95

PDC

Personal Digital Cellular Time Division Multiple Access

TDMA 2.5G is a group of bridging technologies between 2G and 3G wireless 2.5G

communication. It is a digital communication allowing e-mail and simple Web browsing, in addition to voice.

GPRS

General Packet Radio Service

WiDEN

Wideband Integrated Dispatch Enhanced Network

2.75G

2.75G refer to the technologies which don't meet the 3G requirements but are marketed as if they do.

CDMA2000

CDMA-2000 is a TIA standard (IS-2000) that is an evolutionary outgrowth of

1xRTT

cdmaOne. CDMA2000 with 1xRTT is slight weaker than 3G requirements.

EDGE

Enhanced Data rates for GSM Evolution 3G stand for the third generation of wireless communication technologies,

3G

which support broadband voice, data and multi-media communications over wireless networks.

W-CDMA

Wideband Code Division Multiple Access

UMTS

Universal Mobile Telecommunications System

FOMA

Freedom of Mobile Multimedia Access

CDMA2000 1xEV TD-SCDMA 3.5G

More advanced CDMA2000 with 1xEV technology satisfy 3G requirements.

Time Division Synchronous Code Division Multiple Access The 3.5G generally refer to the technologies beyond the well defined 3G wireless/mobile technologies.

HSDPA

High-Speed Downlink Packet Access

3.75G

The 3.75G refer to the technologies beyond the well defined 3G

wireless/mobile technologies.

HSUPA

High-Speed Uplink Packet Access 4G is the name of technologies for high-speed mobile wireless

4G

communications designed for new data services and interactive TV through mobile network.

2.1 Overview of WiMAX WiMAX,

meaning

Worldwide

Interoperability

for

Microwave

Access,

is

a

telecommunications technology that provides wireless transmission of data using a variety of transmission modes, from point-to-multipoint links to portable and fully mobile [citation

needed]

internet access. The technology provides up to 3 Mbit/s broadband speed without the need for cables. The technology is based on the IEEE 802.16 standard (also called Broadband Wireless Access). The name "WiMAX" was created by the WiMAX Forum, which was formed in June 2001 to promote conformity and interoperability of the standard. The forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL".

WiMAX base station equipment with a

A pre-WiMAX CPE of a 26 km

sector antenna and wireless modem on top

connection mounted 13 meters above the ground (2004, Lithuania).

2.2

Wireless Introduction

Before we begin a real thoery of WiMax, let's spend few minutes to understand background concepts on which WiMax has evolved.

Wireless means transmitting signals using radio waves as the medium instead of wires. Wireless technologies are used for tasks as simple as switching off the television or as complex as supplying the sales force with information from an automated enterprise application while in the field. Now cordless keyboards and mice, PDAs, pagers and digital and cellular phones have become part of our daily life.

Some of the inherent characteristics of wireless communications systems which make it attractive for users, are given below: Mobility: A wireless communications system allows users to access information beyond their desk and conduct business from anywhere without having a wire connectivity.

Reachability: Wireless communications systems enable people to be better connected and reachable without any limitation of any location.

Simplicity: Wireless communication system are easy and fast to deploy in comparision of cabled network. Initial setup cost could be a bit high but other advantages overcome that high cost.

Maintainability: Being a wireless system, you do no need to spend too much to maintain a wireless network setup.

Roaming Services: Using a wireless network system you can provide service any where any time including train, busses, airoplans etc.

New Services: Wireless communications systems provide new smart services like SMS and MMS.

2.3

Wireless Network Topologies:

There are basically three ways to setup a wireless network.

Point-to-point bridge: As you know a bridge is used to connect two networks. A point-to-point bridge interconnects two buildings having different networks. For example, a wireless LAN bridge can interface with an Ethernet network directly to a particular access point.

Point-to-multipoint bridge: This topology is used to connect three or more LANs that may be located on different floors in a building or across buildings.

Mesh or ad hoc network: This network is an independent local area network that is not connected to a wired infrastructure and in which all stations are connected directly to one another.

2.4

Wireless Technologies:

Wireless technologies can be classified in different ways depending on their range. Each wireless technology is designed to serve a specific usage segment. The requirements for each usage segment are based on a variety of variables, including Bandwidth needs, Distance needs and Power.

Wireless Wide Area Network (WWAN): This network enables you to access the Internet via a wireless wide area network (WWAN) access card and a PDA or laptop.

These networks provide a very fast data speed compared with the data rates of mobile telecommunications technology, and their range is also extensive. Cellular and mobile networks based on CDMA and GSM are good examples of WWAN.

Wireless Personal Area Network (WPAN): These networks are very similar to WWAN except thier range is very limited.

2.5

Wireless Local Area Network (WLAN):

This network enables you to access the Internet in localized hotspots via a wireless local area network (WLAN) access card and a PDA or laptop.

It is a type of local area network that uses high-frequency radio waves rather than wires to communicate between nodes.

These networks provide a very fast data speed compared with the data rates of mobile telecommunications technology, and their range is very limited. Wi-Fi is the most widespread and popular example of WLAN technology.

2.6

Wireless Metropolitan Area Network (WMAN):

This network enables you to access the Internet and multimedia streaming services via a wireless region area network (WRAN).

These networks provide a very fast data speed compared with the data rates of mobile telecommunication technology as well as other wireless network, and their range is also extensive.

2.7

Issues with Wireless Networks:

There are following three major issues with Wireless Networks.

Quality of Service (QoS): One of the primary concerns about wireless data delivery is that, like the Internet over wired services, QoS is inadequate. Lost packets, and atmospheric interference are recurring problems wireless protocols.

Security Risk: This has been another major issue with a data transfer over a wireless network.

Basic network security mechanisms like the service set identifier (SSID) and Wireless Equivalency Privacy (WEP). These measures may be adequate for residences and small businesses but they are inadequate for entities that require stronger security.

Reachable Range: Normally wireless network offers a range of about 100 meters or less. Range is a function of antenna design and power. Now a days the range of wireless is extended to tens of miles so this should not be an issue any more.

2.8

Wireless Broadband Access (WBA):

Broadband wireless is a technology that promises high-speed connection over the air. It uses radio waves to transmit and receive data directly to and from the potential users whenever they want it. Technologies such as 3G, Wi-Fi, WiMAX and UWB work together to meet unique customer needs.

BWA is a point-to-multipoint system which is made up of base station and subscriber equipment.

Instead of using the physical connection between the base station and the subscriber, the base station uses an outdoor antenna to send and receive high-speed data and voice-to-subscriber equipment.

BWA offers an effective, complementary solution to wireline broadband, which has become globally recognized by a high percentage of the population.

2.9

What is Wi-Fi ?

Wi-Fi stands for Wireless Fidelity. Wi-Fi is based on the IEEE 802.11 family of standards and is primarily a local area networking (LAN) technology designed to provide in-building broadband coverage.

For more detail on Wi-Fi, please look into our Wi-Fi Tutorial.

2.10 What is WiMAX ?

WiMAX is one of the hottest broadband wireless technologies around today. WiMAX systems are expected to deliver broadband access services to residential and enterprise customers in an economical way.

Loosely, WiMax is a standardized wireless version of Ethernet intended primarily as an alternative to wire technologies ( such as Cable Modems, DSL and T1/E1 links ) to provide broadband access to customer premises.

More strictly, WiMAX is an industry trade organization formed by leading communications component and equipment companies to promote and certify compatibility and interoperability of broadband wireless access equipment that conforms to the IEEE 802.16 and ETSI HIPERMAN standards.

WiMAX would operate similar to WiFi but at higher speeds, over greater distances and for a greater number of users. WiMAX has the ability to provide service even in areas that are difficult for wired infrastructure to reach and the ability to overcome the physical limitations of traditional wired infrastructure.

WiMAX was formed in April 2001, in anticipation of the publication of the original 10-66 GHz IEEE 802.16 specifications. WiMAX is to 802.16 as the Wi-Fi Alliance is to 802.11.

WiMAX is: Acronym for Worldwide Interoperability for Microwave Access.

Based on Wireless MAN technology.

A wireless technology optimized for the delivery of IP centric services over a wide area.

A scaleable wireless platform for constructing alternative and complementary broadband networks.

A certification that denotes interoperability of equipment built to the IEEE 802.16 or compatible standard. The IEEE 802.16 Working Group develops standards that address two types of usage models: A fixed usage model (IEEE 802.16-2004).

A portable usage model (IEEE 802.16e).

2.11 What is 802.16a ?

WiMAX is such an easy term that people tend to use it for the 802.16 standards and technology themselves, although strictly it applies only to systems that meet specific conformance criteria laid down by the WiMAX Forum.

The 802.16a standard for 2-11 GHz is a wireless metropolitan area network (MAN) technology that will provide broadband wireless connectivity to Fixed, Portable and Nomadic devices.

It can be used to connect 802.11 hot spots to the Internet, provide campus connectivity, and provide a wireless alternative to cable and DSL for last mile broadband access.

2.12 WiMax Speed and Range: WiMAX is expected to offer initially up to about 40 Mbps capacity per wireless channel for both fixed and portable applications, depending on the particular technical configuration chosen, enough to support hundreds of businesses with T-1 speed connectivity and thousands of residences with DSL speed connectivity. WiMAX can support voice and video as well as Internet data.

WiMax will be to provide wireless broadband access to buildings, either in competition to existing wired networks or alone in currently unserved rural or thinly populated areas. It can also be used to connect WLAN hotspots to the Internet. WiMAX is also intended to provide broadband connectivity to mobile devices. It would not be as fast as in these fixed applications, but expectations are for about 15 Mbps capacity in a 3 km cell coverage area.

With WiMAX users could really cut free from today.s Internet access arrangements and be able to go online at broadband speeds, almost wherever they like from within a MetroZone.

WiMAX could potentially be deployed in a variety of spectrum bands: 2.3GHz, 2.5GHz, 3.5GHz, and 5.8GHz

2.13 Why WiMax ?

WiMAX can satisfy a variety of access needs. Potential applications include extending broadband capabilities to bring them closer to subscribers, filling gaps in cable, DSL and T1 services, Wi-Fi and cellular backhaul, providing last-100 meter access from fibre to the curb and giving service providers another cost-effective option for supporting broadband services.

WiMAX can support very high bandwidth solutions where large spectrum deployments (i.e. >10 MHz) are desired using existing infrastructure keeping costs down while delivering the bandwidth needed to support a full range of high-value, multimedia services.

WiMAX can help service providers meet many of the challenges they face due to increasing customer demands without discarding their existing infrastructure investments because it has the ability to seamlessly interoperate across various network types.

WiMAX can provide wide area coverage and quality of service capabilities for applications ranging from real-time delay-sensitive voice-over-IP (VoIP) to real-time streaming video and non-real-time downloads, ensuring that subscribers obtain the performance they expect for all types of communications.

WiMAX, which is an IP-based wireless broadband technology, can be integrated into both widearea third-generation (3G) mobile and wireless and wireline networks, allowing it to become part of a seamless anytime, anywhere broadband access solution.

Ultimately, WiMAX is intended to serve as the next step in the evolution of 3G mobile phones, via a potential combination of WiMAX and CDMA standards called 4G.

2.14 WiMAX Goals: A standard by itself is not enough to enable mass adoption. WiMAX has stepped forward to help solve barriers to adoption, such as interoperability and cost of deployment. WiMAX will help ignite the wireless MAN industry, by defining and conducting interoperability testing and labeling vendor systems with a "WiMAX Certified™" label once testing has been completed successfully.

2.15 WiMAX Major Benefits Benefits to Component Makers: Creates a volume opportunity for silicon suppliers.

Benefits to Equipment Makers: Innovate more rapidly because there exists a standards-based, stable platform upon which to rapidly add new capabilities.

No longer need to develop every piece of the end-to-end solution.

Benefits to Operators: A common platform which drives down the cost of equipment and accelerates price/performance improvements unachievable with proprietary approaches.

Generate revenue by filling broadband access gaps.

Quickly provision T1 / E1 level and "on demand" high margin broadband services.

Reduce the dollar risk associated with deployment as equipment will be less expensive due to economies of scale.

No longer be locked into a single vendor since base stations will interoperate with multiple vendors' CPEs.

Benefits to Consumers: More broadband access choices, especially in areas where there are gaps: worldwide urban centers where building access is difficult; in suburban areas where the subscriber is too far from the central office; and in rural and low population density areas where infrastructure is poor.

More choices for broadband access will create competition which will result in lower monthly subscription prices.

2.16 WiMAX and Wi-Fi Comparison WiMAX is similar to the wireless standard known as Wi-Fi, but on a much larger scale and at faster speeds. A nomadic version would keep WiMAX-enabled devices connected over large areas, much like today.s cell phones. We can compare it with Wi-Fi based on the following factors.

IEEE Standards: Wi-Fi is based on IEEE 802.11 standard where as WiMAX is based on IEEE 802.16. However both are IEEE standards.

Range: Wi-Fi typically provides local network access for around a few hundred feet with speeds of up to 54 Mbps, a single WiMAX antenna is expected to have a range of up to 40 miles with speeds of 70 Mbps or more. As such, WiMAX can bring the underlying Internet connection needed to service localWi-Fi networks.

Scalability: Wi-Fi is intended for LAN applications, users scale from one to tens with one subscriber for each CPE device. Fixed channel sizes (20MHz).

WiMAX is designed to efficiently support from one to hundreds of Consumer premises equipments (CPE)s, with unlimited subscribers behind each CPE. Flexible channel sizes from 1.5MHz to 20MHz. Bit rate: Wi-Fi works at 2.7 bps/Hz and can peak up to 54 Mbps in 20 MHz channel.

WiMAX works at 5 bps/Hz and can peak up to 100 Mbps in a 20 MHz channel.

Quality of Service: Wi-Fi does not guarantee any QoS but WiMax will provide your several level of QoS. As such, WiMAX can bring the underlying Internet connection needed to service local Wi-Fi networks. Wi-Fi does not provide ubiquitous broadband while WiMAX does.

2.17 Comparsion Table:

Freature

WiMax

Wi-Fi

Wi-Fi

(802.16a)

(802.11b)

(802.11a/g)

Wireless LAN

Wireless LAN

Primary

Broadband

Application

Access

Frequency Band

Licensed/Unlicensed 2 G to 11 GHz

Channel

Adjustable

Bandwidth

1.25 M to 20 MHz

Half/Full Duplex

Radio Technology

Wireless

2.4

2.4 GHz ISM

GHz

ISM

5 GHz U-NII (a)

25 MHz

20 MHz

Full

Half

Half

OFDM

Direct

(256-channels)

Spread Spectrum

Sequence OFDM (64-channels)

(g)

Bandwidth Efficiency

Modulation

FEC

Encryption

Mobility

<=5 bps/Hz

BPSK,

<=0.44 bps/Hz

QPSK,

16-, 64-, 256-QAM

Convolutional

Code

Reed-Solomon

Mandatory-

WiMax

(802.16e)

Mesh

Yes

Access Protocol

Request/Grant

None

3DES Optional-

Optional- AES

Mobile

QPSK

<=2.7 bps/Hz

BPSK,

Convolutional Code

RC4 Optional-

(AES in 802.11i)

(AES in 802.11i)

In development

In development

Vendor Proprietary

CSMA/CA

QPSK,

16-, 64-QAM

RC4

Vendor Proprietary

CSMA/CA

2.18 WiMAX - Salient Features WiMAX is a wireless broadband solution that offers a rich set of features with a lot of flexibility in terms of deployment options and potential service offerings. Some of the more salient features that deserve highlighting are as follows: Two Type of Services:

2.19 WiMAX can provide two forms of wireless service: Non-line-of-sight: service is a WiFi sort of service. Here a small antenna on your computer connects to the WiMAX tower. In this mode, WiMAX uses a lower frequency range -- 2 GHz to 11 GHz (similar to WiFi).

Line-of-sight: service, where a fixed dish antenna points straight at the WiMAX tower from a rooftop or pole. The line-of-sight connection is stronger and more stable, so it's able to send a lot of data with fewer errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz.

2.20 OFDM-based physical layer: The WiMAX physical layer (PHY) is based on orthogonal frequency division multiplexing, a scheme that offers good resistance to multipath, and allows WiMAX to operate in NLOS conditions.

2.21 Very high peak data rates: WiMAX is capable of supporting very high peak data rates. In fact, the peak PHY data rate can be as high as 74Mbps when operating using a 20MHz wide spectrum.

More typically, using a 10MHz spectrum operating using TDD scheme with a 3:1 downlink-touplink ratio, the peak PHY data rate is about 25Mbps and 6.7Mbps for the downlink and the uplink, respectively.

2.22 Scalable bandwidth and data rate support: WiMAX has a scalable physical-layer architecture that allows for the data rate to scale easily with available channel bandwidth.

For example, a WiMAX system may use 128, 512, or 1,048-bit FFTs (fast fourier transforms) based on whether the channel bandwidth is 1.25MHz, 5MHz, or 10MHz, respectively. This scaling may be done dynamically to support user roaming across different networks that may have different bandwidth allocations.

2.23 Adaptive modulation and coding (AMC):WiMAX supports a number of modulation and forward error correction (FEC) coding schemes and allows the scheme to be

changed on a per user and per frame basis, based on channel conditions.AMC is an effective mechanism to maximize throughput in a time-varying channel.

2.24 Link-layer retransmissions:WiMAX

supports automatic retransmission

requests (ARQ) at the link layer for connections that require enhanced reliability. ARQ-enabled connections require each transmitted packet to be acknowledged by the receiver; unacknowledged packets are assumed to be lost and are retransmitted.

2.25 Support for TDD and FDD:IEEE

802.16-2004 and IEEE 802.16e-2005

supports both time division duplexing and frequency division duplexing, as well as a half-duplex FDD, which allows for a low-cost system implementation.

2.26 WiMAX uses OFDM: Mobile WiMAX uses Orthogonal frequency division multiple access (OFDM) as a multipleaccess technique, whereby different users can be allocated different subsets of the OFDM tones.

2.27 Flexible and dynamic per user resource allocation: Both uplink and downlink resource allocation are controlled by a scheduler in the base station.

Capacity is shared among multiple users on a demand basis, using a burst TDM scheme.

2.28 Support for advanced antenna techniques: The WiMAX solution has a number of hooks built into the physical-layer design, which allows for the use of multiple-antenna techniques, such as beamforming, space-time coding, and spatial multiplexing.

2.29 Quality-of-service support: The WiMAX MAC layer has a connection-oriented architecture that is designed to support a variety of applications, including voice and multimedia services.

WiMAX system offers support for constant bit rate, variable bit rate, real-time, and non-real-time traffic flows, in addition to best-effort data traffic.

WiMAX MAC is designed to support a large number of users, with multiple connections per terminal, each with its own QoS requirement.

2.30 Robust security: WiMAX supports strong encryption, using Advanced Encryption Standard (AES), and has a robust privacy and key-management protocol.

The system also offers a very flexible authentication architecture based on Extensible Authentication Protocol (EAP), which allows for a variety of user credentials, including username/password, digital certificates, and smart cards.

2.31 Support for mobility: The mobile WiMAX variant of the system has mechanisms to support secure seamless handovers for delay-tolerant full-mobility applications, such as VoIP.

2.32 IP-based architecture: The WiMAX Forum has defined a reference network architecture that is based on an all-IP platform. All end-to-end services are delivered over an IP architecture relying on IP-based protocols for end-to-end transport, QoS, session management, security, and mobility.

2.33 WiMAX - Building Blocks A WiMAX system consists of two major parts: A WiMAX base station.

A WiMAX receiver.

2.33.1

WiMAX Base Station:

A WiMAX base station consists of indoor electronics and a WiMAX tower similar in concept to a cell-phone tower. A WiMAX base station can provide coverage to a very large area up to a radius of 6 miles. Any wireless device within the coverage area would be able to access the Internet.

The WiMAX base stations would use the MAC layer defined in the standard . a common interface that makes the networks interoperable and would allocate uplink and downlink bandwidth to subscribers according to their needs, on an essentially real-time basis.

Each base station provides wireless coverage over an area called a cell. Theoretically, the maximum radius of a cell is 50 km or 30 miles however, practical considerations limit it to about 10 km or 6 miles.

2.33.2

WiMAX Receiver:

A WiMAX receiver may have a separate antenna or could be a stand-alone box or a PCMCIA card sitting in your laptop or computer or any other device. This is also referred as customer premise equipment (CPE).

WiMAX base station is similar to accessing a wireless access point in a WiFi network, but the coverage is greater.

2.34 Backhaul: A WiMAX tower station can connect directly to the Internet using a high-bandwidth, wired connection (for example, a T3 line). It can also connect to another WiMAX tower using a lineof-sight, microwave link.

Backhaul refers both to the connection from the access point back to the base station and to the connection from the base station to the core network.

It is possible to connect several base stations to one another using high-speed backhaul microwave links. This would also allow for roaming by a WiMAX subscriber from one base station coverage area to another, similar to the roaming enabled by cell phones.

2.35 WiMAX - Reference Network Model The IEEE 802.16e-2005 standard provides the air interface for WiMAX but does not define the full end-to-end WiMAX network. The WiMAX Forum's Network Working Group (NWG), is responsible for developing the end-to-end network requirements, architecture, and protocols for WiMAX, using IEEE 802.16e-2005 as the air interface.

The WiMAX NWG has developed a network reference model to serve as an architecture framework for WiMAX deployments and to ensure interoperability among various WiMAX equipment and operators.

The network reference model envisions a unified network architecture for supporting fixed, nomadic, and mobile deployments and is based on an IP service model. Below is simplified illustration of an IP-based WiMAX network architecture. The overall network may be logically divided into three parts: Mobile Stations (MS) used by the end user to access the network.

The access service network (ASN), which comprises one or more base stations and one or more ASN gateways that form the radio access network at the edge.

Connectivity service network (CSN), which provides IP connectivity and all the IP core network functions.

The network reference model developed by the WiMAX Forum NWG defines a number of functional entities and interfaces between those entities. Fig below shows some of the more important functional entities.

Base station (BS): The BS is responsible for providing the air interface to the MS. Additional functions that may be part of the BS are micromobility management functions, such as handoff

triggering and tunnel establishment, radio resource management, QoS policy enforcement, traffic classification, DHCP (Dynamic Host Control Protocol) proxy, key management, session management, and multicast group management.

Access service network gateway (ASN-GW): The ASN gateway typically acts as a layer 2 traffic aggregation point within an ASN. Additional functions that may be part of the ASN gateway include intra-ASN location management and paging, radio resource management and admission control, caching of subscriber profiles and encryption keys, AAA client functionality, establishment and management of mobility tunnel with base stations, QoS and policy enforcement, foreign agent functionality for mobile IP, and routing to the selected CSN.

Connectivity service network (CSN): The CSN provides connectivity to the Internet, ASP, other public networks, and corporate networks. The CSN is owned by the NSP and includes AAA servers that support authentication for the devices, users, and specific services.

The CSN also provides per user policy management of QoS and security. The CSN is also responsible for IP address management, support for roaming between different NSPs, location management between ASNs, and mobility and roaming between ASNs.

The WiMAX architecture framework allows for the flexible decomposition and/or combination of functional entities when building the physical entities. For example, the ASN may be decomposed into base station transceivers (BST), base station controllers (BSC), and an ASNGW analogous to the GSM model of BTS, BSC, and Serving GPRS Support Node (SGSN).

2.36 WiMAX - Technology WiMAX is a technology based on the IEEE 802.16 specifications to enable the delivery of lastmile wireless broadband access as an alternative to cable and DSL. The design of WiMAX network is based on the following major principles: Spectrum . able to be deployed in both licensed and unlicensed spectra.

Topology . supports different Radio Access Network (RAN) topologies.

Interworking . independent RAN architecture to enable seamless integration and interworking with WiFi, 3GPP and 3GPP2 networks and existing IP operator core network.

IP connectivity . supports a mix of IPv4 and IPv6 network interconnects in clients and application servers.

Mobility management . possibility to extend the fixed access to mobility and broadband multimedia services delivery.

WiMAX has defined two MAC system profiles the basic ATM and the basic IP. They have also defined two primary PHY system profiles, the 25 MHz-wide channel for use in (US deployments) the 10.66 GHz range, and the 28 MHz wide channel for use in (European deployments) the 10.66 GHz range.

WiMAX Physical and MAC Layers are explained in separate chapters of this tutorial.

The WiMAX technical working group is defining MAC and PHY system profiles for IEEE 802.16a and HiperMan standards. The MAC profile includes an IP-based version for both wireless MAN (licensed) and wireless HUMAN (licence-exempt).

IEEE Standard 802.16 was designed to evolve as a set of air interfaces standards for WMAN based on a common MAC protocol but with physical layer specifications dependent on the spectrum of use and the associated regulations.

The WiMAX framework is based on several core principles: Support for different RAN topologies.

Well-defined interfaces to enable 802.16 RAN architecture independence while enabling seamless integration and interworking with WiFi, 3GPP3 and 3GPP2 networks.

Leverage and open, IETF-defined IP technologies to build scalable all-IP 802.16 access networks using common off the shelf (COTS) equipment.

Support for IPv4 and IPv6 clients and application servers, recommending use of IPv6 in the infrastructure.

Functional extensibility to support future migration to full mobility and delivery of rich broadband multimedia.

2.37 WiMAX - Physical Layer The WiMAX physical layer is based on orthogonal frequency division multiplexing. OFDM is the transmission scheme of choice to enable high-speed data, video, and multimedia communications and is used by a variety of commercial broadband systems, including DSL, WiFi, Digital Video Broadcast-Handheld (DVB-H), and MediaFLO, besides WiMAX. OFDM is an elegant and efficient scheme for high data rate transmission in a non-line-of-sight or multipath radio environment.

2.38 Adaptive Modulation and Coding in WiMAX: WiMAX supports a variety of modulation and coding schemes and allows for the scheme to change on a burst-by-burst basis per link, depending on channel conditions. Using the channelquality feedback indicator, the mobile can provide the base station with feedback on the downlink channel quality. For the uplink, the base station can estimate the channel quality, based on the received signal quality.

Following is a list of the various modulation and coding schemes supported by WiMAX.

Downlink

Modulation

Uplink

BPSK, QPSK, 16 QAM, 64 QAM; BPSK, QPSK, 16 QAM; 64 BPSK optional for OFDMA-PHY

QAM optional

Mandatory: convolutional codes Mandatory: at

rate

1/2,

2/3,

3/4,

convolutional

5/6 codes at rate 1/2, 2/3, 3/4, 5/6

Coding

Optional:

convolutional

turbo

codes at rate 1/2, 2/3, 3/4, 5/6; Optional:

convolutional

repetition codes at rate 1/2, 1/3, turbo codes at rate 1/2, 2/3, 1/6, LDPC, RS-Codes for OFDM- 3/4, 5/6; repetition codes at PHY

rate 1/2, 1/3, 1/6, LDPC

2.39 PHY-Layer Data Rates: Because the physical layer of WiMAX is quite flexible, data rate performance varies based on the operating parameters. Parameters that have a significant impact on the physical-layer data rate are channel bandwidth and the modulation and coding scheme used. Other parameters, such as number of subchannels, OFDM guard time, and oversampling rate, also have an impact.

Following is the PHY-layer data rate at various channel bandwidths, as well as modulation and coding schemes.

2.40 WiMAX - OFDM Basics OFDM belongs to a family of transmission schemes called multicarrier modulation, which is based on the idea of dividing a given high-bit-rate data stream into several parallel lower bit-rate streams and modulating each stream on separate carriers.often called subcarriers, or tones.

Multicarrier modulation schemes eliminate or minimize intersymbol interference (ISI) by making the symbol time large enough so that the channel-induced delays.delay spread being a good measure of this in wireless channels . are an insignificant (typically, < 10 percent) fraction of the symbol duration.

Therefore, in high-data-rate systems in which the symbol duration is small, being inversely proportional to the data rate, splitting the data stream into many parallel streams increases the symbol duration of each stream such that the delay spread is only a small fraction of the symbol duration.

OFDM is a spectrally efficient version of multicarrier modulation, where the subcarriers are selected such that they are all orthogonal to one another over the symbol duration, thereby

avoiding the need to have nonoverlapping subcarrier channels to eliminate intercarrier interference.

In order to completely eliminate ISI, guard intervals are used between OFDM symbols. By making the guard interval larger than the expected multipath delay spread, ISI can be completely eliminated. Adding a guard interval, however, implies power wastage and a decrease in bandwidth efficiency.

2.41 WiMAX - MAC Layer The IEEE 802.16 MAC was designed for point-to-multipoint broadband wireless access applications. The primary task of the WiMAX MAC layer is to provide an interface between the higher transport layers and the physical layer.

The MAC layer takes packets from the upper layer.these packets are called MAC service data units (MSDUs).and organizes them into MAC protocol data units (MPDUs) for transmission over the air. For received transmissions, the MAC layer does the reverse.

The IEEE 802.16-2004 and IEEE 802.16e-2005 MAC design includes a convergence sublayer that can interface with a variety of higher-layer protocols, such as ATM TDM Voice, Ethernet, IP, and any unknown future protocol.

The 802.16 MAC is designed for point-to-multipoint (PMP) applications and is based on collision sense multiple access with collision avoidance (CSMA/CA).

The MAC incorporates several features suitable for a broad range of applications at different mobility rates, such as the following: Privacy key management (PKM) for MAC layer security. PKM version 2 incorporates support for extensible authentication protocol (EAP).

Broadcast and multicast support.

Manageability primitives.

High-speed handover and mobility management primitives.

Three power management levels, normal operation, sleep and idle.

Header suppression, packing and fragmentation for efficient use of spectrum.

Five service classes, unsolicited grant service (UGS), real-time polling service (rtPS), non-realtime polling service (nrtPS), best effort (BE) and Extended real-time variable rate (ERT-VR) service.

These features combined with the inherent benefits of scalable OFDMA make 802.16 suitable for high-speed data and bursty or isochronous IP multimedia applications.

Support for QoS is a fundamental part of the WiMAX MAC-layer design. WiMAX borrows some of the basic ideas behind its QoS design from the DOCSIS cable modem standard.

Strong QoS control is achieved by using a connection-oriented MAC architecture, where all downlink and uplink connections are controlled by the serving BS. WiMAX also defines a concept of a service flow. A service flow is a unidirectional flow of packets with a particular set of QoS parameters and is identified by a service flow identifier (SFID).

2.42 WiMAX - Mobility Support WiMAX envisions four mobility-related usage scenarios : Nomadic: The user is allowed to take a fixed subscriber station and reconnect from a different point of attachment.

Portable: Nomadic access is provided to a portable device, such as a PC card, with expectation of a best-effort handover.

Simple mobility: The subscriber may move at speeds up to 60 kmph with brief interruptions (less than 1 sec) during handoff.

Full mobility: Up to 120 kmph mobility and seamless handoff (less than 50 ms latency and < 1% packet loss) is supported.

It is likely that WiMAX networks will initially be deployed for fixed and nomadic applications and then evolve to support portability to full mobility over time.

The IEEE 802.16e-2005 standard defines a framework for supporting mobility management. In particular, the standard defines signaling mechanisms for tracking subscriber stations as they move from the coverage range of one base station to another when active or as they move from one paging group to another when idle.

The standard also has protocols to enable a seamless handover of ongoing connections from one base station to another.

The standard also has protocols to enable a seamless handover of ongoing connections from one base station to another. The WiMAX Forum has used the framework defined in IEEE 802.16e2005 to further develop mobility management within an end-to-end network architecture framework. The architecture also supports IP-layer mobility using mobile IP.

2.43 WiMAX - Security Functions WiMAX systems were designed at the outset with robust security in mind. The standard includes state-of-the-art methods for ensuring user data privacy and preventing unauthorized access, with additional protocol optimization for mobility.

Security is handled by a privacy sublayer within the WiMAX MAC. The key aspects of WiMAX security are as follow: Support for privacy: User data is encrypted using cryptographic schemes of proven robustness to provide privacy.

Both AES (Advanced Encryption Standard) and 3DES (Triple Data Encryption Standard) are supported.

The 128-bit or 256-bit key used for deriving the cipher is generated during the authentication phase and is periodically refreshed for additional protection.

Device/user authentication: WiMAX provides a flexible means for authenticating subscriber stations and users to prevent unauthorized use. The authentication framework is based on the Internet Engineering Task Force (IETF) EAP, which supports a variety of credentials, such as username/password, digital certificates, and smart cards.

WiMAX terminal devices come with built-in X.509 digital certificates that contain their public key and MAC address. WiMAX operators can use the certificates for device authentication and use a username/password or smart card authentication on top of it for user authentication.

Flexible key-management protocol: The Privacy and Key Management Protocol Version 2 (PKMv2) is used for securely transferring keying material from the base station to the mobile station, periodically reauthorizing and refreshing the keys.

Protection of control messages: The integrity of over-the-air control messages is protected by using message digest schemes, such as AES-based CMAC or MD5-based HMAC. Support for fast handover: To support fast handovers, WiMAX allows the MS to use preauthentication with a particular target BS to facilitate accelerated reentry.

A three-way handshake scheme is supported to optimize the reauthentication mechanisms for supporting fast handovers, while simultaneously preventing any man-in-the-middle attacks.

2.44 WiMAX - IEEE Standards

The IEEE 802.16, the Air Interface for Fixed Broadband Wireless Access Systems, also known as the IEEE WirelessMAN air interface, is an emerging suite of standards for fixed, portable and mobile BWA in MAN. These standards are issued by IEEE 802.16 work group that originally covered the wireless local loop (WLL) technologies in the 10.66 GHz radio spectrum, which were later extended through amendment projects to include both licensed and unlicensed spectra from 2 to 11 GHz. The WiMAX umbrella currently includes 802.16-2004 and 802.16e. 802.16-2004 utilizes OFDM to serve multiple users in a time division fashion in a sort of a round-robin technique, but done extremely quickly so that users have the perception that they are always transmitting/receiving.

802.16e utilizes OFDMA and can serve multiple users simultaneously by allocating sets of tones to each user.

Following is the chart of various IEEE 802.16 Standards related to WiMAX.

NOTE: The IEEE 802.16 standards for BWA provide the possibility for interoperability between equipment from different vendors, which is in contrast to the previous BWA industry, where proprietary products with high prices are dominant in the market.

2.45 WiMAX - WiMAXForumâ&#x201E;˘

A nonprofit organization called WiMAX Forum™ was formed in 2001, with the aim of harmonizing standards, and testing and certifying interoperability between equipment from different manufacturers.

WiMAX Forum™ was formed by equipment and component suppliers to support the IEEE 802.16 BWA system by helping to ensure the compatibility and interoperability of BWA equipment which will lead to lower cost through chip-level implementation.

WiMAX Forum™ is doing what WiFi Alliance has done for wireless LAN and IEEE 802.11.

WiMAX Forum Certified™ products adhere to the IEEE 802.16 standard and offer higher bandwidth, lower costs and broader service capabilities than most of the available proprietary solutions.

The WiMAX Forum™ is working on setting up a baseline protocol that allows equipment and devices from multiple vendors to interoperate, and also provides a choice of equipment and devices from different suppliers.

2.46 Members of WiMAXForum: The WiMAX Forum™ has more than 400 members from equipment manufacturers, semiconductor suppliers, and services providers, and membership was recently opened for content providers. Some of the noted members are Alcatel, AT&T, Fujitsu, Intel, Nortel, Motorola, SBC and Siemens.

2.47 Uses The bandwidth and range of WiMAX make it suitable for the following potential applications: Connecting Wi-Fi hotspots to the Internet.

Providing a wireless alternative to cable and DSL for "last mile" broadband access.

Providing data and telecommunications services.

Providing a source of Internet connectivity as part of a business continuity plan. That is, if a business has a fixed and a wireless Internet connection, especially from unrelated providers, they are unlikely to be affected by the same service outage.

Providing portable connectivity.

2.48 Broadband access Companies are closely examining WiMAX for last mile connectivity. The resulting competition may bring lower pricing for both home and business customers or bring broadband access to places where it has been economically unavailable WiMAX access was used to assist with communications in Aceh, Indonesia, after the tsunami in December 2004 All communication infrastructure in the area, other than amateur radio, was destroyed, making the survivors unable to communicate with people outside the disaster area and vice versa. WiMAX provided broadband access that helped regenerate communication to and from Aceh.

In addition, WiMAX was donated by Intel Corporation to assist the FCC and FEMA in their communications efforts in the areas affected by Hurricane Katrina. In practice, volunteers used main ly self-healing mesh, VoIP, and a satellite uplink combined with Wi-Fi on the local link.

2.49 Subscriber units (Client Units) WiMAX subscriber units are available in both indoor and outdoor versions from several manufacturers. Self-install indoor units are convenient, but radio losses mean that the subscriber must be significantly closer to the WiMAX base station than with professionally-installed external units. As such, indoor-installed units require a much higher infrastructure investment as well as operational cost (site lease, backhaul, maintenance) due to the high number of base stations required to cover a given area. Indoor units are comparable in size to a cable modem or

DSL modem. Outdoor units are roughly the size of a laptop PC, and their installation is comparable to the installation of a residential satellite dish.

With the potential of mobile WiMAX, there is an increasing focus on portable unitsThis includes handsets (similar to cellular smartphones), PC peripherals (PC Cards or USB dongles), and embedded devices in laptops, such as are now available for Wi-Fi. In addition, there is much emphasis from operators on consumer electronics devices (game terminals, MP3 players and the like), it is notable this is more similar to Wi-Fi than to 3G cellular technologies.

Current certified devices can be found at the WiMAX Forum web site. This is not a complete list of devices available as certified modules are embedded into laptops, MIDs (Mobile Internet Devices), and private labeled devices

2.50 Mobile handset applications Sprint Nextel announced in mid-2006 that it would invest about US$ 5 billion in a WiMAX technology buildout over the next few years. [17] Since that time Sprint has been dealt setbacks that have resulted in steep quarterly losses. On May 7, 2008, Sprint, Imagine, Google, Intel, Comcast, and Time Warner announced a pooling of an average of 120 MHz of spectrum and formation of a new company which will take the name Clearwire. The new company hopes to benefit from combined services offerings and network resources as a springboard past its competitors. The cable companies will provide media services to other partners while gaining access to the wireless network as a Mobile virtual network operator. Google will contribute Android handset device development and applications and will receive revenue share for advertising and other services they provide. Clearwire Sprint and current Clearwire gain a majority stock ownership in the new venture and ability to access between the new Clearwire and Sprint 3G networks. Some details remain unclear including how soon and in what form announced multi-mode WiMAX and 3G EV-DO devices will be available. This raises questions that arise for availability of competitive chips that require licensing of Qualcomm's IPR. Some analysts have questioned how the deal will work out: Although fixed-mobile convergence has been a recognized factor in the industry, prior attempts to form partnerships among wireless

and cable companies have generally failed to lead to significant benefits to the participants.

Other analysts point out that as wireless progresses to higher bandwidth, it inevitably competes more directly with cable and DSL, thrusting competitors into bed together. Also, as wireless broadband networks grow denser and usage habits shift, the need for increased backhaul and media service will accelerate, therefore the opportunity to leverage cable assets is expected to increase.

2.51 Backhaul/access network applications WiMAX is a possible replacement candidate for cellular phone technologies such as GSM and CDMA, or can be used as an overlay to increase capacity. It has also been considered as a wireless backhaul technology for 2G, 3G, and 4G networks in both developed and poor nations.

[18][19]

In North America, backhaul for urban cellular operations is typically provided via one or more copper wire line T1 connections, whereas remote cellular operations are sometimes backhauled via satellite. In most other regions, urban and rural backhaul is usually provided by microwave links. (The exception to this is where the network is operated by an incumbent with ready access to the copper network, in which case T1 lines may be used). WiMAX is a broadband platform and as such has much more substantial backhaul bandwidth requirements than legacy cellular applications. Therefore traditional copper wire line backhaul solutions are not appropriate.

Consequently the use of wireless microwave backhaul is on the rise in North America and existing microwave backhaul links in all regions are being upgraded.

[20]

Capacities of between

34 Mbit/s and 1 Gbit/s are routinely being deployed with latencies in the order of 1ms. [citation needed] In many cases, operators are aggregating sites using wireless technology and then presenting traffic on to fiber networks where convenient.

Deploying WiMAX in rural areas with limited or no internet backbone will be challenging as additional methods and hardware will be required to procure sufficient bandwidth from the nearest sources â&#x20AC;&#x201D; the difficulty being in proportion to the distance between the end-user and the nearest sufficient internet backbone.

2.52 Technical information

Illustration of a WiMAX MIMO board WiMAX is a term coined to describe standard, interoperable implementations of IEEE 802.16 wireless networks, similar to the way the term Wi-Fi is used for interoperable implementations of the IEEE 802.11 Wireless LAN standard. However, WiMAX is very different from Wi-Fi in the way it works.

2.53 Complexities of deployment Being a standard thought to satisfy the needs of next generation data networks, nomadic and mobile (4G), it is distinguished by a dynamic burst algorithm that adapts the current physical digital modulation according to field variables that are dependent on the radio propagation conditions; the current physical mod is chosen to be spectrally more efficient (more bits per OFDM/SOFDMA symbol), that is, when the bursts have a high signal strength and a high carrier to noise plus interference ratio (CINR) and they can be easily decoded by the digital signal processing (DSP) Algorithms.

In contrast, when some of those conditions are bad, then the system chooses a more robust physical mode (burst profile) which means less bits per OFDM/SOFDMA symbol, but with the advantage that power per bit is higher and therefore accurate decoding is easier. Because of this, higher order burst profiles can only be used (dynamically chosen by an algorithm) when the attenuation is not high which means only for subscriber stations located near the base station antenna and therefore the maximum distance can only be achieved by means of selecting the

more robust burst profile with the MAC frame allocation inconvenience that it implies as more symbols (more portion of the MAC frame) have to be allocated for transmitting a given amount of data than if the subscriber station was close to the base station.

In the MAC Frame the subscriber stations are allocated and their individual burst profiles defined as well as the specific time allocation, but even if that is done automatically practical deployment should avoid high interference and high multipath environments as opposed to what the average radio network planning team (and executive staff from the adopting operator) could think, the reason for it lies in excessive interference and competition during the Initial Ranging (IR) process due to the usage of high transmitting power in base station (BS) and subscriber station (SS) alike, which can result in unwanted delays and ranging attempts that effectively detracts from a good user experience and can even result in wasted allocated symbols due to continuous connections/re-connections.

The system therefore is very complex to deploy as it is necessary to keep in mind not only the signal strength and CINR (as in systems like GSM) but it is also necessary to think how the spectrum is going to be dynamically assigned (resulting in dynamically changing total available bandwidth)) to the served subscriber stations (other dynamic burst systems have 2 or 3 burst profiles, WiMAX developments have showed up to 7 in use at the same time), the DSP algorithms (Decodification) are tougher than in any other wireless systems, yet they cannot reconstruct any burst in any environment; It is usually very effective though, but coupled with OFDM/SOFDMA, it can result in a double edged sword which means by having a tougher set of DSP algorithms, usually deployed on specific purpose chips, the signal could (harmfully) reach farther distances than expected due to tunnel effects (constructive interference with neighbor frequencies) resulting in highly interfered clutters and with highly reflected signals, with very high signal strength though which can fool the non experienced planning staff (usually coming from 3gpp networks).

As a result the system has to be initially deployed in conjunction with product development staff (who are usually involved in the technology development in some way) from the given vendor as opposed to service technical staff (radio planning) from the operator or vendor as is usual

practice, thus raising the cost of deployment. As with all new technologies, configuration and maintenance will become easier to use as more deployments occur.

2.54 Integration with an IP based Network

The WiMAX Forum WiMAX Architecture The WiMAX Forum has proposed an architecture that defines how a WiMAX network can be connected with an IP based core network, which is typically chosen by operators that serve as Internet Service Providers (ISP); Nevertheless the WiMAX BS provide seamless integration capabilities with other types of architectures as with packet switched Mobile Networks.

The WiMAX forum proposal defines a number of components, plus some of the interconnections (or reference points) between these, labeled R1 to R5 and R8: SS/MS: the Subscriber Station/Mobile Station ASN: the Access Service Network BS: Base station, part of the ASN ASN-GW: the ASN Gateway, part of the ASN CSN: the Connectivity Service Network

HA: Home Agent, part of the CSN AAA: Authentication, Authorization and Accounting Server, part of the CSN NAP: a Network Access Provider NSP: a Network Service Provider It is important to note that the functional architecture can be designed into various hardware configurations rather than fixed configurations. For example, the architecture is flexible enough to allow remote/mobile stations of varying scale and functionality and Base Stations of varying size - e.g. femto, pico, and mini BS as well as macros.

2.55 Spectrum allocation issues The 802.16 specification applies across a wide swath of the RF spectrum, and WiMAX could function on any frequency below 66 GHz, (higher frequencies would decrease the range of a Base Station to a few hundred meters in an urban environment).

There is no uniform global licensed spectrum for WiMAX, although the WiMAX Forum has published three licensed spectrum profiles: 2.3 GHz, 2.5 GHz and 3.5 GHz, in an effort to decrease cost: economies of scale dictate that the more WiMAX embedded devices (such as mobile phones and WiMAX-embedded laptops) are produced, the lower the unit cost. (The two highest cost components of producing a mobile phone are the silicon and the extra radio needed for each band.) Similar economy of scale benefits apply to the production of Base Stations.

In the unlicensed band, 5.x GHz is the approved profile. Telecommunication companies are unlikely to use this spectrum widely other than for backhaul, since they do not own and control the spectrum.

In the USA, the biggest segment available is around 2.5 GHz, and is already assigned, primarily to Sprint Nextel and Clearwire. Elsewhere in the world, the most-likely bands used will be the Forum approved ones, with 2.3 GHz probably being most important in

Asia. Some countries in Asia like India and Indonesia will use a mix of 2.5 GHz, 3.3 GHz and other frequencies. Pakistan's Wateen Telecom uses 3.5 GHz. Analog TV bands (700 MHz) may become available for WiMAX usage, but await the complete roll out of digital TV, and there will be other uses suggested for that spectrum. In the USA the FCC auction for this spectrum began in January 2008 and, as a result, the biggest share of the spectrum went to Verizon Wireless and the next biggest to AT&T. Both of these companies have stated their intention of supporting LTE, a technology which competes directly with WiMAX. EU commissioner Viviane Reding has suggested re-allocation of 500â&#x20AC;&#x201C;800 MHz spectrum for wireless communication, including WiMAX. WiMAX profiles define channel size, TDD/FDD and other necessary attributes in order to have inter-operating products. The current fixed profiles are defined for both TDD and FDD profiles.

At this point, all of the mobile profiles are TDD only. The fixed profiles have channel sizes of 3.5 MHz, 5 MHz, 7 MHz and 10 MHz. The mobile profiles are 5 MHz, 8.75 MHz and 10 MHz. (Note: the 802.16 standard allows a far wider variety of channels, but only the above subsets are supported as WiMAX profiles.)

Since October 2007, the Radio communication Sector of the International Telecommunication Union (ITU-R) has decided to include WiMAX technology in the IMT-2000 set of standards.

This enables spectrum owners (specifically in the 2.5-2.69 GHz band at this stage) to use Mobile WiMAX equipment in any country that recognizes the IMT-2000.

2.56 Spectral efficiency One of the significant advantages of advanced wireless systems such as WiMAX is spectral efficiency. For example, 802.16-2004 (fixed) has a spectral efficiency of 3.7 (bit/s)/Hertz, and other 3.5â&#x20AC;&#x201C;4G wireless systems offer spectral efficiencies that are similar to within a few tenths of a percent. The notable advantage of WiMAX comes from combining SOFDMA with smart antenna technologies. This multiplies the effective spectral efficiency through multiple reuse and smart network deployment topologies. The direct use of frequency domain organization

simplifies designs using MIMO-AAS compared to CDMA/WCDMA methods, resulting in more effective systems

2.57 Limitations A commonly-held misconception is that WiMAX will deliver 70 Mbit/s over 50 kilometers (~31 miles). In reality, WiMAX can either operate at higher bitrates or over longer distances but not both: operating at the maximum range of 50 km increases bit error rate and thus results in a much lower bitrate. Conversely, reducing the range (to <1km) allows a device to operate at higher bitrates. There are no known examples of WiMAX services being delivered at bit rates over around 40 Mbit/s Typically, fixed WiMAX networks have a higher-gain directional antenna installed near the client (customer) which results in greatly increased range and throughput. Mobile WiMAX networks are usually made of indoor "Customer-premises equipment" (CPE) such as desktop modems, laptops with integrated Mobile WiMAX or other Mobile WiMAX devices. Mobile WiMAX devices typically have omnidirectional antennae which are of lower-gain compared to directional antennas but are more portable. In current deployments, the throughput may reach 2 Mbit/s symmetric at 10 km with fixed WiMAX and a high gain antenna. It is also important to consider that a throughput of 2 Mbit/s can mean 2 Mbit/s, symmetric simultaneously, 1 Mbit/s symmetric or some asymmetric mix (e.g. 0.5 Mbit/s downlink and 1.5 Mbit/s uplink or 1.5 Mbit/s downlink and 0.5 Mbit/s uplink), each of which required slightly different network equipment and configurations. Higher-gain directional antennas can be used with a WiMAX network with range and throughput benefits but the obvious loss of practical mobility.

Like most wireless systems, available bandwidth is shared between users in a given radio sector, so performance could deteriorate in the case of many active users in a single sector. In practice, most users will have a range of 2-3 Mbit/s services and additional radio cards will be added to the base station to increase the number of users that may be served as required.

Because of these limitations, the general consensus is that WiMAX requires various granular and distributed network architectures to be incorporated within the IEEE 802.16 task groups. This

includes wireless mesh, grids, network remote station repeaters which can extend networks and connect to backhaul.

2.58 Silicon implementations A critical requirement for the success of a new technology is the availability of low-cost chipsets and silicon implementations.

Intel Corporation is a leader in promoting WiMAX, and has developed its own chipset.

However, it is notable that most of the major semiconductor companies have not and most of the products come from specialist smaller or start-up suppliers. For the client-side these include Sequans, whose chips are in more than half of the WiMAX Forum Certified(tm) MIMO-based Mobile WiMAX client devices, GCT Semiconductor, ApaceWave, Altair Semiconductor, Beceem, Comsys, Runcom, Motorola with TI, NextWave Wireless, Wavesat, Coresonic and SySDSoft. Both Sequans and Wavesat manufacture products for both clients and network while Texas Instruments, DesignArt, and picoChip are focused on WiMAX chip sets for base stations.

Kaben Wireless Silicon is a provider of RF front-end and semiconductor IP for WiMAX applications.

2.59 Standards The current WiMAX incarnation, Mobile WiMAX, is based upon IEEE Std 802.16e-2005, approved in December 2005. It is a supplement to the IEEE Std 802.16-2004, and so the actual standard is 802.16-2004 as amended by 802.16e-2005 â&#x20AC;&#x201D; the specifications need to be read together to understand them.

IEEE Std 802.16-2004 addresses only fixed systems. It replaced IEEE Standards 802.16-2001, 802.16c-2002, and 802.16a-2003.

IEEE 802.16e-2005 improves upon IEEE 802.16-2004 by:

Adding support for mobility (soft and hard handover between base stations). This is seen as one of the most important aspects of 802.16e-2005, and is the very basis of 'Mobile WiMAX' (though this has yet to be demonstrated in any installed systems).

Scaling of the Fast Fourier transform (FFT) to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidths (typically 1.25 MHz, 5 MHz, 10 MHz or 20 MHz). Constant carrier spacing results in a higher spectrum efficiency in wide channels, and a cost reduction in narrow channels. Also known as Scalable OFDMA (SOFDMA). Other bands not multiples of 1.25 MHz are defined in the standard, but because the allowed FFT subcarrier numbers are only 128, 512, 1024 and 2048, other frequency bands will not have exactly the same carrier spacing, which might not be optimal for implementations.

Advanced antenna diversity schemes, and hybrid automatic repeat-request (HARQ) Adaptive Antenna Systems (AAS) and MIMO technology Denser sub-channelization, thereby improving indoor penetration Introducing Turbo Coding and Low-Density Parity Check (LDPC) Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa Fast Fourier transform algorithm Adding an extra QoS class for VoIP applications.

802.16d vendors point out that fixed WiMAX offers the benefit of available commercial products and implementations optimized for fixed access. It is a popular standard among alternative service providers and operators in developing areas due to its low cost of deployment and advanced performance in a fixed environment. Fixed WiMAX is also seen as a potential standard for backhaul of wireless base stations such as cellular, or Wi-Fi. SOFDMA (used in 802.16e-2005) and OFDM256 (802.16d) are not compatible thus most equipment will have to be replaced if an operator wants or needs to move to the later standard.

However, some manufacturers are planning to provide a migration path for older equipment to SOFDMA compatibility which would ease the transition for those networks which have already

made the OFDM256 investment. Intel provides a dual-mode 802.16-2004 802.16-2005 chipset for subscriber units.

2.60 Conformance testing TTCN-3 test specification language is used for the purposes of specifying conformance tests for WiMAX implementations. The WiMAX test suite is being developed by a Specialist Task Force at ETSI (STF 252).

2.61 WiMAX Spectrum Owners Alliance

WiSOA logo WiSOA was the first global organization composed exclusively of owners of WiMAX spectrum with plans to deploy WiMAX technology in those bands. WiSOA focussed on the regulation, commercialisation, and deployment of WiMAX spectrum in the 2.3â&#x20AC;&#x201C;2.5 GHz and the 3.4â&#x20AC;&#x201C;3.5 GHz ranges. WiSOA merged with the Wireless Broadband Alliance in April 2008.

2.62 Competing technologies

Speed vs. Mobility of wireless systems: Wi-Fi, HSPA, UMTS, GSM Within the marketplace, WiMAX's main competition comes from existing, widely deployed wireless systems such as UMTS and CDMA2000, as well as a number of Internet-oriented systems such as HiperMAN, and of course long range mobile Wi-Fi and mesh networking.

3G cellular phone systems usually benefit from already having entrenched infrastructure, having been upgraded from earlier systems. Users can usually fall back to older systems when they move out of range of upgraded equipment, often relatively seamlessly.

The major cellular standards are being evolved to so-called 4G, high-bandwidth, low-latency, all-IP networks with voice services built on top. The worldwide move to 4G for GSM/UMTS and AMPS/TIA (including CDMA2000) is the 3GPP Long Term Evolution effort. A planned CDMA2000 replacement called Ultra Mobile Broadband has been discontinued. For 4G systems, existing air interfaces are being discarded in favor of OFDMA for the downlink and a variety of OFDM based techniques for the uplink, similar to WiMAX. In some areas of the world, the wide availability of UMTS and a general desire for standardization has meant spectrum has not been allocated for WiMAX: in July 2005, the EUwide frequency allocation for WiMAX was blocked.

2.63 Mobile Broadband Wireless Access Mobile Broadband Wireless Access (MBWA) is a technology being developed by IEEE 802.20 and is aimed at wireless mobile broadband for operations from 75 to 220 mph (120 to 350 km/h).

The 802.20 standard committee was first to define many of the methods which were later funneled into Mobile WiMAX, including high speed dynamic modulation and similar scalable OFDMA capabilities. It apparently retains fast hand-off, Forward Error Correction (FEC) and cell edge enhancements.

The Working Group was temporarily suspended in mid-2006 by the IEEE-SA Standards Board because it had been the subject of a number of appeals. A preliminary investigation of one of these "revealed a lack of transparency, possible 'dominance,' and other irregularities in the

Working Group".In September 2006, the IEEE-SA Standards Board approved a plan to enable the working group to continue under new conditions, and on 12 June 2008, the IEEE approved the new standard.

Qualcomm, a leading company behind 802.20, has dropped support for continued development in order to focus on LTE.

2.64 Internet-oriented systems Early WirelessMAN standards, the European standard HiperMAN and Korean standard WiBro have been harmonized as part of WiMAX and are no longer seen as competition but as complementary. All networks now being deployed in South Korea, the home of the WiBro standard, are now WiMAX. As a short-range mobile Internet technology, such as in cafes and at transportation hubs like airports, the popular Wi-Fi 802.11b/g system is widely deployed, and provides enough coverage for some users to feel subscription to a WiMAX service is unnecessary.

2.65 Future development Mobile WiMAX based upon 802.16e-2005 has been accepted as IP-OFDMA for inclusion as the sixth wireless link system under IMT-2000. This can hasten acceptance by regulatory authorities and operators for use in cellular spectrum. WiMAX II, 802.16m will be proposed for IMT-Advanced 4G. The goal for the long term evolution of both WiMAX and LTE is to achieve 100 Mbit/s mobile and 1 Gbit/s fixed-nomadic bandwidth as set by ITU for 4G NGMN (Next Generation Mobile Network) systems through the adaptive use of MIMO-AAS and smart, granular network topologies. 3GPP LTE and WiMAX-m are concentrating much effort on MIMO-AAS, mobile multi-hop relay networking and related developments needed to deliver 10X and higher Co-Channel reuse multiples.

Since the evolution of core air-link technologies has approached the practical limits imposed by Shannon's Theorem, the evolution of wireless has embarked on pursuit of the 3X to 10X+ greater bandwidth and network efficiency by advances in the spatial and smart wireless broadband networking technologies.

2.66 Interference A field test conducted by SUIRG (Satellite Users Interference Reduction Group) with support from the U.S. Navy, the Global VSAT Forum, and several member organizations yielded results showing interference at 12 km when using the same channels for both the WiMAX systems and satellites in C-band. The WiMAX Forum has yet to respond.

2.67 Current deployments (Networks) The WiMAX Forum now claims there are over 455 WiMAX networks deployed in over 135 countries.

EVDO TECHNOLOGY (Evolution-Data Optimized)

3.1

Overview of EVDO

Evolution-Data Optimized or Evolution-Data only, abbreviated as EV-DO or EVDO and *often EV, is a telecommunications standard for the wireless transmission of data through radio signals, typically for broadband Internet access. It uses multiplexing techniques including Code division multiple access (CDMA) as well as Time division multiple access (TDMA) to maximize both individual user's throughput and the overall system throughput. It is standardized by 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and has been adopted by many mobile phone service providers around the world â&#x20AC;&#x201C; particularly those previously employing CDMA networks. It is also used on the Globalstar satellite phone network.

[1]

EV-DO was designed as an evolution of the CDMA2000 (IS-2000) standard that would support high data rates and could be deployed alongside a wireless carrier's voice services. An EV-DO channel has a bandwidth of 1.25 MHz, the same bandwidth size that IS-95A (IS-95) and IS-2000 (1xRTT) use.[2] The channel structure, on the other hand, is very different. Additionally, the

back-end network is entirely packet-based, and thus is not constrained by the restrictions typically present on a circuit switched network.

The EV-DO feature of CDMA2000 networks provides access to mobile devices with forward link air interface speeds of up to 2.4 Mbit/s with Rev. 0 and up to 3.1 Mbit/s with Rev. A. The reverse link rate for Rev. 0 can operate up to 153 kbit/s, while Rev. A can operate at up to 1.8 Mbit/s. It was designed to be operated end-to-end as an IP based network, and so it can support any application which can operate on such a network and bit rate constraints.

3.2

Standard revisions

Huawei CDMA2000 EVDO USB wireless modem

A Kyocera PC Card EVDO 3G router with Wi-Fi

There have been several revisions of the standard, starting with Revision 0 (Rev. 0). This was later expanded upon with Revision A to support QoS (to improve latency) and higher rates on the forward link and reverse link. Later in 2006 Revision B was published, that among other features includes the ability to bundle multiple carriers to achieve even higher rates and lower latencies (see TIA-856 Rev. B below). The upgrade from EV-DO Rev. A to EV-DO Rev. B involves a software update to the cell site modem, and additional equipment for the new EV-DO carriers. Existing cdma2000 operators may also have to retune some of their existing 1xRTT channels to other frequencies, since Rev. B requires all DO carriers be within 5 MHz.

3.3

TIA-856 Revision 0

The initial design of EV-DO was developed by Qualcomm in 1999 to meet IMT-2000 requirements for a greater-than-2-Mbit/s down link for stationary communications, as opposed to mobile communication such as a moving cellular phone. Initially, the standard was called High Data Rate (HDR), but was renamed to 1xEV-DO after it was ratified by the International Telecommunication Union (ITU); it was given the numerical designation TIA-856. Originally, 1xEV-DO stood for "1x Evolution-Data Only", referring to its being a direct evolution of the 1x (1xRTT) air interface standard, with its channels carrying only data traffic. The title of the 1xEV-DO standard document is "cdma2000 High Rate Packet Data Air Interface Specification", as cdma2000 (lowercase) is another name for the 1x standard, numerically designated as TIA-2000.

Later, likely due to the possible negative connotations of the word "only", the "DO" part of the standard's name 1xEV-DO was changed to stand for "Data Optimized". So EV-DO now stands for "Evolution-Data Optimized", the 1x prefix has been dropped by the many major carriers, and is marketed simply as EV-DO.[3] This provides a more marketingfriendly emphasis that the technology was optimized for data.

3.4

TIA-856 Rev. 0 forward link channel structure

The primary characteristic that differentiates an EV-DO channel from a 1xRTT channel is that it is Time Multiplexed on the forward link (from the tower to the mobile). This means that a single mobile has full use of the forward traffic channel within a particular geographic area (a sector) during a given slot of time. Using this technique, EV-DO is able to modulate each userâ&#x20AC;&#x2122;s time slot independently. This allows the service of users that are in favorable RF conditions with very complex modulation techniques while also serving users in poor RF conditions with simpler and more redundant signals.[4] The forward channel is divided into slots, each being 1.667 ms long. In addition to user traffic, overhead channels are interlaced into the stream. These include the Pilot which helps the mobile find and identify the channel, the Media Access Channel (MAC) which tells the mobiles when

their data is scheduled, and the Control Channel, which contains other information that the network needs the mobiles to know.

The modulation to be used to communicate with a given mobile is determined by the mobile itself. It listens to the traffic on the channel, and depending on the receive signal strength along with the perceived multi-path and fading conditions, makes its best guess as to what data-rate it can sustain while maintaining a reasonable frame error rate of 1-2%. It then communicates this information back to the serving sector in the form of an integer between 1 and 12 on the "Digital Rate Control" (DRC) channel. Alternatively, the mobile can select a "null" rate (DRC 0), indicating that the mobile either cannot decode data at any rate, or that it is attempting to hand off to another serving sector.[4]

3.5 The DRC values are as follows:

DRC

Data

rate Slots

Payload

Index

(kbit/s)

scheduled

(bits)

Rate

1

38.4

16

1024

1/5

QPSK

-12

2

76.8

8

1024

1/5

QPSK

-9.6

3

153.6

4

1024

1/5

QPSK

-6.8

4

307.2

2

1024

1/5

QPSK

-3.9

5

307.2

4

2048

1/5

QPSK

-3.8

DRC

Data

rate Slots

Index

(kbit/s)

scheduled

(bits)

Rate

6

614.4

1

1024

1/3

QPSK

-0.6

7

614.4

2

2048

1/3

QPSK

-0.8

Payload

size Code

size Code

Modulation

Modulation

SNR Reqd.

SNR Reqd.

8

921.6

2

3072

1/3

8-PSK

1.8

9

1228.8

1

2048

2/3

QPSK

3.7

10

1228.8

2

4096

1/3

16-QAM

3.8

11

1843.2

1

3072

2/3

8-PSK

7.5

12

2457.6

1

4096

2/3

16-QAM

9.7

Another important aspect of the EV-DO forward link channel is the scheduler. The scheduler most commonly used is called "proportional fair". It's designed to maximize sector throughput while also guaranteeing each user a certain minimum level of service. The idea is to schedule mobiles reporting higher DRC indices more often, with the hope that those reporting worse conditions will improve in time.

The system also incorporates Incremental Redundancy Hybrid ARQ. Each sub-packet of a multislot transmission is a turbo-coded replica of the original data bits. This allows mobiles to acknowledge a packet before all of its sub-sections have been transmitted. For example, if a mobile transmits a DRC index of 3 and is scheduled to receive data, it will expect to get data during four time slots. If after decoding the first slot the mobile is able to determine the entire data packet, it can send an early acknowledgement back at that time; the remaining three subpackets will be cancelled. If however the packet is not acknowledged, the network will proceed with the transmission of the remaining parts until all have been transmitted or the packet is acknowledged.

3.6

TIA-856 Rev. 0 reverse link structure

The reverse link (from the mobile back to the Base Transceiver Station) on EV-DO Rev. 0 operates very similar to that of 3G1X CDMA. The channel includes a reverse link pilot (helps with decoding the signal) along with the user data channels. Some additional channels that do not exist in 3G1X include the DRC channel (described above) and the ACK channel (used for HARQ). Only the reverse link has any sort of Power control, because the forward link is always

transmitted at full power for use by all the mobiles. [5] The reverse link has both open loop and closed loop power control. In the open loop, the reverse link transmission power is set based upon the received power on the forward link. In the closed loop, the reverse link power is adjusted up or down 800 times a second, as indicated by the serving sector (similar to 3G1X).

All of the reverse link channels are combined using code division and transmitted back to the base station using QPSK where they are decoded. The maximum speed available for user data is 153.2 kbit/s, but in real-life conditions this is rarely achieved. Typical speeds achieved are between 20-50 kbit/s.

3.7

TIA-856 Rev. A

Revision A of EV-DO makes several additions to the protocol while keeping it completely backwards compatible with Revision 0.

These changes included the introduction of several new forward link data rates that increase the maximum burst rate from 2.45 Mbit/s to 3.1 Mbit/s. Also included were protocols that would decrease connection establishment time (called enhanced access channel MAC), the ability for more than one mobile to share the same timeslot (multi-user packets) and the introduction of QoS flags. All of these were put in place to allow for low latency, low bit rate communications such as VoIP.[7] In the United States, Verizon Wireless and Sprint Nextel have migrated 100% of their EV-DO Rev.0 networks to EV-DO Rev. A.

3.8

The additional forward rates for EV-DO Rev. A are:

DRC Index Data rate in kbit/s Slots scheduled Payload size (bits) Code Rate Modulation 13

1536

2

5120

5/12

16-QAM

14

3072

1

5120

5/6

16-QAM

In addition to the changes on the forward link, the reverse link was enhanced to support higher complexity modulation (and thus higher bit rates). An optional secondary pilot was added, which is activated by the mobile when it tries to achieve enhanced data rates. To combat reverse link congestion and noise rise, the protocol calls for each mobile to be given an interference allowance which is replenished by the network when the reverse link conditions allow it. The reverse link has a maximum rate of 1.8 Mbit/s, but under normal conditions users experience a rate of approximately 500-1000kbit/s but with more latency than cable and dsl.

3.9

TIA-856 Rev. B

EV-DO Rev. B is a multi-carrier evolution of the Rev. A specification. It maintains the capabilities of EV-DO Rev. A, and provides the following enhancements: Higher rates per carrier (up to 4.9 Mbit/s on the downlink per carrier). Typical deployments are expected to include 2 or 3 carriers for a peak rate of 14.7 Mbit/s. Higher rates by bundling multiple channels together enhance the user experience and enables new services such as high definition video streaming.

Reduced latency by using statistical multiplexing across channels -enhances the experience for latency sensitive services such as gaming, video telephony, remote console sessions and web browsing.

Increased talk-time and standby time Reduced interference from the adjacent sectors especially to users at the edge of the cell signal which improves the rates that can be offered by using Hybrid frequency re-use.

Efficient support for services that have asymmetric download and upload requirements (i.e. different data rates required in each direction) such as file transfers, web browsing, and broadband multimedia content delivery.

3.10 TIA-1121

Main article: Ultra Mobile Broadband Ultra Mobile Broadband (UMB) was proposed by Qualcomm as the natural evolution path for CDMA2000, however, after most CDMA carriers chose to adopt the competing 3GPP Long Term Evolution (LTE) standard, development on UMB was cancelled in November 2008.

Qualcomm is now backing the LTE standard.

3.11 Potential competing standards Motorola proposed a new system called 1Xtreme as an evolution of CDMA2000, but it was rejected by the 3GPP2 standardization body. Later, a competing standard called EV-DV developed by Qualcomm, Lucent, Nokia, Motorola, etc. in 3GPP2 was proposed as an alternate evolution of CDMA. EV-DV stands for Evolution-Data and Voice, since the channel structure was backwards compatible with IS-95 and IS-2000 (1xRTT), allowing an in-band network deployment. In comparison, EV-DO requires 1 or more (1.25 MHz) freq. bands in addition to the voice band. (EV-DO Rev. A could potentially support a VoIP overlay network for voice calling, but this has not been pursued except for PTT, see QChat).

At the time, there was much debate on the relative merits of DV and DO. Traditional operators with an existing voice network preferred DV, since it does not require a separate band. Other design engineers, and newer operators without a 1x voice network, preferred EV-DO because it did not have to be backward compatible, and so could explore different pilot structures, reverse link silence periods, improved control channels, etc. And the network cost was lower, since EVDO uses an IP network and does not require a SS7 network and complex network switches such as a mobile switching center (MSC). Also, equipment was not available for EV-DV in time to meet market demands whereas the EV-DO equipment and mobile application-specific integrated circuits (ASIC) were available and tested by the time the EV-DV standard was completed. As a result, the EV-DV standard was less attractive to operators, and has not been implemented.

Verizon Wireless, then Sprint Nextel in 2004 and smaller operators in 2005 announced their plans to deploy EV-DO. In March 2005, Qualcomm suspended development of EV-DV chipsets, and focused on improving the EV-DO product line.

LTE TECHNOLOGY (LONG TERM EVOLUTION TECHNOLOGY)

4.1

Overview of LTE

LTE (Long Term Evolution) is the next major step in mobile radio communications, and it will be introduced in 3rd Generation Partnership Project (3GPP) Release 8.

The aim of this 3GPP project is to improve the Universal Mobile Telecommunications System (UMTS) mobile phone standard. Researchers and development engineers worldwide â&#x20AC;&#x201C; representing more than 60 operators, vendors and research institutes â&#x20AC;&#x201C; are participating in the joint LTE radio access standardization effort.

While 3GPP Release 8 has yet to be ratified as a standard, much of the standard will be oriented around upgrading UMTS towards a 4G mobile communications technology and an all-IP flat architecture system.

The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations, to make a globally applicable third generation (3G) mobile phone well as both FDD (Frequency Division Duplexing) and TDD (Time Division Duplex).

The main advantages with LTE are high throughput, low latency, plug and play, FDD and TDD in the same platform, improved end-user experience and simple architecture resulting in low operating expenditures. LTE system specification within the scope of the International Mobile Telecommunications-2000 project of the International Telecommunication Union (ITU). 3GPP specifications are based on evolved Global System for Mobile Communications (GSM) specifications. 3GPP standardization encompasses Radio, Core Network and Service architecture.

LTE provides downlink peak rates of at least 100Mbit/s, 50 Mbit/s in the uplink and RAN (Radio Access Network) round-trip times of less than 10ms. LTE supports flexible carrier

bandwidths, from 1.4MHz up to 20MHz as will also support seamless connection to existing networks such as GSM, CDMA and WCDMA.

4.2

Current State

While 3GPP Release 8 has yet to be ratified as a standard, much of the standard will be oriented around upgrading UMTS to 4G mobile communications technology, which is essentially a mobile broadband system with enhanced multimedia services built on top.

4.3

The Standard includes:

Peak download rates of 326.4 Mbit/s for 4x4 antennas, 172.8 Mbit/s for 2x2 antennas for every 20 MHz of spectrum.

Peak upload rates of 86.4 Mbit/s for every 20 MHz of spectrum.

5 different terminal classes have been defined from a voice centric class up to a high end terminal that supports the peak data rates. All terminal will be able to process 20 MHz bandwidth.

At least 200 active users in every 5 MHz cell. (i.e., 200 active data clients)

4.4

Sub-5ms latency for small IP packets

Increased spectrum flexibility, with spectrum slices as small as 1.5 MHz (and as large as 20 MHz) supported (W-CDMA requires 5 MHz slices, leading to some problems with roll-outs of the technology in countries where 5 MHz is a commonly allocated amount of spectrum, and is frequently already in use with legacy standards such as 2G GSM and cdmaOne.) Limiting sizes to 5 MHz also limited the amount of bandwidth per handset Optimal cell size of 5 km, 30 km sizes with reasonable performance, and up to 100 km cell sizes supported with acceptable performance

Co-existence with legacy standards (users can transparently start a call or transfer of data in an area using an LTE standard, and, should coverage be unavailable, continue the operation without any action on their part using GSM/GPRS or W-CDMA-based UMTS or even 3GPP2 networks such as cdmaOne or CDMA2000) Supports MBSFN (Multicast Broadcast Single Frequency Network). This feature can deliver services such as Mobile TV using the LTE infrastructure, and is a competitor for DVB-H-based TV broadcast.

PU2RC as a practical solution for MU-MIMO has been adopted to use in 3GPP LTE standard.

The detailed procedure for the general MU-MIMO operation is handed to the next release, e.g, LTE-Advanced, where further discussions will be held.

A large amount of the work is aimed at simplifying the architecture of the system, as it transits from the existing UMTS circuit + packet switching combined network, to an all-IP flat architecture system.

4.5

Timetable

In December 2008, Rel-8 specification was locked. In March 2009, the ASN.1 code was locked.

The standard has been complete enough that hardware designers have been designing chipsets, test equipment and base stations for some time. LTE test equipment has been shipping from several vendors since early 2008 and at the

Mobile World Congress

2008 in Barcelona

Ericsson

demonstrated the worldâ&#x20AC;&#x2122;s first end-to-end mobile call enabled by LTE on a small handheld device.[3]

Motorola

demonstrated a LTE RAN standard compliant eNodeB and LTE chipset at the

same event.

4.6

Standards

3GPP standards are structured as Releases. Discussion of 3GPP thus frequently refers to the functionality in one release or another.

Version Released[3]

Info

Release 1998

This and earlier releases specify pre-3G GSM networks

Release 2000 Q1

Specified the first UMTS 3G networks, incorporating a CDMA air interface[4]

Release 2001 Q2

luding an all-IP Core Network[5]

Release 2002 Q1

Introduced IMS and HSDPA[6]

Release 2004 Q4

as Push to Talk over Cellular (PoC), GAN[7]

Release 2007 Q4

focus on HSPA+ (High Speed Packet Access Evolution), SIM high-speed

2009[9]

8

Release In

an entirely IP based fourth-generation network. progress, SAES Enhancements, Wimax and LTE/UMTS Interoperability

Release In progress

LTE Advanced

Each release incorporates hundreds of individual standards documents, each of which may have been through many revisions. Current 3GPP standards incorporate the latest revision of the GSM standards. 3GPP's plans for the future beyond Release 7 are in the development under the title Long Term Evolution ("LTE").

The documents are available freely on 3GPP's Web site. While 3GPP standards can be bewildering to the newcomer, they are remarkably complete and detailed, and provide insight into how the cellular industry works. They cover not only the radio part ("Air Interface") and Core Network, but also billing information and speech coding down to source code level.

Cryptographic aspects (authentication, confidentiality) are also specified in detail. 3GPP2 offers similar information about its system.

4.7

An "All IP Network" (AIPN)

A characteristic of next generation networks are that they are based upon core internet protocol TCP/IP.

In 2004, 3GPP proposed Transmission Control Protocol/Internet Protocol (TCP/IP) as the future for next generation networks and began feasibility studies into All IP Networks (AIPN).

Proposals developed included recommendations for 3GPP Release 7(2005), [4] which are the foundation of higher level protocols such as LTE. These recommendations are part of the 3GPP System Architecture Evolution (SAE). Some aspects of All-IP networks, however, were already defined as early as release 4.[5] The 3GPP is defining IP-based, flat network architecture as part of the System Architecture Evolution (SAE) effort. LTEâ&#x20AC;&#x201C;SAE architecture and concepts have been designed for efficient support of mass-market usage of any IP-based service. The architecture is based on an evolution of the existing GSM/WCDMA core network, with simplified operations and smooth, costefficient deployment.

4.8

E-UTRAN Air Interface

Release 8's air interface, E-UTRA (Evolved UTRAN, the E- prefix being common to the evolved equivalents of older UMTS components) would be used by UMTS operators deploying their own wireless networks. It's important to note that Release 8 is intended for use over any IP network, including WiMAX and WiFi, and even wired networks.[6] The proposed E-UTRAN system uses OFDMA for the downlink (tower to handset) and Single Carrier FDMA (SC-FDMA) for the uplink and employs MIMO with up to four antennas per station. The channel coding scheme for transport blocks is turbo coding and a contention-free quadratic permutation polynomial (QPP) turbo code internal interleaver.[7] The use of OFDM, a system where the available spectrum is divided into many thin carriers, each on a different frequency, each carrying a part of the signal, enables E-UTRAN to be much more flexible in its use of spectrum than the older CDMA based systems that dominated 3G. CDMA networks require large blocks of spectrum to be allocated to each carrier, to maintain high chip rates, and thus maximize efficiency. Building radios capable of coping with different chip rates (and spectrum bandwidths) is more complex than creating radios that only send and receive one size of carrier, so generally CDMA based systems standardize both. Standardizing

on a fixed spectrum slice has consequences for the operators deploying the system: too narrow a spectrum slice would mean the efficiency and maximum bandwidth per handset suffers; too wide a spectrum slice, and there are deployment issues for operators short on spectrum. This became a major issue with the US roll-out of UMTS over W-CDMA, where W-CDMA's 5 MHz requirement often left no room in some markets for operators to co-deploy it with existing GSM standards.

LTE supports both FDD and TDD mode. While FDD makes use of paired spectra for UL and DL transmission separated by a duplex frequency gap, TDD is alternating using the same spectral resources used for UL and DL, separated by guard time [8]. Each mode has its own frame structure within LTE and these are aligned with each other meaning that similar hardware can be used in the base stations and terminals to allow for economy of scale. The TDD mode in LTE is aligned with TD-SCDMA as well allowing for coexistence. Ericsson demonstrated at the MWC 2008 in Barcelona for the first time in the world both LTE FDD and TDD mode on the same base station platform.

4.9

Downlink

LTE uses OFDM for the downlink â&#x20AC;&#x201C; that is, from the base station to the terminal. OFDM meets the LTE requirement for spectrum flexibility and enables cost-efficient solutions for very wide carriers with high peak rates. It is a well-established technology, for example in standards such as IEEE 802.11a/b/g, 802.16, HIPERLAN-2, DVB and DAB. In the time domain you have a radio frame that is 10 ms long and consists of 10 sub frames of 1 ms each. Every sub frame consists of 2 slots where each slot is 0.5 ms. The subcarrier spacing in the frequency domain is 15 kHz. Twelve of these subcarriers together (per slot) is called a resource block so one resource block is 180 kHz. 6 Resource blocks fit in a carrier of 1.4 MHz and 100 resource blocks fit in a carrier of 20 MHz. In the downlink there are three different physical channels. The Physical Downlink Shared Channel (PDSCH) is used for all the data transmission, the Physical Multicast Channel (PMCH) is used for broadcast transmission using a Single Frequency Network and the Physical Broadcast

Channel (PBCH) is used to send most important system information within the cell [9]. Supported modulation formats on the PDSCH are QPSK, 16QAM and 64QAM. For MIMO operation, a distinction is made between single user MIMO, for enhancing one user's data throughput, and multi user MIMO for enhancing the cell throughput.

4.10 Uplink In the uplink, LTE uses a pre-coded version of OFDM called Single Carrier Frequency Division Multiple Access (SC-FDMA). This is to compensate for a drawback with normal OFDM, which has a very high peak-to-average power ratio (PAPR). High PAPR requires expensive and inefficient power amplifiers with high requirements on linearity, which increases the cost of the terminal and drains the battery faster. SC-FDMA solves this problem by grouping together the resource blocks in such a way that reduces the need for linearity, and so power consumption, in the power amplifier. A low PAPR also improves coverage and the cell-edge performance.

In the uplink there are two physical channels. While the Physical Random Access Channel (PRACH) is only used for initial access and when the UE is not uplink synchronized [10], all the data is being send on the Physical Uplink Shared Channel (PUSCH). Supported modulation formats on the uplink data channel are QPSK, 16QAM and 64QAM. If virtual MIMO / Spatial division multiple access (SDMA) is introduced the data rate in the uplink direction can be increased depending on the number of antennas at the base station. With this technology more than one mobile can reuse the same resources.[11]

4.11 Technology Demos In September 2006, Siemens Networks (today Nokia Siemens Networks) showed in collaboration with Nomor Research the first live emulation of a LTE network to the media and investors. As live applications two users streaming an HD-TV video in the downlink and playing an interactive game in the uplink have been demonstrated.[12]

The first presentation of an LTE demonstrator with HDTV streaming (>30 Mbit/s), video supervision and Mobile IP-based handover between the LTE radio demonstrator and the commercially available HSDPA radio system was shown during the ITU trade fair in Hong Kong in December 2006 by Siemens Communication Department. â&#x20AC;˘ In February 2007, Ericsson demonstrated for the first time in the world LTE with bit rates up to 144 Mbit/s[13] In September 2007, NTT docomo demonstrated LTE data rates of 200 Mbit/s with power consumption below 100mW during the test.[14]

4.12 At the February 2008 Mobile World Congress: Huawei demonstrated Long Term Evolution ("LTE") applications by means of multiplex HDTV services and mutual gaming that has transmission speeds of 100 Mbps.

Motorola demonstrated how LTE can accelerate the delivery of personal media experience with HD video demo streaming, HD video blogging, Online gaming and VoIP over LTE running a RAN standard compliant LTE network & LTE chipset.[15] Ericsson demonstrated the worldâ&#x20AC;&#x2122;s first end-to-end LTE call on handheld

[16]

Ericsson

demonstrated LTE FDD and TDD mode on the same base station platform.

Freescale Semiconductor demonstrated streaming HD video with peak data rates of 96 Mbit/s downlink and 86 Mbit/s uplink . [17] NXP Semiconductors demonstrated a multi-mode LTE modem as the basis for a softwaredefined radio system for use in cellphones. [18] picoChip and Mimoon demonstrated a base station reference design. This runs on a common hardware platform (multi-mode / software defined radio) with their WiMAX architecture. [19] In April 2008, Motorola demonstrated the first EV-DO to LTE hand-off - handing over a streaming video from LTE to a commercial EV-DO network and back to LTE.[20]

In April 2008, LG Electronics and Nortel demonstrated LTE data rates of 50 Mbit/s while travelling at 110 km/h. [21] In April 2008 Ericsson unveiled its M700 mobile platform, the worldâ&#x20AC;&#x2122;s first commercially available LTE-capable platform, with peak data rates of up to 100 Mbit/s in the downlink and up to 50 Mbit/s in the uplink. The first products based on M700 will be data devices such as laptop modems, Expresscards and USB modems for notebooks, as well other small-form modems suitable for consumer electronic devices. Commercial release is set for 2009, with products based on the platform expected in 2010.

Researchers at Nokia Siemens Networks and Heinrich Hertz Institut have demonstrated LTE with 100 Mbit/s Uplink transfer speeds.[11]

4.13 At the February 2009 Mobile World Congress: Huawei demonstrated the world' s first unified frequency-division duplex and time-division duplex (FDD/TDD) long-term evolution (LTE) solution at the Mobile World Congress in Barcelona.

4.14 Carrier adoption Most carriers supporting GSM or HSUPA networks can be expected to upgrade their networks to LTE at some stage: Rogers Wireless has stated that they intend on initially launching their LTE network in Vancouver by February 2010, just in time for the Winter Olympics.

AT&T Mobility has stated that they intend on upgrading to LTE as their 4G technology in 2011, but will introduce HSUPA and HSPA+ as bridge standards.

TeliaSonera has started network built up in Stockholm and Oslo, and will follow up in Copenhagen when a license in Denmark has been bought/granted. The networks are still only for testing. There are no indication of a public live date.

T-Mobile, Vodafone, France Télécom and Telecom Italia Mobile have also announced or talked publicly about their commitment to LTE. Despite initial development of the rival UMB standard, which was designed as an upgrade path for CDMA networks, most operators of networks based upon the latter system have also announced their intent to migrate to LTE, resulting in discontinuation of UMB development.

Verizon Wireless is presently testing its LTE network and selects Ericsson and Alcatel-Lucent as Primary Network Vendors for LTE Network.

Bell Mobility plans to start LTE deployment in 2009-2010Telus Mobility has announced that it will adopt LTE as its 4G wireless standard.

MetroPCS recently announced that it would be using LTE for its upcoming 4G network.

The newly formed China Telecom/Unicom and Japan's KDDI have announced they have chosen LTE as their 4G network technology.

In January 2009 TeliaSonera signed a contract for an LTE network with Huawei covering Oslo, Norway. Under the agreement, Huawei will provide an end-to-end LTE solution including LTE base stations, core network and OSS (Operating Support System).

In January 2009 Ericsson and TeliaSonera announced the signing of a commercial LTE network.

The roll-out of the 4G mobile broadband network will offer the highest data rates ever realized, with the best interactivity and quality. This network will cover Sweden’s capital Stockholm and the contract is Ericsson’s first for commercial deployment of LTE.

W-CDMA TECHNOLOGY (WIDEBAND CODE DIVISION MULTIPLE ACCESS)

5.1

Overview of W-CDMA

W-CDMA (Wideband Code Division Multiple Access), UMTS-FDD, UTRA-FDD, or IMT2000 CDMA Direct Spread is an air interface found in 3G mobile telecommunications networks.

It is the basis of Japan's NTT DoCoMo's FOMA service and the most-commonly used member of the UMTS family.

While not an evolutionary upgrade on the airside, it uses the same core network as the 2G GSM networks deployed worldwide, allowing dual-mode operation along with GSM/EDGE; a feat it shares with other members of the UMTS family.

5.2

Technical features

a) Radio channels are 5MHz wide. b) Chip rate of 3.84 Mcps c) Supports two basic modes of duplex: frequency division and time division. Current systems use frequency division, one frequency for uplink and one for downlink. For time division, FOMA uses sixteen slots per radio frame, whereas UMTS uses fifteen slots per radio frame. d) Employs coherent detection on both the uplink and downlink based on the use of pilot symbols and channels[1]. e) Supports inter-cell asynchronous operation. f) Variable mission on a 10 ms frame basis. g) Multicode transmission. h)Adaptive power control based on SIR (Signal-to-Interference Ratio). i) Multiuser detection and smart antennas can be used to increase capacity and coverage. j) Multiple types of handoff (or handover) between different cells including soft handoff, softer handoff and hard handoff.

5.3

Development

W-CDMA was developed by NTT DoCoMo as the air interface for their 3G network FOMA. Later NTT DoCoMo submitted the specification to the International Telecommunication Union (ITU) as a candidate for the international 3G standard known as IMT-2000. The ITU eventually accepted W-CDMA as part of the IMT-2000 family of 3G standards, as an alternative to CDMA2000, EDGE, and the short range DECT system. Later, W-CDMA was selected as the air interface for UMTS. Code Division Multiple Access communication networks have been developed by a number of companies over the years, but development of cell-phone networks based on CDMA (prior to WCDMA) was dominated by Qualcomm, the first company to succeed in developing a practical and cost-effective CDMA implementation for consumer cell phones, its early IS-95 air interface standard. IS-95 evolved into the current CDMA2000 (IS-856/IS-2000) standard.

In the late 1990s, NTT DoCoMo began work on a new wide-band CDMA air interface for their planned 3G network FOMA. FOMA's air interface, called W-CDMA, was selected as the air interface for UMTS, a newer W-CDMA based system designed to be an easier upgrade for European GSM networks compared to FOMA. FOMA and UMTS use essentially the same air interface.

Qualcomm created an experimental wideband CDMA system called CDMA2000 3x which unified the W-CDMA (3GPP) and CDMA2000 (3GPP2) network technologies into a single design for a worldwide standard air interface. Compatibility with CDMA2000 would have beneficially enabled roaming on existing networks beyond Japan, since Qualcomm CDMA2000 networks are widely deployed, especially in the Americas, with coverage in 58 countries as of 2006. However, divergent requirements resulted in the W-CDMA standard being retained and deployed.

Despite incompatibilities with existing air-interface standards, the late introduction of this 3G system, and despite the high upgrade cost of deploying an all-new transmitter technology, W-

CDMA has been adopted and deployed rapidly, especially in Japan, Europe and Asia, and is already deployed in over 55 countries as of 2006.

5.4

Rationale for W-CDMA

W-CDMA transmits on a pair of 5 MHz-wide radio channels, while CDMA2000 transmits on one or several pairs of 1.25 MHz radio channels. Though W-CDMA does use a direct sequence CDMA transmission technique like CDMA2000, W-CDMA is not simply a wideband version of CDMA2000. The W-CDMA system is a new design by NTT DoCoMo, and it differs in many aspects from CDMA2000. From an engineering point of view, W-CDMA provides a different balance of trade-offs between cost, capacity, performance, and density; it also promises to achieve a benefit of reduced cost for video phone handsets. W-CDMA may also be better suited for deployment in the very dense cities of Europe and Asia. However, hurdles remain, and crosslicencing of patents between Qualcomm and W-CDMA vendors has not eliminated possible patent issues due to the features of W-CDMA which remain covered by Qualcomm patents.

5.5

Deployment

The world's first commercial W-CDMA service, FOMA, was launched by NTT DoCoMo in Japan in 2001.

UMTS TECHNOLOGY (UNIVERSAL MOBILE TELECOMMUNICATIONS STSTEM)

6.1

Overview of UMTS

Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile telecommunications technologies, which is also being developed into a 4G technology.

Currently, the most common form of UMTS uses W-CDMA as the underlying air interface.

UMTS and its use of W-CDMA is standardized by the 3GPP, and is the European answer to the ITU IMT-2000 requirements for 3G cellular radio systems.

To differentiate UMTS from competing network technologies, UMTS is sometimes marketed as 3GSM, emphasizing the combination of the 3G nature of the technology and the GSM standard which it was designed to succeed.

6.2

Preface

This article discusses the technology, business, usage and other aspects encompassing and surrounding UMTS, the 3G successor to GSM which utilizes the W-CDMA air interface and GSM infrastructures. Any issues relating strictly to the UMTS W-CDMA interface itself may be better described in the W-CDMA (UMTS) page.

6.3

Features

UMTS, using W-CDMA, supports up to 21 Mbit/s data transfer rates in theory (with HSDPA),[1] although at the moment users in deployed networks can expect a transfer rate of up to 384 kbit/s for R99 handsets, and 7.2 Mbit/s for HSDPA handsets in the downlink connection. This is still much greater than the 9.6 kbit/s of a single GSM error-corrected circuit switched data channel or multiple 9.6 kbit/s channels in HSCSD (14.4 kbit/s for CDMAOne), andâ&#x20AC;&#x201D;in competition to other network technologies such as CDMA2000, PHS or WLANâ&#x20AC;&#x201D;offers access to the World Wide Web and other data services on mobile devices.

Precursors to 3G are 2G mobile telephony systems, such as GSM, IS-95, PDC, CDMA PHS and other 2G technologies deployed in different countries. In the case of GSM, there is an evolution path from 2G, to GPRS, also known as 2.5G. GPRS supports a much better data rate (up to a theoretical maximum of 140.8 kbit/s, though typical rates are closer to 56 kbit/s) and is packet switched rather than connection oriented (circuit switched). It is deployed in many places where GSM is used. E-GPRS, or EDGE, is a further evolution of GPRS and is based on more modern coding schemes. With EDGE the actual packet data rates can reach around 180 kbit/s (effective).

EDGE systems are often referred as "2.75G Systems".

Since 2006, UMTS networks in many countries have been or are in the process of being upgraded with High Speed Downlink Packet Access (HSDPA), sometimes known as 3.5G.

Currently, HSDPA enables downlink transfer speeds of up to 21 Mbit/s. Work is also progressing on improving the uplink transfer speed with the High-Speed Uplink Packet Access (HSUPA). Longer term, the 3GPP Long Term Evolution project plans to move UMTS to 4G speeds of 100 Mbit/s down and 50 Mbit/s up, using a next generation air interface technology based upon Orthogonal frequency-division multiplexing.

The first national consumer UMTS networks launched in 2002 with a heavy emphasis on telcoprovided mobile applications such as mobile TV and video calling. The high data speeds of UMTS are now most often utilised for Internet access: experience in Japan and elsewhere has shown that user demand for video calls is not high, and telco-provided audio/video content has declined in popularity in favour of high-speed access to the World Wide Web - either directly on a handset or connected to a computer via Wi-Fi, Bluetooth, Infrared or USB.

6.4

Technology

UMTS transmitter on the roof of a building UMTS combines the W-CDMA, TD-CDMA, or TD-SCDMA air interfaces, GSM's Mobile Application Part (MAP) core, and the GSM family of speech codecs. In the most popular cellular mobile telephone variant of UMTS, W-CDMA is currently used. Note that other wireless standards use W-CDMA as their air interface, including FOMA. UMTS over W-CDMA uses a pair of 5 MHz channels in the case of UTRA/FDD technology (UTMS Terrestrial Radio Access / Frequency Division Duplex). In contrast, the competing CDMA2000 system uses one or more arbitrary 1.25 MHz channels for each direction of communication. UTRA/TDD (UTRA/Time Division Duplex) uses one 5 MHz channel. UMTS

and other W-CDMA systems are widely criticized for their large spectrum usage, which has delayed deployment in countries that acted relatively slowly in allocating new frequencies specifically for 3G services (such as the United States).

The specific frequency bands originally defined by the UMTS standard are 1885–2025 MHz for the mobile-to-base (uplink) and 2110–2200 MHz for the base-to-mobile (downlink). In the US, 1710–1755 MHz and 2110–2155 MHz will be used instead, as the 1900 MHz band was already utilized.[2] While UMTS2100 is the most widely-deployed UMTS band, some countries' UMTS operators use the 850 MHz and/or 1900 MHz bands (independently, meaning uplink and downlink are within the same band), notably in the US by AT&T Mobility, and in Australia by Telstra on the Next G network.

For existing GSM operators, it is a simple but costly migration path to UMTS: much of the infrastructure is shared with GSM, but the cost of obtaining new spectrum licenses and overlaying UMTS at existing towers is high.

UMTS is an alternative Radio Access Network (RAN) to GERAN (which is the 2G GSM air interface including GSM/EDGE). UMTS and GERAN can share a Core Network (CN), allowing (mostly) transparent switching between the RANs according to available coverage and service needs. The CN can be connected to various backbone networks like the Internet, ISDN. UMTS (and GERAN) include the three lowest layers of OSI model. The network layer (OSI 3) includes the Radio Resource Management protocol (RRM) that manages the bearer channels between the mobile terminals and the fixed network, including the handovers.

6.5

UMTS 3G handsets and modems

T-Mobile UMTS PC Card modem

All of the major 2G phone manufacturers (that are still in business) are now manufacturers of 3G phones. The early 3G handsets and modems were specific to the frequencies required in their country, which meant they could only roam to other countries on the same 3G frequency (though they can fall back to the older GSM standard). Canada and USA have a common share of frequencies, as do most European countries. The article UMTS frequency bands is an overview of UMTS network frequencies around the world.

There are almost no 3G phones or modems available supporting all 3G frequencies (UMTS850/900/1700/1900/2100MHz). However, many phones are offering more than one band which still enables extensive roaming. For example, a tri-band chipset operating on 850/1900/2100MHz, such as that found in Apple's iPhone, allows usage in the majority of countries where UMTS is deployed.

6.6

External modemsUsing a cellular router, PCMCIA or USB card, customers are

able to access 3G broadband services, regardless of their choice of computer (such as a tablet PC or a PDA). Some software installs itself from the modem, so that in some cases absolutely no knowledge of technology is required to get online in moments.

Using a phone that supports 3G and Bluetooth 2.0, multiple Bluetooth-capable laptops can be connected to the Internet. The phone acts as gateway and router, but via Bluetooth rather than wireless networking (802.11) or a USB connection.

6.7

Interoperability and global roamingUMTS

phones (and data cards) are

highly portableâ&#x20AC;&#x201D;they have been designed to roam easily onto other UMTS networks (assuming your provider has a roaming agreement). In addition, almost all UMTS phones are UMTS/GSM dual-mode devices, so if a UMTS phone travels outside of UMTS coverage during a call the call may be transparently handed off to available GSM coverage. Roaming charges are usually significantly higher than regular usage charges.

Most UMTS licensees consider ubiquitous, transparent global roaming an important issue. To enable a high degree of interoperability, UMTS phones usually support several different frequencies in addition to their GSM fallback. Different countries support different UMTS

frequency bands – Europe initially used 2100MHz while the most carriers in the USA use 850Mhz and 1900Mhz. T-mobile has launched a network in the US operating at 1700MHz (uplink) /2100MHz (downlink), and these bands are also being adopted elsewhere in the Americas. A UMTS phone and network must support a common frequency to work together.

Because of the frequencies used, early models of UMTS phones designated for the United States will likely not be operable elsewhere and vice versa. There are now 11 different frequency combinations used around the world—including frequencies formerly used solely for 2G services.

UMTS phones can use a Universal Subscriber Identity Module, USIM (based on GSM's SIM) and also work (including UMTS services) with GSM SIM cards. This is a global standard of identification, and enables a network to identify and authenticate the (U)SIM in the phone.

Roaming agreements between networks allow for calls to a customer to be redirected to them while roaming and determine the services (and prices) available to the user. In addition to user subscriber information and authentication information, the (U)SIM provides storage space for phone book contact. Handsets can store their data on their own memory or on the (U)SIM card (which is usually more limited in its phone book contact information). A (U)SIM can be moved to another UMTS or GSM phone, and the phone will take on the user details of the (U)SIM, meaning it is the (U)SIM (not the phone) which determines the phone number of the phone and the billing for calls made from the phone.

Japan was the first country to adopt 3G technologies, and since they had not used GSM previously they had no need to build GSM compatibility into their handsets and their 3G handsets were smaller than those available elsewhere. In 2002, NTT DoCoMo's FOMA 3G network was the first commercial W-CDMA network—it was initially incompatible with the UMTS standard at the radio level but used standard USIM cards, meaning USIM card based roaming was possible (transferring the USIM card into a UMTS or GSM phone when travelling).

Both NTT and SoftBank Mobile (which launched 3G in December 2002) now use the standard UMTS.

6.8

Spectrum allocation

Over 130 licenses have already been awarded to operators worldwide (as of December 2004), specifying W-CDMA radio access technology that builds on GSM. In Europe, the license process occurred at the tail end of the technology bubble, and the auction mechanisms for allocation set up in some countries resulted in some extremely high prices being paid for the original 2100 MHz licenses, notably in the UK and Germany. In Germany, bidders paid a total â&#x201A;Ź50.8 billion for six licenses, two of which were subsequently abandoned and written off by their purchasers (Mobilcom and the Sonera/Telefonica consortium). It has been suggested that these huge license fees have the character of a very large tax paid on future income expected many years down the road. In any event, the high prices paid put some European telecom operators close to bankruptcy (most notably KPN). Over the last few years some operators have written off some or all of the license costs. More recently, a carrier in Finland has begun using 900 MHz UMTS in a shared arrangement with its surrounding 2G GSM base stations, a trend that is expected to expand over Europe in the next 1â&#x20AC;&#x201C;3 years.

The 2100 MHz UMTS spectrum allocated in Europe is already used in North America. The 1900 MHz range is used for 2G (PCS) services, and 2100 MHz range is used for satellite communications. Regulators have, however, freed up some of the 2100 MHz range for 3G services, together with the 1700 MHz for the uplink. UMTS operators in North America who want to implement a European style 2100/1900 MHz system will have to share spectrum with existing 2G services in the 1900 MHz band.

AT&T Wireless launched UMTS services in the United States by the end of 2004 strictly using the existing 1900 MHz spectrum allocated for 2G PCS services. Cingular acquired AT&T Wireless in 2004 and has since then launched UMTS in select US cities. Cingular renamed itself AT&T and is rolling out some cities with a UMTS network at 850 MHz to enhance its existing UMTS network at 1900 MHz and now offers subscribers a number of UMTS 850/1900 phones.

T-Mobile's rollout of UMTS in the US will focus on the 2100/1700 MHz bands, whereas UMTS coverage in Canada is being provided on the 850 MHz band of the Rogers Wirless network. In 2008, Australian telco Telstra replaced its existing CDMA network with a national 3G network, branded as NextG, operating in the 850 MHz band. Telstra currently provides UMTS service on this network, and also on the 2100 MHz UMTS network, through a co-ownership of the owning

and administrating company 3GIS. This company is also co-owned by Hutchison 3G Australia, and this is the primary network used by their customers. Optus is currently rolling out a 3G network operating on the 2100 MHz band in cities and most large towns, and the 900 MHz band in regional areas. Vodafone is also building a 3G network using the 900 MHz band. The 850 MHz

and

900 MHz

bands

provide

greater

coverage

compared

to

equivalent

1700/1900/2100 MHz networks, and are best suited to regional areas where greater distances separate subscriber and base station.

Carriers in South America are now also rolling out 850 MHz networks.

Other competing standards There are other competing 3G standards, such as CDMA2000 and TD-SCDMA, though UMTS can use the latter's air interface standard.

On the Internet access side, competing systems include WiMAX and Flash-OFDM. Different variants of UMTS compete with different standards. While this article has largely discussed UMTS-FDD, a form oriented for use in conventional cellular-type spectrum, UMTS-TDD, a system based upon a TD-CDMA air interface, is used to provide UMTS service where the uplink and downlink share the same spectrum, and is very efficient at providing asymmetric access. It provides more direct competition with WiMAX and similar Internet-access oriented systems than conventional UMTS. Both the CDMA2000 and W-CDMA air interface systems are accepted by ITU as part of the IMT-2000 family of 3G standards, in addition to UMTS-TDD's TD-CDMA, Enhanced Data Rates for GSM Evolution (EDGE) and China's own 3G standard, TD-SCDMA. CDMA2000's narrower bandwidth requirements make it easier than UMTS to deploy in existing spectrum along with legacy standards. In some, but not all, cases, existing GSM operators only have enough spectrum to implement either UMTS or GSM, not both. For example, in the US D, E, and F PCS spectrum blocks, the amount of spectrum available is 5 MHz in each direction. A standard UMTS system would saturate that spectrum.

In many markets however, the co-existence issue is of little relevance, as legislative hurdles exist to co-deploying two standards in the same licensed slice of spectrum.

Most GSM operators in North America as well as others around the world have accepted EDGE as a temporary 3G solution. AT&T Wireless launched EDGE nationwide in 2003, AT&T launched EDGE in most markets and T-Mobile USA has launched EDGE nationwide as of October 2005. Rogers Wireless launched nation-wide EDGE service in late 2003 for the Canadian market. BitÄ&#x2014; Lietuva (Lithuania) was one of the first operators in Europe to launch EDGE in December 2003. TIM (Italy) launched EDGE in 2004. The benefit of EDGE is that it leverages existing GSM spectrums and is compatible with existing GSM handsets. It is also much easier, quicker, and considerably cheaper for wireless carriers to "bolt-on" EDGE functionality by upgrading their existing GSM transmission hardware to support EDGE than having to install almost all brand-new equipment to deliver UMTS. EDGE provides a short-term upgrade path for GSM operators and directly competes with CDMA2000.

Problems and issues Some countries, including the United States and Japan, have allocated spectrum differently from the ITU recommendations, so that the standard bands most commonly used for UMTS (UMTS2100) have not been available. In those countries, alternative bands are used, preventing the interoperability of existing UMTS-2100 equipment, and requiring the design and manufacture of different equipment for the use in these markets. As is the case with GSM900 today, standard UMTS 2100 MHz equipment will not work in those markets. However, it appears as though UMTS is not suffering as much from handset band compatibility issues as GSM did, as many UMTS handsets are multi-band in both UMTS and GSM modes. Quad-band GSM (850, 900, 1800, and 1900 MHz bands) and tri-band UMTS (850, 1900, and 2100 MHz bands) handsets are becoming more commonplace.

The early days of UMTS saw rollout hitches in many countries. Overweight handsets with poor battery life were first to arrive on a market highly sensitive to weight and form factor. The Motorola A830, a debut handset on Hutchison's 3 network, weighed more than 200 grams and even featured a detachable camera to reduce handset weight. Another significant issue involved

call reliability, related to problems with handover from UMTS to GSM. Customers found their connections being dropped as handovers were possible only in one direction (UMTS → GSM), with the handset only changing back to UMTS after hanging up. In most networks around the world this is no longer an issue.

Compared to GSM, UMTS networks initially required a higher base station density. For fullyfledged UMTS incorporating video on demand features, one base station needed to be set up every 1–1.5 km (0.62–0.93 mi). This was the case when only the 2100 MHz band was being used, however with the growing use of lower-frequency bands (such as 850 and 900 MHz) this is no longer so. This has led to increasing rollout of the lower-band networks by operators since 2006.

Even with current technologies and low-band UMTS, telephony and data over UMTS is still more power intensive than on comparable GSM networks. Apple, Inc. cited[3] UMTS power consumption as the reason that the first generation iPhone only supported EDGE. Their release of the iPhone 3G quotes talk time on UMTS as half that available when the handset is set to use GSM. As battery and network technology improves, this issue is lessening in severity.

Next Generation Cellular Technology in Bangladesh

Overview Bangladesh has six mobile operators to serve mobile service among 150 million people.

In the world many mobile operators to serve 3G or 3.5G services which have so much speed. But Bangladesh uses 2G or 2.5G service which are low speed facility.

3G is a technology that enables to services include wide-area wireless voice telephony, video calls, and broadband wireless data all in a mobile environment. Interms of high broadband technology, 3G can help the nation rather than any other upcoming technology. 3G technologyenabled network offers the users a wider range of more advanced services while achieving greater network capacity through improved spectral efficiency.

Laying new fixed-line connections is expensive and inefficient, so high-speed mobile networks are Bangladesh’s best bet to realize the many social and economic benefits that arise from widespread access to broadband services. 2100 MHz spectrum band for 3G services would enable Bangladeshi operators to launch mobile broadband services, which their customers can use to gain fast and easy access to the Internet and online services.

BTTB’s chairman in 2008, BTTB arrange a bid for 3g license in Bangladesh. It will be an open bid, where the operators will participate. So we can now think about 3G. Though 3G generation service is yet to launch in Bangladesh but we hope by this year we will be able to start this service as it is customer required.

Grameen Phone Grameenphone Limited

Type Limited Founded 1997 Headquarters Celebration Point, Road # 113 A, Plot 3 Key people Industry Products Revenue Net income Employees Website

& 5, Gulshan, Dhaka, Bangladesh Oddvar Hesjedal, CEO Mobile Telecommunication Telephony, EDGE, GSM 891Million USD ▲ 6,403.8 Million Taka[2] 5052 www.grameenphone.com

Grameenphone, widely known as GP, is the leading telecommunications service provider in Bangladesh. With more than 20 million subscribers (as of June 2008), Grameenphone is the largest cellular operator in the country. It is a joint venture enterprise between Telenor and Grameen Telecom Corporation, a non-profit sister concern of the internationally acclaimed microfinance organization and community development bank Grameen Bank. Telenor, the largest telecommunications company in Norway, owns 62% shares of grameenphone and Grameen Telecom owns the rest 38%.

Grameenphone was the first company to introduce GSM technology in Bangladesh). It also established the first 24-hour Call Center to support its subscribers. With the slogan Stay Close, stated goal of Grameenphone is to provide affordable telephony to the entire population of Bangladesh.

Banglalink Orascom Telecom Bangladesh Limited

Type Subsidiary Founded 1999 Headquarters Tiger House, House # SW(H) 04, Gulshan Avenue, Gulshan Model Town, Area served Key people Industry Products Revenue Parent Website

Dhaka, Bangladesh 61 districts and 446 thanas Rashid Khan, CEO Telecommunication Telephony, GPRS â&#x2013;˛ US $ 26.3 million Orascom Telecom www.banglalinkgsm.com

banglalink, is the second largest cellular service provider in Bangladesh after grameenphone. As of August, 2008, banglalink has a subscriber base of more than 10 million. It is a wholly owned subsidiary of Orascom Telecom. banglalink had 1.03 million connections until December, 2005. The number of banglalink users increased by more than 253 per cent and stood at 3.64 million at the end of 2006, making it the fastest growing operator in the world of that year.

In August, 2006, banglalink became the first company to provide free incoming calls from BTTB for both postpaid and prepaid connections.

Aktel TMIB (Telekom Malaysia International Bangladesh)

Type Founded Headquarters Industry Products Parent Website

Joint Venture 1996 9th Floor, BRAC Center, 75 Mohakhali C/A, Gulshan Dhaka, Bangladesh Telecommunication Mobile Telephony, GPRS Telekom Malaysia Sdn. Bhd. (70%) and NTT DoCoMo (30%) www.aktel.com

Telekom Malaysia International Bangladesh (TMIB) Limited is a joint venture between Telekom Malaysia Sdn. Bhd. (70%) and NTT DoCoMo (30%).

Aktel is the third largest mobile phone operator in Bangladesh in terms of revenue and subscribers (8.59 million as of February 2009). In early 2008 Aktel slipped from the second position to the third after facing fierce competition from banglalink.

AKTEL boasts of the widest international roaming service in the market, connecting 315 operators across 170 countries. It is the first operator in the country to introduce GPRS. AKTEL uses GSM 900/1800 MHz standard and operates on allocated 12.8MHz frequency spectrum.

Warid Telecom Warid Telecom International Ltd.

Type Private Founded 2005 Headquarters House 34, Road 19/A, Banani, Dhaka Key people

1213, Bangladesh Sheikh Nahayan Mabarak Al Nahayan, Chairman

Industry Products Website

Mr. Muneer Farooqui, CEO Telecommunication Telephony, EDGE, GPRS, GSM www.waridtel.com.bd

Warid Telecom International Ltd. is a GSM-based cellular operator in Bangladesh. Warid is the sixth mobile phone carrier to enter the Bangladesh market. It is wholly owned subsidiary of Warid Telecom International LLC which is the part of an Abu Dhabi based consortium led by His Highness Sheikh Nahayan Mabarak Al Nahayan, a Member of the Royal Family of Abu Dhabi, and the Honorable Minister of Higher Education and Scientific Research of the United Arab Emirates.

Warid officially launched their commercial services in Bangladesh on the May 10, 2007 with a GSM Mobile Cellular network covering 64 districts of the country and encompassing 70% of the mobile phone using population- the single largest launch the country has ever seen.

On July 19, 2007 Warid Telecom announced in major dailies of having achieved one million subscribers in the first of 70 days of operation. As of September, 2008 Warid has secured 3.86 million subscribers and is ranked fourth among the six operators.

Citycell Pacific Bangladesh Telecom Limited

Type Limited Founded 1989 Headquarters 8th Floor Pacific Center, 14, Mohakhali Area served Key people Industry Products Parent Website

C/A, Dhaka, Bangladesh 61 districts and 470 thanas Micheal Saymour (CEO) Telecommunication Telephony, CDMA Singtel 45%, Pacific Motors Limited 31.43%, Far East Telecom Limited 23.57% www.citycell.com

Citycell (Pacific Bangladesh Telecom Limited) is the first mobile communications company of Bangladesh. It is the only CDMA network operator in the country. As of 1 March, 2008, Citycell's total mobile subscriber base is 1.56 million, up 137 per cent or 680,000 from two years ago, giving it the best growth rate of the company till date. Citycell is currently owned by Singtel with 45% stake and the rest 55% owned by Pacific Group and Far East Telecom.

By the end of 2007 Citycell had refurbished its old brand identity and introduced a new logo and corporate identity; the new logo is very reminiscent of the old logo. However the slogan has remained unchanged "because we care".

As of July, 2008 Citycell has 1.67 million subscribers.

TeleTalk Teletalk Bangladesh Limited Type Public company Limited Founded 2004 Headquarters House no: 41, Rd no: 27,Block: A Industry Products Website

Banani, Dhaka.

Celluler Telecommunication Provider Telephony, EDGE, GSM www.teletalk.com.bd

TeleTalk (Bengali: েটিলটক) (Teletalk Bangladesh Ltd) is a GSM based state-owned mobile phone company in Bangladesh. TeleTalk started operating on 29 December, 2004. It is a Public Limited Company of Bangladesh Government, the state-owned telephone operator. TeleTalk provide GPRS internet connectivity. Teletalk is the first operator in the country that gave BTTB (now BTCL) incoming facility to its subscribers.

The mission statement of Tele Talk is "Desher Taka Deshey Rakhun" ("Keep your Money in your Country") TeleTalk is the 6th largest mobile phone operator in Bangladesh with 0.98 million subscribers as of October, 2008 .

Future Scope of Cellular Technology Basically, 3G opens the door to anything we can imagine. We will be able to do a multitude of things while going through our daily schedule, whether at work or at leisure. The scenarios below demonstrate just a few applications for 3G and only hint at what will be on offer in the future.

•

Broadband internet connection in the mobile handset.

•

The data transfer rates for 3G mobile telecommunications is up to 2 Megabits per second.

•

3G cellular phones also have conventional voice, fax and data services, as well as highresolution video and multimedia services.

•

Mobile office services such as virtual banking and online-billing, video conferencing, online entertainment and access to the Internet.

•

Ability to watch television shows on phone, and it also allows to have video conversations with other people who also use the same 3G technology.

•

Map and positioning services.

•

Pay our bills and balance our checks by logging on to our bank account using the 3G devices that we have.

SUMMARY We briefly listed all the key technologies and protocols used in each generation of the mobile wireless communications. 2.5th Generation is a group of bridging technologies between 2G and 3G wireless communication. It is a digital communication allowing e-mail and simple Web browsing, in addition to voice. 2.75th Generation refer to the technologies which don't meet the 3G requirements but are marketed as if they do. 3rd Generation stands for the third generation of wireless communication technologies, which support broadband voice, data and multi-media communications over wireless networks. The 3.5th Generation generally refers to the technologies beyond the well defined 3G wireless/mobile technologies. The 3.75th Generation refers to the technologies beyond the well defined 3G wireless/mobile technologies. 4th Generation is the name of technologies for high-speed mobile wireless communications designed for new data services and interactive TV through mobile network. We have presented the overview, general characteristics and evolution of cellular network. We discussed about WiMAX technology which is 2.75th generation data services technology, EVDO technology which is 3rd generation data services technology, LTE technology which is 3.5th generation radio services technology, W-CDMA and UMTS technology which is 4th generation data services technology. We discussed about the current situation and future scope of cellular technology in Bangladesh and also discussed about all mobile operators in Bangladesh.

CONCLUSION We briefly listed all the key technologies and protocols used in each generation of the mobile wireless communications in the followings: 2.5G is a group of bridging technologies between 2G and 3G wireless communication. It is a digital communication allowing e-mail and simple Web browsing, in addition to voice.

2.75G refer to the technologies which don't meet the 3G requirements but are marketed as if they do.

3G stand for the third generation of wireless communication technologies, which support broadband voice, data and multi-media communications over wireless networks.

The 3.5G generally refer to the technologies beyond the well defined 3G wireless/mobile technologies.

The 3.75G refer to the technologies beyond the well defined 3G wireless/mobile technologies.

4G is the name of technologies for high-speed mobile wireless communications designed for new data services and interactive TV through mobile network.

9.2

REFERENCES

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LTE 1. Gardner, W. David. "Freescale Semiconductor To Demo LTE In Mobile Handsets", Information Week, February 8 2008.

2. http://cp.literature.agilent.com/litweb/pdf/5989-7898EN.pdf 3. Nomor Research Newsletter: Overview LTE Time Division Duplex 4. Nomor Research: World's first LTE demonstration 5. NTT DoCoMo develops low power chip for 3G LTE handsets 6. 3GPP LTE - See System Architecture Evolution

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W-CDMA 1. Common Pilot Channel

2. GSMWorld Press Release 3. Qualcomm says it doesn't need Nokia patents

WiMAX 1. "IEEE 802.16 WirelessMAN Standard: Myths and Facts". ieee802.org.

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9.

http://www.wimaxforum.org/files/case_studies/wimax_telecom.pdf/. Retrieved on 200903-30.

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