Wimax basics 2

Prepared by: Eng. Ahmed Zaaza

• Wimax is a IEEE 802.16 standard.

• So, What is the 802?

• IEEE is a committee formed for developing networking standards .

• It was formed in February 1980, that why it is called 802 (2: month, 80: year).

• It is a non profit committee.

• It works on a group based hierarchy.

Example: IEEE 802.3 IEEE 802.15 IEEE 802.11 IEEE 802.5 IEEE 802.16

Ethernet Zigbee WiFi Token Ring WIMAX

LAN PAN WLAN LAN WMAN

WAN 3GPP, EDGE (GSM)

IEEE 802.20 (proposed) IEEE 802.16 WirelessMAN IEEE 802.11 WirelessLAN

IEEE 802.15 Bluetooth

MAN

LAN

PAN

ETSI HiperMAN & HIPERACCESS ETSI HiperLAN

ETSI HiperPAN

Properties of the OSI Model 7

Application

6

Presentation

5

Session

4

Transport

3

Network

2

Data Link

1

Physical

Seven layers for the description of communication processes Logical combination of sub-functions within one layer Defined interfaces between layers: offer services

nu mmo Cl aci tr eV

Computer 1

Computer 2

7

Application

7

Application

6

Presentation

6

Presentation

5

Session

5

Session

4

Transport

4

Transport

3

Network

3

Network

2

Data Link

2

Data Link

1

Physical

1

Physical

Horizontal Communication

Sending and Receiving Data in the Layer Model Receive

Send

Data

Data

5-7 Data 4 5-7 Data

5-7 Data 4 5-7 Data

3 4 5-7 Data

3 4 5-7 Data

2 3 4 5-7 Data

2

2 3 4 5-7 Data

2

1 2 3 4 5-7 Data

2

1 2 3 4 5-7 Data

2

E-mail Data

Data

Segment Data Header

Segment

Network Segment Data Header Header Frame Network Segment Data Header Header Header

Packet Frame Trailer

Frame (Hardware-dependent)

0111111010101100010101101010110001

Bits

Network

Data Link

e

Physical

Personal Area Networks (PANs)

Metropolitan Local Area Area Networks Networks (MANs) (LANs)

Blue-tooth Blue-tooth

WMAN (802.16d)

WLAN WLAN 802.1 802.1 11

50 feet

500 feet

Wide Area Networks (WANs)

WMAN (802.16e)

10’s miles

Cellular Cellular 2.5 2.5 G, G, 3G 3G

Range

802.16

802.11b/g(WI -FI)

Technical difference

Range

Up to 50 Km typical cell size (5-8Km)

Sub -500m add access points for greater) (coverage

tolerates greater multipath delay spread via 256 FFT vs 64 802.16 FFT

Coverage

Outdoor NLOS performance standard support for advanced antenna techniques

Optimized for indoor performance ,short range

systems has an overall higher system gain dellvering 802.16 greater penetration through obstacles at longer distances

Designed to support hundreds of CPES with unlimited subscribers behind each CPE

Intended for LAN applications ,users scale from one to tens with one subscriber for each CPE device

can use all available BW ,multiple channel support cellular 802.16 deployment,802.11 is limited to license exempt spectrum

Bit Rate

Up to 75 MB/S in 20 MHZ channel

Up to 54MB/S in 20MHZ channel

Higher modulation coupled with flexible error correction

QoS

Built in to MAC voice/video service levels

No QOS support

is contention based MAC )CSMA/CA( ,802.16 dynamic 802.11 TDMA-based MAC with on-demand BW allocation

MAC

Polling –based MAC layer

Contention based MAC

Scalability

• In 1998, the Institute of Electrical and Electronics Engineers (IEEE) formed a group called 802.16 to develop a standard for what was called a wireless metropolitan area network, or wireless MAN. Originally, this group focused on developing solutions in the 10GHz to 66GHz band.

• IEEE 802.16 The IEEE 802.16 group produced a standard that was approved in December 2001. This standard, Wireless MAN-SC, specified a physical layer that used single-carrier modulation techniques and a media access control (MAC) layer with a burst time division multiplexing (TDM) structure that supported both frequency division duplexing (FDD) and time division duplexing (TDD).

• IEEE 802.16a (OFDM) After completing this standard, the group started work on extending and modifying it to work in both licensed and license-exempt frequencies in the 2GHz to 11GHz range, which would enable NLOS deployments. This amendment, IEEE 802.16a, was completed in 2003.

•IEEE 802.16-2004 (Fixed & Portable) Further revisions to 802.16a were made and completed in 2004. This revised standard, IEEE 802.16-2004, replaces 802.16, 802.16a with a single standard, which has also been adopted as the basis for HIPERMAN (high-performance metropolitan area network) by ETSI (European Telecommunications Standards Institute).

•IEEE 802.16e (Mobile) In 2003, the 802.16 group began work on enhancements to the specifications to allow vehicular mobility applications.The 802.16e, was completed in December 2005 and was published formally as IEEE 802.16e-2005.It specifies scalable OFDM for the physical layer and makes further modifications to the MAC layer to accommodate high-speed mobility.

•

As it turns out, the IEEE 802.16 specifications are a collection of standards with a very broad scope. In order to accommodate the diverse needs of the industry, the standard incorporated a wide variety of options. In order to develop interoperable solutions using the 802.16 family of standards, the scope of the standard had to be reduced by establishing consensus on what options of the standard to implement and test for interoperability. The IEEE developed the specifications but left to the industry the task of converting them into an interoperable standard that can be certified. The WiMAX Forum was formed to solve this problem and to promote solutions based on the IEEE 802.16 standards.

Fixed Licensed and Unlicensed E1/ T1 & DSL level service

Portable

Mobile

Licensed and Unlicensed Licensed Consumer DSL level serviceWideband Data Rates

Enterprise / Backhaul

Residential access

Portable

802.16 HiperMAN

802.16 HiperMAN

802.16d

Nomadic

Cellular Wideband

802.16d, 2.5G, 3G, 802.16e 802.11 Hot Spots

Carrier Band -----------------------------------------------------------------------------------3.5 GHz 3.5, 7 MHz -----------------------------------------------------------------------------------5.8 GHz 10 MHz -----------------------------------------------------------------------------------2.3 GHz - 2.4 GHz 5, 10, 8.75 MHz ------------------------------------------------------------------------------------2.305 GHz - 2.320 GHz 3.5, 5, 10 MHz 2.345 GHz - 2.360 GHz ------------------------------------------------------------------------------------2.496 GHz - 2.69 GHz 5, 10 MHz ------------------------------------------------------------------------------------3.3 GHz – 3.4 GHz 5, 7, 10 MHz ------------------------------------------------------------------------------------3.4 GHz – 3.8 GHz 5, 7, 10 MHz 3.4 GHz – 3.6 GHz 3.6 GHz – 3.8 GHz

802.16

802.16d

802.16e

Completed

December 2001

January 2004

Dec. 2005

Spectrum

10 - 66 GHz

2 -11 GHz

< 6 GHz

Channel Conditions

Line of Sight Only

Non Line of Sight

Non Line of Sight

Bit Rate

32 â&#x20AC;&#x201C; 134 Mbps in 28MHz channel bandwidth

Up to 75 Mbps in 20MHz channel bandwidth

Up to 15 Mbps in 5MHz channel bandwidth

Modulation

single-carrier modulation technique

OFDM 256 sub-carriers QPSK, 16QAM, 64QAM

OFDM 256, 512, 1024, 2048 sub-carriers QPSK, 16QAM, 64QAM

Multiplexing

TDMA

TDMA

TDMA/OFDMA

Mobility

Fixed

Fixed, Portable

Nomadic Mobility (limited to 120 KM/h)

Channel Bandwidths

20, 25 and 28 MHz

Scalable 1.5 to 20 MHz

Same as 802.16d

Typical Cell Radius

2-5 km

7 to 10 km (Max range 50 km for backhauling)

2-5 km

Non Line of Sight Point to Multipoint

Point to Point BACKHAUL

802.1 1

E1/T1+ LEVEL SERVICE ENTERPRISE

FRACTIONAL E1/T1 for SMALL BUSINESS

Telco Core Network or Private (Fiber) Network INTERNET BACKBONE

OUTDOOR CPE 802.1 1

INDOOR CPE

Non Line of Sight Point to Multipoint

802.1 1 & 802.1 6

Point to Point BACKHAUL

Telco Core Network or Private (Fiber) Network INTERNET BACKBONE

ASN BS MS

BS BS BS

NSP

ASN-GW CSN ASN-GW

MS: Mobile station BS: Base-station ASN-GW: Accessing service Network-Gateway CSN: Connectivity service Network NSP: Network Service Provider

another

CSN

Internet Or IP-network

MS

• • • • •

Consist of receiver & antenna systems.

Allow User to connect to the network.

MS Integrated or external antenna.

Self and easy to install.

Access voice, video & high speed data services .

ASN BS BS BS BS

NSP

ASN-GW CSN ASN-GW

• Subscriber terminal (CPE) may support one type of services or may support more than one type such as (Voice, Video & Data).

another CSN

Internet Or IP-network

BS

1. Air interface handling. â&#x20AC;˘ â&#x20AC;˘

Power control.

Network entry (SS initialization).

2.

3.

4.

5.

6.

7.

8.

QoS providing Via air interface through Service flow management.

ASN Traffic classification.

BS MS activity status update.

ASN-GW BS Radio resource management update (agent).

MS BS Paging agent.

ASN-GW BS Deliver TEK & KEK from ASN-GW to MS. Deliver authentication messages from ASN-GW to MS.

NSP

CSN

another CSN

Internet Or IP-network

Omni Antenna

Plane Antenna Sectorial Antenna

Desk-top Antenna

Tower with antenna

Transmission line (Coaxial cable)

shelter

Network operator will update the site database in the equipment remotely

ASN-GW 1.

2.

3.

4.

5.

6.

Radio Resources Controller (RRC), act as BSC in GSM network.

Paging controller.

Temporary caching of subscriber profiles & Encryption keys.

Perform routing to selected CSN. Act as server to perform mobility sessions.

Provides mobility tunnel establishment & management with BS for handover.

7. DHCP server.

8. Authenticator & perform Key management, act as AAA client ASN to the AAA server in the CSN. BS

MS

BS BS BS

NSP

ASN-GW CSN ASN-GW

another CSN

Internet Or IP-network

1.

2.

3.

4.

5.

6.

7.

IP Address allocation for users.

Subscriber billing.

AAA proxy server ( Authentication, Authorization & Accounting).

QoS management based on SLA (contract with user).

Connection with other CSN. Connect several ASN. Connectd to internet or any IP-network.

ASN BS MS

BS BS BS

CSN

NSP

ASN-GW CSN ASN-GW

another CSN

Internet Or IP-network

Simultaneously support hundreds of businesses with E1/T1 speed connectivity and thousands of homes with DSL speed connectivity.

Promise of potential low cost and flexibility in building broadband networks.

Scalability, as extra channels and base stations can be added incrementally as bandwidth demand grows.

Support for both voice and video as well as Internet data.

Semiconductor vendors envisage WiMax-enabled chips appearing in PCs in 2006 and in notebook computers and PDAs by 2007

ATM Overview Asynchronous transfer mode

ATM Overview â&#x20AC;˘ Developed to carry multimedia real-time application (video - speech) and non real-time application (data)

Overhead and Payload :

Payload

Overhead

2

2

3

4

5-7

Data

Packet (Max 1500 byte)

Frame

Variable

2

2

What is the problem?

TDMA Frame 1

Frame 2

125 usec.

Synchronies

•No delay.

•Best for real time application (QOS >>>) •Limited number of bits.

•Not suitable for data (data traffic is burst)

Frame 3

Packet switching A

A

packet length

A

Spacing interval

•PKT is variable length and asynchronous •Suitable for data •Bad QOS for real-time application

ATM Solution: Based on packet switching but packet are at fixed length (cell)

A

B

A

C

B

A

C

A

B

Cell Less time variation with packet switches but not as TDM to be able to integrate real and non- real application

ATM Solution: Cell size is a compromise Small size selected to minimize packet delay for voice transmission Cell size is a compromise Larger cell size would be

ď&#x192;&#x2DC;more efficient for data Per packet processing ď&#x192;&#x2DC;Header overhead

Header Header

Data Data

Bytes 5

Bytes 48

ATM Solution: ATM is a (Vir tual Circuit ) network Switched vir tual circuit (SVC)--connection and paths through the network are established on an as-needed basis i.e each connection you must make virtual circuit setup so, QoS is not guaranteed.

Permanent vir tual (PVC) -- connection and paths through the network are established when network is established as a leased line for a period of time so, QoS is guaranteed and no virtual circuit setup is needed.

Packing Ethernet frame into ATM cell.

Ethernet frame

Packet (Max 1500 byte)

2

H

Data

ATM Cell

H

Data

H

2

Data

ATM transport

IP transport

Layer 3

LLC Convergence Sub-layer Layer 2

Common part Sub-layer Privacy Sub-layer Physical Sub-layer

Layer 1

ATM transport

IP transport

Convergence Sub-layer Common part Sub-layer

• CS adapts higher layer protocols to MAC SDU it maps ATM cells or IPpackets to certain Unidirectional connection identified by CID Associated with certain QoS. • Packet Header Suppression.

Privacy Sub-layer Physical Sub-layer IP packet or ATM cell

Convergence Sub-layer

MAC service data unit (MAC SDU)

ATM transport

IP transport

Connection Identifier CID

Convergence Sub-layer Common part Sub-layer Privacy Sub-layer Physical Sub-layer

• Wimax MAC layer is a connection oriented so, it defines a logical connection between the MS & BS by A CID. • CID can be considered as layer 2 addressing.

• The MS informed by its CID from the BS depending on: 1.Application and also QoS. 2.SFID (Service Flow ID).

3.Destination address.

ATM transport

IP transport

Convergence Sub-layer Common part Sub-layer Privacy Sub-layer Physical Sub-layer

PHS (Packet Header Suppression) â&#x20AC;˘ Convergence sub-layer do PHS to decreas the data overhead on the packet and its repeating according to the PHS rule.

Packet

Header

PHSM come from the PHS rule

Packet

PHSI

MAC

SDU

ATM transport

IP transport

• Fragment and reassembly of large MAC SDUs into smaller MAC PDU (Protocol Data Unit).

Convergence Sub-layer

• Automatic repeat request (ARQ).

Common part Sub-layer

• Bandwidth request.

Privacy Sub-layer Physical Sub-layer

• QoS control & scheduling.

• Mobility management.

• Power-saving operation.

ATM transport

IP transport

MAC PDU (Protocol Data Unit) & (ARQ)

MAC

Convergence Sub-layer 1 2 12

Common part Sub-layer

3

4

5

6

fragment

Privacy Sub-layer

SDU 7

8

9

10 11

ARQ block

fragment

Physical Sub-layer

GMH

fragment MAC PDU

CRC

GMH

fragment MAC PDU

•Each ARQ block has a BSN (Block Sequence Number).

•GMH contain the BSN of the first block.

•Tx must receive an acknowledgment on each MAC PDU which has two types: •Selective ARQ: receive acknowledgment on each ARQ block.

•Cumulative ARQ: receive acknowledgment that all block less than BSN are received without errors.

•If no acknowledgment is received, then the CP sub-layer will transmit the ARQ block again.

CRC

ATM transport

IP transport

MAC PDU (Protocol Data Unit) & (ARQ)

Convergence Sub-layer Common part Sub-layer

GMH

Privacy Sub-layer

MAC PDU fragment

CRC Payload field

Physical Sub-layer

Header for Data payload & signaling messages.

Header for Bandwidth request.

6 Bytes GMH

4 Bytes fragment

CRC

ATM transport

MAC PDU Header for Data

IP transport

Convergence Sub-layer Common part Sub-layer

HT EC

Type (6)

EKS (2)

LEN (3)

Privacy Sub-layer Physical Sub-layer

LEN (8) CID CID(8)(8)

CID (8) HCS (8)

HT 1 Header type (set to 0 for such header) EC 1 Encryption control (0 = payload not encrypted; 1 = payload encrypted) Type 6 Type of the internal Sub-header ESF 1 Extended sub-header field (1 = ES present; 0 = ES not present) CI 1 CRC indicator (1 = CRC included; 0 = CRC not included) EKS 2 Encryption key sequence (index of the traffic encryption key and the initialization vector used to encrypt the payload) Rsv 1 Reserved LEN 11 Length of MAC PDU in bytes, including the header CID 16 Connection identifier on which the payload is to be sent HCS 8 Header check sequence; generating polynomial D8 + D2 + D + 1

ATM transport

MAC PDU Header for BW request

IP transport

Convergence Sub-layer Common part Sub-layer

HT EC

Type (3)

BR (11)

Privacy Sub-layer Physical Sub-layer

BR (8) CID CID(8)(8)

CID (8) HCS (8)

HT 1 Header type (set to 0 for such header) EC 1 Encryption control (0 = payload not encrypted; 1 = payload encrypted) Type 3 Type BR 19 Bandwidth request (the number of bytes of uplink bandwidth requested by the SS for the given CID) CID 16 Connection identifier on which the payload is to be sent HCS 8 Header check sequence; generating polynomial D8 + D2 + D + 1

ATM transport

IP transport

MAC PDU (Protocol Data Unit) sub-header MAC PDU

Convergence Sub-layer Common part Sub-layer

GMH

SH

Payload

CRC

Privacy Sub-layer Physical Sub-layer

Fragmentation sub-header Packing sub-header

Grant-management subheader •Fragmentation sub-header: Follows the generic MAC header and indicates that the SDU is fragmented over multiple MAC PDUs. •Packing sub-header: Indicates that multiple SDUs or SDU fragments are packed into a single MAC PDU and are placed at the beginning of each SDU or SDU fragment.

•Grant-management sub-header: Used by piggybacking BW request on generic MAC PDU

ATM transport

IP transport

Bandwidth request

Convergence Sub-layer Common part Sub-layer Privacy Sub-layer

GMH GMSH

BW request

CRC

Piggyback MAC PDU

Physical Sub-layer

GMH

Stand alone MAC PDU header.

• Messages sent by the MS to request an additional PHY resources to a specific application (CID).

• The BS receives these messages from MS (carrying specific CID) and decide to give this MS additional BW depending on it’s QoS.

ATM transport

IP transport

Convergence Sub-layer Common part Sub-layer Privacy Sub-layer

Bandwidth request Bandwidth request may be: • Incremental • Aggregate.

Physical Sub-layer

• Incremental: the BW request message contains a number of steps which the MS needs to add to the currently available BW. • Aggregate: the BW request message contains a number of BW which the MS needs.

Type (3)

BR (11)

BR (8)

CID (8)

CID (8)

HCS HCS (8)

• The type field indicates that whether the request is Incremental or Aggregate.

• In piggyback on MAC PDU the request is Incremental only.

ATM transport

IP transport

Convergence Sub-layer Common part Sub-layer Privacy Sub-layer Physical Sub-layer

Bandwidth request mechanism â&#x20AC;˘ BW request must send from MS after the BS has send a polling message to it. â&#x20AC;˘ Polling may be Unicast Polling or Multicast Polling.

Unicast Polling: the BS sends a polling message to each connected MS individually.

3. Accept & allow additional BW 2. BW request message 1. Polling (contain specific CID) MS

BS

Multicast Polling: the BS sends a polling message to group of MS in stead of one by one.

MS1

Random number 1

1. Polling (contain specific CID) MS1

Sends a MAX back off window size Random number 2

2. BW request message from MS2 3. BW request message from MS2

X

4. Accept & allow additional BW to MS2

BS

ATM transport

IP transport

Convergence Sub-layer Common part Sub-layer Privacy Sub-layer

QoS control & scheduling • One of the key functions of the WiMAX MAC layer is to ensure that QoS requirements for MAC PDUs belonging to different service flows are met as reliably as possible given the loading conditions of the system.

Physical Sub-layer

• This implies that various negotiated performance indicators that are tied to the overall QoS, such as jitter, data rate, packet error rate, and system availability, must be met for each connection.

WIMAX handles QoS through: • Scheduling Services.

• Service Flow.

ATM transport

IP transport

QoS Scheduling Services.

Convergence Sub-layer

• WIMAX defines four Scheduling Services:

Common part Sub-layer

• • • •

Privacy Sub-layer Physical Sub-layer

Unsolicited grant service (UGS) Real-time polling services (rtPS) Non-real-time polling services (nrtPS) best-effort service (BE)

1.Unsolicited grant service (UGS): Is designed to support real-time service flows that generate fixed-size data packets on a periodic basis, such as T1/E1 and VoIP. UGS offers fixed-size grants on a real-time periodic basis and does not need the SS to explicitly request bandwidth, thus eliminating the overhead and latency associated with bandwidth request.

ATM transport

IP transport

QoS Scheduling Services.

Convergence Sub-layer

• WIMAX defines four Scheduling Services:

Common part Sub-layer

• • • •

Privacy Sub-layer Physical Sub-layer

Unsolicited grant service (UGS) Real-time polling services (rtPS) Non-real-time polling services (nrtPS) best-effort service (BE)

2.Real-time polling services (rtPS): is designed to support real-time services that generate variable-size data packets on a periodic basis, such as MPEG (Motion Pictures Experts Group) video. In this service class, the BS provides unicast polling opportunities for the MS to request bandwidth. The unicast polling opportunities are frequent enough to ensure that latency requirements of real-time services are met. This service requires more request overhead than UGS does but is more efficient for service that generates variable-size data packets.

ATM transport

IP transport

QoS Scheduling Services.

Convergence Sub-layer

• WIMAX defines four Scheduling Services:

Common part Sub-layer

• • • •

Privacy Sub-layer Physical Sub-layer

Unsolicited grant service (UGS) Real-time polling services (rtPS) Non-real-time polling services (nrtPS) best-effort service (BE)

3.non-real-time polling services (nrtPS): is very similar to rtPS except that the MS can also use contention-based polling in the uplink to request bandwidth. In nrtPS, it is allowable to have unicast polling opportunities, but the average duration between two such opportunities is in the order of few seconds, which is large compared to rtPS. All the MSs belonging to the group can also request resources during the contention-based polling opportunity, which can often result in collisions and additional attempts.

ATM transport

IP transport

QoS Scheduling Services.

Convergence Sub-layer

• WIMAX defines four Scheduling Services:

Common part Sub-layer

• • • •

Privacy Sub-layer Physical Sub-layer

Unsolicited grant service (UGS) Real-time polling services (rtPS) Non-real-time polling services (nrtPS) best-effort service (BE)

4.Best-effort service (BE): provides very little QoS support and is applicable only for services that do not have strict QoS requirements. Data is sent whenever resources are available and not required by any other scheduling-service classes. The MS uses only the contention-based polling opportunity to request bandwidth.

ATM transport

IP transport

Convergence Sub-layer Common part Sub-layer Privacy Sub-layer Physical Sub-layer

QoS Service Flow.

• Each service flow is associated with a unique set of QoS parameters, such as latency, jitter throughput, and packet error rate, that the system strives to offer.

• A service flow has the following components:

• Service flow ID: a 32-bit identifier for the service flow.

• Connection ID: a 16-bit identifier of the logical connection to be used for carrying the service flow. The CID is the identity of an MS at the PHY layer. MS can have more that one CID at a time, that is, a primary CID and multiple secondary CIDs. The MAC management and signaling messages are carried over the primary CID. • Provisioned QoS parameter set: the recommended QoS parameters to be used for the service flow, usually provided by a higher-layer entity.

• Admitted QoS parameter set: the QoS parameters actually allocated for the service flow and for which the BS and the MS reserve their PHY and MAC resources.

The admitted QoS parameter set can be a subset of the provisioned QoS parameter set when the BS is not able, for a variety of reasons, to admit the service with the provisioned QoS parameter set.

GMH

MAC Management Message

CRC

MAC SDU fragment

CRC

GMH

FSH

GMH

PSH

MAC SDU fragment

PSH

MAC SDU fragment

CRC

GMH

GMSH

PSH ARQ feedback

PSH

MAC SDU fragment

CRC

ATM transport

IP transport

Convergence Sub-layer Common part Sub-layer Privacy Sub-layer Physical Sub-layer

â&#x20AC;˘ The privacy sub layer provides authentication, key management and encryption.

ATM transport

IP transport

Convergence Sub-layer Common part Sub-layer Privacy Sub-layer Physical Sub-layer

OFDM/OFDMA Modulation/Coding

OFDM Basic Concept OFDM is a multi-carrier modulation scheme that transmits data over a number of orthogonal sub-carriers A conventional transmission uses only a single carrier, which is modulated with all the data to be sent OFDM breaks the data to be sent in to small chunks, allocating each sub-data stream to a sub-carrier and the data is sent in parallel orthogonal sub-carriers.

OFDM Spectral Overlap

Conventional Frequency Division Multiplex (FDM) Multi-carrier Modulation Technique OFDM subcarriers have a sinc (sin(x)/x) frequency response resulting in overlap in the frequency domain.

This overlap does however not cause any interference due to the orthogonality of the subcarriers.

Saving of the bandwidth

Orthogonal Frequency Division Multiplex (OFDM) Multi-carrier Modulation Technique The OFDM receiver uses a time and frequency synchronized FFT to convert the OFDM time waveform back into the frequency domain. In this process the FFT picks up discrete frequency samples, corresponding to just the peaks of the carriers. At these frequencies, all other carriers pass through zero amplitude eliminating any interference between the subcarriers.

Multipath and OFDM Faded Path

[ ak ,τ k ]

LOS Path

[a0 ,τ 0 ]

[a1 ,τ 1 ] Reflected Path

K −1

h)t ( = ∑ ak δ )t − τ k ( k =0

Multipath and OFDM OFDM Offers Advantage in Frequency Selective Fading Environments Channel Response

Only a few subcarriers are lost due to fading. This can be overcome with proper channel coding.

F1

f2

f3

f4

f5

fn

F

T

10

10

11

01

11

01

I

Q

Site coverage

F1, f2, f3

5.2 KM 4.4 KM 3 KM 2 KM 64QAM 16QAM QPSK

15% 18%

BPSK

39% 28% rate = 3.8 Mbps

•Supported services VOIP Web Browsing Video call

Sector coverage •Supported services VOIP

64QAM 16QAM QPSK BPSK

â&#x20AC;˘ WIMAX supports TDD & FDD full duplex modes but the most used mode is TDD due to its capacity performance.

TDD: F1 Sub-Frame

Sub-Frame

Sub-Frame

Sub-Frame

Uplink

Downlink

Uplink

Downlink Variable

Variable

FDD: F1 F2

Frame

Frame

Frame

Frame

Uplink Downlink

• According to WIMAX TDD framing, each frame consist of Uplink sub-frame & Downlink sub-frame.

• WIMAX support variety of frame length (10ms, 7ms, 5ms, 2ms).

• The length of each sub-frame is variable according to the traffic.

……...

Frame

Frame

Sub-Frame

Sub-Frame

Downlink

Uplink Variable

Frame

…

……...

Frame

Frame

…

Frame

Uplink sub-frame

Downlink Sub-Frame

Contention Contention slot A slot B

Variable

UL PHY Burst 1

.…

UL PHY Burst n

……...

Frame

Frame

…

Frame

Uplink sub-frame

Downlink Sub-Frame

Contention Contention slot A slot B

UL PHY Burst 1

.…

UL PHY Burst n

Variable

• The first UL Burt for initial ranging that the MS use in the network attach process by sending Initial Attach Messages.

……...

Frame

Frame

…

Frame

Uplink sub-frame

Downlink Sub-Frame

Contention Contention slot A slot B

UL PHY Burst 1

.…

UL PHY Burst n

Variable

• The second UL Burt for Bandwidth request that the MS use to ask for additional BW (PHY resources) ex.: sub-carriers, modulation & coding schemes in UL or DL by sending BW request Messages.

……...

Frame

Frame

…

Frame

Uplink sub-frame

Downlink Sub-Frame

Contention Contention slot A slot B

UL PHY Burst 1

.…

UL PHY Burst n

Variable

• In the UL PHY Burst, the MS can send it’s data to the BS in different modulation & coding schemes.

• UL PHY Burst also called UL PHY PDU.

……...

Frame

Frame

…

Frame

Uplink sub-frame

Downlink Sub-Frame

Contention Contention slot A slot B

UL PHY Burst 1

.…

UL PHY Burst n

Have the same modulation Variable Preamble GMH

fragment

CRC GMH

fragment

CRC

…

UL PHY PDU

• Each UL PHY Burst consist of several PDUs with a previous Preamble to ensure synchronization & equalization for this burst and followed by Pad indicating the end of this burst.

Pad

……...

Frame

Preamble FCH

Frame

MAPs

UL PHY Burst 1

.…

Frame

UL PHY Burst n

Uplink Sub-frame

• DL Sub-frame starts by a Preamble which necessary for frame synchronization and help in equalization.

…

……...

Frame

Preamble FCH

Frame

MAPs

DL PHY Burst 1

.…

Frame

DL PHY Burst n

…

Uplink Sub-frame

FCH (Frame Control Header) contain the location and provides frame configuration information, such as the MAP message length, the modulation and coding scheme, and the usable subcarriers of each burst in the DL Subframe.

•FCH is one OFDM symbol long and transmitted using BPSK modulation.

……...

Frame

Preamble FCH

• • • • •

Frame

MAPs

DL PHY Burst 1

.…

Frame

DL PHY Burst n

The first burst of the DL Sub-frame contains: DL map.

UL map.

UCD (Uplink Channel Descriptor) Optional.

DCD (Downlink Channel Descriptor) Optional.

Uplink Sub-frame

…

……...

Frame

Preamble FCH

Frame

MAPs

DL PHY Burst 1

.…

Frame

DL PHY Burst n

…

Uplink Sub-frame

• DL map & UL map: Indicates the starting times of the UL & DL bursts and specify the data regions of the various users in the DL and UL sub-frames.

• UCD & DCD: which contains additional control information to the description of channel structure and the various burst profiles that are allowed within the given BS. UDC & DCD are not transmitted every DL frame.

……...

Frame

Preamble FCH

Frame

MAPs

DL PHY Burst 1

.…

BPSK

Frame

DL PHY Burst n

…

Uplink Sub-frame

64QAM

Have the same modulation

GMH

fragment

CRC GMH

fragment

CRC

…

Pad

• Each DL PHY Burst consist of several MAC PDUs ended with pad to indicate the end of burst.

……...

Frame

Frame Uplink Sub-frame

Downlink Sub-frame Preamble FCH

MAPs

UL PHY Burst 1

.…

UL PHY Burst n

BPSK Contention slot A

Contention slot B

Preamble

GMH

…

Frame

PDU

fragment

64QAM

.…

UL PHY Burst 1

PDU

CRC

…

Pad

UL PHY Burst n

WiMax 802.16 MAC Convergence Sub layer When a SS is joining the network, three CIDs are assigned to it for management, each one with different QoS requirements: Basic, Primary Management and Secondary management connections .

The network operator defines a set of PROFILES for each base station. All these profiles are listed in table and will control the connections that will be created for each terminal station.

Profile is defined as a set the following information: •Profile Name.

•Class of service of radio connection (UGS, rtPS, nrtPS, BE).

•List of QoS rules that the operator will handle services classes.

•MSTR (Maximum Sustained Traffic Rate) •MRTR (Minimum Reserved Traffic Rate) •CRC (Cyclic Redundancy check) enabling.

Ex: Terminal station connection setup (1)

Ex: Terminal station connection setup (2)

Ex: Terminal station connection setup (3)

Ex: Terminal station connection setup (4)

Ex: Terminal station connection setup (Downlink)

Network Entry

OFDM

Physical Layer

OFDM Basic Concept OFDM is a multi-carrier modulation scheme that transmits data over a number of orthogonal sub-carriers A conventional transmission uses only a single carrier, which is modulated with all the data to be sent OFDM breaks the data to be sent in to small chunks, allocating each sub-data stream to a sub-carrier and the data is sent in parallel orthogonal sub-carriers.

OFDM Spectral Overlap

Conventional Frequency Division Multiplex (FDM) Multi-carrier Modulation Technique OFDM subcarriers have a sinc (sin(x)/x) frequency response resulting in overlap in the frequency domain.

This overlap does however not cause any interference due to the orthogonality of the subcarriers.

Saving of the bandwidth

Orthogonal Frequency Division Multiplex (OFDM) Multi-carrier Modulation Technique The OFDM receiver uses a time and frequency synchronized FFT to convert the OFDM time waveform back into the frequency domain. In this process the FFT picks up discrete frequency samples, corresponding to just the peaks of the carriers. At these frequencies, all other carriers pass through zero amplitude eliminating any interference between the subcarriers.

Multipath and OFDM Faded Path

[ ak ,τ k ]

LOS Path

[a0 ,τ 0 ]

[a1 ,τ 1 ] Reflected Path

K −1

h)t ( = ∑ ak δ )t − τ k ( k =0

Multipath and OFDM OFDM Offers Advantage in Frequency Selective Fading Environments Channel Response

Only a few subcarriers are lost due to fading. This can be overcome with proper channel coding.

Generation of OFDM Symbol

Carrier frequency

• BPSK • QPSK • 16QAM • 64QAM

Ex: 5 GHz

……… …

High speed data

……… …

011011010 1

……… …

Cyclic Prefix

baseband signal in frequency domain.

d = (I + jQ) × KMOD (20)

OFDM Symbol

Analog baseband multicarrier signal

Cyclic Prefix

More Multipath Mitigation…Cyclic Prefix Delay spread exceeds symbol time

Add a gap to capture delay spread

Can’t have gaps in transmission…copy part of symbol and put it in the front