ericsson White paper 284 23-3188 Uen | June 2013
Wi-Fi in heterogeneous networks an integrated approach to delivering the best user experience Delivering additional radio network capacity and coverage through the deployment of small cells as part of a heterogeneous network is central to most mobile operators’ mobile broadband strategies, and Wi-Fi is a key element to satisfying the hungry data appetites of millions of smartphone and tablet users. With Wi-Fi fully integrated into mobile access and core networks – offering seamless, secure roaming, intelligent radio access type selection, session mobility and carrier-grade scalability and manageability – operators will be able to optimize the user experience and take advantage of a variety of flexible new business models.
CATCHING THE WI-FI WAVE The main driver for the heterogeneous network vision – that Wi-Fi, along with other small-cell technologies, should become an integral part of a complete mobile-broadband solution – is to deliver high-quality services wherever users need them. By the end of 2018, it is estimated that the typical mobile PC will generate 11GB, a tablet 3.1GB and a smartphone around 2GB per month. Wi-Fi delivers the high-speed, convenient access to the internet that can satisfy the hungry data appetites of millions of smartphone, tablet and PC users. Operators are uniquely positioned to bring Wi-Fi access into the telecom mainstream, as users do not care if they are connected over 3G, LTE or Wi-Fi. With Wi-Fi fully integrated into mobile access, whether they are connected over a cellular network or Wi-Fi, operators will be able to optimize the user experience and take advantage of new business opportunities by supporting a variety of flexible business models. Consumers, enterprises, venue operators and mobile-device makers love Wi-Fi. It delivers high-speed, convenient access to the internet and satisfies the interactive, always-connected and video-oriented online desires of millions of smartphone and tablet users. As people have become accustomed to an all-you-can-eat, wire-grade fixed-broadband experience at home and in the office, they expect to maintain that experience when they are out and about. And they are willing to pay for it. This new market reality presents both a challenge and an opportunity to mobile operators, which are uniquely positioned to bring Wi-Fi access into the telecom mainstream and to make the mobile-broadband user experience as convenient, responsive and seamless as possible. This must be the end goal, because users do not care if they are connected over 3G, LTE or Wi-Fi: the underlying technology should be invisible. On the flip side, if mobile operators do not make Wi-Fi an integral part of their service offerings, they risk handing over their customer relationships to operators that do offer Wi-Fi, as more and more devices favor Wi-Fi access and users are potentially exposed to competing Wi-Fi services. WHY WI-FI? The current mobile-data explosion is largely being driven by smartphones, which have provided mobile operators with a welcome boost to average revenue per user (ARPU). Total smartphone subscriptions reached 1.2 billion at the end of 2012 and are expected to grow to 4.5 billion in 2018. Mobile data traffic is also expected to rise 12-fold between 2012 and 2018, as shown in Figure 1. Mobile video traffic is expected to grow 60 percent annually until the end of 2018. The amount consumed per user is also growing rapidly. At the end of 2012, the average mobile PC generated approximately 2.5GB per month versus 450MB per month produced by a hightraffic smartphone, with the difference partially related to screen size. By the end of 2018, it is estimated that the typical mobile PC will generate 11GB, a tablet 3.1GB and a smartphone around 2GB per month [1].
Monthly exabytes (1018 B) 15
Monthly consumption per device type by 2018
Data: mobile PCs, tablets and mobile routers Data: mobile phones Voice
12
11.0 GB
9
3.1 GB 6
3
0
1.9 GB
2010
2011
2012
2013
2014
2015
2016
2017
2018
Source: Ericsson June 2013
Figure 1: Mobile data traffic to grow 12-fold by 2018 (source: Ericsson Mobility Report, June 2013)
Wi-Fi in heterogeneous networks • CATCHING THE WI-FI WAVE
2
Wi-Fi has become an almost ubiquitous feature on high-end, mass-market devices with 97.5 percent of smartphones currently supporting Wi-Fi. In fact, Wi-Fi penetration on all types of handsets is set to grow from 44 percent in 2013 to 60 percent in 2017 [2]. The growing tablet market will only drive Wi-Fi usage higher, with a typical tablet using three times the data of a typical smartphone. Tablet users are also more likely to select Wi-Fi over cellular, and some analysts put Wi-Fi-only use of tablets in the US as high as 90 percent [3], while 70 percent of Apple iPads are Wi-Fi only [4]. In these situations, mobile operators who don’t offer Wi-Fi may, in effect, be handing their subscriber relationships and the user experience to competing operators who do. There are several other reasons for Wi-Fi being more than simply a stopgap solution to offload data traffic. It will become increasingly central to the mobile experience. The reasons for this include: >> shared data plans that encourage more subscribers to take advantage of 3G/LTE on their tablets, which could dramatically increase network traffic >> new Wi-Fi standards like Hotspot 2.0 that will enable seamless, secure roaming, and Institute of Electrical and Electronics Engineers (IEEE) 802.11ac that will deliver Gbps-plus throughput >> Wi-Fi-related business models that are already enabling operators to differentiate their service offerings.
Wi-Fi in heterogeneous networks • CATCHING THE WI-FI WAVE
3
THE WI-FI CHALLENGE If operators use Wi-Fi as a stand-alone capacity-offload solution alone, they are going to limit their ability to offer their subscribers a consistently high-performance, seamless mobile broadband experience. They will also lose control over their relationship with a growing proportion of their customers and potentially miss out on new business opportunities. Currently, connecting to public Wi-Fi is often a cumbersome and inconsistent process. Users typically have to search on their devices for a network, enable a connection to that network and enter account credentials by launching a web browser. Some of this process has been automated as part of some mobile device operating systems, or embedded in third-party connectionmanager applications, but the experience is far from seamless or hidden from the user. The automation of the process as it happens today can also lead directly to a degraded user experience. Many mobile devices on the market automatically select a known Wi-Fi network as soon as it comes into range. The classic example is when a mobile device enters a building with both Wi-Fi and 3G coverage: even if the Wi-Fi coverage is poor and the 3G coverage is good, the device may still select the Wi-Fi network. Such device-based access selection can lead to a significant degradation in data rate provided to the user, unless and until the user moves closer to the Wi-Fi access point (AP). On top of this, there is always a risk that the Wi-Fi network being joined is not what it claims to be or offers poor security, or that the user would actually get a better signal and data rate by staying connected to the mobile cellular data network. When the mobile device is selecting the access network, it can’t determine whether the Wi-Fi network is going to provide a better link rate than the 3GPP network. It cannot know whether there is sufficient backhaul capacity to deliver the expected service either. BARRIERS TO WI-FI ROLLOUT A recent multi-country survey of smartphone users by Ericsson ConsumerLab reveals that network performance is the principal driver of loyalty to mobile operators [1]. So, while operators may want to leverage Wi-Fi for additional mobile broadband capacity, they need to ensure that the use of Wi-Fi does not threaten their customers’ perceptions of network performance. With device-driven WiFi access, users can experience service degradation. The performance-impacting issues inherent in device-driven Wi-Fi are shown in Figure 2, and can be summarized as: Reaching: “Reaching” refers to the Wi-Fienabled device’s habit of attaching to Wi-Fi when it’s within range, even if that connection won’t deliver a good user experience. Reaching not only affects the devices that connect from too far away, it also saps resources from the Wi-Fi AP, resulting in a bad user experience even for user devices closer to the AP. Unhealthy choices: “Unhealthy choices” refers to the Wi-Fi-enabled device’s common practice of attaching to a loaded Wi-Fi network, even while 3G (and LTE) remain more lightly loaded.
Reaching
Unhealthy choices
Data rate [Mbps]
Smartphone
LOAD
3GPP LTE
MS Wi-Fi
Wi-Fi Distance to cell
Dribbling
Ping Pong xDSL (e.g. 10/2 Mbps)
3GPP Fiber
50 vs 2 Mbps
Wi-Fi
Figure 2: With device-driven access, many users experience unnecessary service degradation from Wi-Fi’s bad habits
Wi-Fi in heterogeneous networks • THE WI-FI CHALLENGE
4
Dribbling: “Dribbling” refers to the fact that, in many cases, Wi-Fi employs a lower speed backhaul to enable cost-efficient network deployment. In such scenarios, the user experience – coming from a higher capacity 3GPP network – will be degraded in the move to Wi-Fi. Ping-pong: “Ping-pong” refers to the Wi-Fi-enabled device’s habit of connecting to Wi-Fi, even when only temporary access is available. This can apply to pedestrians on the move or commuters on a bus.
Wi-Fi in heterogeneous networks • THE WI-FI CHALLENGE
5
IT’S ALL ABOUT INTEGRATION The main driver for the heterogeneous network vision – that Wi-Fi, along with other small-cell technologies, should become an integral part of a complete mobilebroadband solution – is to deliver highquality services wherever users need them. Heterogeneous networks accomplish this by combining radio-access technologies (RATs) to boost peak capacity at hotspots and improve performance at cell edges and in buildings. This requires cost-efficient, easy-to-install radio solutions that complement the existing macro network in high-traffic areas. Mobile operators have three ways to enhance network capacity and coverage to meet growing mobile-broadband demand, as illustrated in Figure 3 [5]: >> Enhance the macro network with additional licensed spectrum, more antennas and better processing capabilities, possibly through carrier aggregation. >> Densify the macro network. Such site densification offers an attractive solution by keeping the total number of sites relatively low, while network performance is less sensitive to traffic location. >> Add capacity through small-cell deployment using low-power nodes.
Improve macro
Required capacity
Currrent capacity
Seamless user experience everywhere
Densify macro
Add small cells Figure 3: Three-pronged approach to delivering a seamless user experience through heterogeneous networks
However, in some high-traffic areas, typically where deploying new radio-network resources is more of a challenge (for example, in public areas such as airports, railroad stations, conference centers and hotel lobbies) it may not be feasible to improve or densify the macro network within the specific time, cost or spectrum constraints. Operators can then identify where they require additional capacity and add small, low-power cells to make use of both licensed and unlicensed bands, including the rollout of integrated Wi-Fi. While this improve-densify-add process is logical and sequential, successfully building highperformance heterogeneous networks requires an effective, holistic approach to network design. In this respect, Wi-Fi is simply another RAT like 2G, 3G or 4G, to be connected to the cellular core data network. But bringing Wi-Fi and cellular access networks together in a heterogeneous network is about more than simply providing capacity offload or enabling a secure, seamless roaming experience for users. With solutions that are scalable, integrated with both the core and radio access networks, and that enable good visibility and management of the user experience, Wi-Fi can be used to deliver all the same services available from the cellular data network. It maximizes the entire user experience by helping to deliver consistently high performance through the addition of a large amount of widely available unlicensed spectrum.
Wi-Fi in heterogeneous networks • IT’S ALL ABOUT INTEGRATION
6
This kind of integrated Wi-Fi-3GPP solution will enable network-based access selection and real-time traffic steering according to specific policies, applications and services, user mobility and local radio characteristics. MOVING TO INTELLIGENT RADIO ACCESS SELECTION AND REAL-TIME TRAFFIC STEERING In order to provide a high-performance experience for mobile-broadband users, operators need greater control over when a device uses the mobile cellular network and when it uses the operator’s Wi-Fi network, and which Wi-Fi network is used. Operator policy has been specified for some time in 3GPP – for example, through the interworking wireless local area network (iWLAN) specification – and has been augmented by Access Network Discovery and Selection Function (ANDSF). In addition, the Wi-Fi Alliance has introduced its Hotspot 2.0 policy specifications. These policy tools go a long way to shifting control from the device to the network, but still cannot deal with the rapid changes in the radio environment experience by a typical mobile device in a multi-technology network. The best user experience can only be Not loaded achieved if Wi-Fi-selection decisions are 3GPP network based on information available from both the 3GPP and Wi-Fi networks, which Loaded 3GPP network includes: >> user-equipment mobility and location >> total loading on both networks including cell load, transport load and processing >> an estimate of link rates in each network including radio link and transport. With comprehensive visibility of the KPIs in both the Wi-Fi and the cellular network, an integrated Wi-Fi 3GPP solution can make informed, real-time traffic-steering decisions, as shown in Figure 4. The beauty of this integrated approach is that even legacy devices can benefit from a better user experience. The ANDSF and Hotspot 2.0 standards, where supported on specific devices, will also complement real-time traffic steering.
Better user experience in Wi-Fi
Macro cellular
Small cell Cellular
Wi-Fi
Figure 4: Real-time traffic steering leverages the visibility of KPIs in both the Wi-Fi and cellular networks to dynamically shift users between networks, ensure the best user experience and optimize network resources
Best effort
Wi-Fi 3GPP integrated
INTEGRATION FROM CORE TO CELL A seamless user experience requires endto-end integration all the way from the mobile packet core network to the individual cell or AP, encompassing controllers and management systems along the way, as illustrated in Figure 10. Integration of Wi-Fi into the cellular network encompasses a broad range of elements. Wi-Fi and multi-mode small-cell licensed-band radios can be housed in compact pico-base-station packages; aggregation and control of cellular RAN and Wi-Fi networks can be performed by common controllers; network management of cellular and Wi-Fi networks is unified; and, the core network elements are integrated, Figure 5: All users connected to 3GPP enabling common billing, authentication, authorization and accounting (AAA) and policy. With Wi-Fi supporting seamless integration with both existing mobile core and fixed edge infrastructure, operators can leverage existing assets to improve the user experience, while reducing their total cost of ownership (TCO).
Wi-Fi in heterogeneous networks • IT’S ALL ABOUT INTEGRATION
7
FAST PLANNING, PROVISIONING AND SCALABILITY The nature of small-cell deployment means there will likely be many hundreds of thousands of units installed across an operator’s network. This means the effort and cost involved in planning, provisioning and installing these small cells must be kept to a minimum. One way to achieve this is through collocation and integration with micro and pico cells, in order to reduce mounting, power and backhaul requirements. This will require advanced features, such as radio frequency (RF) interference management and dual-band architecture that can support backhaul between APs – enabling operators to make the most of their available cell site, fiber or hybrid fiber-coaxial (HFC) assets. Addressing the power, mounting and backhaul challenges alone does not ensure a costeffective and replicable deployment model, however. Business intelligence tracks usage data by device, location and time of day, enabling proactive network planning and investment that optimize the operator’s return on investment. Network management needs to be scalable to support hundreds of thousands of APs in a single network, and to be able to offer real-time and remote management with detailed visibility – from a single AP to network-wide. The operating system can help provide carrier-grade features, such as edge-based policy enforcement integrated with the operator’s AAA, mobility and support for virtual APs. Self-organizing networks (SON) capabilities will help drive automation in everything from planning, through installation to ongoing maintenance and optimization. These capabilities will span several nodes and technologies, and help ensure the Wi-Fi solution is scalable [6].
Wi-Fi in heterogeneous networks • IT’S ALL ABOUT INTEGRATION
8
A SEAMLESS TRANSITION How would a fully integrated Wi-Fi-3GPP heterogeneous network function in practice for the user? A good way to illustrate this is through a use case – in this case, friends meeting up at a coffee shop – though the case would also be valid for a range of indoor and outdoor situations, from the coffee shop to a busy city square, to a stadium on game day. In this first section, Figure 5, we see that the four friends are all outside of Wi-Fi range, so their devices are attached to the 3GPP network (they could be macro or small cell) in both the best-effort and Wi-Fi 3GPP integrated scenarios. In Figure 6, we see three friends getting into the traditional Wi-Fi range; the best-effort scenario shows the effect of “reaching.” The users are in an area where 3GPP still provides the best user experience, but they are autoconnected to the Wi-Fi anyway. In the “Wi-Fi3GPP integrated” scenario, SON-based access selection could determine that, in this location, network performance statistics indicate that the 3GPP is best suited to handle this traffic. Alternatively, a similar determination could be made by real-time traffic steering through its visibility of both the Wi-Fi and the 3GPP networks. In Figure 7, we see the three friends moving into the coffee shop, where the quality of the Wi-Fi signal is sufficient to deliver a good connection. But, the limited, or “dribbling,” backhaul delivers a less than satisfying broadband experience for the three users. In the “Wi-Fi-3GPP integrated” coffee shop, after two users have connected to Wi-Fi, the third user is steered, via real-time traffic steering, to 3GPP, where network resources are available to deliver a better user experience. This could also be accomplished with SON-based access selection, but it would not be real time on a per-user basis, so there might be some delay in delivering the best user experience and optimizing the network resources.
Data rate [Mbps]
Best effort
Wi-Fi 3GPP integrated
Reaching
Access selection or real-time traffic steering
Smartphone 3GPP
Wi-Fi Distance to cell
Figure 6: Effects of Wi-Fi “reaching” impact best effort Wi-Fi while a Wi-Fi 3GPP integrated network uses real-time traffic steering or SON-based access selection to deliver the best user experience
Best effort
Wi-Fi 3GPP integrated
Dribbling
Real-time traffic steering xDSL (e.g. 10/2 Mbps)
3GPP Fiber
50 vs 2 Mbps
Wi-Fi
Figure 7: When dribbling impacts best effort Wi-Fi, users are addressed in a Wi-Fi 3GPP integrated network.
Wi-Fi in heterogeneous networks • A SEAMLESS TRANSITION
9
In Figure 8, we see more users in and around the coffee shop illustrating the besteffort Wi-Fi concept of “unhealthy choices.” In the best-effort context, despite the fact that the Wi-Fi network is obviously more heavily loaded with traffic than the 3GPP network, devices keep trying to connect. Whereas in the “Wi-Fi-3GPP integrated” scenario, real-time traffic steering dynamically directs users to the best network. In Figure 9, we see the fourth friend decide to skip going to the coffee shop. While passing nearby, they decide to tweet their friends. The best effort Wi-Fi would subject the friend to the ping-pong effect, and they could lose their connection even if well within range of good 3GPP coverage. In contrast, in the Wi-Fi 3GPP integrated scenario, the friend stays connected and maintains the best possible user experience FLEXIBLE BUSINESS MODELS There are four typical scenarios in which operators are deploying Wi-Fi: >> indoors – typified by the traditional hotspots in cafés, malls, airports and now extending to retail stores and chains >> indoors/outdoors – for example campus, resort and marina locations >> stadiums and other special events – these are a specific use case of particular complexity because the high user density and nature of the venue provides both business opportunities and significant networking challenges >> outdoors – in locations where people gather, such as parks, city centers, shopping areas and busy intersections. The operator business models driving Wi-Fi deployments are not specific to any given deployment scenario, however, and there is an opportunity for operators to leverage their Wi-Fi deployments for multiple business models. Multiple business models can be supported simultaneously via virtual APs that enable single physical APs to offer multiple secure and independent branded Wi-Fi services to an operator’s subscribers, as well as to other network operators and enterprises as a managed service. Access selection and real-time traffic steering can even be activated on a per Service Set Identifier (SSID) basis.
Best effort
Wi-Fi 3GPP integrated
Unhealthy choices
Real-time traffic steering
LOAD
LTE
MS Wi-Fi
Figure 8: Unhealthy choices impact the best effort user experience, but, with real-time traffic steering, network resources are optimized, and the user experience is better
Best effort
Wi-Fi 3GPP integrated
Ping Pong
Real-time traffic steering
Figure 9: A user passing by the coffee shop experiences ping-pong in a best effort context while a Wi-Fi 3GPP integrated user enjoys a consistent, high-performance mobile broadband connection
Wi-Fi in heterogeneous networks • A SEAMLESS TRANSITION
10
With integrated, centralized policy and charging across 3GPP and Wi-Fi networks, operators have the flexibility to implement a variety of business models with service packages and billing and charging tailored to each one. These business models can be categorized as: >> direct – which includes Wi-Fi access as part of an individual’s subscription bundle, free public Wi-Fi (funded by location-based advertising, for example) and paid-for public Wi-Fi (hourly, daily, weekly) >> wholesale – which includes Wi-Fi access sold to other operators either through reciprocal roaming agreements or charged-for offload (per MB or per month, for example), and to local authorities (for example, so they can offer free city-wide Wi-Fi in return for operator access to sites and power supply and potential marketing opportunities) >> operator managed services to enterprises – which include managed Wi-Fi services for large venues, enterprises or special events, charged as a monthly fixed fee or consumption-based rate, or potentially through sponsorship value in kind.
Internet
Mobile packet core GGSN PDN-SW Fixed Edge
AAA Wa
Ericsson Wi-Fi access network L2VPN (Wn)
HLR GTP Wa
GTP
Wi-Fi controller
LBO
Wi-Fi manager Venue LAN
Wi-Fi controller
CAPWAP
CAPWAP
Wi-Fi access points
Wi-Fi business analyzer
OS
Figure 10: Wi-Fi access network is integrated into the Mobile Packet Core.
Wi-Fi in heterogeneous networks • A SEAMLESS TRANSITION
11
Conclusion Delivering additional radio network capacity and coverage through the deployment of small cells as part of a heterogeneous network is central to most mobile operators’ mobilebroadband strategies, and Wi-Fi is a key element. With Wi-Fi fully integrated into mobile access and core networks – offering seamless, secure roaming, SON-based access selection, real-time traffic steering and carrier-grade scalability and manageability – users will enjoy seamless access to high-performance mobile broadband, whether they are connected over 3GPP or Wi-Fi, and operators will be able to choose connectivity to optimize the user experience. In addition, having Wi-Fi access included in operators’ policy and charging systems opens up new business opportunities by supporting a variety of business models simultaneously, for individual subscribers, enterprise customers and partners.
Wi-Fi in heterogeneous networks • conclusion
12
GLOSSARY AAA authentication, authorization and accounting ANDSF Access Network Discovery and Selection Function AP access point ARPU average revenue per user CAPWAP control and provisioning of wireless access points GGSN/PDN Gateway GPRS Support Node/Packet Data Network GTP GPRS Tunneling Protocol HFC hybrid fiber-coaxial HLR home location register IEEE Institute of Electrical and Electronics Engineers iWLAN interworking wireless local area network KPI key performance indicator L2VPN Layer 2 Virtual Private Networks LBO Local Break Out MS Mobile Station OS operating system RAT radio-access technology RF radio frequency SON self-organizing networks SSID Service Set Identifier TCO total cost of ownership
Wi-Fi in heterogeneous networks • glossary
13
References 1.
Ericsson Mobility Report, June 2013: http://www.ericsson.com/ericsson-mobility-report
2.
Mobile Device Enabling Technologies, ABI Research, October 15, 2012
3.
Chetan Sharma, US Wireless Market Update Q4 2011 and Full Year 2011, March 19, 2012: http://www.chetansharma.com/USmarketupdate2011.htm
4.
CNET, The new iPad has 4g LTE, but should you care?, March 7, 2012: http://news.cnet.com/8301-13579_3-57392917-37/the-new-ipad-has-4g-lte-but-should-you-care/
5.
Ericsson, White Paper, Heterogeneous networks – meeting mobile broadband expectations with maximum efficiency, February 27, 2012: http://www.ericsson.com/res/docs/whitepapers/WP-Heterogeneous-Networks.pdf
6.
Ericsson, White Paper, Smarter self-organizing networks – intelligent support to address the mobile-broadband growth challenge, February 22, 2012: http://www.ericsson.com/res/docs/whitepapers/WP-Self-Organizing-Networks.pdf
© 2013 Ericsson AB – All rights reserved
Wi-Fi in heterogeneous networks • references
14