As printed in the February issue of Next Gen Mobility Magazine.
We hear a lot about mobile operators’ 4G strategies – technology choices, spectrum licenses, capital requirements and deployment schedules. Typically unmentioned is their approach to Wi-Fi offload; yet the way an operator integrates with Wi-Fi will have a dramatic effect on costs, on user experience, and ultimately on its success in the market.
Wi-Fi is a big deal. Wi-Fi systems carry much more data than is carried by all the mobile operators in the world. Cisco’s (News – Alert) VNI report puts total 2010 Wi-Fi traffic as 36 times greater than mobile data traffic. Of course, most of that Wi-Fi data was going to and from computers and other local devices that lack mobile access, but it’s the scale of the Wi-Fi phenomenon that’s important.
With the advent of smartphones, mobile data traffic is exploding. The ability to use your communications devices almost anywhere is compelling and, with the advent of 3G, it’s become technically and commercially feasible. But Wi-Fi at short range will always be faster than mobile data, so the existence of Wi-Fi means mobile technology alone will never match user desires and expectations.
What about 4G? Unfortunately, neither 4G nor subsequent generations of mobile technology can catch up with the parallel evolution of Wi-Fi. Mobile networks are costly. They require centralized planning, deployment and management, and they require dedicated spectrum. But most significantly, they’ve been optimized for a relatively extreme case – wide area roaming at automobile speeds. Wi-Fi is optimized for short-range access by fixed or slowly moving devices. This difference in approach is the key to Wi-Fi’s continuing speed advantage, even over 4G femtocells at close range.
Perhaps more surprising is Wi-Fi’s relative ubiquity. Mobile networks were designed to allow complete coverage with a minimum of spectrum. Their wireless links are more efficient than Wi-Fi. Mobile’s signaling overheads are lower, mobile spectrum utilization is better, and mobile networks support seamless handover when users roam between cells. But mobile deployments are inherently centralized, and in the end, deployment models are more important than wireless link efficiency.
Wi-Fi is deployed directly by organizations and individuals exactly where coverage matters the most, in the workplace and at home. And when problems arise, individuals decide where and what to fix. As a result, enormous Wi-Fi traffic levels are handled in just 60mHz of spectrum (the 2.4gHz band) while mobile operators tie up hundreds of mHz and are seeking more. Despite mobile’s link-level efficiency, Wi-Fi carries more data per mHz of spectrum. And it is Wi-Fi’s distributed deployment model that guarantees Wi-Fi’s continued place in the wireless ecosystem.
But what about QoS? Wi-Fi will never match mobile’s support for rich QoS. True, but in real deployments mobile’s complicated QoS schemes are overkill. Today, corporate networks routinely support VoIP telephony, and virtually all new PBX (News – Alert) installations use VoIP. The corporate approach to QoS is pretty simple: you give absolute priority to voice, knowing that voice bits will always be a trivial subset of the data bits and thus of the capacity on your network. Various fudges come into play when you have to go over expensive wide area links or when you want to protect interactive HD video, but QoS on local Wi-Fi links is simple and being deployed today.And in any event, the mobile data explosion is for access to the Internet where there is no QoS. Indeed, the only mobile application that really requires QoS is voice telephony. For now, voice can stay on 3G networks, moving to the LTE (News– Alert) networks once they support voice. There’s enough 3G/4G capacity for voice. What’s exploding is Internet access, and that’s where Wi-Fi comes into play.
Already, about 40 percent of “mobile” data traffic is being successfully offloaded to Wi-Fi networks. Since most people’s mobile use actually occurs in just two cells (home and work), it’s clear 80-90 percent of future “mobile” traffic can be offloaded to faster Wi-Fi networks. The critical question is who makes this work well – the handset vendors or the operator.
The mobile operator that wins will be the one that provides a seamless experience for its subscribers while offloading the majority of traffic to local and faster Wi-Fi networks.