Still less than four years old, HSPA Mobile Broadband, embedded in smartphones, netbooks and dongles, has brought about a mobile data revolution around the world. Nokia Siemens Networks estimates that mobile data traffic grew fourfold in 2008 and will rise a staggering 300-fold in the next five years. Deutsche Telekom CEO Rene Obermann has also said that mobile data traffic is up several hundred percent year-on-year and that he expects that trend to continue.
Now mobile operators have to figure out how to deal with this extraordinary growth in data traffic on their capacity-constrained networks. In the U.S., in particular, raising the capacity issue often leads to the emotive and political debate around the pros and cons of net neutrality – the concept that all data traffic is equal and should be treated as such. But regardless of how that debate is ultimately resolved, mobile operators have a more mundane technical issue to contend with – the need to ensure that real-time services, such as telephone calls and video streaming, have the bandwidth to provide the user with a good quality of experience.
HSPA users are watching videos on YouTube and its rivals just as they would on a fixed-line broadband connection. Unlike opening a Web page or downloading a picture message, which can be completed in bursts, streaming video requires a consistently high data throughput for the duration of the clip – potentially five minutes or more. The growing popularity of streaming music, as opposed to downloading tracks, via services such as Spotify, will further exacerbate the shift away from bursty applications toward services requiring continual access to plenty of bandwidth.
Operators are responding by upgrading their radio access network, moving through the various iterations of HSPA to take their networks from a peak downlink rate of 3.6Mbps up to 14.4Mbps. From there, operators can move to HSPA+, which makes use of MIMO (Multiple-Input, Multiple-Output) capabilities and higher order modulation enhancements to enable greater throughput speeds and higher performance.
By the end of 2009, Telstra in Australia is aiming to raise the peak speed of its HSPA+ network to 42Mbps. Compared to the first iterations of HSPA, HSPA+ can double the data and voice capacity available to the operator. If they have access to the right spectrum, operators will be able to increase the data capacity in their radio network further still by deploying LTE (Long-Term Evolution) technology.
But operators also need to ensure the links between their base stations and their core network, known as backhaul, don’t become a bottleneck. Up to now, they have tended to install fatter and fatter pipes, over-provisioning these backhaul links, so they have enough capacity even at peak times. But with the exponential growth in mobile data traffic, operators are finding this approach increasingly expensive.
As they grapple with the rapidly rising levels of mobile data traffic, operators are also seeking to make the transition to “all-IP” networks. In the long term, moving entirely to IP could reduce their costs significantly, because they will no longer have to own, operate and maintain multiple, parallel networks.
To make this transition work, mobile operators will eventually need to take the radical step of moving their voice traffic onto IP as well. Radical because their customers have grown accustomed to the reliability, availability and good quality of experience (meaning that you can actually hold a conversation with the person you’re calling) provided by today’s circuit-switched mobile voice services.
In moving to all-IP, voice traffic has to share the same pipes with all the other IP-based services, including video and music streaming. And voice is fundamentally different from many other real-time services. Technically speaking, it is relatively tolerant of glitches on the line (Bit Error Rate or BER), but is highly sensitive to excessive delay. By contrast, a service like video-on-demand is not sensitive to delay in the same way, but highly sensitive to glitches (which result in screen blocking).
One solution is deep packet inspection (DPI) – the ability to look inside the traffic crossing the edge of the operator network in order to determine, at a fine level of detail, the characteristics of each packet and to which application or service it belongs. This information enables the operator to shape the traffic, giving priority to voice calls and other real-time applications, such as video and music streaming, while reducing the network capacity allocated to Web browsing, downloads, e-mails and other messaging applications.
Whatever you think about net neutrality, there is no escaping the fact that many mobile networks have or will soon reach a point where the quantity of data traffic exceeds the available capacity to transport it. Operators have to be allowed, and be trusted, to implement technologies to ensure users can have high-quality voice calls, without degrading the quality of service provided to other applications.
Dan Warren is director of technology at GSMA.
Filed Under: Infrastructure
