How do you make mobile broadband work for everyone? As speeds get faster, users will be watching videos and listening to streaming music. At the same time, operators want to make sure telephone callers can still conduct conversations. Dan Warren considers the questions the industry will have to answer

Dan Warren: operators have to be allowed to
implement technologies to maintain the
quality of experience on voice calls

Though it is still less than four years old, HSPA mobile broadband has gone through an extraordinary growth spurt in the past 12 months. And the mobile industry, like any parent, is justifiably proud of what HSPA has achieved in the early years of its life.

But mobile operators are going to have to watch out for the inevitable growth pains and figure out how best to deal with them.

Let’s look first at how fast this remarkable toddler is growing. Since making its commercial debut in the US in late 2005, HSPA — high-speed packet access — has already spread across much of the planet.

Today, there are more than 250 live HSPA networks in 109 countries and about 1,600 types of HSPA-enabled devices available worldwide. Between September 2008 and September 2009, the number of HSPA connections worldwide doubled to more than 150 million and we expect the 200 million milestone to be reached during the first quarter of 2010.

The broadband experience offered by HSPA is a major step change in performance compared with its predecessors and it is not surprising that mobile data traffic is growing very rapidly.

Even so, the rate of growth is extraordinary. Nokia Siemens Networks estimates that mobile data traffic grew fourfold in 2008 and will rise an eye-watering 300-fold in the next five years.

And it is not just network equipment vendors talking up the traffic growth. Deutsche Telekom CEO René Obermann has also said that mobile data traffic is up several hundred percent year-on-year and that he expects that trend to continue.

Traffic growth

The rapid rise in HSPA users is not the only driver behind the startling growth in traffic. HSPA smartphones, netbooks, laptops and dongles are being used to stream video in a way that just wasn’t possible via vanilla WCDMA, EDGE or GPRS.

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 hasten the shift away from bursty applications towards services requiring continual access to plenty of bandwidth.

So, how should an operator adapt its network to cope with both the rapid rise in traffic levels and the growing popularity of streaming video and music?

The first step would be to upgrade the radio access network. Mobile broadband technology is evolving rapidly, enabling operators moving through the various iterations of HSPA to smoothly take their networks from a peak downlink rate of 3.6 megabits a second up to 14.4 megabits.

From there, operators can move to HSPA+, which makes use of Mimo — or multiple-input, multiple-output — capabilities and higher order modulation enhancements to enable greater throughput speeds and higher performance.

The first HSPA+ networks, capable of peak downlink speeds of 21 megs, went into commercial use in early 2009 in Australia, Hong Kong, Singapore and Austria.

Doubled data capacity

By the end of 2009, Telstra in Australia is aiming to raise the peak speed of its HSPA+ network to 42 megs. 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 or long-term evolution technology. The first commercial LTE networks are scheduled to go live in 2010.

But the radio access network is only part of the story. What about the links between the base stations and the operator’s core network, known as backhaul? Up to now, operators 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, over-provisioning backhaul links is becoming very expensive, requiring the operator to install fibre-optic cables, which can be difficult to justify given that the revenues operators earn from mobile data services are not growing anywhere near as fast as traffic volumes.

If the operator doesn’t actually own the backhaul links, instead leasing them from another telecoms company, they may not be able to lay their hands on sufficient bandwidth to cover their peak-time traffic.

Moving to all-IP

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.

Instead, they will have one “flat” network where services exist as applications and traffic flows smoothly from one point to another without translation from one protocol variant to another.

Ideally, all interconnecting operators, be they mobile or fixed, will move to an entirely-IP architecture, so traffic can travel seamlessly between networks, lowering everyone’s operating costs. In this way, mobile networks would become fully aligned with the internet.

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.

Along with compatibility with a wide range of handsets, high levels of reliability, availability and quality differentiate a mobile operator’s voice service from internet-based VoIP services.

Understandably, operators don’t want to lose those advantages.

Sharing the pipes

But 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.

The operator also needs to take the security of their network and of their customers into account. At the point where data traffic enters the network, technologies such as firewalls and network address translation are being used to prevent those on the outside from seeing the topology of the network within, and to prevent direct and malicious access to users’ traffic.

One way to ensure both a good quality of experience and security for users is for the mobile operator to use deep packet inspection — 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, emails and other messaging applications.

Net neutrality

Of course, all this may raise the heckles of proponents of net neutrality — the concept that all data traffic is equal and should be treated as such.

They worry that operators will prioritise traffic on their own services, while giving less bandwidth to so-called over-the-top services, such as the voice over IP services offered by some internet companies.

The complex arguments for and against net neutrality are inextricably bound in with governments’ competition policies and vary country-by-country depending on local market conditions.

However, for the technical, and more mundane, reasons discussed earlier, operators may be forced to traffic-shape, possibly by establishing a set of rules, specifying that voice services and other real-time applications will be treated differently by the network to ensure all users still have a good quality of experience.

It is likely that many mobile networks will eventually reach a breaking point, where the quantity of data traffic generated from the large numbers of subscribers using mobile broadband exceed the available capacity to transport it.

When voice calls become a part of this overall IP traffic load, perhaps in three to four years’ time, operators have to be allowed, and be trusted, to implement technologies to enable the quality of experience on voice calls to be maintained, without degrading the quality of service provided to other applications.

It could be disastrous if someone making an emergency phone call couldn’t get through simply because of the number of people surfing the internet at that point in time. GTB

Dan Warren is director of technology at the GSM Association