The Ovum view: Going over the Edge

For the last few years most documents about the future of mobile communications have contained a now-familiar diagram. It shows the roadmap from the current second-generation mobile networks (2G), through the intermediate step of data-friendly packet upgrades like GPRS (2.5G), and on to high-speed third-generation (3G) networks. Most versions of the roadmap show separate but aligned paths for the four main digital cellular families - the largely European GSM, the US TDMA and CDMA standards, and the Japanese PDC.

Naturally, this roadmap may yet get us all lost. It rarely has dates on it, and the neat little arrows between the blocks representing technologies give little indication of just how tricky each particular stage is in the evolution. On the other hand, it does at least show where the various stages sit in relation to each other.

There is one little area of the roadmap that has always looked a bit confusing. In the GSM pathway and indeed in the TDMA route - there's a little box marked 'Edge' sitting uncomfortably between the 2.5G blocks and the 3G blocks. The arrows eddy around it in a very confusing way.

For example, there's an arrow that goes directly from GSM to GPRS to 3G. But there is also another arrow taking the same journey, but going via the Edge block. The overall effect is to make Edge look like a non-essential stop on the road to 3G - somewhere you might pull into if you were running out of gas or needed a comfort break, but not somewhere you really needed to go.

How did this happen? Why go to the trouble of defining a technology upgrade and then simultaneously define a by-pass around it? It's even more difficult to understand when you consider how clever and useful Edge is. Edge stands for Enhanced Data rates for GSM Evolution.

It comes in two flavours, a circuit switched variant called ECSD, and a packet switched version called EGPRS. The latter offers a tripling of the network capacity of GPRS, and/or a tripling of the data rate which GPRS can support, with the side benefit of a stronger signal that will push further into buildings.

What's more, upgrading a 2.5G network to support Edge is a relatively small and cheap step. Edge uses all the same core network elements (like switches and gateway nodes) as GPRS. For some network operators, implementing Edge will just mean adding a new transceiver unit to the GPRS base stations - although this does depend on which vendor supplied them, and from which generation of infrastructure they are drawn.

Either way, though, Edge comes with another advantage, in that it uses the same frequencies as GSM and GPRS - rather than the new spectrum which 3G requires. This means that operators who ended up without a 3G licences could still use Edge to offer higher-bandwidth data services.

Operators who hold both 2G and 3G licences could also deploy Edge, not as a stopgap until 3G W-CDMA networks are ready, but as a permanent complement to the 3G technology. Edge would allow them to increase the capability and capacity of the 2G spectrum, and provide a wider deployment of high-bandwidth coverage than would be economically feasible using 3G alone. (3G technologies need more base stations to cover an area compared to 2G and 2.5G technologies.)

Of course, this could be done with 'classic' GPRS alone, but there would be a greater disparity between the data rates and service quality available in the two different coverage areas than if an operator uses Edge.

If Edge is so wonderful, why is it a rather grimy motorway service station on the 3G roadmap, rather than a grand and glorious waypoint? Why have so few operators announced plans to deploy it?

The most important reason is the likely availability of Edge-compatible handsets. While the infrastructure vendors have all announced their plans and schedules for Edge equipment, the handset vendors have been much less forthcoming - even though they are largely different branches of the same companies.

The availability of handsets to support network technologies has been a problem for every upgrade within the GSM family. Handsets were in short supply when GSM itself launched (leading to the witticism that the acronym stood for 'God Send Mobiles').

Late availability dogged the early months of WAP (before the more serious problems kicked in) and has had the same effect on GPRS. There is every reason to expect the availability of handsets will be the limiting factor for the commercial introduction of 3G services too.

There has been talk about Edge handsets being available in commercial quantities by 2003 - but operators who are already worried about the availability of W-CDMA handsets are scared about committing to yet another network technology on the basis of talk. To be really useful, especially to operators who hold both 2G and 3G licences and spectrum, the handsets would need to support GSM/GPRS, Edge and 3G.

For their part, the handset vendors say that they could commit to product availability if they get firm orders from network operators - thereby closing this rather tight vicious circle.

Which all means Edge's problem is something of a self-fulfilling prophecy. Because it's a non-obligatory stop on the roadmap no operator can afford to be the only one planning to go there. This makes handset vendors wary, which makes operators even less likely to include Edge in their individual service plans.

It's all a crying shame. There is still time for operators to put a parallel team on Edge development to ensure there is an alternative path in place if W-CDMA all goes horribly wrong, or a useful complement if it turns out right. Governments could help too, by making it clear that Edge coverage would be recognised as fulfilling operators' 3G licence obligations. But no one is holding their breath to see if any of this happens - so it probably won't.