There are still only a limited number of operators providing fixed WiMax (mostly pre-WiMax and not certified WiMax) services in the UK, including Telabria in Kent and Metranet in Brighton.

The issue is the domination of the incumbent carrier BT, which maintains a high penetration of wired broadband links. Pipex is planning to launch fixed wireless services in the London area in 2007, which if it succeeds will probably become the largest provider of last mile access using WiMax.

I am not aware of WiMax being used specifically in carrier or service provider backhaul networks at the moment, but BT's recent announcement of wireless cities will see fixed WiMax playing a role there as well as in the last mile.

The biggest role for fixed WiMax will be in the developed world in the next few years, primarily to provide last mile access to SMEs. The advantages include fast installation, high speed, and quality of service (QoS) features that leased line/DSL services cannot match.

Some providers, especially the larger ones, are playing the wait and watch game for mobile WiMax. But the smaller ISPs, like Telabria, are taking advantage of the delay and serving rural communities where the quality of DSL infrastructure has deteriorated, so there is a difference in strategy depending on the size of the service provider.

Mobile WiMax certified equipment will be available in Q1 2007 and you will see commercial services being rolled out in the same year, either on pre-WiMax or certified WiMax equipment.

These will complement rather than compete with 3G mobile services, however. Operators' billion dollar 3G investments will not be affected by Mobile WiMax. Instead they will use Mobile WiMax as either a filler or complementary network to existing 3G provision.

In my view Mobile WiMax will also see large adoption in fixed wireless services initially and so will affect fixed WiMax take-up. Unlike 3G, which has a large voice component, mobile WiMax will be primarily data driven, according to Juniper Research's own estimates, voice will be a very small component.

Mobile WiMax is built upon orthogonal frequency division multiple access (OFDMA), which is superior to 3G's code division multiple access (CDMA) technology. In general CDMA suffers from issues like multipath fading (poor signal reception), cell shrinkage and interference issues with neighboring cells.

All of these issues have been taken care of in OFDMA, which has a higher spectral efficiency and lower cost per bit. This makes it commercially viable for a service provider or network operator to deliver a larger amount of data to a wider subscriber base at a lower cost.

3G, however, has a big head start in the market. It is already supported by a large base of operators, whereas mobile WiMax will take until 2007-2008 to appear.