Broadband

There’s a lot of talk of WiMax currently, largely originating from company PR departments hoping to recover their development costs or sell lots of WiMax chips and devices. But what does it offer to the average broadband user ?

To be honest, not a lot right now. You may have heard that WiMax has a range of 70 km and a speed of 70 Mbits/s, but even if the figures were true you would get either one or the other but not both at the same time.

The ultimate range of any wireless device depends on the regulated power output of the transmitter, the losses due to distance and the sensitivity of the receiver plus the associated noise or interference. There is nothing about WiMax that changes the rules here, if you run at an OFCOM permitted power output the signal will go just as far with WiMax as it will with 802.11a, b or g at the same frequency.

The term “WiMax”, which refers to the 802.16 standards family, does not even define the frequency of operation. It could be 800 Mhz, 2.5 GHz, 3.4 or 5.8 GHz - basically anything up to 64 GHz. So any intelligent discussion of WiMax needs to be aware of the frequencies used and power limits that apply - the FCC in the USA permit higher power limits than we have in the UK for example.

In essence WiMax is designed to provide managed “carrier class” wireless broadband services to multiple users, rather than using the collision based approach of earlier standards which are more suited to LANs.

A single 10 MHz WiMax channel will offer 37 Mbits/s of total bandwidth (up and downstream) which is then shared across all the users on that channel - 37 users using a symmetrical 0.5M / 0.5M service at the same time for example. With contention the service might be offered to 1000 users in a built up area and this is the type of residential service being offered now where WiMax services are available. For example, in Estonia services are available at 768k down and 256k up, whereas Denmark offer a variety of packages up to 1.5Mbps down but all with 192k upstream. Russia lead the pack in Eastern Europe with 2Mbps symmetric services available in some places.

Other active networks can be found on Wikipedia.

The scarce component is the bandwidth and radio spectrum, one operator in Bulgaria for example has a single 21 MHz channel and 2 channels of 10.5MHz each. Clearly there is an incentive to stack as many users as possible into the available bandwidth as well as the usual incentive of getting plenty of subscribers to cover the fixed costs of providing the wireless base station and its backhaul.

If the user density exceeds a certain level then additional channels and transmitters are required in the same area to duplicate coverage in order to provide the extra bandwidth - just as many mobile phone base stations in urban areas are there to carry load rather than provide coverage.

In the UK we have a handful of WiMax based business offerings. For example, Urban WiMax, who are listed on our availability checker, offer 2M to 10M symmetrical services in London. On the Isle of Man WiManx have business services from 1M to 4M at prices from £150 to £425 per month plus £350 installation.

WiMax may offer broadband without a land line and quick connections but it isn’t going to be beaming a 50M service into your living room any time soon, nor is it going to feed remote communities in Lincolnshire or South Derbyshire from a mast in the nearest city centre. At a minimum it may bring more competition to the areas that already have plenty and the technological advantages may help address rural notspots with ADSL type services, but not, we suspect, at an affordable price without some subsidy.

Tags: Wi-Max