Over the past couple of weeks, since I submitted my Blog on “WiMAX Again” and an article on crikey.com, a number of people have raised issues with my arguments. Some of them are valid misunderstandings, others are the empty words of armchair critics who have never built or operated a network. I am not going to try and answer everyone individually, but shall cover a couple of the general points.

First let’s talk about coverage. There has been a significant amount of confusion around my statement “… when a fixed line is advertised as offering 6Mbps, all customers within the nominated coverage area will achieve those speeds”. The key words are ‘nominated coverage area’ because if I want to offer everyone in a given area 6Mbps, I can design the network by placing the DSLAM within the appropriate distance of the customers to ensure that they all achieve a line speed of least 6Mbps (i.e. that is the worst speed in the nominated coverage area – most customers will get more). I don’t know why so many people had such difficulty with the concept, other than a failure to understand that this is an economic design choice.

By contrast, with a wireless system, when they advertise data rates of 6Mbps they mean a cell may be capable of producing 6Mbps (i.e. it is the best possible speed in the cell), but you can’t guarantee that anyone in that cell will actually achieve that rate. It depends on their distance from the base station (as for a wired system), but it also is influenced by terrain, fading, scattering and interference. The actual equivalent of a line speed that any customer will achieve is very difficult to predict – you often have to measure it and even then it may vary over time.

The second aspect of coverage that has caused confusion is the much quoted distance limitation of ADSL. In fact, however, the number of customers who are beyond the distance limits (somewhere around 4.5km to achieve a basic ADSL service) is relatively low – less than 10% of the overall customer base. Even for those customers there are possibilities to extend the ADSL service distance.

The second item of confusion is the pricing of fixed and mobile services. Mobile services are more expensive than fixed services (always have been) because the design constraints to deliver a signal to a handset that is moving around are tighter than for the same service delivered to an appropriately placed fixed antenna. It is thus more costly to implement the service. However, the same network technology can be used to provide fixed or mobile services (providing you have the right software). In fact, the 2nd generation of WiMAX proposes to do exactly that, which is why the current generation is an orphan. So I am mystified by those who think that WiMAX will deliver cheaper services to those customers who can’t get a fixed broadband service. Technically there is no basis for that claim. Politically of course there is the almost billion dollars of tax payers’ money being used to subsidise these services, so of course they will be cheaper.