What is WiMAX
The name WiMax defines one of technologies of cordless access to teleinformatic networks, and in practice – simply to the Internet. The transmission mediums used by WiMax are radio waves, whereas the technology in itself has been designed from the point of view of high efficiency in sending information on long distances. The maximum theoretical WiMax line bandwidth amounts to around 75 Mb/s. However, in practice gaining such a result is possible only on a distance between a transmitter and a receiver which does not exceed 10 kilometers. Additionally, the closest local obstacle should be placed several dozen meters from a transmitter and cannot obscure the view of line-of-sight link between a transmitter and a receiver called Fresnel zone. In practice conditions of this type are difficult to realize, and in real, well designed installations it is possible to obtain a bandwidth of 50 Mb/s. In Polish reality transmission speeds obtained on the WiMax lines do not exceed 4 Mb/s due to the small interest of telephone and network operators. On that account the infrastructure of the WiMax system is brushed off. Started installations of this system use devices earmarked for other standards, so the full taking advantage of the possibilities offered by the WiMax is simply impossible.
The WiMax in itself has a wide range of advantages, among others:
- High bandwidth possible to obtain on relatively long distances.
- A real transmitter’s range which works with the use of this technology amounts to 50 kilometers. If within a radius of its functioning there are local obstacles crossing the Fresnel zone, a range drops to 30 kilometers, and in extremely unfavorable local conditions – to 10 kilometers. These are, in spite of everything, results putting the WiMax in front of other solutions using radio waves for digital data transmission.
- Protocols of data control enable easy transfer of information even in situations when a receiver is able to pick up only a signal reflected from a local obstacle. In this situation a data packet will be transmitted without errors. The only noticeable problem is a transmission speed dropping below 1 Mb/s. The aforementioned two features predestine the WiMax to working, e.g. in conditions of dense high city buildings where it is difficult to assure the clear line-of-sight link and the untouched Fresnel zone.
Unlike other radio technologies, especially WiFi, WiMax uses licensed radio bands (from 2 to 11 GHz) for its functioning. Thanks to this phenomenon, a sender is obliged only to get a permit for sending a signal, but does not have to conduct a law procedure in order to get a license to sending in a band unavailable for private senders.
On the other hand, there are the following disadvantages of WiMax:
- A high cost of devices – to design a modem working in the WiMax system it was necessary to design completely new electronic systems due to untypical band used while transmitting. They were designed instead of, as it usually happens in such cases, using the already existing possibilities. This feature translates directly into considerably higher market prices of modems, transmitters and receivers, what certainly has an effect on relatively small popularity of this technology.
- A relatively narrow range of interests – the WiMax project was aimed at creating a method of gaining high data transmission in conditions in which former radio technologies did not perform well or their functioning was strongly hindered. These include the described earlier areas of high buildings distinguished by lack of optical visibility between a transmitter and a receiver, and completely or partly obscured Fresnel zone. This goal has been achieved; however, the above-mentioned cost of this solution and rather small portability of technologies to other categories of using have a certainly significant effect on a slowly increasing number of the implementation of the WiMax infrastructure.