Monday, May 22, 2006

Hung up on broadband Wireless Technologies

We are sometimes hung upon technologies that comes our way. We also tend to take news about technologies on face values that we tend to be gullible on its claims. Take the example of Wimax and 3 G,there are so much claims on its speed and capabilities that we sometimes fails to examine them in relation to the laws of physics.

To demonstrate this claim in relation to reality, let us look at the claimed performance vis-a-vis to the reality on the ground. The common claim is that WIMAX will be a solve all technology due to its endless performance capabilities in broadband performance. Let us examine this claim in reality.

Limitation of Spectrum (Frequency).
Transmitters using WiMAX usually is deployed at base station to transmit broadcast signal to the end users for broadband usage. To transmit it effectively in a one to many configuration, the base station will be configured to transmit in a sectorial mode. The operators deploying these base stations will choose how many sectors depending on the amount of spectrum resource that is available to them. Normally, in a typical country, these spectrum resource allocated is around 20 Mhz. If the planning calls for 4 sector to cover the 360 degrees coverage, then the spectrum reserved for the deployment maybe 2 (with adjacent sectors using a different frequency). The client set may opt to use a different frequency band for transmitting back to base station, hence effectively u will have 3 frequency band to be allocated within the 20Mhz spectrum.

That will mean roughly per band you can only have 6 Mhz of spectrum. When U have 6 Mhz of spectrum , there is no way u can pump out more then 10 Mbits of bandwidth per band. It just defies the law of physics (at this present moment).

Transmitting Distance
Another myth is that WiMAX can transmit more then 25 km in distance. Generally this is true if and only if, u have a transmitter that has high enough wattage that may fry the birds (or at least causing hazardous health concern - in regulatory speak) coming close to the transmitter and u are only transmitting one way - to a passive reciever.

What most people forget is that if U are just receiving broadcast from the transmitter that maybe OK, but the client system also has to broadcast back to the base station. With current limit of 1 watt at the client devices, there is no way on earth that the client system can transmit back beyond 5 km (or thereabouts) unless using some high gain antenna. That would defeat the idea of portability, wud it.

So people, lets us not go and repeat this story without realizing the fact and reality on the ground.

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