Wireless Basics

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Wireless Basics

Post by asd on Thu Jan 03, 2008 10:58 pm

There are multiple wireless technologies available...802.11 B,G,N etc...But have you thought about the working behind them?
The very basic technology behind wireless is spread spectrum technology........In very simple terms if we have to describe it.....say we transmit data at one frequency it requires more power.....It is more prone to wireless interference.. so what we do is to spread the data over a frequency so that the power requirement is reduced.....also if we have interference on a particular frequency it is not going to affect it ......the data being evenly transmitted even if some data over a particular frequency is lost ...it could be regenerated by error detection and correction algorithms.........and even if they need to be retransmitted very little has to be retransmitted....

This became the basis of FHSS or frequency Hop spread spectrum technology....It used 79 channels.....It used a mechanism in which it hopped from one frequency to the other and it stayed at a particular frequency for a small period of time known as dwell time and during this dwell time it transmitted data.....It was very effective against interference but as a lot of time was spent hopping between frequencies Throughput was less typically 1-2 MBps........



To Improvise on the through put a new technology named as DSSS(direct sequence spread spectrum ) was introduced....In this it used a smaller frequency range consisting of 11 overlapping channels in 20.4 Ghz range
It sent data on two non overlapping channels like 1 6 11 ........as it required lesser no of jumps higher through put was achieved but at a small cost.......it became more prone to interference.....(to be CONTD.)

asd
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