Wi-Fi question .. really it's driven me too confused !!

[afesheir]

Dear Everybody ...

From wi-fi standards (IEEE 802.11 b/g/a/n), I know that its range doesn't exceed hunders of meters, not because of low transmission power but due to ISI. ISI was solved in 802.11n using OFDM.

But now I see outdoor wifi equipments that can cover an area exceeding 5 KM. Even if these equipments use high gain antennas and amplifiers, how to overcome ISI in this too large coverage area ????

Please help because I am loosing trust in science, theory & equations

 

[bulx]

What makes you think that ISI limits communication range? We are able to commincate even with satellites based on the outer reaches of the solar system! Wireless comm range is limited by attennuation & fading.

ISI affects the speed at whuch we can communicate (how closely symbols can be sent). Thus at long distances, bit rates would be lesser, however complicated schemes can still keep it reasonably high
- b

 

[msabeel]

Whatever the transission speed or power, channel induced ISI can be compensated for using an Equilizer on the Receiver side. You may want to google on what is an equilizer.

 

[afesheir]

First of all I am very sorry for the late reply but my internet connection is too bad (may be due to ISI )

anyway .. thanks bulx for help .. but according to your words, out-door wi-fi's speed is much more lower than indoor ones. The theoretical limit of 802.11g is 54Mbps. What will be this speed in outdoor system ?

thanks msabeel for reply .. I know equalizers but I don't know that wi-fi includes equalizer !!