UWB long distance communications

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praveen450

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Hi,

I'm working in UWB systems. It is mentioned that as distance increases data rate decreases.

Can anyone please give detailed explanation on it?
 

Search for the shannon-Hartley capacity formula ( bits/s = C = BW*log2(1+S/N) ).

This formula sets the maximum bitrate that you can get from a system with certain bandwidth and S/N ratio. In real world it is less due to non-optimum modulation/demodulation and other then gaussian noise.

When increasing distance, the received signal drops, hence the S/N ratio. This will increase the Bit error rate. To compensate for this you need to change the modulation format and/or channel coding (for example using stronger error correction code). The outcome will be a lower net bitrate for the communiction link.
 
Thank you for the reply. Can you let me know about any text book or paper that describes more about this concept.
 

you do not need papers, just common sense. There is a maximum allowed radiated power due to government regulations. So as you get further away, you have less and less detectable signal. So you need more time to integrate the signal power before you can make an error free bit determination.
 

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What do you mean with "concept"? Do you mean the radio propagation path, or the shannon capacity formula and digital modulation/coding?

There is lots of info on antennas and basics of digital communication (including error correction coding) on the internet. It may save you money. Depending on your background, you may need some knowledge of the concept of probability, noise density, CDF, PDF and the effect of filtering on noise power/voltage.
 

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