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How to design a robust communication system?

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machael

machael

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hi, everyone:
I'm working on a communication system. It must communicated via some "bad" communication channel such as power line, which have horrible noise and heave attenuation and non-linearity transmission function and other disadvantageous conditions.
Forunately, the system has no requriment on speed, it can be as slow as it can, only if it is robust.
So if anyone can recommend some materials to me about the technique about how to design communication in such horrible environment? Thank you very much!
 

one possible improvement is to add in error detection & correction.

for e.g. turbo code was adopted for the pathfinder on Mars so that i could send clear images to earth.

you can look for books on information theory or error correction codes in this forum.
 

Another thing to do is have several frequencies used to send the same data. At the receivers you can estimate the signal to noise ratio and use the data from the receiver that has the best SNR. Use a modulation that is not sensitive to amplitude so that you can use a limiter. PSK and FSK are examples.
 

Hi,
you may try

1) CDMA
2) check the frequency response of line and use it in the range where noise is less with any simple modulations. This is a preferable approach.

brmadhukar
 

h**p://www.eccpage.com/

h**p://www.sims.berkeley.edu/~rosario/projects/error_correcting_codes.html
 

hi

simple approach will be to use high transmit power if possible to increase over SNR level.
or
try to receive your same signal by multiple antennas and combine the signal after that to increase the SNR level...

cheers
 

try to receive your same signal by multiple antennas and combine the signal after that to increase the SNR level...
Click to expand...

hi, can you elaborate on this scheme..
 

hello..

This is known as receiver diversity..... That you transmit a signal and receive the same signal by different antennas.....say 3 antennas now you have same signal in 3 receiving antennas with noise also...Now if you combine those signal then noise will also addup but since it is a random process so it will be equal to the same noise which was on one antenna...but your actual signal will add up constructively and will produce stronger signal with the same noise level so your overall SNR level will increase.In 3G mobile com system also they are employing this scheme receiver diversity to increase the SNR level and to overcome a multipath effect.

banh said:
try to receive your same signal by multiple antennas and combine the signal after that to increase the SNR level...
Click to expand...

hi, can you elaborate on this scheme..
Click to expand...
 

Try turbo coding.........very useful nowadays
 

I recommend this book to solution your problem.

Warning 1. Prentice Hall - Digital Communication Systems (Peebles)- Deleted. Post link () to the e-book forum instead of reuploading the entire book. Marie65
 

hi, Thanks for all the kindly reply above!

However, I think that for a practical communication system, the first and the most important thing is the detection and synchronization --- to detect the exist of useful signal and synchronizes with it including carrier frequency and symbol or the frame. Only the synchronization is done, the FEC can be utilized, or it will be useless. But how to detect and synchronized the signal in a terrible communication environment? I would like to hear you guys to talk about it.
thank you!

Machael
 

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