SparkFun Forums

[madeinoz]

I would like to implement some type of FEC in a point to multipoint link in broadcast mode. What are my options? Am I better off just retransmitting the packet (about 5 bytes) 3 times as a basic form of FEC? What other forms of FEC are there? I've done the google shuffle but could not really find much information.


Stephen...

[riden]

How likely is it that you will get interference from other transmitters (i.e., are there multiple transmitters in the immediate area)? Multiple transmitters will probably require collision avoidance strategies (resending packets at random intervals, etc.) However, if you are talking about a single transmitter, sending the packets multiple times will probably suffice. With your packet size, you could implement a simple FEC where the data is redundantly encoded such that a few bit errors could tolerated and the original data extracted from the rest of the packet.

There is a lot of information on the web about forward error correction (Hamming, Reed-Solomon, etc.), even a WikiPedia entry (check the references at the bottom) http://en.wikipedia.org/wiki/Forward_error_correction. Try Googling "FEC Hamming", you'll get pages and pages of useful information.

[madeinoz]

How likely is it that you will get interference from other transmitters (i.e., are there multiple transmitters in the immediate area)? Multiple transmitters will probably require collision avoidance strategies (resending packets at random intervals, etc.) However, if you are talking about a single transmitter, sending the packets multiple times will probably suffice. With your packet size, you could implement a simple FEC where the data is redundantly encoded such that a few bit errors could tolerated and the original data extracted from the rest of the packet.

There is a lot of information on the web about forward error correction (Hamming, Reed-Solomon, etc.), even a WikiPedia entry (check the references at the bottom) http://en.wikipedia.org/wiki/Forward_error_correction. Try Googling "FEC Hamming", you'll get pages and pages of useful information.

The system has only a single transmitter (master) and many slave units, the broadcast is the packet that I want to get through error free as much as possible.

Thanks for the info about hamming codes, a search lead me to this paper
http://www.accutechinstruments.com/down ... eWorld.pdf that explained everything for me in a bit more detail.

Stephen