I've been thinking about the design of a fairly simple wireless (RF)
telemetry system, and would appreciate some guidance on encoding methods
and error correction.

Essentialy I will have multiple transmitters and one receiver.  The plan
is to have transmitters transmit a small packet of data at a period
determined by both the transmitters address and a PRBS generator, to try
to prevent transmitters being synchoronised to each other and
continuously colliding.  By keeping the packets as short as possible
relative to the transmission period this will help further.  I'm
planning on using the small license free RF modules available cheaply,
most likely the FM ones running at approximately 2000bps.

Initialy I was planning on using Manchester encoding to get a DC
balanced bit stream and include a CRC to detect bit errors.  However,
the way I see it, manchester encoding is effectively transmitting the
data twice, with one set inverted and interleaved with the original
simply to maintain DC balance.  I'm thinking that there has to be a
better use for the extra 50% bandwidth that manchester uses. Could these
bits contain some kind of Forward Error Correction (like a hamming code)
which also maintains DC balance (within reason, dosen't have to be
perfect)?  Would a scrambling system be usefull for DC balancing?

Thanks for any pointers 

Mike

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