Multistage Decoding of Frequency-Hopped FSK System
Uzi Timor · Bell System Technical Journal · 1981
A recent paper described an unproved decoding scheme for a frequency-hopped multilevel FSK system. We examined this multiple access communication system for possible application in satellite communication and mobile radio telephony. The new decoder, using the known algebraic structure of the users' addresses, reduces mutual interference and achieves a 50 to 60 percent increase in efficiency over conventional decoding. The present paper shows how additional decoding can further increase the efficiency, bringing it very close (within half a percent) to optimum. The scheme makes use of information derived while decoding the messages of other users and thus is especially attractive for the base station, where such information is readily available and does not require a significant increase in complexify. Compared to conventional decoding, the new scheme more than doubles the number of simultaneous users.