CHARLIE@UMVMA.BITNET (Charlie Turner) (02/06/91)
There are several technical terms that appear often in modem discussions, that I am somewhat unsure of. I'm thinking specifically of: - trellis coding, and - forward error correction. From the context of some techical discussions of 9600 speed modems I've read in this digest, trellis coding must have something to do with encoding the data bits on the digital side of a modem into the analog signal changes on the phone line side of the modem. A bps into baud conversion (if that makes any sense). When talking about MNP or LAPM error protocols, are those error *correction* protocols or just error *detection* techniques, ie. just a fancier CRC checking scheme? I think forward error correction means extra bits are encoded and transmitted. The receiver then can not only detect transmission errors, but can reconstruct what the original data had to have been, thus avoiding a retransmission. Is this the proper meaning of 'forward error correction'? Does trellis coding have anything to do with this? Do MNP or LAPM perform this data reconstruction processing? Thanks.