PERFORMANCE OF TRELLIS CODED DIRECT - SEQUENCESPREAD - SPECTRUM MULTIPLE - ACCESS WITH NONCOHERENTRECEPTION IN A FADING ENVIRONMENTVictor

In this paper the performance of diierent coding schemes for direct-sequence spread-spectrum (DS-SS) with multiple-access (MA) interference in a nonselective Rayleigh fading channel is considered. A conventional 64-ary orthogonal code (M 64) transmitting 6 bits of information is examined rst. Each of the 64 code symbols in the M 64 code is assumed to be spread by a random sequence of length N, and the channel is assumed to be interleaved every N chips. We consider a M 64 DS-SS code concatenated with a (63; k) Reed-Solomon (RS) outer code and vary the amount of spreading and the code rate for a xed data rate and bandwidth. Our analysis based on Gaussian approximation shows, when the number of users is reasonably large, an optimal value k to achieve minimum bit error probability of the (63,k) RS code can be found. Furthermore, we extend the results by substituting the M 64 code with the trellis coded Nordstrom-Robinson code (TCNR), and the trellis coded Reed-Muller code (TCRM), which have the same data rate as that of the M 64 code. An optimal value k to achieve minimum bit error probability can also be found when the TCNR code or the TCRM code is concatenated with a (63; k) RS outer code.