Coding for asynchronous-CDMA systems
A coding scheme for asynchronous code-division multiple-access (CDMA) systems with finite delays is presented in this paper. All transmitted codewords are assumed to reach the receiver within finite delay of D digits. This coding scheme combines source encoding, synchronous-CDMA (S-CDMA) spreading sequences, and interleaving to support error-free asynchronous multiple-access communications. It can support at least m(log/sub 2/m-2)/(2log/sub 2/3)+1/log/sub 2/3 users and the lower bound of its maximum code rate approaches asymptotically to (1-D/T)(log/sub 2/m)/(2log/sub 2/3) where m is the length of S-CDMA spreading sequence, and T>D+log(D+2).