Stripping CDMA-an asymptotically optimal coding scheme for L-out-of-K white Gaussian channels

摘要

We introduce a new multi-access coding strategy called stripping CDMA for a L-out-of-K (LOOK) additive white Gaussian noise (AWGN) channel. Stripping CDMA can be viewed as a generalization of the regular CDMA scheme to one that can achieve arbitrarily high bandwidth efficiency. It can also be viewed as a modification of the pure stripping scheme to one that is suited for a multi-access channel with bursty users. In this scheme, each user is split into M sub-users and the decoder consists of M stripping stages using only single-user decoders. All transmitters of all users are identical, making it suitable for bursty user environments where the set of active users is not known in advance. No synchronization between users at the phase, symbol, or frame level is needed. Although the scheme is only optimal asymptotically in M, it is close to optimal for small M, depending on the bandwidth efficiency. Performance of this scheme using existing non-optimal codes is also investigated.