Iterative detection in code-division multiple-access with error control coding

A code-division multiple-access system with channel coding may be viewed as a serially-concatenated coded system. In this paper we propose a low complexity method for decoding the resulting inner code (due to the spreading sequence), which allows iterative (turbo) decoding of the serially-concatenated code pair. The per-bit complexity of the proposed decoder increases only linearly with the number of users. Performance within a fraction of a dB of the single user bound for heavily loaded asynchronous CDMA is shown both by simulation and analytically.