Near-Optimum Trellis-Coded DS/CDMA Multiuser Communications

We propose two classes of sub-optimum receivers for coded direct-sequence code-division multiple-access (DS/CDMA) systems based on a generalized transmitter model. Compare to the optimum detector with complexity grows exponentially with the number of active user, the proposed detectors have linear complexity and near-optimum performance. The first class is to remove the multiple-access interference by modify the channel decoder. The second class is to separate the multiuser detection and channel decoder, and apply sub-optimum multiuser detector at the front stage. Because the proposed detectors are based on a generalized model, the detectors can be applied for many different transmitter schemes. Numerical results show that the proposed detectors are able to alleviate the near-far problem and the performance achieved by those detectors is near that by the optimum detector.