Computationally efficient multiuser detection for coded CDMA

Abstract: Computationally efficient multiuser detection for coded asynchronous CDMA systems is investigated. The particular receiver studied is a near-far resistant multi-user detector known as the projection receiver (PR) [originally developed in [1, 2]]. The PR perfoms multiple access interference resolution for CDMA with error control coding. The output of the front-end of the projection receiver yields a metric for decoding of the coded sequences. This metric allows the use of a standard sequence decoder (e.g., Viterbi algorithm, M-algorithm) for the error control code. The metric computation can be performed adaptively by an extension of the familiar recursive least-squares (RLS) algorithm. The adaptive PR operates on a single sample per chip. In chis paper it is shown that for random spreading codes this algorithm simplifies and can be executed an order of magnitude faster by exploiting the average cross-correlation of the spreading sequences. The performance of boll1 algorithms are studied for CDMA with random spreading sequences aid compared to theorctical performance bounds.