Spreading sequence design for MC-CDMA systems

The paper presents a new approach of optimal spreading sequence allocation in the uplink of a Multi-Carrier Code Division Multiple Access (MC-CDMA) system. The algorithm is implemented as a distributed optimization problem, where each user will minimize its cost function, by choosing a codeword that suits better to the interference pattern. The optimization problem is treated as a constrained problem over a convex set, for which the optimal spreading sequences are designed based on feasible direction approach. For the optimal spreading sequence, the matched filter (MF) receiver has the same performances as a minimum mean squared (MMSE) receiver in the presence of multi-access interference (MAI) and white noise. The proposed algorithm is analyzed and illustrated with numerical examples obtained from simulations.