Precoding in downlink MC-CDMA systems using EM algorithm

In this paper a precoding technique based on Expectation Maximization (EM) algorithm for downlink of Multi-Carrier Code Division Multiple Access (MCCDMA) systems is proposed. In multiuser precoding techniques, the transmitter is optimized to combat channel impairments by the use of new spreading sequences that are obtained by solving an optimization problem based on some criterion. Among these optimization problems, the problem based on Maximum Likelihood (ML) is hard and complex to solve. In the proposed precoding scheme, the well suited EM algorithm is used to solve this problem. The proposed technique is simulated and its performance is analyzed and compared with some other precoding and detecting techniques.

Keywords:

Expectation Maximization algorithm , Multi-Carrier Code Division Multiple Access systems , Multiuser precoding