Performance of a broadband multiple access system by spreading of OFDM symbols in a multipath channel

In this paper, we propose a radio mobile access technique which combines OFDM and CDMA advantages in a multipath environment. It is a synchronous multiuser M-QAM OFDM transmission system with the spreading of OFDM symbols. The chosen spreading codes are OVSF codes. The targeted objective is to be able to evaluate the performance of such an approach in comparison with an easy access on OFDM in view of proposing a candidate technique for 5G. The found results give better performance for the 4-QAM OFDM systems with spreading. This performance increases with the spreading factor SF. Thus with SF equal to 32, it´s possible to have at least 9 users in the same channel for obtaining the performance of a single user 4-QAM OFDM system without spreading. The proposed system presents the advantage of being able to assign the same OFDM carriers to all users identified by their code.