CA-CDMA: channel adapted CDMA for MAI/ISI free burst transmission

Abstract

In this paper, a new precoding scheme is designed allowing the complete orthogonalization of the users in the uplink of a multiuser CDMA system based on burst transmission. With this channel adapted precoding, all the inter-symbol and inter-user interferences are eliminated thanks to the appropriate linear processing at the receiver. If the received power is fixed, this system minimizes the variance of the symbol estimation error. An infinity of solutions exists to orthogonalize the system. Two objectives are added: a possible recursion in the number of users and a minimization of the average emitted power. The last optimization problem is a complex one. An approximate solution is proposed. It is shown that the system introduced in this paper outperforms burst system using a conventional set of codes.