Dynamic signature assignment for direct sequence CDMA systems

Multiple access interference (MAI) is one of the major impediments in the reverse link of wide band CDMA systems, due to the synergy of the users´ spreading codes, transmission delays and the channel characteristics. We propose to dynamically assign the users´ spreading codes and transmission delays, i.e., to assign the user signature, in order to minimize mutual cross-correlations at the receiver. This dynamic signature assignment (DSA) approach helps to avoid (as opposed to combating) MAI at the base station. In assigning the signatures, we present a low-complexity iterative algorithm which utilizes channel information and is able to minimize signal-to-interference-plus-noise (SINR) ratio at receivers. Computer simulation results are presented which show a potential 2-3 fold capacity increase over conventional systems.