Reduced-state maximum-likelihood multiuser detection for down-link TD-CDMA systems

In order to defeat both intersymbol and multiple access interference arising in code division multiple access systems, numerous multiuser detection techniques have been investigated . Actually, the computational complexity of the optimum maximum-likelihood multiuser detector (MLMD) increases exponentially with the number of users, therefore it is infeasible. We propose two suboptimum versions of MLMD, especially designed for down-link connections, which are based on a computational efficient reduced-state technique. It has been found that these algorithms have a significant performance gain as compared with other suboptimum joint detection criteria, such as zero forcing and minimum mean squared error. Moreover, they have a computational complexity which is proportional to the number of users.