Maximizing system capacity in a sub-symbol based DS-CDMA multiuser detector

A sub-symbol based multiuser detector for DS-CDMA systems was proposed in Uzmi and Mujtaba (1999). This paper addresses the optimization of such detectors to maximize the system capacity. It is shown that the maximum number of simultaneous users supported in a DS-CDMA system using a sub-symbol scheme can be increased by the proper selection of certain thresholds delineated in Uzmi and Mujtaba, and by imposing moderate synchronization requirements on the transmitters. It is also shown that, in a synchronized environment, performing with only one sub-symbol is enough for accommodating a fairly large number of users, if the system signal to noise ratio (SNR) is medium to high. It has been verified through simulations that the maximum number of simultaneous users depends on the degree of synchronism and is approximately given by the number of chips in the longest sub-symbol.