Increasing user capacity by using multimodes turbo en-decoding for CDMA systems

With the number of mobile users rapidly increasing, the capacity of CDMA systems becomes a pressure. Classical turbo en-decoding is only used to channel en-decoding for CDMA systems, in this paper we present multimodes turbo en-decoding to increasing the capacity of the CDMA systems. The proposed scheme is based on the code division multiple access scheme and turbo en-decoding filtering. In a CDMA cell, base station adopts K turbo en-decoders to divide the mobile users in the cell into K different groups. The N spreading codes of a cell can be assigned to different mobile stations in the K different turbo en-decoding groups, so the number of users in a CDMA cell can be increased K times. The bank of matched filters is used to detect user signals in the same turbo group, so the number of users can be K times of original one. Simulations verified the approach to be effective.