Increasing the User Capacity of CDMA Systems by Using the Multi-mode Turbo En-decoder
Yang Xiao · Journal of the China Railway Society · 2005
With rapid increasing of the number of mobile users, the capacity of CDMA systems is becoming a pressure. The classical Turbo en-decoder is only used to channel en-decoding for CDMA systems. In this paper we used multi-mode Turbo en-decoder to increase the capacity of the CDMA system. The scheme is based on the code division multiple access scheme and the Turbo en-decoding filtering technique presented in this paper. In a CDMA cell, the 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 by 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 the original . Simulations verify the approach to be effective.