Simplified Group Interference Cancelling for Asynchronous DS-CDMA

Document Type


Subject Area(s)

Electrical and Computer Engineering


A simplified group interference cancelling (IC) approach is investigated for asynchronous direct-sequence code-division multiple access on flat fading channels. The technique employs grouping by estimated signal-to-noise-plus-interference ratio (SNIR), and interference cancellation is performed blockwise, for a subset of the total number of users. We consider long random spreading codes, and include the effects of imperfect amplitude, carrier phase, and delay estimation. Performance of the technique shows SNIR gains of several dB, and concomitant improvements in error probability, with lower computational complexity than that of parallel or serial interference cancelling techniques. We also show that our SNIR expressions are applicable to both the AWGN and flat fading channels, and for moderate near–far conditions. In addition, we determine optimal group sizes for our technique, where optimality is in terms of average error probability over all users.