Performance issues in successive interference cancellation with reference symbol assisted channel estimation

Abstract

Direct sequence code division multiple access (DS-CDMA) is a leading candidate scheme to be used in the second generation cellular and personal communication systems. A novel multi-stage successive interference cancellation scheme is proposed which operates on the reverse CDMA link using BPSK modulation, coherent detection and reference symbols to obtain channel estimates. The results of a single cell multi-user investigation show that the traffic capacity can be increased. However, the total traffic capacity is somewhat disappointing because the channel estimates are corrupted significantly by interference from symbols not yet demodulated and cancelled by the receiver. The transmitted signal structure is, therefore, modified to decrease that interference. The results of a single cell analysis of the modified cancellation scheme demonstrate that the system's traffic capacity reaches approximately 80% of that of a multistage successive interference cancelling receiver operating on perfect channel parameters. The multi-cell results show that for hexagonal cell geometry with path loss exponent of 4 and without any forward error correction coding the capacity of the system is between 1.5 and 2.5 times that using the conventional matched filter receiver.