Comparative study of interference cancellation schemes in multi-user detection

Abstract

The use of conventional matched filter receivers for DS-CDMA systems is common, but known for being restricted by multi-user interference and subject to near/far problems. Multi-user detection provides one possible solution to alleviate the previously mentioned problems. Two types of interference cancellation (IC) schemes are available: successive IC (SIC) and parallel IC (PIC). A hybrid interference cancellation (HIC) scheme of PIC and SIC is introduced. Two proposed hybrid configurations are evaluated and compared with SIC and PIC schemes. The issues discussed include delay, complexity, BER performance and power control requirements. The BER performance of all four IC schemes are evaluated by simulations in Rayleigh fading channels. It is shown that, the hybrid IC scheme has more advantages overall than PIC or SIC. However, more research needs to be done into the optimum K-P-S configuration since it is shown that differences exist in the complexity and delay between the two hybrid configurations. In addition, the method used to select the users for the PIC stage needs to be studied more, in order to enhance the BER performance of the system. Furthermore, extended research is required on the area of midamble estimation in a multi-user environment as well as further investigation of new channel interpolation techniques.