Interference Reduction in fading environment using Multistage Multiuser Detection Techniques

Direct Sequence Code Division Multiple Access (DS-CDMA) system is one of the multiple access technique. Multiple Access Interference (MAI) is a major problem in DS-CDMA system caused by its users. When the number of users increases the MAI is also increases, hence the system performance gradually decreases especially in fading environment. In this paper, the interference is reduced in fading environment by using multiuser detection methods were introduced to detect the users data in presence of MAI. Multistage Multiuser Parallel Interference Cancellation (PIC) and Partial Parallel Interference Cancellation (PPIC) methods are introduced, which gives good system performance that means no.of stages increases the MAI gradually decreases but computational complexity is raised. The computational complexity is minimized by using Multistage Difference PIC (DPIC) detection method is introduced based on the convergence nature of interference cancellation, but system performance cannot be improved. Finally, Multistage Multiuser Partial Differencing Parallel Interference Cancellation (PDPIC) method is proposed in fading environment (combination of Difference PIC and Partial PIC). By using method, system performance is improved and computational complexity is minimized both are performed at a time. Simulation results shows that the PDPIC better performed (in terms of Bit Error Rate (BER)) than PIC and PPIC in fading environment. Keywords— Multiuser detection, MAI, PIC, PPIC, DPIC, PDPIC, fading channel.