Reduced and differential parallel interference cancellation for CDMA systems

Abstract

Since code division multiple access systems in multipath environments suffer from multiple access interference (MAI), multiuser detection schemes should be used in the receivers. Parallel interference cancellation (PIC) is a promising method to combat MAI due to its relatively low computational complexity and good performance. It is shown in this paper that the complexity of PIC is still high for realistic scenarios in terms of the symbol rate, the number of users, spreading gain, and multipath components. However, two novel methods are introduced to reduce significantly the complexity without sacrificing performance. The first approach, called reduced PIC, takes advantage of the composition of the interference to concentrate interference cancellation only on significant terms. The second approach, called differential PIC, exploits the multistage character of PIC to avoid unnecessary double calculations of certain terms in consecutive stages. It is shown that a combination of both approaches leads to a performance very close to the single-user bound whereas the complexity can be kept on the order of the conventional RAKE receiver.

New Parallel Interference Cancellation/Decoding for Convolutionally Coded CDMA Systems over Fading Channel

“…Among these MUDs, one suboptimal, but less complex method is the parallel interference cancellation (PIC) [3], which takes a multi-stage structure in general. Recently, conventional PIC for uncoded and coded CDMA are studied, and the exploration in implementation aspects is also made in [4].…”

Multiuser detection with neural network and PIC in CDMA systems for AWGN and Rayleigh fading asynchronous channels

“…Linear parallel interference cancellation schemes are described and analyzed using matrix algebra in [8]. Reduced PIC that takes advantage of the composition of the interference to concentrate interference cancellation only on significant terms, and differential PIC that exploits the multistage character of PIC to avoid unnecessary double calculations of certain terms in consecutive stages were proposed in [9].…”

Robust blind PIC with adaptive despreader and improved interference estimator

“…It can be seen that the increase in complexity is very low compared with significant gain in user capacity and improvement in BER, which will be shown in the following sections. It is also worth noting that further complexity reduction techniques for a PIC, such as reduced and differential PIC [11] and also block update of CMA weights, where the weight vectors are updated once every block (several symbols) [22], can be used in a straightforward manner.…”