Improved Linear Parallel Interference Cancellers

TL;DR

This paper introduces new linear matrix filters for linear parallel interference cancellers that improve bit error rates without added complexity, applicable to multicarrier DS-CDMA systems with different receiver configurations.

Contribution

The paper proposes novel linear matrix filters that avoid interference and noise generation in LPIC stages by zeroing diagonal elements, enhancing performance with fewer stages and extending to multicarrier systems.

Findings

Proposed filters outperform existing LPICs in bit error rate.

Type-II receiver with MCC performs better than Type-I.

Fewer LPIC stages needed for desired error performance.

Abstract

In this paper, taking the view that a linear parallel interference canceller (LPIC) can be seen as a linear matrix filter, we propose new linear matrix filters that can result in improved bit error performance compared to other LPICs in the literature. The motivation for the proposed filters arises from the possibility of avoiding the generation of certain interference and noise terms in a given stage that would have been present in a conventional LPIC (CLPIC). In the proposed filters, we achieve such avoidance of the generation of interference and noise terms in a given stage by simply making the diagonal elements of a certain matrix in that stage equal to zero. Hence, the proposed filters do not require additional complexity compared to the CLPIC, and they can allow achieving a certain error performance using fewer LPIC stages. We also extend the proposed matrix filter solutions to a multicarrier DS-CDMA system, where we consider two types of receivers. In one receiver (referred to as Type-I receiver), LPIC is performed on each subcarrier first, followed by multicarrier combining (MCC). In the other receiver (called Type-II receiver), MCC is performed first, followed by LPIC. We show that in both Type-I and Type-II receivers, the proposed matrix filters outperform other matrix filters. Also, Type-II receiver performs better than Type-I receiver because of enhanced accuracy of the interference estimates achieved due to frequency diversity offered by MCC.