A Family of Likelihood Ascent Search Multiuser Detectors: Approach to Single-User Performance via Quasi-Large Random Sequence CDMA

TL;DR

This paper introduces a family of likelihood ascent search multiuser detectors that approach single-user performance in large random sequence CDMA systems, achieving unit asymptotic multiuser efficiency with practical complexity.

Contribution

It presents a new detector family that attains unit AME in LRS-CDMA and proposes a quasi-LRS approach for practical systems to improve high SNR performance.

Findings

WSLAS detector achieves unit AME with linear complexity

Quasi-LRS-CDMA approaches single-user performance at high SNR

Achieves near-optimal detection in large random sequence CDMA

Abstract

Since Tse and Verdu proved that the global maximum likelihood (GML) detector achieves unit asymptotic multiuser efficiency (AME) in the limit of large random spreading (LRS) CDMA, no suboptimal detector has been found to achieve unit AME. In this letter, we obtain that the WSLAS detector with a linear per-bit complexity achieves unit AME in the LRS-CDMA with a channel load < 1/2 - 1/(4ln2) bits/s/Hz. For a practical system with any user number, a quasi LRS-CDMA is then proposed to approach the single-user performance in the high SNR regime.