Sum Capacity Bounds and Design of Suboptimal Codes for Asynchronous CDMA Systems

TL;DR

This paper derives sum capacity bounds for asynchronous CDMA systems and proposes practical suboptimal codes that perform well at high SNR, offering a balance between complexity and capacity.

Contribution

It introduces new sum capacity bounds for finite and asymptotic asynchronous systems and designs suboptimal codes optimized for high SNR conditions.

Findings

Suboptimal codes outperform known codes at high SNR

Proposed bounds are tight for finite and asymptotic cases

Codes perform comparably at low SNR

Abstract

In this paper, we study two issues in asynchronous communication systems. The first issue is the derivation of sum capacity bounds for finite dimensional asynchronous systems. In addition, asymptotic results for the sum capacity bounds are obtained. The second issue is the design of practical suboptimal codes for binary chip asynchronous CDMA systems that become optimal for high Signal-to-Noise (SNR) ratios. The performance of such suboptimal codes is also compared to Gold and Optical Orthogonal codes. The conclusion is that the proposed suboptimal codes perform favorably compared to other known codes for high SNR asynchronous systems and perform more or less the same as the other codes for the low SNR values.