New Bounds for Binary and Ternary Overloaded CDMA

TL;DR

This paper introduces new bounds and algorithms for constructing binary and ternary matrices used in overloaded CDMA systems, aiming for interference-free communication in noiseless scenarios, with improved code performance.

Contribution

It proposes novel algorithms for constructing injective CDMA matrices and uses an information theoretic approach to explore their existence, outperforming some existing codes.

Findings

New algorithms for CDMA matrix construction

Codes outperforming binary Welch Bound Equality codes

Low-complexity ML decoding for the proposed codes

Abstract

In this paper, we study binary and ternary matrices that are used for CDMA applications that are injective on binary or ternary user vectors. In other words, in the absence of additive noise, the interference of overloaded CDMA can be removed completely. Some new algorithms are proposed for constructing such matrices. Also, using an information theoretic approach, we conjecture the extent to which such CDMA matrix codes exist. For overloaded case, we also show that some of the codes derived from our algorithms perform better than the binary Welch Bound Equality codes; the decoding is ML but of low complexity.