Optimal Binary/Quaternary Adaptive Signature Design for Code-Division Multiplexing

TL;DR

This paper introduces optimal adaptive binary and quaternary signature design algorithms for code-division multiplexing, improving signal-to-interference ratio in wireless channels with reduced computational complexity.

Contribution

It develops a novel algorithm based on modified Fincke-Pohst method for optimal binary signatures and extends it to quaternary signatures, addressing NP-hard digital signature optimization.

Findings

Algorithms achieve optimal performance with low complexity

Numerical results confirm optimality and efficiency

Extension to quaternary alphabet broadens application scope

Abstract

We consider signature waveform design for synchronous code division multiplexing in the presence of interference and wireless multipath fading channels. The adaptive real/complex signature that maximizes the signal-to-interference-plus-noise ratio (SINR) at the output of the maximum-SINR filter is the minimum-eigenvalue eigenvector of the disturbance autocovariance matrix. In digital communication systems, the signature alphabet is finite and digital signature optimization is NP-hard. In this paper, first we convert the maximum-SINR objective of adaptive binary signature design into an equivalent minimization problem. Then we present an adaptive binary signature design algorithm based on modified Fincke-Pohst (FP) method that achieves the optimal exhaustive search performance with low complexity. In addition, with the derivation of quaternary-binary equivalence, we extend and propose the optimal adaptive signature design algorithm for quaternary alphabet. Numerical results demonstrate the optimality and complexity reduction of our proposed algorithms.