Almost-optimum signature matrices in binary-input synchronous overloaded CDMA

Abstract

The everlasting bandwidth limitations in wireless communication networks has directed the researchers' thrust toward analyzing the prospect of overloaded Code Division Multiple Access (CDMA). In this paper, we have proposed a Genetic Algorithm in search of optimum signature matrices for binary-input synchronous CDMA. The main measure of optimality considered in this paper, is the per-user channel capacity of the overall multiple access system. Our resulting matrices differ from the renowned Welch Bound Equality (WBE) codes, regarding the fact that our attention is specifically aimed at binary, rather than Gaussian, input distributions. Since design based on channel capacity is computationally expensive, we have focused on introducing a set of alternative criteria that not only speed up the matrix formation procedure, but also maintain optimality. The Bit Error Rate (BER) and Constellation measures are our main criteria propositions. Simulation results also verify our analytical justifications.

Finding sub‐optimum signature matrices for overloaded code division multiple access systems

“…Alishahi et al [6] generalized these previous works [4] and [5] to finite none binary descrete input and matrix entries. In [8] we got some partial results for optimal real matrices base on GA.…”

“…Furthermore, a new maximum-likelihood (ML) decoder was introduced in [3] for large-scale COW matrices. In our previous work [10] binary input synchronous CDMA systems are investigated with real-valued signature matrices and partial results for sub-optimal matrices based on the genetic algorithm (GA) are reported.…”