A Joint Design of Complex Signatures Sets for Multicellular Synchronous CDMA Network

P Cotae

doi:10.14209/jcis.2006.12

Abstract

A design using total squared correlation (TSC) measure for the overloaded complex spreading sequence sets on the uplink of multicellular synchronous CDMA systems is introduced. For equal power users, the design provides orthogonal Welch Bound Equality (WBE) complex spreading sequences with constant chip magnitude. We developed an algorithm, which allows obtaining a structured Gram matrix having a particular pattern for cross correlations of the multicellular signature sequence sets without alphabet constraints. By using the proposed algorithm spreading sequences with maximum equicorrelated amplitude are also obtained. The mathematical formalism is supported with selected numerical examples in the multicellular S-CDMA context.

Highlights

THE problem of designing complex spreading sequences (a.k.a codewords or signature waveforms) for single cell synchronous code division multiple access (S-CDMA) systems is a traditional one
Much attention has been paid to the problem of constructing and optimizing the signature sequences for synchronous DS-CDMA systems [15], and [16] in order to understand the impact of such sequences on the wireless system performances
We developed an algorithm, which allows obtaining a structured Gram matrix having a particular pattern for cross correlations of the multicellular signature sequence sets without alphabet constraints

Summary

INTRODUCTION

THE problem of designing complex spreading sequences (a.k.a codewords or signature waveforms) for single cell synchronous code division multiple access (S-CDMA) systems is a traditional one (see [9], [12] ,[13], [14], and references therein). We developed an algorithm, which allows obtaining a structured Gram matrix having a particular pattern for cross correlations of the multicellular signature sequence sets without alphabet constraints It is an extension of the one presented in [1] in single cell case and it overcomes the limitations of the previous algorithms presented in [6], [15][17]. It is based on Gram matrix approach using TSC ([4], [5]) as a design criterion and Givens rotations [21] By using this algorithm it is possible to obtain complex spreading sequences with maximum equicorrelated amplitude and constant chip magnitude in the absence of multipath.

SYSTEM MODEL AND TOTAL SQUARED CORRELATION

CONSTANT CHIP MAGNITUDE DESIGN

THE PROPOSED ALGORITHM

NUMERICAL RESULTS

CONCLUSIONS AND FUTURE WORK