Generating Spreading Codes for MC-CDMA with Desirable Crest Factor and Error Weight Distribution

Abstract

In this paper, criteria for designing spreading codes for multicarrier code division multiple access (MC-CDMA) are derived, and a novel approach for generating customized codesets without any length and size restrictions is proposed. In addition to cross-correlation requirements, MC-CDMA systems have to deal with the issue of high peak to average power ratio (or crest factor). In this work, we map the crest factor requirement to the mean-square aperiodic auto-correlation measure of the spreading codes. Using the proposed trellis approach, we design spreading codes with desired aperiodic auto-correlation, while offering the best possible aperiodic cross-correlation properties. Additionally, we improve the diversity gain by improving the error weight distribution. We demonstrate that this is achieved by increasing the number of allowable phases in the spreading code. To the best of the authors' knowledge, this is the first approach that considers a wide range of performance metrics for code design in MC-CDMA, while offering a flexible approach to design custom codesets