Multi-carrier platform for wireless communications - Part 2: OFDM and MC-CDMA systems with high-performance, high-throughput via innovations in spreading

摘要

Multi-carrier technologies in general, and OFDM and MC-CDMA in particular, are an integral part of the wireless landscape. In this second part of a two-part survey, the authors present an innovative set of spreading codes known as CI codes, and demonstrate how these significantly increase performance and capacity in OFDM and MC-CDMA systems, all the while eliminating PAPR concerns. Regarding OEDM: the spreading of each symbol over all N carriers using CI spreading codes (replacing the current one symbol per carrier strategy) are presented. CI codes are ideally suited for spreading OFDM since, when compared to traditional OFDM, Cl-based OFDM systems achieve the performance of coded OFDM (COFDM) while maintaining the throughput of uncoded OFDM, and, at the same time, eliminate PAPR concerns. When applied to MC-CDMA, CI codes provide a simple means of supporting 2N users on N carriers while maintaining the performance of an N -user Hadamard Walsh code MC-CDMA system, i.e., CI codes double MC-CDMA network capacity without loss in performance. The CI codes used in OFDM and MC-CDMA systems are directly related to the CI pulse (chip) shapes used to enhance TDMA and DS-CDMA (see part 1): hence, the CI approach provides a common hardware platform for today's multi-carrier(multiple-access technologies, enabling software radio applications.