Design Of Complementary-Coded Scrambling Multiple Access Systems Enabling Diversity And Multiplexing

Complementary codes(CCs) are new generation of spread spectrum codes with ideal autocorrelation and cross correlation properties compared with Pseudo random sequences.Research works on complementary coded CDMA(CC-CDMA) are quite mature and it has been proved that CCs can indeed improve the performance of CDMA systems. Considering that multi-input-multi-output(MIMO) technology is capable of improving system performance and capacity, several works combined CCs with MIMO to achieve complementary advantages, even appeared compatible three-dimensional complementary codes.Nevertheless, these CCs are based on the spread spectrum technology to achieve ideal correlation characteristics, which reduces the spectrum utilization. The complementarycoded scrambling multiple access(CCSMA) system combines CCs, scrambling, and MIMO technology. Accordingly, it is able to overcome the interference perfectly and reduce the bandwidth consumption.In this paper, two CCSMA codes which can realize diversity and multiplexing are designed. On the basis of giving clear mathematical methods, we analyze the structure characteristics of CCSMA codes, and prove that they have ideal correlation properties and separating antenna characteristics.Secondly, with CCSMA codes applied to MIMO system, the transceiver structure of CCSMA diversity system and CCSMA multiplexing system in the downlink are obtained.On this basis, the error rate formula of each system is derived. The results show that the performance of diversity system is better than that of multiplexing system. Using”diversity / multiplexing control” module to combine the two systems and we can get a complete CCSMA system, and the two models can be switched at any time.Thirdly, spectrum utilization calculation of CDMA, CC-CDMA, MIMO-CC-CDMA and CCSMA shows that CCSMA system has a higher spectrum utilization. Then several methods for further optimization of spectrum utilization are discussed.Lastly, we simulate CCSMA system error rate with the number of multipath, the number of users, the maximum support number of users and the number of receiving antennas,respectively. Then we compare the performance and throughput of several systems, and it shows that when SNR is low, the throughput of diversity mode is higher than that of multiplexing mode, while when SNR is high, the throughput of multiplexing mode is higher than that of diversity mode.