High Spectral Efficiency Transmission Scheme in Multiple Antenna CDMA Systems

CDMA system combined with multiple antennas is very promising in the B3G and 4G wireless communication because its high spectral efficiency. Multiple antennas in CDMA system always perform on two sides: providing diversity gain or spatial multiplexing, which lead to the tradeoff between system BER performance and its capacity. In this paper, a new multiple antenna transmission scheme which not only provides better BER performance, but also higher capacity in CDMA system employing ZCZ (zero correlation zone) codes has been proposed. It fulfills the multiplexing by placing more than one symbol at each antenna each time and provides the diversity with each symbol on different transmitting antennas. With the character of ZCZ, the transmitting diversity can be assured. Analysis and simulation results show that, when there are two transmitting and receiving antennas, this scheme provides nearly two times the capacity comparing to MIMO-CDMA system, while system BER performance has also been improved