Close Loop Transmit Antennaselection Deversity Based On Limited Feedback

Wireless communications is a broad and dynamic field over the last few decades and is the fastest growing segment of the communications industry. The efficient use of spectrum resources is becoming much important as radio resource; particularly spectrum resource is becoming increasingly strained.The multiple antennas diversity technology can increase the system capacity and performance considerably and the closed-loop diversity with the feedback of the channel state information (CSI) has a better performance. On the other hand, the hybrid automatic repeat request (HARQ) has been widely used in many systems.In this paper, we present a new transmit diversity scheme which uses the hybrid automatic repeat request (HARQ) feedback message ACK/NACK as the antenna selection indicator. The proposed scheme is simpler than the conventional selective transmit diversity (STD) plus HARQ scheme or the Alamouti's space-time block coding (STBC) plus HARQ scheme. For the chase combining HARQ and two-branch diversity, we have derived the closed form expression of the outage rate and the throughput for the STBC/HARQ, STD/HARQ and the proposed scheme under static flat Rayleigh fading channel.The results show that the three diversity systems have the same diversity order. The STD/HARQ scheme requires the most feedback load and has the best performance.STBC/HARQ and the proposed scheme have the same feedback load and the same outage rate while the proposed scheme has better throughput performance which is close to STD/HARQ. Then a new system based on slow code rate adaptive is proposed for the slow-varying channel, which chooses the code rate according to the average channel SNR to maximum throughput.The system of the propose scheme with slow code rate adaptive method has the closed performance with the STD/HARQ scheme with that.The proposed scheme with slow code rate adaptive method has good performance, at same time it can significantly reduce the feedback load and the complexity.