Hybrid automatic repeat request（HARQ） is a well-known technique for improving system throughput and link performance of wireless communication systems,including cooperative communication systems.The amplify-and-forward（AF） relaying method is one of the most attractive cooperative diversity schemes because of its low complexity.In this article,the end-to-end performance in terms of block error rate（BLER） and normalized throughput of AF relaying with HARQ transmission under the Rayleigh fading channel is analyzed.Numerical results validate the proposed analysis and demonstrate the gain of HARQ schemes in AF relaying systems.This analytical method can be extended to the systems with other HARQ protocols and other cooperative relaying schemes.
In this article, the authors consider joint design of a linear precoder and power allocation for uplink multiuser multiple input multiple output （MIMO） communication systems with limited feedback to improve the bit error rate （BER） performance for all users. Precoder selection from the codebook set is directly based on the exact BER performance, instead of other suboptimal criteria, to achieve the optimal precoder matrix, but closed-form expressions may not exist in the view of power allocation based directly on the BER criterion. From this perspective, the authors propose the joint transmitter optimization algorithm for the consideration of precoder design, with total power constraint for asymptotic MBER （AMBER） criterion. In this AMBER criterion, a closed-form solution has been derived for power allocation with an optimal precoder. The simulation results show that the proposed joint design algorithm can achieve a much better performance than precoding with uniform power allocation and only consideration of power allocation.
