Distributed Spatial Diversity And Multiplexing Research In The Distributed Cooperative Multiple Antenna System

There are varies application for Multiple-Input Multiple-Output (MIMO) technology in the present and future wireless communication systems. However, it is difficult to equip multiple antennas, with weak spatial correlation, in the mobile set owing to the limited space. Therefore, cooperative relay has been proposed to achieve the distributed spatial diversity gain and spatial multiplexing gain by constructing distributed relay nodes to form virtual MIMO or STBC.However, those centralized distributed relay networks need lots of centralized control information. Recent years, the signaling problem has been solved by the randomized distributed STBC scheme. Although they can achieved the same diversity as that of the centralized STBC scheme, those bit error rate (BER) performance can approach that of the centralized scheme only when the number of the active relay node is large.Based on the random STBC scheme, we propose a limited feedback based scheme to improve its BER performance. In the proposed feedback scheme, the receiver will give an evaluation of the performance of the random signature vector(SV) in every frame. According to the evaluation, the active RNs can choose to keep the random SV, which has a good performance, or randomly generate a new SV for the current frame. Since the time correlation of the channel is utilized well in the proposed feedback scheme, the implicit channel information can be got at the relay nodes,i.e.,more array gains can be obtained.What's more, we extend the signature vector idea to the distributed MIMO with multistream to increase the spectrum efficiency and eliminate the centralized control information. We analyze the constraints of the proposed scheme, and derive an optimization criterion for the SVs based on the maximization of the channel capacity of the relay network. To solve this optimization problem, a gradient-based algorithm is provided.