Researches On Distributed Space-time Transmission Scheme With Imperfect CSI

Relaying cooperative networks have been widely investigated for its ability of extending the communication coverage and enhancing the receiving signal quality for the cell-edge users.Distributed space-time code(DSTC)studied in the relaying cooperative systems originates from the physical-layer multi-antenna process technology,which can greatly help the communication reliability.Most researches not only focus on how to design a DSTBC structure to achieve the high diversity gain,but also focus on how to efficiently detect and decode with low complexity.Generally speaking,the channel state information should be acquired in advance,so as to successfully abstract the transmitted information from the received signals.Therefore,the accuracy of channel information estimation is directly related with the detection performance at receiver.However,due to the channel noises and the inaccuracy of channel estimation,some error generally always exists between the estimated channel information and the idea channel.In order to improve the transmission performance of the DSTC,this paper considers the distributed Alamouti space-time code(STC)transmission scheme,and then investigates the receiving performance loss caused by the channel information error.In addition,this paper also investigates the channel information estimation algorithms for the considered system.The contributions in this paper can be included as follows:(1)In order to analyze the performance loss caused by the channel information error,a channel information error model is firstly build.Then,this paper analyzes the receiving signal-noise-ratio(SNR)in one-way relaying networks and the two-way relaying networks.Finally,the theoretical upper bound is derived,and the theoretical floor of error symbol ratio(SER)is also derived,which are also validated with the simulation results.(2)For the considered DSTBC transmission system,this paper proposes the pilot-based channel information estimation algorithm and the non-coherent Alamouti STC transmission scheme which does not need any channel information at the receiver.In the proposed pilot-based channel estimation scheme,we propose the equivalent channel information acquisition method.The normalized mean square error(NMSE)of the estimated channel information is also derived.In addition,in the non-coherent Alamouti STC transmission,we dedicatedly design the transmitting symbols so that no channel information is required for the signal detection at receiver.Simulation results also verify the effectiveness and veracity.Summarily,this paper considers the distributed Alamouti STC transmission scheme in the relaying cooperative networks.The theoretical receiving performance is analyzed and the effective channel information estimation is proposed for the considered distributed Alamouti STC transmission.Finally,a non-coherent Alamouti STC scheme is explanatorily proposed.