Research On Near-Full Diversity Distributed Space-Time Code In Relaying Networks

Relaying transmission is one of the important techniques in wireless communication systems,which can largely extend the communication coverage,enhance the system capacity and provide cooperative diversity.From the very beginning,relaying cooperative transmission has been facing two fundamental problems either in theoretical researches or engineering practices:one is how to enhance the receiver robustness at the destination nodes,and the other is how to improve the spectral efficiency while attaining the full diversity gain.Recent years,with the research achievements on relaying modes,performance optimization algorithms and physical security techniques,the transmission effectiveness and reliability in the relaying networks have been greatly improved.To catering the high demands in future communication systems,such as the next generation wireless communication(5G)and the spatial information network,many challenges arise for the new cooperative strategy,higher diversity transmission scheme and low-complexity algorithms,etc.In this dissertation,we make in-depth investigations into the near full diversity distributed space-time code transmissions in two-way,multi-way and the large-scale antennas networks.The main achievements in this dissertation include:(1)A fuse-and-forward distributed space-time code is proposed for the two-way relaying network in which the relay node also has its local information to transmit to the other nodes.This scheme achieves an efficient transmission of both the users' and relay's information by using the same time-frequency resources.Based on the theory of "Uniquely Factorable Constellation Pair(UFCP)",the transmitted signals are carefully designed so as to ensure the destination node can concurrently decode the information from both users and relay node by using maximum likelihood detector.Specially,when the relay node is deployed with two antennas,an Alamouti-based concatenated fuse-and-forward distributed space-time block code is presented.Theoretical analyses and simulation results show the proposed scheme can achieve the theoretical near-full diversity.(2)The full-diversity distributed space-time code design in multi-antenna multi-relay networks is studied.Considering the two-way transmission and every relay node deploying multiple antennas,a universal distributed space-time code transmission scheme is presented with the linear dispersion(LD)coding at every relay node.In addition,two receiving signal models are also derived for signal detection and performance analyses,and a pairwise error probability(PEP)lower bound is also derived,i.e.lnAN ?/?MN,where ? denotes the signal to noise ratio,and M respectively denote the number of relays and the number of antennas at each relay.Furthermore,by jointly considering signal precoding at user nodes and the signal combining process at relay nodes,a concatenated recursive Alamouti-circulant STBC is designed for the network with 2b dual-antenna relays.By deriving the PEP upper and lower bounds of proposed scheme,its theoretical PEP decay function is obtained as lnN ?/?2N,which achieves the lower bound of universal STBC scheme.(3)Extended distributed space-time code in multi-way relaying network is studied.Considering that multiple users form a single group to share information with each other by using amplify-and-forward(AF)half-duplex relaying cooperative transmission,a multi-way distributed space-time block code is proposed,which extends the one-way and two-way relaying networks and obtains higher transmission efficiency.A universal theoretical PEP lower bound is derived as in ?/?M(K,),where K denotes the number of users.This bound shows that the multi-way distributed space-time code can also obtain higher diversity performance.(4)Non-coherent distributed space-time block code is considered when relay node has large-scale antennas.Based on the asymptotical orthogonality property of large-scale channel matrix,the optimal non-coherent space-time code detector and the code design criterion are investigated.Specially,an optimal non-coherent code structure is designed based on PSK signal for the dual-antenna user node.Analysis shows that a full receiving diversity gain can be obtained when the number of antennas is large.In addition,a non-coherent two-way relaying transmission scheme is also studied.The relay node first non-coherently detects the two users' signals,then performs channel estimation,and finally braodcasts in downlink phase.By using the constellation rotation,an optimal non-coherent distributed space-time block code is presented and the optimal rotation angle is also obtained.This dissertation can enrich the theoretical frameworks of the distributed space-time code for two-way,multi-way and large-scale antenna relaying networks,and shows the high-efficiency and high-diversity performance advantages of distributed space-time code.This work can provide an effective research idea to solve wireless cooperative communications in more complex heterogeneous networks and can provide a theoretical basis for the application of cooperative transmission techniques in practical engineering.