Channel Estimation In Wireless Communication And Relay Networks

With the wireless communication technology developed very fast,Orthogonal Frequency Division Multiplexing(OFDM)technology effectively improve the spectrum efficiency and realize high data transmission.However,in order to achieve higher data transmission rate,the OFDM technology still cannot meet the needs of people.Instead,Multiple Input Multiple Output(MIMO)technology can further improve the communication system capacity and develop rapidly.The MIMO-OFDM system combines the advantages of these twe technologies,which has higher data transmission rates,greater coverage and higher spectrum efficiency.According to the current trend,however,even if using the MIMO-OFDM system,the tranditional point to point communication cannot meet the demand for communication network and bandwith.In present,the wireless relay network is becoming a very meaningful research topic which can deploy and use the relay flexibly according to the actual needs of users,enlarge the area covered by the base station,improve the system capacity and reduce the economic cost without increasing the number of base stations.All these communication technology development should consider the selective fading of wireless channel.In particular,the multipath relative delay and frequency selective fading channel caused by the increasing of the system bandwith result in serious distortion.Only a good knowledge of wireless channel state information can effectively overcome the interference caused by distortion of the signal,reduce the influence of the channel and demodulate signal accurately.In addition,the communication system of power allocation and adaptively transmission technology also need the channel state information.Channel estimation in wireless communication and relay networks were studied in this article based on the above problem.The main research work of this dissertation summarized as follows:1.The basic theories of cooperative relay networks are reviewed.The fundmental of the networks protocols which are Amplify and Forward and Decode and Forward are analyzed,the performance of the system in different combine methods are compared.Finally,the performance of the network communication system are analyzed based on the relay location,which can provide theoretical guidance for the practical application of relay network system.2.Summmarized the existing channel estimation algorithm,especially,analyzed the channel estimation based on adaptively algorithm and verified its effectiveness and feasibility by theoretical analysis and computer simulation.3.According to point to point single carrier communication system model,a joint estimation method based on CS-Gibbs Sampler was proposed for CFO and Multipath sparse channel.For point to point multicarrier communication system model,the proposed MCMC-based channel estimation can solve the computational complexity problem compared with the traditional ML channel estimation.The simulation results show that the proposed method can effectively estimate the CFO and wireless channel jointly,improve the system performance.4.The channel estimation for two-way relay networks data transmission system were studied.A modified channel estimation method was studied based on ML channel estimation,which can simplify the computational complexity in the process of search,reduce the search number of unknow variables and realize the joint estimation for CFO and relay casded channel.