MMSE Decoding Method Of Array Antennas In Satellite Communication Systems

With the development of the information theory and the arrival of the era of mobile Internet,satellite communication applications are also being constantly expanded.At present,Internet,big data as the representative of new generation of information technology are developing rapidly.As an important communication infrastructure,satellite communication systems should actively respond to the development direction of these information technologies.However,to face Internet of Things "all things interconnected" demands,the traditional broadband multimedia satellite communication systems will be difficult to meet such a large number of access requirements.Therefore,it is necessary to further study the multiple access problems to meet the requirements of the network access as much as possible within the limited spectrum resources.A large number of research results have shown that massive Multiple-Input,Multiple-Output(MIMO)systems can not only provide higher spectral efficiency than traditional MIMO systems,but also improve system capacity and channel reliability.Moreover,simple linear detection can achieve the best performance.With well-developed array antenna technology,more and more applications have been made on satellite communication.Based on facts that the satellite has an array antenna and massive MIMO systems have advantages above,satellite communication can effectively support massive access networking information nodes by applying the techniques of the massive MIMO systems to array antenna systems,which is different from the traditional multi-beam SDMA in satellite communication technology.Satellite communication channel is different from the ground communication channels.One of the most important features is that strong direct components of received signals exist.In this thesis,a satellite communication uplink system equipped with uniform linear array antenna is reconsidered.For this system,the asymptotic orthogonality of the channel vector is verified.Based on this orthogonality,some linear decoding methods are proposed,and its maximum achievable rates and corresponding lower bounds are derived based on an assumption that the channel state information(CSI)is known.On the basis of these formulas,the decoding performance of the proposed maximum ratio combining(MRC)decoding method and the minimum mean square error(MMSE)decoding method are analyzed.Comparisons on performances are given.Simulation results show that the proposed method is feasible,and the decoding performance of MMSE decoding method is much better than that of MRC decoding method,but the corresponding calculation complexity is higher.Under the same conditions,the achievable rate of MMSE detection is higher than that of MRC.The simulation results confirm these results above.Usually,the channel state information(CSI)is unknown and the channel estimation is to be implemented.The accuracy of the channel estimation has an important influence on the communication quality of the system.In this thesis,several new channel estimation methods are proposed,and the principle of the proposed channel estimation method is analyzed in detail.The efficiency of the proposed method is also verified by simulation comparisons with the traditional channel estimation methods.