Research On Precoding Theories And Techniques Of High Throughput Satellite System

Satellite communications can provide ubiquitous multipoint communications on a global scale.In high-density terrestrial scenarios with existing infrastructure,satellite communication networks can be exploited to resolve wireless network collisions and enhance terrestrial 5G services.A high-throughput satellite can serve a whole satellite throughput of several times than that of a traditional communication satellite.With the increasing demand for broadband data services,high-throughput satellite system has become the development trend of current satellite communication systems.High-throughput satellites improve spectral efficiency through multi-spot beam technique combined with full-frequency multiplexing technique,but these techniques also introduce severe inter-beam interference problems.Precoding technique is the key technique to reduce the inter-beam interference of high-throughput satellite systems effectively.This paper mainly studies the precoding theories and techniques of high-throughput satellite system.This paper first reviews and summarizes the related literatures of high-throughput satellite systems and the key techniques of high-throughput satellite systems at home and abroad.Through the analysis of the related literatures,the main problems and the key techniques of high-throughput systems are given.After presenting the high-throughput satellite system architecture and the antenna subsystem of high-throughput satellites,this paper analyzes three beamforming techniques of high-throughput satellite systems and the sources of systematic errors in the beamforming process.Due to the high bandwidth requirement of high-throughput satellite feeder links,coarse beamforming is an architecture to compress the bandwidth of feeder links.Two coarse beamforming algorithms are proposed in this paper,which are suitable for efficient bandwidth compression of feeder uplinks.and low complexity compression of the feeder downlink respectively.Linear precoding techniques are precoding techniques with low complexity.This paper studies the precoder based on matched filter,zero-forcing algorithm and regularized zero-forcing algorithm,and uses the idea of dirty paper coding combined with regularized zero-forcing algorithm as a reference upper bound to measure the performance of linear precoding techniques in high-throughput satellite systems.In addition,this paper also studies the influence of the outdated channel state information caused by the high round-trip time of geostationary satellites and the influence of terrestrial terminal distribution on the throughput of high-throughput satellite systems using precoding algorithms.Finally,the feed power constraints and specific throughput requirements of high-throughput satellite systems in practical applications are considered in this paper,and a general precoding algorithm that can optimize the arbitrary objective function of user throughput is proposed.The proposed precoding algorithm is an iterative precoding algorithm based on convex optimization theory and gradient descent method.The pre-coding problem is solved by convex optimization and the power function is optimized by gradient descent method to continuously optimize the objective function,so as to maximize the capacity potential of the system.In this paper,the performance of the proposed precoding algorithm and the classical linear precoding algorithm are compared,proving that the performance of the proposed algorithm is better than that of the classical linear precoding algorithm with the respect of throughput,and the performance of the proposed algorithm under three different objective functions is compared.