Research On Precoding Technology In Multi-beam Mobile Satellite Communication System

In the wake of wide usage of bandwidth-hungry application in mobile satellite communication systems,the demand for explosive data traffic is rapidly growing.Multi-beam joint precoding technique also has received extensive attention from the aerospace industry and scientific research academia.Because this technology can not only solve the problem of the inter-beam interference,but also overcome the problem of signal fading caused by time-varying satellite channels.Therefore,this technology has become a new direction for green broadband multimedia satellite communication since its capability of improving the transmission rate and service quality in multi-beam satellite system.However,the existing works assume the availability of accurate channel-state information(CSI)at the satellite transmitter,but ignore the influence of channel estimation error and feedback delay in the actual mobile satellite communications.There is no doubt that the precoding method has suffered considerable limitations.Thereby,it is a significant research direction to tackle the challenge of CSI feedback delay,break the limitations of the traditional methods,and utilize the corresponding optimization method to improve the system transmission rate.Therefore,this paper mainly studies the precoding problem of multi-beam mobile satellite communication system in the Shadowed-Rice(SR)channel environment.Firstly,the multi-beam mobile satellite communication system model is researched in detail.Here we mainly study the link transmission characteristics,channel statistical model as well as forward link model.This paper introduces the link transmission characteristics such as multipath and shadow effect.Then,based on the traditional mobile communication channel model,we further study the classical satellite channel statistical model including the rice shadow model.Lastly,the paper mainly researches the system forward link model and structural features,which builds the simulation platform for the study of the algorithm in the subsequent chapters.Secondly,the technical theory of precoding methods is analyzed.This paper firstly gives an overview of precoding implementation principle and technical classification.According to different preprocessing ways,we separately research the nonlinear precoding and linear precoding techniques.In terms of the system sum-rate and bit error rate performance indicators,the simulation results demonstrate the performance differences between various precoding algorithms in terrestrial and satellite mobile communication systems.The simulation results also verify the performance effects caused by the rice coefficient and isolation in multi-beam satellite systems.Finally,the open-loop precoding techniques in multi-beam mobile satellite communication systems are studied.To cope with the CSI feedback delay in the existing precoding schemes,this paper proposes a precoding scheme based on open-loop channel estimation,where the transmitter utilizes the open-loop partial CSI to achieve multi-beam joint precoding.Based on the shadow Rice channel model,this paper derives the system transmission rate in closed analytical form.Moreover,an optimal power allocation scheme is also presented to put the system resource to good use and further eliminate the effects of inter-beam interference as well as time-varying channel fading.In addition,a hybrid precoding scheme is also presented to deal with the performance deterioration in strong interference environment.According to the openloop slowly-time-varying user location and channel statistics information,the transmitter adaptively chooses precoding and frequency refuse method.Lastly,the simulation results validate substantial performance gains compared with traditional interference elimination schemes and demonstrate that our proposal also overcomes the limitation of conventional techniques.