卫星移动通信信道研究及性能仿真

【作者】 胡君；

【导师】 吴诗其；

【作者基本信息】 电子科技大学 ， 通信与信息系统， 2005， 硕士

【摘要】 移动卫星通信系统是下一代移动系统中必不可少的一个组成部分,本文对移动卫星通信系统中的部分关键技术-信道模拟技术、信道编码技术、交织技术、非线性效应进行了研究,对目前航空领域的发展热点-航空移动卫星通信进行了综合性的分析,并对它的信道特点和信道模型进行了研究。本文首先对移动卫星通信系统进行了概括性的介绍,分析了移动卫星通信系统的特点及与一般移动通信系统的相比的特殊性。并且对移动卫星通信系统的设计重点和设计难点进行了分析。概括性地介绍了移动卫星通信信道的特点-时变、存在多径效应、遮蔽效应和多普勒频移。然后介绍了经典的移动卫星通信信道模型,分析了这几种经典信道模型的特点;其次对移动卫星通信信道上的通信技术-信道编码、交织技术进行了分析;再次,对卫星通信中的放大器非线性特性进行了简单的分析;最后,分析了航空移动卫星通信的信道特点,并提出了研究重点。因此,本章重点是对本文研究内容的国、内外现状进行了分析,并提出本文的研究意义和全文结构安排。提出了高斯色噪声的模拟方法,并确定了具有较好逼真度的路径数量。在此基础上,给出了其它移动卫星信道建模常用的分布函数-Rayleigh、Lognormal 和Rice的仿真模型,经过与理论概率分布函数的比较,验证了仿真模型的有效性。分析了3 种经典的信道模型,在参考C.Loo 模型的基础上,提出了基于实测数据的UHF 频段的信道模型;给出了不同通信仰角下的信道参数,并经过最小二乘拟合,给出了信道参数全仰角下的拟合公式,使信道模型具备了一定的通用性;经过仿真运算,得到了信道的一阶和二阶特性-累计概率分布、电平交叉率和平均衰落时长,并将仿真数值与实测数据进行比较,从而验证了本文提出信道模型及相关参数的有效性。移动卫星通信系统为功率受限系统,为了增大系统容量,设计的系统链路裕度均不大,通常链路裕度仅为10dB 左右,而在移动卫星通信系统中,当移动终端工作在小仰角时,信道传输所造成的信号衰落可达到25-30dB。因此需要采用相关的通信技术以保证一定的通信QoS。本文在信道模型的基础上,完成了小仰角下移动卫星通信系统性能的改善研究。对信道编码和交织技术(时间分集技术的一种)进行了研究,在理论分析和仿真计算的基础上,提出了交织技术的关键参数-交织深度的设计标准,给出了相应的数学解析式,得到通信仰角越小,所需的最佳交织深度越大这一结论,并对卷积编码的解码深度进行了分析;通过仿真运算,得到了采用卷积编码和采用最佳深度的交织技术后对系统性能的改善。本文对星载放大器进行了分析,在经典的Saleh 非线性模型的基础上,提出了更多还原

【Abstract】 Mobile satellite communication system is a necessary part of next generation wireless communication system. Some of the key technologies such as channel model simulation, channel coding, interleaving and nonlinear effect studied in this paper, and current popular study in aviation-Aviation Mobile Satellite System has been analyzed, plus, its channel character and corresponding simulation model has been studied. Firstly, the paper has an overview of mobile satellite communication system, analyzes its character and the peculiarity compared with terrestrial wireless system. Design emphasis and difficulties of mobile satellite system has been widely analyzed. Has a brief introduction of the system channel character-time varying, multipath, shadowing and Doppler frequency. Secondly, typical channel models that have been widely accepted has been introduced, and their character analyzed; Thirdly, technologies such as channel coding and interleaving has been analyzed; Fourthly, has a brief overview of the nonlinear effect of the amplifier equipped in the satellite; At last, AMSS channel character has been analyzed, and the study emphasis been put forward. Generally speaking, this chapter deals with the analysis of current status of the world, and briefed the signification of the study of this paper. The way of colored Gaussian noise process has been put forward, and the optimum path in the simulation model been determined. Based on the Gaussian simulation, presents the simulation realization of other random processes that commonly used in channel simulation such as Rayleigh, Lognormal and Rice. The pdf resulted from the simulation model been compared with the theorization, results in verification of the validity of the simulation models. 3 commonly accepted channel model has been analyzed, New channel model at UHF presented based on C.Loo theory; The model parameters at different elevation angle provided, with polyfitting process, the equations for the parameters provided at elevation angle 15 ～80; Through simulation computation, first and second order of statistic-Cumulative density function, LCR and AFD achieved, plus, compared with the measured data, the validity of the simulation model and corresponding parameters put through in the paper has been verified. Mobile satellite system is power limited system, in order to enhance the capacity of the system, the link margin is always small, typically, about 10dB. However, when the communication terminal operates at small elevation angle, the attenuation of the signal更多还原