宽带卫星移动通信系统上行链路传输技术研究

发布时间：2018-11-03 10:41

【摘要】：卫星通信技术具备覆盖范围大、通信距离远、频带宽、容量大、信道质量好、性能稳定及设备成本不随通信距离增加而增加等优点,能够支持用户在任何地点相互通信,是实现人们能在任何时间、任何地点与任何人通信的目标过程中必不可少的一种关键技术。本文研究卫星移动通信系统上行链路设计与实现,致力于设计一种可与地面移动通信系统兼容的卫星移动通信上行链路传输方案。首先,本文对卫星移动通信技术进行了探究。重点关注卫星通信中的多波束天线技术及数字波束形成技术,并对卫星信道的特性进行了分析。由于通信距离、大尺度衰落、小尺度衰落及多普勒效应的影响,卫星传输链路存在长延时、大损耗、高频偏等特性,地面移动通信技术无法直接应用于卫星场景。其次,本文针对卫星传输过程中的长延时特点,对卫星移动通信系统中随机接入信道的发送和接收方法进行了研究。基于地面移动通信的随机接入序列,在研究了多种扩展方法后,提出了一种基于极性扩展的随机接入序列。同时,本文对发送及检测方法进行了设计,发送端采用基于剪枝DFT的混合时频发射机,接收端采用基于降采样的频域接收机。仿真结果表明,扩展后的序列自相关能够保持单峰特性,并满足卫星通信的长延时特性,从而保证有效的随机接入。接着,本文研究了卫星移动通信系统上行链路中的信道估计方法。在传统变换域MMSE估计方法的基础上,利用卫星系统中多波束阵列天线带来的空间相关性,提出一种基于空间-频率域的二维变换域滤波方法,能够有效滤除空间域噪声,提升信道估计性能。仿真结果表明,该方法相对传统的变换域MMSE滤波方法有显著的增益,尤其在低信噪比情况下增益更为明显。最后,对本文设计的随机接入信道的发送端与接收端实现方法进行了研究。首先,对本文提出的极性扩展随机接入发送端和接收端进行了定点化,并建立定点仿真链路。仿真结果表明,与浮点链路性能相比,定点化后的链路仍能保持较好的性能。仿真完成后,对定点化后的发送和接收过程,采用Verilog进行编程并在Xilinx公司Kintex-7系列410T型号FPGA上进行了实现,实现测试结果与定点化仿真结果一致。
[Abstract]:Satellite communication technology has the advantages of wide coverage, long communication distance, wide frequency bandwidth, large capacity, good channel quality, stable performance, and the equipment cost does not increase with the increase of communication distance, so it can support users to communicate with each other at any location. It is an essential technology to achieve the goal that people can communicate with anyone at any time, anywhere. This paper studies the uplink design and implementation of satellite mobile communication system, and devotes to designing a satellite mobile communication uplink transmission scheme compatible with terrestrial mobile communication system. First of all, this paper explores the satellite mobile communication technology. The multi-beam antenna technology and digital beamforming technology in satellite communication are focused on, and the characteristics of satellite channel are analyzed. Because of the influence of communication distance, large scale fading, small scale fading and Doppler effect, the satellite transmission link has the characteristics of long delay, high loss and high frequency deviation, so the ground mobile communication technology can not be directly applied to satellite scene. Secondly, according to the characteristics of long delay in satellite transmission, the transmission and receiving methods of random access channel in satellite mobile communication system are studied in this paper. Based on the random access sequence of terrestrial mobile communication, a new random access sequence based on polarity expansion is proposed after studying various expansion methods. At the same time, the transmission and detection methods are designed. The transmitter adopts a hybrid time-frequency transmitter based on pruning DFT, and the receiver adopts a frequency-domain receiver based on down-sampling. Simulation results show that the extended sequence autocorrelation can preserve the single-peak characteristic and satisfy the long delay characteristics of satellite communication, thus ensuring effective random access. Then, the channel estimation method in the uplink of satellite mobile communication system is studied. Based on the traditional MMSE estimation method in transform domain and the spatial correlation brought by multi-beam array antenna in satellite system, a two-dimensional transform domain filtering method based on space-frequency domain is proposed, which can effectively filter noise in spatial domain. Improve channel estimation performance. The simulation results show that the proposed method has a significant gain over the conventional MMSE filter in transform domain, especially in the case of low SNR. Finally, the implementation method of the random access channel in this paper is studied. Firstly, the proposed polarity extended random access is fixed to the sender and receiver, and a fixed-point simulation link is established. The simulation results show that compared with the performance of floating-point link, the fixed-point link can still maintain better performance. After the simulation is completed, the sending and receiving process after fixed point is programmed by Verilog and implemented on the 410T FPGA of Kintex-7 series of Xilinx Company. The test results are consistent with the simulation results.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN927.23

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