基于LTE的卫星移动通信上行链路关键技术研究

发布时间：2018-08-01 16:56

【摘要】：随着全球宽带移动通信的飞速发展,构建覆盖全球的高速宽带网络具有重要的意义。地面长期演进(Long Term Evolution,LTE)技术已经发展成熟,能够为用户提供高速宽带网络服务,但是在部分偏远地区还没有部署LTE网络;卫星通信系统可以实现全球覆盖,但是目前大部分卫星通信系统是窄带通信系统,数据传输速率较低。因此,将LTE技术与卫星通信的优势进行结合具有重要意义。但是,卫星通信存在较长的传输时延、较大的多普勒频移、高动态、功率放大器的非线性失真等问题,给LTE应用于卫星通信带来了挑战。例如,长传输时延导致相关信息的更新滞后,影响相关流程的时效性;传统的频率同步算法无法对低地球轨道(Low Earth Orbit,LEO)卫星环境下大的多普勒频移做出有效估计。这些问题对卫星LTE移动通信系统上行链路带来的影响是不可避免的,因此,研究卫星LTE移动通信系统上行链路关键技术具有重要意义。本文主要对卫星LTE移动通信系统上行链路中的随机接入技术、频率同步技术进行了深入研究。首先,本文介绍了LTE应用于卫星通信存在的问题以及发展现状,分析了卫星LTE移动通信系统中随机接入技术和频率同步技术的国内外研究现状。其次,建立了卫星信道模型,分析了LTE上行链路传输模型。再次,介绍了LTE随机接入过程,以及LTE随机接入前导序列的传统检测方法;针对对地静止轨道(Geostationary Earth Orbit,GEO)卫星环境下多用户发起随机接入时存在的多址干扰问题,提出了一种基于串行干扰消除(Successive Interference Cancellation,SIC)的卫星LTE随机接入前导检测算法,该算法相对于传统检测算法,降低了漏检概率,提高了卫星随机接入一次成功率。然后,针对多普勒频移对随机接入前导相关检测的峰值大小、位置等产生的影响,利用这些峰值信息,本文提出了一种频偏粗估计算法,可以实现地面终端初始接入卫星时的频偏粗估计。最后,针对LEO卫星存在的大的多普勒频移的问题,本文提出了一种基于多普勒特征的最大后验概率估计算法,该算法适用于卫星LTE上行链路,并且具有多普勒频移估计范围大、估计精度高等优点。
[Abstract]:With the rapid development of global broadband mobile communication, it is of great significance to construct a high-speed broadband network covering the world. The long-term evolution of terrestrial (Long Term evolution technology has been developed to provide users with high-speed broadband network services, but in some remote areas have not been deployed LTE network; satellite communication systems can achieve global coverage, However, most satellite communication systems are narrowband communication systems, and the data transmission rate is low. Therefore, it is of great significance to combine LTE technology with the advantages of satellite communication. However, there are many problems in satellite communication, such as long transmission delay, large Doppler frequency shift, high dynamic, nonlinear distortion of power amplifier and so on, which brings challenges to the application of LTE in satellite communication. For example, the long transmission delay leads to the update delay of the related information, which affects the timeliness of the related process. The traditional frequency synchronization algorithm can not effectively estimate the large Doppler frequency shift in the low Earth orbit (Low Earth Orbit-Leo) satellite environment. The influence of these problems on the uplink of satellite LTE mobile communication system is inevitable. Therefore, it is of great significance to study the key technologies of satellite LTE mobile communication system uplink. In this paper, the random access technology and frequency synchronization technology in the uplink of satellite LTE mobile communication system are studied. Firstly, this paper introduces the existing problems and development status of LTE application in satellite communication, and analyzes the research status of random access technology and frequency synchronization technology in satellite LTE mobile communication system at home and abroad. Secondly, the satellite channel model is established and the LTE uplink transmission model is analyzed. Thirdly, the process of LTE random access and the traditional detection method of LTE random access preamble are introduced, and the problem of multiple access interference (mai) when launching random access to geostationary orbit (Geostationary Earth Orbit-geo) satellite environment is discussed. A pilot detection algorithm for satellite LTE random access based on serial interference cancellation (Successive Interference cancellation (sic) is proposed. Compared with the traditional detection algorithm, this algorithm reduces the probability of missing detection and improves the primary success rate of satellite random access. Then, in view of the influence of Doppler frequency shift on the peak value and position of random access preamble correlation detection, this paper proposes a method to calculate the frequency offset by using these peak information. The coarse estimation of frequency offset can be realized when the ground terminal is initially connected to the satellite. Finally, aiming at the problem of large Doppler frequency shift in LEO satellite, this paper proposes a maximum posterior probability estimation algorithm based on Doppler characteristics. This algorithm is suitable for satellite LTE uplink and has a wide range of Doppler frequency shift estimation. High estimation accuracy and other advantages.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN927.23

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