【摘要】：隨著全球?qū)拵б苿油ㄐ诺娘w速發(fā)展,構(gòu)建覆蓋全球的高速寬帶網(wǎng)絡(luò)具有重要的意義。地面長期演進(jìn)(Long Term Evolution,LTE)技術(shù)已經(jīng)發(fā)展成熟,能夠為用戶提供高速寬帶網(wǎng)絡(luò)服務(wù),但是在部分偏遠(yuǎn)地區(qū)還沒有部署LTE網(wǎng)絡(luò);衛(wèi)星通信系統(tǒng)可以實現(xiàn)全球覆蓋,但是目前大部分衛(wèi)星通信系統(tǒng)是窄帶通信系統(tǒng),數(shù)據(jù)傳輸速率較低。因此,將LTE技術(shù)與衛(wèi)星通信的優(yōu)勢進(jìn)行結(jié)合具有重要意義。但是,衛(wèi)星通信存在較長的傳輸時延、較大的多普勒頻移、高動態(tài)、功率放大器的非線性失真等問題,給LTE應(yīng)用于衛(wèi)星通信帶來了挑戰(zhàn)。例如,長傳輸時延導(dǎo)致相關(guān)信息的更新滯后,影響相關(guān)流程的時效性;傳統(tǒng)的頻率同步算法無法對低地球軌道(Low Earth Orbit,LEO)衛(wèi)星環(huán)境下大的多普勒頻移做出有效估計。這些問題對衛(wèi)星LTE移動通信系統(tǒng)上行鏈路帶來的影響是不可避免的,因此,研究衛(wèi)星LTE移動通信系統(tǒng)上行鏈路關(guān)鍵技術(shù)具有重要意義。本文主要對衛(wèi)星LTE移動通信系統(tǒng)上行鏈路中的隨機(jī)接入技術(shù)、頻率同步技術(shù)進(jìn)行了深入研究。首先,本文介紹了LTE應(yīng)用于衛(wèi)星通信存在的問題以及發(fā)展現(xiàn)狀,分析了衛(wèi)星LTE移動通信系統(tǒng)中隨機(jī)接入技術(shù)和頻率同步技術(shù)的國內(nèi)外研究現(xiàn)狀。其次,建立了衛(wèi)星信道模型,分析了LTE上行鏈路傳輸模型。再次,介紹了LTE隨機(jī)接入過程,以及LTE隨機(jī)接入前導(dǎo)序列的傳統(tǒng)檢測方法;針對對地靜止軌道(Geostationary Earth Orbit,GEO)衛(wèi)星環(huán)境下多用戶發(fā)起隨機(jī)接入時存在的多址干擾問題,提出了一種基于串行干擾消除(Successive Interference Cancellation,SIC)的衛(wèi)星LTE隨機(jī)接入前導(dǎo)檢測算法,該算法相對于傳統(tǒng)檢測算法,降低了漏檢概率,提高了衛(wèi)星隨機(jī)接入一次成功率。然后,針對多普勒頻移對隨機(jī)接入前導(dǎo)相關(guān)檢測的峰值大小、位置等產(chǎn)生的影響,利用這些峰值信息,本文提出了一種頻偏粗估計算法,可以實現(xiàn)地面終端初始接入衛(wèi)星時的頻偏粗估計。最后,針對LEO衛(wèi)星存在的大的多普勒頻移的問題,本文提出了一種基于多普勒特征的最大后驗概率估計算法,該算法適用于衛(wèi)星LTE上行鏈路,并且具有多普勒頻移估計范圍大、估計精度高等優(yōu)點。
[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.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN927.23

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