航空信道下的OFDM信号检测技术研究

发布时间：2018-10-24 21:47

【摘要】：正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)是当今移动宽带通信的关键技术。传统的航空通信技术已经不能满足通信容量需求的迅速增长,将OFDM技术应用到航空通信系统中,可以满足航空通信系统对大容量、可靠通信的需求。本论文主要研究宽带空地无线通信系统中的OFDM信号检测与信道估计技术。在本论文的第一章中,简单的介绍了航空通信的研究背景,并重点阐述了将OFDM技术应用到航空通信系统中的必要性。深入理解航空信道是研究信号检测与信道估计技术的前提。因此在第二章讨论了航空信道的基本特性,介绍了航空信道中各种场景下的信道模型特点,并详细分析了OFDM技术应用于航空通信中的优势以及面临的高移动性问题。在高速移动的OFDM系统中,为了抑制子载波之间的干扰并降低算法复杂度,现有检测算法通常把频域信道矩阵近似为一个带状矩阵,以在保证系统性能的同时降低算法复杂度。但是这些检测算法大多没有考虑针对信道编码提供软信息输出。为此,在第三章,本论文基于带状部分最小均方误差的顺序检测均衡算法,考虑了残留干扰抵消误差的影响,提出了一种软解调算法。可有效提高输出软信息的可靠性,且算法复杂度低,易于实现。针对航空信道巡航场景的仿真结果表明:该算法可以获得较好的系统误比特率性能。可靠的信道估计是进行航空通信OFDM系统信号检测的前提。因此,本论文的第四章研究了航空信道在巡航和降落场景下的信道估计算法。在巡航场景下,由于飞机的飞行速度大,航空信道的时变性强,且多径时延大,对信道估计提出了新的挑战。本论文在现有线性模型基础上提出一种适用于巡航场景下的信道估计算法,该算法根据巡航场景下两条径的信道特性,在信道离散化后,把这两条径之间的时域信道冲激响应置零,以减少估计量数目。从而降低算法复杂度和导频开销。仿真结果表明,该信道估计算法可以获得逼近理想信道估计下的检测误比特率性能。在降落场景下,本论文采用基于变换域降噪的信道估计算法,对航空通信OFDM系统的检测性能进行了仿真研究。最后,在第五章给出了全文总结,指出了基于OFDM的航空通信系统中下一步的研究方向。
[Abstract]:Orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division Multiplexing,OFDM) is the key technology of mobile broadband communication. Traditional aeronautical communication technology can not meet the rapid growth of communication capacity. The application of OFDM technology to aviation communication system can meet the requirement of large capacity and reliable communication in aviation communication system. In this paper, OFDM signal detection and channel estimation techniques in broadband air-to-ground wireless communication systems are studied. In the first chapter of this paper, the research background of aeronautical communication is introduced briefly, and the necessity of applying OFDM technology to aeronautical communication system is emphasized. Deep understanding of aeronautical channel is the premise of signal detection and channel estimation. In the second chapter, the basic characteristics of aeronautical channel are discussed, and the characteristics of channel models in various scenarios are introduced. The advantages of OFDM technology in aviation communication and the problem of high mobility are analyzed in detail. In high speed mobile OFDM systems, in order to suppress the interference between subcarriers and reduce the complexity of the algorithm, the existing detection algorithms usually approximate the frequency-domain channel matrix to a band matrix, so as to reduce the complexity of the algorithm while ensuring the performance of the system. However, most of these detection algorithms do not consider providing soft information output for channel coding. Therefore, in chapter 3, a soft demodulation algorithm is proposed based on the sequential detection equalization algorithm of band partial minimum mean square error and considering the influence of residual interference cancellation error. It can effectively improve the reliability of output soft information, and the complexity of the algorithm is low and easy to implement. The simulation results for the aviation channel cruise scene show that the proposed algorithm can achieve better bit error rate (BER) performance. Reliable channel estimation is the premise of signal detection in aeronautical communication OFDM system. Therefore, the fourth chapter of this paper studies the channel estimation algorithm in cruise and landing scenarios. In cruising scenarios, due to the high flight speed, the time-varying of the aviation channel, and the large multipath delay, a new challenge to channel estimation is put forward. Based on the existing linear models, this paper proposes a channel estimation algorithm for cruise scenarios. According to the channel characteristics of two paths in cruise scenarios, the channel is discretized. The time-domain channel impulse response between the two paths is set to zero to reduce the number of estimators. Therefore, the algorithm complexity and pilot overhead are reduced. Simulation results show that the proposed channel estimation algorithm can obtain the detection bit error rate performance under the approximation of ideal channel estimation. In the landing scene, the performance of the OFDM system in aeronautical communication is simulated by using the channel estimation algorithm based on transform domain de-noising. Finally, in the fifth chapter, a summary is given, pointing out the next research direction of aeronautical communication system based on OFDM.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN911.23

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