基于OFDM协作通信系统同步算法研究

发布时间：2018-11-26 17:34

【摘要】：正交频分复用(OFDM)技术能有效地提高数据传输速率和频谱效率,已成为下一代移动通信的关键技术。在多径环境中,协作通信技术能利用空间分集来抵抗信道衰落,提高系统性能。OFDM技术和协作通信技术的结合成为未来宽带移动通信的研究热点。本文着重研究了OFDM协作通信系统的同步问题。论文主要内容如下：首先,介绍了OFDM系统及协作通信系统关键技术的基本原理,分析了定时同步误差及载波频率误差对OFDM系统的性能影响。然后针对基于OFDM协作通信系统在放大转发和译码转发两种协议下,分析了定时同步误差及载波频率误差对系统性能的影响。然后,研究了OFDM协作通信系统的时间同步问题。首先介绍几种经典的OFDM协作通信系统的时间同步算法。在此基础上,提出了一种充分利用CAZAC序列及信道多径衰落特性的新算法。该算法在信道长度已知的情况下,在一个OFDM符号内实现多个时间偏移估计。此外,无需花费额外开销,就能同时实现多个信道估计。仿真结果表明,与经典的不同周期同步模式(UPSPs)方法相比,在任何信噪比情形下,本文算法准确性更高。最后,研究了OFDM协作通信系统联合定时和频率偏移的同步问题。设计了一种可变参数的训练符号,其中定时偏移估计可以通过相关类型的算法得到,并利用基于FFT和IFFT来降低滑动相关运算的复杂度。载波频率估计可以通过计算复杂度比较低的子空间类算法得到,通过调节训练符号的参数,能够有效的估计定时偏移和载波频率偏移。
[Abstract]:Orthogonal Frequency Division Multiplexing (OFDM), which can effectively improve the data transmission rate and spectral efficiency, has become the key technology of the next generation mobile communication. In multipath environment, cooperative communication technology can use spatial diversity to resist channel fading and improve system performance. The combination of OFDM technology and cooperative communication technology has become the research hotspot of broadband mobile communication in the future. This paper focuses on the synchronization of OFDM cooperative communication systems. The main contents of this paper are as follows: firstly, the basic principles of the key technologies of OFDM system and cooperative communication system are introduced, and the effects of timing synchronization error and carrier frequency error on the performance of OFDM system are analyzed. Then, the effects of timing synchronization error and carrier frequency error on the performance of the system are analyzed under the two protocols of amplifying and forwarding and decoding and forwarding based on OFDM cooperative communication system. Then, the time synchronization problem of OFDM cooperative communication system is studied. Firstly, several classical time synchronization algorithms for OFDM cooperative communication systems are introduced. On this basis, a new algorithm is proposed to make full use of CAZAC sequences and channel multipath fading characteristics. When the channel length is known, the algorithm realizes multiple time offset estimation in one OFDM symbol. In addition, multiple channel estimation can be realized simultaneously without additional cost. The simulation results show that the proposed algorithm is more accurate than the classical synchronization mode (UPSPs) method under any SNR. Finally, the synchronization of joint timing and frequency offset in OFDM cooperative communication system is studied. A variable parameter training symbol is designed in which the timing offset estimation can be obtained by correlation algorithm and the complexity of sliding correlation operation is reduced based on FFT and IFFT. Carrier frequency estimation can be obtained by subspace algorithms with low computational complexity. By adjusting the parameters of training symbols, the timing offset and carrier frequency offset can be estimated effectively.
【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53

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