高阶QAM盲均衡技术研究及实现

发布时间：2018-05-29 18:26

本文选题：高阶QAM + 盲均衡　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：与低阶调制相比,高阶QAM调制由于其较高的频带利用率,更多地应用在高速宽带通信系统中。在实际信道上进行高速数字信号的传输时,由传输信道的带宽受限和多径效应而引起的码间串扰,会造成接收信号在幅度和相位上的失真,导致在接收端进行符号检测时产生较大的误码率,因而需要对接收信号进行均衡。而在不能提供训练序列的场景下,就必须采用盲均衡技术。在矢量信号分析系统中,随着QAM调制阶数和传输符号速率的增大,由信道引入的码间串扰将对接收信号造成更加恶劣的影响,与此同时,在接收端进行盲均衡的复杂度也会随之加大。因此,研究适用于矢量信号分析系统的高阶QAM盲均衡算法具有重要意义。本文以实现矢量信号分析系统中64QAM、256QAM的盲均衡为目标,针对是否存在载波频偏两种条件展开理论研究。首先,建立全数字调制解调系统等效基带模型,为后续研究奠定基础;然后,在不考虑载波频偏的条件下,对适用于高阶QAM调制的多模盲均衡算法及其改进算法进行深入研究和仿真分析,最终采用基于SMMA的双模式盲均衡算法作为无频偏条件下的高阶QAM盲均衡方案;接着,针对存在较大频偏的情况,在分析载波频偏、相偏对盲均衡算法的影响和对几类闭环载波恢复算法研究的基础之上,给出了两种盲均衡与载波恢复联合结构,通过仿真分析,联合结构II与联合结构I相比达到收敛需要的符号数更少,但前置的CMA均衡器达到稳态需要消耗一定的时间,进而确定适用于矢量信号分析系统的盲均衡与载波恢复联合方案。最后,在算法实现上,给出适用于矢量信号分析系统中高符号速率下高阶QAM的盲均衡与载波恢复联合实现框架。理论分析和实际数据测试表明,该方案引入的理论残差可以忽略不计,在实际300Msps符号速率下消除ISI的同时,能够实现符号速率10%范围内的频偏校正,且三种频偏测试条件下系统输出的EVM都达到了1%左右,从而验证其有效性。
[Abstract]:Compared with low order modulation, high order QAM modulation is more applied in high speed broadband communication system because of its high bandwidth utilization. When transmitting high speed digital signal on the actual channel, inter code crosstalk caused by bandwidth limitation and multipath effect of the transmission channel will result in distortion on amplitude and phase of received signal. It is necessary to equalizer the received signal, and the blind equalization technique must be adopted in the scene where the training sequence can not be provided. In the vector signal analysis system, the inter code crosstalk introduced by the channel will be butted with the increase of the QAM modulation order and the transmission symbol rate. At the same time, the complexity of blind equalization at the receiver will increase. Therefore, it is of great significance to study the high order QAM blind equalization algorithm for vector signal analysis system. This paper aims at the blind equalization of 64QAM and 256QAM in vector signal analysis system. Firstly, the equivalent baseband model of all digital modulation and demodulation system is established, which lays the foundation for the follow-up study. Then, under the condition of carrier frequency offset, the multi mode blind equalization algorithm and its improved algorithm suitable for high order QAM modulation and its improved algorithm are deeply studied and simulated. Finally, the SMMA based method is used. The double mode blind equalization algorithm is used as the high order QAM blind equalization scheme without frequency offset. Then, based on the analysis of the influence of carrier frequency offset, the phase offset to the blind equalization algorithm and the study of several closed loop carrier recovery algorithms, two kinds of blind equalization and carrier recovery joint structures are given. In comparison with the joint structure II, the number of symbols required for convergence is less than that of the joint structure I, but the pre CMA equalizer needs a certain amount of time to reach the steady state, and then the joint scheme of blind equalization and carrier recovery for vector signal analysis system is determined. Finally, the algorithm is applied to the vector signal analysis system. The blind equalization of high order QAM and carrier recovery are combined to implement the framework. Theoretical analysis and actual data test show that the theoretical residuals introduced by the scheme can be ignored and can eliminate ISI at the actual 300Msps symbol rate, and can realize the frequency offset correction in the 10% range of symbol rate, and the system is under the condition of three frequency offset tests. The output EVM reaches about 1%, so as to verify its effectiveness.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN911.5

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