水声通信中的盲均衡算法研究Word格式.docx

1、研 究 生 姓 名:李莹泽学 号:200722120132指导教师姓名、职称:茹国宝 教授学 科、专 业 名 称:通信与信息系统研 究 方 向:通信理论研究二九年四月Research on Blind Equalization Algorithm in Underwater Acoustic ChannelLi Ying Ze郑 重 声 明本人的学位论文是在导师指导下独立撰写并完成的, 学位论文没有剽窃、 抄 袭、造假等违反学术道德、学术规范和侵权行为,否则,本人愿意承担由此而产 生的法律责任和法律后果,特此郑重声明。学位论文作者（签名 :年 月 日摘 要水声信道是一种极其复杂多变的时间 -空

2、间 -频率变参信道,其频带有限,强 多径干扰, 信号起伏衰落严重, 一直是水下信息可靠高速传输的主要障碍, 因此 如何在水声信道中高速率准确地传输数据, 就成为世界性的热门课题。 信道均衡 技术是解决该问题的有效方法之一。传统的自适应均衡技术需要周期性地发送接收端已知的训练序列, 虽然提高 了数据传输的可靠性, 但是进一步减小了本己严重受限的通信带宽, 从而降低了 信道利用率, 而盲均衡具有无需训练序列的优良特性, 在特定约束条件下, 能获 得比传统自适应均衡技术更好的均衡性能。 因此, 对水声通信盲均衡理论和算法 进行分析和研究具有重要意义。论文首先概述了水声通信和盲均衡技术的背景和水声信道

3、的信道特性, 系统 地分析了盲均衡的基本理论、 算法形式以及盲均衡采用的决策指向 （DD 、 Sato 、 Godard 三种常用的 Bussgang 类盲均衡算法,强调了均衡算法的收敛性能对整体 系统的影响。然后, 在重点分析、 理论推导恒模盲均衡算法的基础上, 对传统恒模盲均衡 算法的收敛性能进行了仿真。仿真结果表明,采用大步长,能够加快收敛速度, 但同时会带来较大的稳态剩余误差; 采用小步长, 虽然减小了算法收敛后的稳态 剩余误差,但算法收敛速度过慢。最后, 为了解决收敛速度和收敛精度之间存在的矛盾, 论文将剩余误差的非 线性变换作为步长的控制因子, 建立了一种新的变步长恒模盲均衡算法。

4、 理论分 析和计算机仿真实验表明:改进算法与传统恒模盲均衡算法相比, 能够有效地加 快收敛速度, 并能收敛到更小且稳定的剩余误差, 从而降低了传输误码率, 极大 地改善了水声通信的质量。关键词 :盲均衡算法,恒模算法,剩余误差的非线性变换,变步长AbstractOne of the main obstacles to reliable underwater acoustic digital communications is considered to be Inter-Symbol Interference（ISI, which is mainly caused by multipath p

5、ropagation. Equalization technique is an effective approach to suppress ISI.Underwater acoustic channel is severely band-limited due to high absorption, and conventional adaptive equalizations, which require training sequences transmitted periodically, will reduce the usable bandwidth further. Howev

6、er blind equalization does not need the training sequence, the theory and the practice proved, blind equalization may under certain traditional, adaptive equalization technology invalid conditions, still has good performance, under specific constraint condition, it can obtain better equalization per

7、formance than traditional adaptive equalization technology. With the development of modernized underwater acoustic communication to the high speed information transmission demand, it has the vital significance that analysis and the research of blind equlization throry algorithm. The main jobs of thi

8、s thesis are as follows:First, the background and the development of the underwater acoustic communication and the blind equalization are resumptively introduced, the characteristic of the underwater acoustic channel is summarized.Second, the basic theory, algorithm form of blind equalization, the b

9、asic algorithm and convergence criterion of it are systematically analyzed. The basic theory and property of Bussgang blind equalization algorithm are described and three algorithms including Decision-Directed algorithm、 Sato algorithm、 Godard algorithm in common used of Bussgang are introduced.Fina

10、lly, CMA blind equalization algorithm of Bussgang algorithms is the emphasis. The CMA algorithm is derived and the convergence performance of traditional CMA algorithm is analyzed. Simulation results proved to show that the convergence speed is quicker, but with a larger residual error if bigger ste

11、p is adopted. In order to minimize the residual error after convergence, the smaller step should be adopted, but at the same time, the convergence speed is slow. And then, a new variable step-size CMA blind equalization algorithm is proposed in order to solve the antinomy between the convergence rat

12、e and accuracy because of using the fixed step.The new algorithm makes use of the non-linear function of error signal as the parameter to produce the new variable step size. The theoretical analysis and the simulation results proved to show that the new algorithm has improved performance of the conv

13、ergence speed and residual error than traditional CMA algorithm and can be applied in the self-adaptive blind equalization system availably.KEY WORDS: blind equalization, constant modulus algorithm, bussgang property, the non-linear function of error signal, variable step-size摘 要 . I Abstract . II 目 录 . 1 1. 绪 论 . 1 1.1. 引言 . . 1 1.2. 水声通信的发展与现状 . . 2 1.3. 盲均衡技术的发展与现状 . . 3