【作者】 沈文丽；

【导师】 仇佩亮； 赵民建；

【作者基本信息】 浙江大学 ， 通信与信息系统， 2009， 博士

【摘要】 人们对信息需求的增长与有限的可利用的频谱资源之间的矛盾,要求下一代的通信系统必须具有更高的频谱效率,才能满足通信容量迅速增长的需求。多输入多输出(MIMO)技术可以显著提高系统的频谱利用率、传输效率和性能。在未来无线通信系统中具有良好的应用前景。连续相位调制(CPM)模式,通过平滑符号间过渡相位来改善谱密度特性。它是一种性能优良的调制模式,是各种新型移动通信、无线电台的主要调制模式之一。本文从MIMO和CPM的基本原理出发,针对MIMO-CPM系统的几项关键技术进行了探索与创新性研究。无线信道是影响传输系统数学模型和算法设计的关键因素。基于已有的理论成果,本文给出了一种非线性相关信道模型的建模方法,从空间相关性着手,采用经典的Jakes模型来生成衰落信号并结合非线性功放的特性,提出了非线性MIMO相关衰落系数矩阵的产生方法。另一方面,本文分析了2天线正交空时编码的CPM(OST-CPM)系统的最大似然序列检测算法(MLSD)在非线性MIMO相关信道中的性能特性。信道相关性对OST-CPM系统的影响与对空时编码结合线性调制模式时的影响类似,它将导致OST-CPM系统MLSD算法的编码性能下降,但是分集增益不变,而且仍可达到满增益。当存在非线性失真时,本文采用预失真电路来补偿非线性功放对OST-CPM系统MLSD算法性能的影响。由于CPM信号的恒包络特性,非线性功放对OST-CPM系统的非相干检测算法的编码性能基本没有影响。这也是MIMO-CPM系统优于多天线结合线性调制模式系统的主要性能之一。MIMO-CPM系统的另一个关键技术是空时编译码问题。利用CPM信号的Rimoldi分解思想,本文提出了两种空时编码CPM系统的设计方法,空时编码采用Zp域上的卷积编码和空时网格编码方式。这两种联合编码的CPM系统不仅适用于RC和REC成形的全响应CPM信号,而且适用于部分响应CPM信号。通过将空时编码与CPM信号中的CPE模块联合编码设计后,系统的整体编码方式相当简单。虽然空时编码结合部分响应CPM信号的STC-2RC-CPM系统比全响应的STC-1RC-CPM性能略差,但是由于部分响应CPM信号具有更高的频谱利用率,因此在实际通信系统中具有更广的应用前景。针对OST-CPM系统,本文又提出了一种适用于RC以及REC成形的全响应CPM信号的非相干检测算法。在准静态衰落信道中,非相干检测算法的性能虽然比MLSD算法的性能略差,但是由于该算法不需要知道信道状态信息,因此具有实用价值。然而在快Rayleigh衰落信道中,当增加观察窗口长度时,非相干检测算法的性能急剧恶化,这也是该算法的应用局限。同步是通信系统接收机工作的基础。针对MIMO-CPM系统,本文提出了两种基于不同形式的训练序列的符号定时估计算法。两种符号定时同步算法均不依赖于具体的空时码型,因此适用于任意的空时编码结合CPM信号的MIMO-CPM系统,具有很强的通用性。方法二较方法一具有更简单的结构、更少的运算量、更广的应用范围以及更优的估计性能。空时网格编码CPM系统在非理想同步情况下采用方法二时的误帧率(Frame Error Rate,FER)性能下降不大。但是,当衰落速度增加时,方法二的均方误差性能逐渐下降,因此该算法不适用于快衰落的Rayleigh信道。更多还原

【Abstract】 The growth in demand for information and the limited spectrum resources of available are in the conflict. Thus the requirements of the next generation of communication systems must have higher spectrum efficiency to meet rapidly growing demand in communication capacity. MIMO (Multiple Input Multiple Output) technology can significantly improve the system spectrum efficiency, transmission efficiency and performance. In the future it will have good prospects in wireless communication systems. Continuous phase modulation (CPM) improves the properties of spectral density by smoothing the transition phase between symbols. It is a mode of good performance, and is one of the main modulation modes of a variety of new mobile communication and wireless radio. In this thesis, based on the basic principle of MIMO and CPM, a number of key technologies of MIMO-CPM systems are in-depth investigated from theoretical aspects.The impact of wireless channel is a key factor in a mathematical model and algorithm design of transmission system. Based on the existing theoretical results, the modeling method of the non-linear and correlated channel is given. It starts from the spatial correlation, and then uses the classic Jakes model to generate the fading signals in combination with the characteristics of non-linear power amplifier. A generating method of the coefficient matrix of a non-linear and correlated MIMO fading is proposed. On the other hand, the performance characteristics are analyzed, of 2- antenna orthogonal space-time coded CPM (OST-CPM) system for maximum likelihood sequence detection algorithm (MLSD) in the non-linear and corrected MIMO channel. The impact of channel correlation on the OST-CPM system is similar with that on space-time coding combined with a linear modulation mode. It will lead to performance degradation of MLSD algorithm for OST-CPM system, but have the same diversity gain, and can attain full diversity gain. When the nonlinear distortion exists, a pre-distortion circuit is applied to compensate the impact of non-linear power amplifier on the MLSD algorithm of OST-CPM systems. There is little effect of non-linear power amplifier on encoding performance of non-coherent detection algorithm for OST-CPM system, due to the characteristic of constant envelope of CPM signals. This is one of the main advantages of MIMO-CPM systems than multi-antenna systems combined with linear modulation modes.Another key technology MIMO-CPM system is the issue of space-time encoding and decoding. In this paper, two design methods of space-time coded CPM systems are proposed, based on Rimoldi decomposition of CPM signals. And the space-time coding could be Zp- domained convolutional coding and space-time trellis coding. Both the joint coded CPM systems are applicable not only to RC and REC shaped full response CPM signals, but also to partial response CPM signals. The overall encoding system could be quite simple through joint coding design of the space-time coding and CPE module of CPM signals. Although the performance of the STC-2RC-CPM system is slightly worse than that of the STC-1RC-CPM system, the STC-2RC-CPM system will have wider application prospects in the actual communication systems, due to higher spectrum efficiency of partial response CPM signals. An improved non-coherent detection algorithm for OST-CPM system is proposed, which is mainly applied to RC and REC shaped full response CPM signals. The performance of the non-coherent detection algorithm is slightly worse than that of the MLSD algorithm over quasi-static fading channels. However the non-coherent algorithm does not need to know the channel state information, it has more practical values. In fast Rayleigh fading channels, when the length of observation window increases, the performance of the non-coherent detection algorithm degrades rapidly, which is the application limitations of this algorithm.Synchronization is the basis of the receiver of communication systems. Two symbol timing estimation algorithms are proposed, based on different forms of training sequences. The two symbol timing synchronization algorithms do not depend on the specific types of space-time codes, thus it is applied to MIMO-CPM systems of any space-time coding combined with CPM signals. The second method has a simpler structure, less computational complexity, a broader range of applications and better estimation performance than the first method. The frame error rate (FER) performance of space-time trellis coded CPM (STTC-CPM) system decreases a little in case of non-ideal synchronization when the second timing algorithm is employed. However, when the fading rate increases, the mean-square error performance of the second method gradually decreased. Consequently this algorithm does not apply to the Rayleigh fast fading channels.更多还原