无线信道中信号传输的自适应调制技术

【作者】 臧道华；

【导师】 赵惠昌；

【作者基本信息】 南京理工大学 ， 通信与信息系统， 2002， 硕士

【摘要】 自适应调制技术是近几年来移动通信领域的热点。本文针对移动通信中的变速率QAM调制进行了较为深入的研究。首先，阐述了移动通信中信道的衰落特性，分别分析信道的阴影衰落、慢衰落、快衰落几种模型；接着对QAM的调制原理进行了分析，着重研究了这种调制方式的参数设置以及星座图的设计，文中示出了8QAM和16QAM的框图和波形情况。然后作者的精力转入信道的自适应方案的研究中，首先通过研究发现Nakagami衰落因子的适当调整可以近似于常见的瑞利衰落和莱斯衰落，接着研究在无线信道中采用三种不同自适应方案时的信道容量，研究表明速率的调整是增加信道容量的关键，在此基础上，着重研究了离散变速率QAM的情况，表明这种调制方案无论在频带利用率还是在系统平均误码率比其它情况提高很多。在文章的最后一节通过仿真研究了一基站和一移动终端通过上述调制方案的情况，进一步证明了这种方案的可行性。更多还原

【Abstract】 Adaptive modulation has become the subject of intensive study in recent years. This paper focus on the variable rate QAM for Mobile Radio. Firstly we introduce mobile radio fading channel variations, Shadow fading. Slow fading. Rapid fading and so on. Then we introduce the QAM schemes of modulation about the design of parameters and constellations of QAM and show the result of 8QAM and 16QAM. Afterward we switch to the study of adaptive project, above all, we find that we can alter the parameter of Nakagami fading channels to other fadings, and then we study three different adaptive projects. We then present numerical results showing that rate adaptation is the key to achieving high link spectral efficiency. Based on these advantages we analyze the performance of constant-power variable-rate M-QAM schemes for spectrally efficient data transmission over NMF channels. By introducing the adaptive modulation approach , we gain two things: 1) the error rate is kept at a constant level. 2) the achievable spectral efficiency comes within 5 dB of the Shannon capacity limit.At the last chapter , the presentation of a single base station and a single mobile scenario proved the feasibility of adaptive schemes.更多还原