And diversity is a technique of extensive use and maturation , a technique of more inexpensive investment with more improvement in wireless communication . the common diversity be classified as space diversity , polarization diversity , frequency diversity , and time diversity etc . this paper focus on implement of space diversity and polarization diversity in digital field 无线传输在自然界中存在大量不相关的多径信号,分集技术是通信中的一种广泛应用的、成熟的技术,一种用相对较低廉的投资就可以大幅度的改进无线链路性能的强有力的接收技术。
With the trend that cdma will be the dominant multi - access scheme in the new generation of wireless communication , how to apply spatial processing in cdma system has been becoming the emphasis of research in smart antenna . a proper method is space - time processing due to the space - time structure of wireless channel . beamforming can be combined with rake to form 2d rake receiver , which can effectively weaken the enhancement of mai in conventional rake receiver . however a more effective method is to use space - time filtering . these two scheme will be discussed and the structure and realization will be presented 码分多址技术逐渐成为新一代通信系统的主流多址技术,如何在码分多址系统中引入空域处理以改善系统性能是当前智能天线技术研究的重点之一.考虑到无线信道的时空二维结构特征,一种合理的实现方式是采用时空处理方法,将波束形成技术与时域分集技术相结合;另一种更有效的方法是在接收端采用时空二维联合处理,对无线信道进行时空二维均衡
In this part , the two anterior chapters mainly discuss the various basic theories used by the designing for the propagation paths of the electric wave . the theories include the computation methods for the fade and the loss of various propagation paths and obstructions , the engineering estimation methods of the flat fading and frequency selected fading , the designing methods of space diversity and frequency diversity , etc . at the same time , the special designing method of the sea - across path is discussed in detail 本文首先阐述了微波中继通信工程设计中的相关知识，其中前两章主要论述了线路设计中所用到的种种理论基础知识，包括对于各种路径情况、障碍情况的衰落与损耗的不同计算方法，平衰落与选择性衰落中断率的估算方法，天线分集和频率分集技术的理论知识和设计方法等等。
However , in practical systems , the deployment of antenna array is difficult due to the size and / or price limitation . recently a new form of space diversity , which is based on relay channel model and through users ’ help for each other , named cooperative diversity has become an atructive technology 但是由于尺寸,能量,价格等因素限制,在移动终端使用多根天线具有一定的困难,最近一种基于中继信道模型的,同时利用多个用户的互相协助而实现空间分集的技术? ?协同分集技术,成为一个新的研究热点。
It has been proven that the spread spectrum technologies have good capabilities of overcoming isi in electromagnetic wireless channel . the feasibilities of their applications to underwater acoustic channel have been analyzed , the frequency hopping technology is chosen . instead of using time - frequency diversity , convolutional coding and viterbi decoding are employed to combat signal fading , consequently the bit - rate and bit - error - rate performance of the underwater acoustic voice communication system can be balanced and controlled 由于扩频技术在抗码间干扰方面具有优良的特性，因此在分析了各种扩频技术于本研究应用的可行性之后，确定了跳频技术作为具体实现方案；在克服幅度衰落方面，选用卷积编码和维特比译码方法来替代原有的分集技术以综合调节系统的通信速率与误码性能，达到差错可控的目的。
The key technique of telemetry digital diversity receiver is diversity technique , which combines independent multi - path signal or extremely irrelevant multi - path signal at less , and improves instant snr and average snr in receiver and enhances communication quality . there are many irrelevant multi - path signal in wireless 遥测数字分集接收机一个重要关键是分集技术,分集技术是对独立的或至少是高度不相关的多径信号进行相加,从而改善接收端信号的瞬时信噪比和平均信噪比,提高通信质量。
Meanwhile , because of the characteristics of uwb , the performances of many traditional communication techniques ( such as diversity , modulation and so on ) change a lot when they are applied in the uwb communication systems , which results in the necessity of re - evaluating the performances of these techniques 同时,由于uwb技术本身的特点,很多传统通信技术(如分集技术,调制技术等)在应用于uwb系统时性能发生了改变,为此需要重新评估这些技术在uwb系统中的适用性和可靠性。
This dissertation researches on wavelet theory applied to information transmission , including cdma spreading code design , waveform coding in digital modulation , over - saturated multi - access communication , diversity techniques for multi - path fading channels , and peak - to - average power ratio ( papr ) reducing methods for the wavelet packet modulation signals , etc . 本文以子波理论为工具，较深入地研究了信道传输方面的几个问题，内容包括cdma扩展码的设计、数字基带波形成形技术、过饱和多址通信、克服衰落的分集技术和减小子波包调制信号的峰值功率/平均功率比值的方法等。
According to the channel state information ( csi ) , transmit diversity was classified into coherent transmit diversity and non - coherent transmit diversity . coherent transmit diversity usually depends on the accurate csi , which is difficult to acquire as the channel varies relatively fast . so the non - coherent transmit diversity becomes more interesting 由于相干发送分集技术依赖于对信道的准确估计，在信道处于快时变时，工程上难以实现，因此无需信道估计的非相干发送分集技术引起了学者们广泛的关注，差分发送分集就是其中十分引人注目的重要组成部分。
Because of the affection of noise and signal fading , in order to high data rate access and high quality , wireless communication need new technology to improve the link reliability and enhance the spectrum efficiency . mimo ( multiple input and multiple output ) can enhance the spectrum efficiency and increase channel capacity greatly , and reduce the multipath affection without spectrum band and power increasing . the 3th generation mobile communication wcdma is coming , with the purpose of putting mimo , stbc ( space time block coding ) , space diversity into practice of wcdma systems , in order to lay the foundation of 3g toward 4g , this dissertation has done some research under this background 在发射机和接收机使用多个天线进行数据传输的多输入多输出( mimo )技术,可以在不增加带宽和天线发送功率的条件下,成倍的提高频谱利用率,提高系统的信道容量,还可以抗多径干扰。第三代移动通信wcdma即将到来,为了将多天线技术( mimo ) ,空间分集技术,空时编码技术用到wcdma系统中去,为第三代移动通信向第四代移动通信系统平稳过渡奠定一定的基础,需要做一些理论上的研究。
