【作者】 刘威鑫；

【导师】 李少谦；

【作者基本信息】 电子科技大学 ， 通信与信息系统， 2007， 博士

【摘要】 在无线移动通信系统中,空间、时间和频率的随机波动将使无线信道中的信号受到损害。分集技术则是一个对抗衰落的强有力的技术。空间或多天线分集技术由于可以与其它如时间分集,频率分集技术相结合,并在其基础上提供很大的性能增益,而成为一种很有吸引力的技术。空间分集技术的一种传统的应用技术是通过天线阵列实现,并在3G,Beyond 3G等系统中得到研究和应用,如:MIMO技术。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。最近利用用户间协同、中继协同、天线间协同等方式提出的协同分集技术给出了一种全新的解决方案。其原理是各用户通过分布式传输和处理,分享他们的天线和其它资源从而形成一个虚拟阵列,构成虚拟MIMO系统。本文根据协同分集技术中急需解决的协同策略问题进行了研究。本文主要安排如下:第一部分首先分析协同分集的特点以及协同分集的研究现状,总结了需要进一步解决的问题。本文的第二部分给出了协同分集的基本策略AF和DF的理论研究。详细研究了AF与DF协同分集实现方式和性能,并进行了理论分析和仿真。并对AF模式和DF模式进行了深入的比较。并与相关的MIMO技术进行了相对应的比较。针对DF模式,研究DF协同分集模式下在中继节点是否需要CRC校验的问题,并对其在DF模式下中继节点带CRC和不带CRC的情况进行了理论分析。针对AF的功率分配问题,综合考虑所有信道和噪声功率,提出了把发送端MRC与接收端MRC联合考虑的功率分配优化方法。针对频率选择性衰落信道。本文在第三部分提出了多载波协同分集。提出了差分正交频分复用协同分集系统,把协同分集与差分OFDM相融合,并对此性能进行了分析。基于速度和距离的协同伙伴选择问题是一个重要问题,提出了以BER为尺度的协同伙伴选择方法并应用到V2V的系统中。针对日益增多的多媒体通信系统,本文在第四部分提出了一种新的分布式协同图像通信策略,仅仅传输经过DCT变换后重组的重要部分数据,这样以性能的微小牺牲为代价换取能量和频带的节约。在协同分集网络中,协同伙伴的选择从来就是一个非常关键的问题。以前关于这个问题的解决方案本质上是基于收发的性能而忽略了协同伙伴选择的公平性。本文最后针对协同分集系统的公平性问题,提出了一种通过跨层设计来趋向公平性的新策略。能够在性能,公平性和节点寿命方差之间达到动态平衡,从而利于整个网络的公平。更多还原

【Abstract】 In wireless communication systems, the signal of wireless channel is impaired by the random fluctuations across space, time and frequency. The diversity is a powerful technology to combat the fading. Space or multi-antenna diversity techniques are particularly attractive as they can be readily combined with other forms of diversity, e.g., time and frequency diversity, and still offer dramatic performance gains under these bases. One of the traditional technologies of space diversity is antenna array, which is studied and utilized in 3G and beyond 3G systems , e.g., MIMO (Multiple Input Multiple Output). Due to the size, energy, cost limitations, the deployment of antenna array is difficult to realize. Recently a brand-new solution scheme is put forward basing on the user cooperation, relay cooperation, or antennas cooperation etc. which is called cooperative diversity technology. The essence of this technology is that users in a group sharing their antennas and resource through distributed process and transmition to form a "virtual array", forming the virtual MIMO system. This dissertation develops the research according the schemes starved for the solution to cooperative diversity.The characteristic of cooperative diversity is introduced at first in this dissertation and the current research situation is present . Some questions need to be further solved are summarized.The basic two schemes of cooperative diversity, AF (Amplify-and-Foreword) and DF (Decode-and-Forward) are studied deeply at the second part of this dissertation. The performance and realization are studied in detail. Also the theoretic analyses and simulations are presented .The comparison between AF and DF is list deeply . Also comparisons between AF and some other corresponding MIMO technologies are done. Aiming the DF model, the analysis is given about the relay nodes with CRC (Cyclic Redundancy Check) and without CRC . About the power allocation of AF model, the method of combining the transmit-MRC and MRC at the receiver is put forward to allocate the power jointly.Aiming the frequency selective fading channel, the multi-carrier cooperative diversity is put forward. The system of cooperative differential detection OFDM (Orthogonal Frequency Division Multiplexing), combining the differential detection OFDM and the cooperative diversity, is put forward. Also the performance is analyzed. The selection of cooperative partner based velocity and distance is a key problem. The method of partner selection based on BER is discussed and used into the V2V system.Aiming the increasing of the communication of multimedia, a new distributed scheme is put forward. Only the main part through DCT and recombined is transmitted cooperatively, at the little performance cost, the energy and the frequency band are saved.In the cooperative network, the selection of cooperative partner is a very key problem all along. All the former solutions to this problem in essence base on the performance of the transceiver while neglecting the fairness among the cooperative partners. In the end, a new scheme through cross layer design to obtain the dynamic balance among the performance, the fairness and the lifetime of the network. So it is advantage of the fairness of the network.更多还原