协作通信中的双向中继系统增强技术研究

发布时间：2018-06-16 17:53

本文选题：双向中继 + 放大转发　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：随着移动通信的高速发展,人们对数据速率和服务质量的要求也越来越高。然而,由于传统的无线通信技术的限制,人们的通信体验并没有得到很好地满足。为了解决这种突出的矛盾,通信领域的专家们一直在探寻并不断提出了许多高效的通信技术用以改善用户体验,如OFDM技术、MIMO技术、协作中继技术等等。其中,中继技术因具有扩大小区覆盖范围、提高系统容量、改善小区边缘用户性能等诸多优点,受到了人们的广泛关注。协作中继技术分为单向和双向两类。与单向中继技术相比,双向中继具有更高的频谱效率,因而具有更强的实用价值。因此,本文即以双向AF中继通信系统为研究背景,先后深入研究了单天线场景下的机会中继选择机制和多天线场景下的OSTBC(正交空时分组码)传输方案。本文的主要工作体现在以下两点:1.针对单天线双向多中继场景,为了提升系统性能,以最小化系统中断概率为优化目标,首先介绍了典型的基于最大最小准则的集中式中继选择算法。研究表明,该算法是一种中断最优的中继选择算法。为了降低算法复杂度,随后介绍了一种简单的分布式中继选择算法,该算法是一种次最优算法,在保证较高系统性能的同时降低了实现复杂度。考虑到实际系统中存在信道估计误差和反馈时延等因素,非理想CSI(信道状态信息)会对系统性能产生较大影响。因此,文中分析了非理想CSI条件下系统性能,给出了中断概率闭合表达式,最后仿真并分析了非理想CSI对中继选择机制的影响。2.针对多天线双向中继系统中的正交空时分组码传输方案进行了研究。首先通过介绍单天线双向中继平均和速率的上下界,分析了双向中继和速率性能的改善情况。在此基础上,针对两源节点均配备双天线并采用Alamouti OSTBC传输方案、中继只配备单天线并采用放大转发协议的双向中继场景,文中分析了该方案的平均和速率上下界以及PEP(成对错误概率)上界,同时给出了两种双向中继方案的最优功率分配。研究结果表明,双向中继能极大地减少传统单向中继的频谱效率损失,与单天线情况相比,OSTBC方案能获得更高的和速率,并且能够获得2阶分集阶数。接下来,对以上讨论的Alamouti空时码传输方案进行了推广,扩展到双向中继系统中源节点和中继节点具有任意天线数时如何使用正交空时分组码进行通信,并对该模型下的误符号率性能进行了理论分析,最后的仿真结果验证了理论分析的正确性。
[Abstract]:With the rapid development of mobile communication, the demand of data rate and quality of service is becoming higher and higher. However, due to the limitation of traditional wireless communication technology, people's communication experience is not well satisfied. In order to solve this outstanding contradiction, communication experts have been exploring and proposing many efficient communication technologies to improve the user experience, such as OFDM technology, MIMO technology, cooperative relay technology and so on. Among them, relay technology has attracted wide attention because of its advantages such as expanding the coverage of the cell, increasing the system capacity and improving the performance of the edge users of the cell. Cooperative relay technology can be divided into two categories: one-way and two-way. Compared with one-way relay technology, bidirectional relay has higher spectral efficiency and more practical value. Therefore, based on the bidirectional AF relay communication system, this paper has studied the opportunity relay selection mechanism in single antenna scene and the OSTBC (orthogonal space-time block code) transmission scheme in multi-antenna scene. The main work of this paper is reflected in the following two points: 1. In order to improve system performance and minimize system outage probability, a typical centralized relay selection algorithm based on maximum-minimization criterion is introduced for single-antenna bidirectional multi-relay scenarios. The research shows that this algorithm is an optimal relay selection algorithm with interrupt. In order to reduce the complexity of the algorithm, a simple distributed relay selection algorithm is introduced, which is a sub-optimal algorithm, which can reduce the implementation complexity while ensuring high system performance. Considering that the channel estimation error and feedback delay exist in the real system, the non-ideal CSI (channel state information) will have a great impact on the performance of the system. Therefore, the system performance under the condition of non-ideal CSI is analyzed, and the closure expression of interrupt probability is given. Finally, the influence of non-ideal CSI on relay selection mechanism is simulated and analyzed. The transmission scheme of orthogonal space-time block codes in multi-antenna bidirectional relay system is studied. Firstly, by introducing the upper and lower bounds of the average and rate of bidirectional relay with single antenna, the improvement of the performance of bidirectional relay and rate is analyzed. On this basis, the two source nodes are equipped with two antennas and adopt Alamouti OSTBC transmission scheme. The relay is only equipped with a single antenna and adopts the amplification and forwarding protocol in the bidirectional relay scene. In this paper, the upper and lower bounds of average and rate and the upper bound of PEP (pairwise error probability) are analyzed, and the optimal power allocation for two bidirectional relay schemes is given. The results show that bidirectional relay can greatly reduce the loss of spectrum efficiency of traditional one-way relay. Compared with single antenna, OSTBC scheme can obtain higher sum rate, and can obtain the second order diversity order. Then, the Alamouti space-time code transmission scheme discussed above is extended to how to communicate with orthogonal space-time block code when the source node and relay node have any number of antennas in the two-way relay system. The performance of symbol error rate in this model is analyzed theoretically, and the simulation results verify the correctness of the theoretical analysis.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.5

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