无线网络中的分布式机会信道接入研究

发布时间：2018-10-10 15:58

【摘要】：随着当今无线通信与移动互联网产业的蓬勃发展,高速数据传输成了未来通信业务发展的一个核心方向。然而,由于可用的频谱资源日益紧缺,导致了高速数据传输技术的研究面临瓶颈。因此,如何更合理地分配以及更有效地利用现有的频谱资源,成为解决频谱资源紧缺的一个突破口。在这种情形下,一种能够有效地提高频谱资源利用率的机会式信道接入技术应运而生。机会式信道接入是一种结合PHY层和MAC层的跨层信道接入协议,在进行信道接入决策时,系统根据信道状态的好坏决定是否接入信道。在集中式网络中,中心控制节点能够获取全局状态信息,因此机会信道接入对集中式网络尤其适用,并且基于该领域的研究也取得了很多成果。然而,由于分布式网络中不存在中心控制节点,机会信道接入在这种特定网络下的研究还处于初步发展阶段。基于上述认识,本文将此方向作为研究重点。本文的主要工作及贡献如下:1.研究了连续传输速率下DF中继网络中的分布式机会信道接入。连续传输速率是指系统采用信道所能提供的最大速率进行传输。在最优停止理论的指导下,以最大化系统平均吞吐率为目标,首先给出了需要获取DF两跳信道信息的完全信道接入策略。由于DF中继网络中系统的总体信噪比由两跳中较小的决定,又提出了只需获取第一跳信道信息即可进行决策的部分信道接入策略。相较于完全信道接入策略,该策略可以节约信道探测时间,进而改善系统性能。为了更充分地利用时间分集所提供的性能增益,又研究了在多个信道相干时间内传输的中继等待策略。根据部分信道接入策略与中继等待策略的特点,提出了结合各自优势的混合双层信道接入策略。上述四种策略均为在实际应用中简单易行的纯门限策略,门限由快速收敛且计算复杂度较低的迭代算法得出。仿真结果分析了策略之间的性能增益,并证明了所提理论算法的可靠性。2.在固定中继与非固定中继两种场景下,研究了离散传输速率下DF中继网络中的分布式机会信道接入。离散传输速率是指系统采用特定的离散传输速率集内的元素进行传输。由于离散传输速率的特有结构,最优接入策略的求解与在连续传输速率下的求解存在较大差异。此外,连续传输速率下非固定中继系统的机会信道接入研究面临一定困难,因此,离散速率下非固定中继系统的研究成果对连续速率下的相关研究具有重要的启示意义。在固定中继DF协作网络中,首先提出了离散传输速率下的完全信道与部分信道接入策略。随后,利用离散传输速率的特性,提出了对系统性能有重大改善的增强型中继等待策略。最后研究了结合部分信道接入策略与增强型中继等待策略的增强型混合双层信道接入策略。在非固定中继DF协作网络中,分别提出了离散传输速率下的完全信道接入策略、部分信道接入策略以及增强型中继等待策略。上述各项策略均为计算复杂度较低的纯门限法则。仿真结果体现了上述各项策略之间的性能增益,并验证了所提理论算法的可靠性。3.研究了引入队列状态信息后,队列稳定约束下Ad-hoc网络中的分布式机会信道接入。首先给出了充分数据下的信道接入策略,随后提出了实际传输数据下的信道接入策略。为了更进一步保证队列的稳定性,又提出基于Lyapunov算法的信道接入策略。该策略将结合信道信息与队列信息的信道接入建模为一个约束优化模型,利用Lyapunov优化理论将其转化为一个无约束优化问题,并采用最优停止理论对其进行求解。最后,提出了实际传输数据下基于Lyapunov算法的信道接入策略,该策略通过将实际传输数据引入目标函数,使得系统平均吞吐率与队列稳定性均得到了进一步提高。以上各项策略均遵循纯门限法则。仿真结果有效地验证了所提策略的可靠性。
[Abstract]:With the rapid development of wireless communication and mobile Internet industry, high-speed data transmission becomes a core direction of future communication service development. However, due to the shortage of available spectrum resources, the research of high-speed data transmission technology is facing the bottleneck. Therefore, how to allocate more reasonably and effectively utilize the existing spectrum resources becomes a breakthrough to solve the shortage of spectrum resources. In this case, an opportunistic channel access technology that can efficiently improve the utilization of spectrum resources has emerged. opportunistic channel access is a cross-layer channel access protocol that combines the phy layer and the mac layer and determines whether to access the channel according to the quality of the channel state when the channel access decision is made. In a centralized network, the central control node is able to acquire global status information, so opportunistic channel access is particularly applicable to a centralized network, and a number of results have been achieved based on the research in this field. However, due to the absence of a central control node in the distributed network, the research of opportunistic channel access under this particular network is still at a preliminary stage of development. Based on the above knowledge, this paper focuses on this orientation. The main work and contribution of this paper are as follows: 1. Distributed opportunistic channel access in DF relay network under continuous transmission rate is studied. The continuous transmission rate refers to the maximum rate that the system can provide with a channel. Under the guidance of the optimal stopping theory to maximize the average throughput rate of the system, the complete channel access strategy for obtaining the DF two-hop channel information is given. because the overall signal-to-noise ratio of the system in the DF relay network is determined by a small decision in two hops, a partial channel access strategy of decision-making only needs to be obtained by acquiring the first hop channel information. Compared with the full-channel access strategy, the strategy can save the channel detection time and improve the performance of the system. In order to sufficiently utilize the performance gain provided by the time diversity set, a relay latency strategy for transmission over a plurality of channel coherence times is also investigated. According to the characteristics of partial channel access strategy and relay waiting strategy, a hybrid double-layer channel access strategy combining the advantages is proposed. The above four strategies are pure threshold strategy which is simple and feasible in practical application, and the threshold is obtained by iterative algorithm with fast convergence and lower computational complexity. The simulation results show the performance gain between the strategies and prove the reliability of the proposed algorithm. Distributed opportunistic channel access in DF relay network at discrete transmission rate is studied in two scenarios of fixed relay and non-fixed relay. A discrete transmission rate means that the system uses elements within a particular set of discrete transmission rates for transmission. Due to the unique structure of the discrete transmission rate, the solution of the optimal access strategy and the solution of the continuous transmission rate differ greatly. In addition, the research on opportunistic channel access of non-fixed relay system at continuous transmission rate is confronted with some difficulties. Therefore, the research results of the non-fixed relay system at discrete rate are of great significance to relevant research at continuous rate. In the fixed relay DF cooperative network, the complete channel and partial channel access strategy under the discrete transmission rate are first proposed. Then, using the characteristics of the discrete transmission rate, an enhanced relay waiting strategy with significant improvement on the performance of the system is proposed. Finally, the enhanced hybrid double-layer channel access strategy combining partial channel access policy and enhanced relay waiting strategy is studied. In the non-fixed relay DF cooperative network, the complete channel access strategy, partial channel access strategy and enhanced relay waiting strategy under the discrete transmission rate are presented. All these strategies are pure threshold rules with lower computational complexity. The simulation results show the performance gain between the above strategies, and verify the reliability of the proposed algorithm. Distributed opportunistic channel access in Ad-hoc networks is constrained by queue stability after introducing queue status information. Firstly, the channel access strategy under sufficient data is given, and then the channel access strategy under actual transmission data is proposed. In order to further ensure the stability of the queue, a channel access strategy based on Lyapunov algorithm is proposed. The strategy combines channel information and channel access of queue information into a constrained optimization model, transforms it into an unconstrained optimization problem by using Lyapunov optimization theory, and solves the problem by using the optimal stopping theory. Finally, we propose a channel access strategy based on Lyapunov algorithm under actual transmission data, which introduces the actual transmission data into the target function, so that the average throughput rate and queue stability of the system are further improved. All the above strategies comply with the rules of pure threshold. The simulation result effectively verifies the reliability of the proposed strategy.
【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN92

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