【作者】 陈杰；

【导师】 李式巨； 赵民建；

【作者基本信息】 浙江大学 ， 通信与信息系统， 2008， 博士

【摘要】 随着通信技术的飞速发展、IC产业的不断进步以及Internet的广泛普及,随时随地向任何用户提供任意方式的可靠的个性化服务成为无线网络发展的目标。无线信道的传输特性以及频谱资源的稀缺性与高速高服务质量的网络业务需求之间的矛盾对无线资源管理问题提出了新的挑战。本文以无线网络为背景,利用跨层设计的思想和认知无线电技术,研究了无线网络中的资源分配问题及频谱接入问题,并在以下的四个方面进行了深入地研究:为了在无线蜂窝网络中向各个上行及下行链路上具有不同速率以及延时要求的多条数据连接提供QoS保障,节约网络中总的传输能耗,并获取多用户分集增益,本文研究了集中式的资源分配问题,并利用跨层设计思想,提出了一套面向连接的资源分配与QoS保障联合算法。上述目标被建模为接入控制,速率分配以及资源分配这三个子问题。来自物理层的信道状态信息,来自媒体接入控制层的队列状态信息,来自应用层的速率及延时请求信息在系统模型中得到了综合地考虑。子问题可以分别通过贪婪算法及凸规划算法顺序地进行求解,从而得出每条数据连接上最优的传输时隙及功率分配结果。与层次式网络协议栈中的资源分配算法相比,该算法能够更加有效地利用网络资源。为了在点到多点(Point to Multi-Point,PMP)结构的认知无线网络中,维持各个节点的传输频率同步,本文基于POMDP模型提出了一种公共信道维护算法(Common Communication Channel Maintenance Algorithm,CCCMA)。该算法可以利用前面各个时隙中的频谱感知过程以及数据传输过程所获得的信息,来指导当前时隙的频谱接入过程,从而在较小的硬件开销下获得较高的频谱利用率。在此基础上,为了将上述的集中式资源分配算法引入到认知网络中,本文还提出了一种基于跨层设计思想的联合频谱接入及资源分配协议框架(Joint Spectrum Access andResource Allocation,JSARA)。利用JSARA协议框架,可以在信道占用情况变化较快的认知环境中,以较小的协议开销为中心式架构的认知网络提供良好的QoS保障。为了将认知无线电技术引入到当前已经存在的无线网络中,本文提出了一种混合拓扑的认知无线电网络架构。基于该架构还研究了提升网络吞吐量的方法,建立了以最大化网络中同时传输链路个数为目标的规划问题,并提出了一种次优的信道、传输模式及传输功率联合分配算法(Joint Channel,Mode and Power AllocationAlgorithm,JCMPA)来对该问题进行快速求解。本文所提出的混合拓扑的网络架构是一种以较低的硬件成本将认知无线电技术引入现有无线网络的有效解决方案,而JCMPA算法则可以充分发挥中心式认知网络的复用程度,提高频谱的使用效率。为了在分布式认知无线网络中提供有效的频谱接入机制,并提高网络的整体性能,本文提出了一种分布式的信道接入算法(Distributed Spectrum AccessAlgorithm for Cognitive Wireless Network,DSAC),并给出了与之相匹配的MAC协议(DSACM)。本文以最优化网络的效用值为目标,以各个认知节点的接入概率作为求解对象,建立了一个通用的凸规划模型,并利用分布式的DSAC算法对目标问题进行了求解。而DSACM协议则能够有效地支持DSAC算法的运行,同时还能够克服多信道场景中的隐终端问题。与普通的DCF算法相比,DSAC算法可以有效地提高网络中同时传输的链路个数,从而提高了信道利用率以及网络吞吐量。更多还原

【Abstract】 With the rapid development of wireless communication technologies and integrated circuit (IC) industry as well as the widespread application of Internet, providing reliable service for any user at any time and any where has become one of the most important objectives of wireless networks. It is challenging to manage the wireless resource efficiently as there is a contradiction between the demands for high rate high quality wireless service and the characteristics of wireless channel as well as the sparsity of spectrum resource. In this dissertation, the problems of resource allocation and spectrum access in wireless networks are intensively studied based on cross-layer design and cognitive radio. The contents of this work are listed as follows:In order to provide quality of service (QoS) guarantee for the connections with different rate and delay requirements on both uplinks and downlinks in cellular networks, the problem of resource allocation is studied. Saving the total energy cost and realizing the multi-user diversity are also considered. A cross-layer design based algorithm is proposed. The objectives are formulated as an admission control problem, a rate allocation problem and a resource allocation problem. The channel status from the physical layer, the queuing status from the MAC layer as well as the rate and delay requirements from the application layer are considered comprehensively. The problems can be solved by greedy algorithm and convex optimization algorithm sequentially. Compared with the algorithms in layered protocol scheme, the proposed algorithm can make efficient use of the resources in the wireless networks.In order to maintain the frequency synchronization among the users in point to multipoint (PMP) networks, a common communication channel maintenance algorithm (CC-CMA) is proposed based on partially observable Markov decision process (POMDP). CC-CMA makes full use of the spectrum sensing results and transmission results in previous time slots and controls the sensing process in current slot. CCCMA can acquire high spectrum efficiency with lower hardware costs. A joint spectrum access and resource allocation (JSARA) scheme is also proposed to introduce the cross-layer design based algorithm into the cognitive radio network. JSARA scheme can provide QoS guarantee to cognitive users in PMP networks with fewer protocol overhead even in the environment with rapid changes of spectrum opportunities.In order to introduce cognitive radio technology into current PMP networks with lower hardware costs, a hybrid topology network framework is proposed. Based on this framework, an optimization model is formulated to maximize the total link number in the network so as to increase the network throughput. Power allocation, mode selection and channel allocation problems are considered together in this model. The model is transformed into a integer programming problem and can be solved by a joint channel, mode and power allocation algorithm (JCMPA). JCMPA can allocate the channels, modes and transmission power efficiently as well as improve the reusable degree of the network.In order to make efficient use of the spectrum in distributed cognitive wireless networks, a distributed spectrum access algorithm for cognitive wireless networks (DSAC) is proposed. The corresponding media access control (MAC) protocol DSACM is also given in this part. A general convex programming problem is formulated to optimize the performance of the network, and DSAC can solve the problem efficiently. Meanwhile, DSACM can support the overcome the multi-channel hidden terminal problem in distributed cognitive wireless networks as well as improve the performance of the network. Compared to normal distributed coordination function (DCF), DSAC can improve the performance of distributed wireless networks efficiently.更多还原