Research On Resource Allocation And Spectrum Access In Wireless Networks

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.