Research On Key Techniques Of Radio Resource Allocation In Relay-enhanced Cellular Networks

Wireless Local Area Network(WLAN) has been gaining its popularity extensively nowadays. On the one hand, its transmission rate has sped up dramatically which has exceeded 1Gbps. On the other hand, the requirements of transmission service have been trending toward a diverse development. Considering the status quo that it is converging with network such as 3G network and that disadvantages of the single-channel access method in traditional WLAN’s MAC layer are emerging, a more optimal channel access method should be designed to adapt to the current development of WLAN.In this paper, single-channel access and hybrid channel access in WLAN are analyzed, pointing out that traditional competition access method cannot provide the high Qo S required by multimedia services, and the performance of the method that is based on competition and collision resolution drops as transmission rate increases; although traditional centralized scheduling access can meet the Qo S required by real-time services, it is not able to handle the access of bursty service flexibly. Researches that combine competition access and scheduling access has been increasingly active, but these researches were primarily conducted via software simulation, and lacked the theoretical support of questions such as the way to optimize the performance of networks.In this paper, a centralized scheduling access method combined with some ingredient of competition is mainly researched and it is established based on the research status quo of WLAN access methods. The method in this paper allocates the channel resources by central controlled way which allows some of resources are accessed by competition and others are accessed by centralized scheduling. The ratio of contention and contention free period which needs to be solved in the design and implementation of the method are also raised and analyzed in this paper. By analyzing the theoretical analysis model of different access methods, the mathematical analysis model of a typical centralized scheduling access method combined with competition is established on top of it, and by using the feedbacks of two network performance parameters: throughput and access delay, the relation between the hybrid ratio of competition and centralized scheduling and the network load, by which can be used to optimize the performance of network, is obtained, and then the dynamical adjustment scheme for changing the hybrid ration is put forward, along with the simulation that compares the scheme in this paper and schemes already existed. Therefore, this paper lays a foundation for further research of optimizing the hybrid access method based on competition centralized scheduling access method in WLAN.