Research On Dynamic Bandwidth Allocation And QoS In Broadband Wireless Multimedia Networks

The great new era of information has witnessed rapid growth in the development and deployment of wireless services, evident from the proliferation of cellular data services and the emerging wireless multimedia applications. The new generation of wireless networks is expected to eventually carry multimedia traffic, including voice, video, images, data, or combinations of these, thus makes the quality of service (QoS) guarantee essential. However, to guarantee quality of multiservices usually comes at the expense of potentially poor bandwidth utilization. It's well known that the bandwidth is extremely valuable resource in wireless networks. So an efficient bandwidth allocation scheme is urgent to balance these two conflicting requirements. This paper addresses issues of the effective bandwidth allocation policy to guarantee the quality of service (QoS) for multiple services in mobile wireless cellular networks. This thesis aims to apply dynamic and adaptive techniques to bandwidth allocation and consists of two parts. The first part concerns a dynamic and effective call admission control policy, which is belong to coarse-granularity bandwidth allocation based on call connection level, while the second part presents an intelligent bandwidth allocation scheme, which is belong to delicate-granularity bandwidth allocation based on PDU level, all for multi-services wireless cellular networks. In the first part, we apply dynamic stochastic control methods to call admission control for multi-services in wireless cellular networks. To guarantee the quality of service (QoS) for multi-services as well as achieve optimum utility of valuable bandwidth in wireless networks, an effective call admission control is urgent. Recently, the dynamic call admission mechanism was found to be more stable and precise. But, it is still hard to get an effective dynamic call admission mechanism for multi-services. The variety and complexity of traffic, the various requirements of bandwidth and QoS guarantee make it a complicated problem. Most of the relative studies cope with this problem by setting up a multiple dimensions'stochastic model with high computational complexity. In this paper, we propose some new methods to solve this problem. At first, we put forward a novel method to cope with the multi-services by setting up a fictitious stochastic model to turn the multi-dimensions stochastic processes into single-dimension one. We found a very interesting fact that the approximation of CDP is a little larger than the actual one. This fact facilitates our estimation for the acceptance ratio vector subject to QoS strict requirement. In broadband condition, the control is more precise. As a result, we get a multi-services dynamic call admission scheme called MDCA to adapt for multiple types of services in mobile wireless networks. Secondly, we study the boundary conditions impacting the control precision so as to get a more precise one. This novel study method and the fictitious stochastic model can be widely applied to many other areas with multi-dimensions birth death process. At last, we found it is enough to use a simplified stochastic states transition model to compute the key parameters, such as call dropping probability and admission probability. Although the computation is more complex than that of the MDCA, a fast numerical method has been found to decrease computational complexity and get a scheme named OMDCA steadily satisfies the hard constraints on call dropping probability for multi-services while maintaining a very high channel throughput. In the second part, we study PDU-based bandwidth allocation. The traditional methods, which allocate bandwidth according to the information of bandwidth application, are hard to avoid the allocation surplus or shortage because of delay. To overcome the shortcoming, we propose some adaptive forecast methods to improve bandwidth utility and feed back the information of bandwidth requirement by piggyback to further lower bandwidth cost. As a result, we get a high bandwidth utility while meet the multi-services QoS. In short, this paper aims to apply all kinds of adaptive technologies into bandwidth allocation. We propose some improved methods and put forward a novel stochastic model, which can be widely applied to other applications with multi-dimensions stochastic processes. Some practical control schemes are given. Numerical results of simulations show that these proposed schemes are better than the traditional schemes.