Research On The Dynimic Mechanism Of QoS In Broadband Wireless Access Network

Contradictions of scarcity and fluctuation of wireless resource and the requirement of QoS lead to dynamic mechanism of QoS in broadband wireless access network. The Dynamic mechanism is studied in this paper, which is consisted of the cross-layer framework of QoS, the optimal mapping of QoS parameters in link-independent layer, the cross-layer mapping of QoS parameters in the link-dependent layer and dynamic admission control. The realization of that dynamic mechanism is studied from the three aspcets—the whole cnfinguration and the QoS mapping as well as the crucial control in these five parts,respectively.1,The framework of QoS layered by the link-independent layer, the interface of link-independent layer to the service and link-dependent layer is presented to surpport the optimal or cross-layer stratage.In the interface,the virtual queen identity and its resource manager shield the information of the wire-less link so that it need not be considered in the link-independent layer.In the link-independent layer, a comman optical algorithm for QoS mapping based the general interface is given out to overcome the scarcity of wireless resource.In the link-dependent layer,the QoS manage structure of te link and physics layer and its functional moduels as well as the iteraction mechnical are defined to suport the cross-layer design between physics and link layer and the realization of dynamic control The simulation results show this framework outperform the layered one of the OSI. 2,The optimal mapping in the link-independent layer is addressed.The optimal muitiple line mapping between the user layer and the applying layer based on maximum likelihood decision of the statistical theory is presented to minimize the mapping error.The algorithm combining the best-quality-guarantee mapping with the moduel mapping is presented in appling layer to the IP layer,which can not only realize the best quality of service but also each packet.In the optimal mapping of the IP layer to the link layer, the dual optimal bandwidth allocation combining the highest efficiency algorithm for the sevice class and the laest error aigorithm for the bandwidth is presented. The simulation results show that these optimal algorithm enhance the quality of the service and the efficiency of the network.3,The AMC/ARQ cross-layer design and QoS mapping is suggested. The finite state Markov channel model(FSMM) based on the same time of the state of the subcarrier of the OFDM signal is build up as the base of that at first and it can support the AMC/AQ that the FSMM based on the amplitude can't be used for.As the the results,the biggest frequency spectrum efficiency under the gurentee of the service is obtained. And then the futher improment on the AMC/ARQ of subcarrier of the OFDM aiming at its sensitivity to the vehicles based on FSMM and the QoS mapping are made,which result in the adapth of the AMC/ARQ to the vehicle. To use the design for the mapping,the loss ration and the delay of the paccket is addressed.The simulation results show that our optimal statage this design rsiae the through rate and low the bit error ratio greatly.4,The dynamic admission control is presented in some wide bandth access wirlees networks. In EDCA of the IEEE802.11e,the dynamic characteristics of the channel and service is tracked by adaptively allocation of bits in the subcarrier of OFDM and updating the granting bandwidth.The increasment of the efficiency of the system under the guarantee of the service is obtained by the improvement on the measurement of the control variables and the computation of the network model in the semi-model and center-asisted admission control per flow.All that is showed by the simulation.In HCCA of the IEEE802.11e,the optimization of the physical resources obtained by allocation of the bits in the subcarrier of OFDM.The effective TXOP is presented as the control variable of the admission based on the analysis of the drop characteristics of the single varable bits rate flow and the multiplexity of flows,which results in the bandwidth and the restriction of the drop are guranteed at the same time.The simulation is showed that the improved admission adopting the bits allocation and the effective TXOP outperformed that aforetime in throughout.And in HCCA,the adaptive subarrier allocation according to the service's priority inter the station is also presented.The simulation shows it has better effect on multimedia flow by better synchronization.In 802.16d/e,the optimization of the efficiency of the frequency spectrum subject to the restriction of the ratio of the station's service and the power of the station is obtained by the subcarrier assigned and the bits allocation. Adopting the optimized bandwidth threshold make the user's satisfaction dgree in resourse reserve biggest.The two-level schedule is adopted to select the channel according to the service quality so that it guarantee the service effectively and the effective bandwidth as the control variable in admission so that the bandwidth and packet drop ratio are ensured at the same time.The simulation shows that the admission control based on the above methods optimize the efficiency of the system subject to the service's quality.