Bandwidth Allocation And Service Handoff In IEEE 802.16 Wireless Metropolitan Area Networks

With the quick development of communication and network technology, theprocess of information exchanging and cooperation have been accelerated. Meanwhile,with the development of wireless network, people want to access the network servicesat any time, at any place and with any method. A lot of services which were providedby the wired network have been supported by the wireless equipments now.Compared to the wired network, the communication bandwidth in the wirelessnetwork is limited. In order to achieve QoS guaranteed wireless services, efficientutilization of bandwidth resources becomes a fundamental issue. This paper hasanalyzed the bandwidth allocating process of wireless network with different servicestypes and compared the performance of different bandwidth allocating schemes. Atthe same time, this paper also gives an eye to the impact brought by handoff process.We have optimized the handoff rerouting process to improve the performance whenthe handoff process tack place. The main work and contributions are presented in thefollowing aspects.1. Compared to the wired network, the communication bandwidth in the wirelessnetwork is limited. In order to achieve the QoS guaranteed wireless services, efficientutilization of bandwidth resources becomes a fundamental issue. A number of channelallocation schemes have been proposed to fully utilize the wireless bandwidth, butmany of them just proposed the channel allocation scheme without presenting aspecific channel allocation model. In this paper, we propose and analyze threedifferent channel allocation schemes for wireless networks. We build three systemmodels based on two-dimensional Markov chain to compute the performance of basestation in terms of the new call blocking probability, the handover droppingprobability, and the channel utilization.2. The IEEE 802.16 MAC, which is connection-oriented, regulates uplinkchannel access using a Demand Assigned Multi Access (DAMA) TDMA system. Inthe WiMAX PMP mode, BS control uplink bandwidth allocation and SS request fortransmission opportunities on the uplink Sub frame. In this paper, we use multi-layersqueue system to describe the different bandwidth allocating state in Base station and Subscriber station. Meanwhile, Markov chain is used to analysis the performance ofdifferent bandwidth allocating schemes. We also provide some performance metrics toevaluate different bandwidth allocating scheme with this model.3. In order to optimize the bandwidth scheduling, a concept of neighborhood forbandwidth allocation and a new bandwidth scheduling scheme are introduced basedon two classical scheduling algorithms: round-robin and random choice. The proposedscheme first optimizes the bandwidth scheduling for a subset of Subscriber Station(SS), and then provides the optimal performance based on bandwidth scheduling forthe whole WiMAX (world interoperability for microwave access) network, especiallyin the Mesh mode with step-wise approach. Extensive simulation results using NS2show that the proposed scheme incurs a short delay and increases system throughputwhile using the network resource efficiently.4. Reconstruct a new route for network services during the handoff process is afundamental issue of wireless communication. This paper proposes a new reroutingalgorithm to achieve a fast handoff based on k-hop backtracking mechanism. Thealgorithm can dynamically decide the backtracking hops according to the velocity ofwireless devices and the current network band-width through iterative strategy.During the backtracking process, our algorithm is able to find out an optimized routefor the handoff network services and require all intermediate nodes which hasreceived the Location Update informa-tion forward all received packets to MobileTerminal with their optimal route to the destination subscriber station. This willgreatly reduce the cost of packet forwarding during the handoff process.