Study On Routing Algorithm And MAC Performance Improvement Technology In Wireless Network

The wireless network is a combining product which integrated mobile communication technology with computer network technology. It has overcome the insufficiency in the traditional network and realized the movable data exchange. Meanwhile, it has also opened up a new area of technology and application for the local area network. Because of the high flexibility, mobility, low cost and relatively high through-put capacity, the wireless local area network (WLAN) is going to play vital role in the wireless communication network applications.There are some differences between wireless and wired network. Wireless network not only has some flaws such as high error rate, interference and hidden terminal\exposure terminal problem, but also shows the characteristics of sharing medium and mobility and so on. Therefore, the protocol designed for the routing algorithm in wireless network is obviously different from the wired network. In addition, the impact of the network scale and other properties deliver obvious different results to wired network and wireless local area network. Considering the factors described above, it is vital important to improve the performance of the routing algorithm and the MAC protocol in wireless local area network.In this paper, the routing algorithm and the MAC protocol in wireless local area network are analyzed and studied. Several algorithms are proposed for the wireless local area network to improve the network performance based on the existing protocols. The proposed algorithms are implemented in the simulated environment and the performance is analyzed. New approaches and methods are provided for the research of the routing algorithms and MAC layer protocol in wireless LAN. The reliability and controllability for the routing algorithm and MAC layer protocol in WLAN are enhanced, and the applications in different occasions are expanded. The compendious novelty and description of the thesis are given as follows:(1) Realizes the node localization based on the OLSR protocol in the Ad Hoc networkWe propose that the wireless Ad Hoc network node knows its position (three-dimensional coordinates, through the node equipped with a GPS or other positioning devices), based on the OLSR routing protocol in wireless network, the routing computation algorithm is modified, and the target node’s location information is added in the routing table for every node. We try to let the node achieve the positions of its surrounding nodes or the entire wireless Ad Hoc network nodes. Additionally, the OLSR routing protocol which has localization function is analyzed and compared with the original protocol. The content of the research can provide conditions and bring convenience to location-based wireless network applications such as routing algorithm’s optimization, packet transmission strategy and so on.(2) Improving the node localization technology in Ad Hoc networkIf the destination node is far from the source node, the transmission of the routing control information for the destination node has some delay and will then affect the accuracy of the node localization. An algorithm is proposed to predict the actual location of the distination node based on its current position information in routing table. The original algorithm is analyzed, and the primary reason that the node localization has some deficiency is pointed out. The node localization forecast algorithm is designed and realized, and the forecast algorithm is used to improve the accuracy of the node localization as far as possible. The algorithm is simulated and analyzed, and it proved that the proposed algorithm can effectively reduce the impact of positioning accuracy caused by the node transmission delay and other factors.(3) Improving MPR selection algorithm in OLSR protocol based on node localization technologyThe MPR technology in the OLSR routing protocol is described, it is pointed out that there are some limitations when the default heuristic algorithm in this protocol is used to find the minimum MPR. In this paper, an improved algorithm based on node localization is proposed combined with node localization technology. Node localization information is used in this algorithm, the blindness is reduced in the MPR selection algorithm in the OLSR protocol, it can make full use of the network resources, the number of routing packets needed to deliver in the network is reduced to a certain extent, and therefore it can improve the network transmission capacity. The improved algorithm is implemented in network simulation environment, the results are analyzed, it shows that the proposed improved algorithm is feasible and applicable, and the location-based heuristic selection strategy is appropriate and correct. (4) A heuristic routing algorithm based on node localization and ACO technologies for Ad Hoc networksA new routing algorithm is proposed which is based on the ant colony optimization algorithm for mobile Ad Hoc networks (MANETs). It also uses the location information from node localization technology and OLSR routing protocol which has the localization function as heuristic information. By analysis, according to its 1-hop and 2-hop location information of the neighbor nodes, every node in different position should use different probability to let the ant forward the routing information to the next hop, so as to greatly reduce the overhead of the packets used for maintaining the route information. The algorithm selects one or two of the paths recorded in its local routing table for the robustness reason. In order to further promote the robustness of the routing algorithm, a mechanism by creating an alternative path to repair the wrong path is proposed. Simulation results show that our algorithm achieves good packet delivery ratio with low communication delay.(5) Analysis and Utilizing of the Error Models in Wireless NetworkThe reasons which cause data packets transmission error is analyzed in the wireless network, it is highlighted that the data packets transmission error will cause transmission failure and the network performance drops. The common error models used in 802.11 standards are introduced and the correlated theories are analyzed and studied. The characteristics of a variety of transmission errors are discussed when the applications use 802.11a and 802.11b as its protocol. Several common error models are simulated using the simulation software, and the results are analyzed. This chapter has not only provided helps to understand and evaluate the characteristics and performance of wireless network, but also brought great convenience to researchers and scholars.(6) United of channel contention management based on IEEE 802.11e NetworksThe shortcomings in the current 802.11e protocol for WLAN to which support the QoS are analyzed. We proposed a united channel contention algorithm based on the platform of IEEE 802.11e protocol. In order to realize the computational methods that can be used to get the measurement parameters of the network state, the principle of the DCF mechanism is further analyzed using the existing two-dimensional markov chain model. An algorithm is designed and implemented to dynamically adjust the probabilities of using the wireless channel for different priority queues. It can improve the resource sharing among the active queues and the efficient using of the bandwidth, preventing the occurrence of the phenomenon of starvation and optimizing the fairness among the different virtual queues in 802.11e. Finally, the throughput, delay and fairness and other aspects of the algorithm are analyzed in the simulation.