Research On Cache Distribution And Access Scheduling For Mulithop Wireless Networks

The gobal mark of wireless networks and data storage keep growing rapidly due to the strong demand for various multimedia application, data management and widely used of portable devices such as smartphone, tablet computer, notebook computer etc. The multihop wireless network is able to provide a variety of users with convenient, low-cost data access, sharing, management and other services. However, platform Diversity and complexity of wireless network environment become a huge challenge for multihop wireless network data transmission. The research found that existing technology could not satisfy the new demands of users, the traditional caching techniques and access scheduling lack of optimization for wireless networks. Therefore, to concentrate on the characteristics of the multihop wireless transmission, and provide high performance, reliability and low energy consumption data transmission service is an urgent task.Having considered the performance of the wireless system, a low access delay cooperative caching strategy-adjacent clusters convergence cooperative caching has been proposed. The strategy divides the whole network into non-overlapping clusters, and the nodes within each cluster synchronize with other node which has updated its caching data by using Clusterfile. The Clusterfile is a sync file that is used to avoid caching data redundancy and wasting of the limited memory space. Based on this formation, the adjacent clusters have been used for their location advantages to extend the nodes' cooperative range while keep the overhead low. The strategy has been proved for its caching hit ratio of the data request, and the lowered delay of data transmission. So the adjacent clusters convergence cooperative caching is a high performance strategy for wireless data transmissions.In the real application environment, many nodes are powered by battery, such as notebook computer, PDA and smartphone. For the purpose of running the wireless nodes for long time, the data transmission energy consumption should be reduced. To solve these problems, a new type caching distribution strategy which named HRCCache has been proposed, and the strategy could achieve power and performance balance. By reducing the multihop wireless networks relay hops, may lead to lower node energy consumption. The main idea of the strategy is to use the transmission path navigation graph mining potential relationship between nodes, and clustering scheme divided all nodes into non-overlapping clusters. Then the most active node in each cluster is found out, and set the Node as the Cache placement node. Strategy HRCCache could significantly reduce overall system cost and data access latency; improve the efficiency of Cache to reduce the number of nodes in the relay. Therefore, the strategy can effectively meet the multi-hop wireless network performance demand for data transmission and energy requirements.In multihop networks with IEEE 802.11 wireless interface, the process of user node acquiring data may encounter problems such as high latency, low reliability, etc. These problems are caused by the original DCF of 802.11 protocol which has time slot resources and the unfairness of access scheduling problems. To solve these problems, two algorithms for multi-hop wireless access scheduling have been proposed:Delay Dynamic optimization Algorithm-DDoA, and Performance Balanced Dynamic optimization-PBDoA. DDoA and PBDoA collect the number of nodes'competitive backoff times, and with the help of DSDV routing protocol these information updated periodically in the local area. The main idea is that each node based on locally collected information to determine their own state, if the backoff times of the node is more than neighbor nodes', then the node need to reduce the length of backoff time and change its own priority of medium access. Algorithm DDoA sacrifice little reliability for high performance, which achieves low transmission delay, suit for applications environments with delay requirements. Algorithm PBDoA rates nodes within the region to improve accuracy of node status determination, so the nodes of different types have more targeted strategies to reduce backoff time and to maintain the balanced growth between performance and reliability.The research concentrates on multihop wireless network data access and transmission technology, try to improve service performance, reliability and energy efficiency. Some innovative ways have been proposed to explore and study new techniques which could be applied in multihop wireless network environment.