Critical Technologies Research On Routing In Multi-hop Wireless Networks

Multi-hop wireless networks do not require network infrastructure, and have advantages of flexible networking, flexible expansibility, self-organization, self-repairing and low deployment cost, etc. Therefore, they are widely used in scenarios which are inconvenient to establish network infrastructure, or only need temporary networking. Routing is crucial to the performance of multi-hop wireless networks. This dissertation focused on routing metric and opportunistic routing for static single-channel multi-rate and multi-hop wireless networks. Routing metric is the criterion for routing selection, and opportunistic routing is a novel routing technology crossing network layer and MAC layer for multi-hop wireless networks. This dissertation has achived the creative results as follows:1. Channel competition aware end-to-end delay routing metricLink quality, link transmission rate, channel competition and interference among adjacent links all have impacts upon the transmission performance of multi-hop wireless networks. However, existing routing metrics for multi-hop wireless networks cannot accurately and effectively measure those impacts, as a result they cannot select the best route. This dissertation first established the transmission model of wireless link based on IEEE 802.11 MAC DCF; next established the channel competition model of wireless links according to the protocol model of interference, and defined the channel competition degree of wireless link and node as the ratio of their channel holding time to their channel backoff time; last proposed channel competition aware end-to-end delay routing metric for multi-hop wireless networks, based on the proposed channel competition model and the transmission model of wireless link. The proposed routing metric can measure link quality, link transmission rate and channel competition among adjacent links accurately and effectively.2. Transmission coordination mechanism for opportunistic routingThe rate of successful transmssion coordination of existing batch map-based transmission coordination mechanism for opportunistic routing oscillates up and down during a communication session, as a result the performance of opportunistic routing is degraded. This dissertation first defined batch sliding window mechanism, and proposed batch sliding window-based transmission coordination mechanism, which improves the rate of successful transmission coordination by transmitting packets in continuous batch mode; and then proposed bit map-based transmission coordination mechanism by replacing batch map with bit map, which impoves the performance of opportunistic routing by reducing the overhead of transmission coordination.3. Multi-flow and autonomous scheduling opportunistic routingExisting opportunistic routing schemes schedule transmissions of candidate forwarders according to a global transmission scheduling strategy, which destructs the spatial reusability of multi-hop wireless networks, and increases the transmission delay of nodes; existing opportunistic routing schemes also do not take account of multiple data flows scenario, and do not address MAC channel access distributed coordination function for opportunistic routing. This dissertation first proposed an autonomous transmission scheduling strategy for opportunistic routing by decomposing global transmission scheduling ring into autonomous transmission scheduling ring centring each candidate forwarder, and then proposed the transmission scheduling strategy and transmission coordination mechanisms for opportunistic routing supporting multiple data flows, last proposed a batch transmitting and no hand-shake channel access distributed coordination function for opportunistic routing supporting multiple data flows and autonomous transmission scheduling.4. Transmission rate aware candidate forwarder selection and ordering algorithmExisting candidate forwarder selection and ordering algorithms for opportunistic routing select and order candidate forwarders based on expected transmission count (ETX) of nodes, thus they cannot reflect the effect of transmission rate of nodes on the transmission performance of opportunistic routing. The dissertation computed shortest expected transmission delay of opportunistic routing iteratively, and proposed a transmission rate aware candidate forwarder selection and ordering algorithm based on expected transmission delay of nodes.