Study On Reliability Of Routing Protocol In Wireless Linear Mesh Networks

In wireless mesh networks, nodes are usually assumed to be distributed randomly in two or three dimensional space. Nowadays, more and more applications have linear topology, such as online monitoring system of high voltage transmission lines, street lamps energy-saving system and so on. In such networks, packets are forwarded hop-by-hop in a linear way. Once an intermediate node fails, the route will be broken. Therefore, reliability is one of the key issues in linear wireless mesh network. From the perspective of power adjustment and network coding, this paper propose two protocols, power adjustment based routing protocol and network coding based routing protocol. Both protocols aim to improve the reliability in wireless linear mesh network.Power adjustment based routing protocol adopes cross-layer design. Neighbor nodes obtain link quality from MAC layer, and send them back to the current node. Current node makes decisions including routing decisions, path restoration, and the power adjustment through feedback link quality. We find the throughput does not increase with the increasing of RSSI after it exceeds a certain threshold value. So RSSI is used as linke quality metic. When none of the neighbor nodes is above the RSSI threshold, current node increases the transmission power to improve network reliability; when there are multiple neighbors nodes are above the RSSI threshold, the current node reduces transmission power to save energy.Network coding uses store-encoding-forward mode instrad of the traditional store-forward to improve network capacity and the robustness. NCR(Network Coding based Routing) is proposed to improve routing reliability. In this paper, NCR sends redundant packets to improve performance of network flow in terms of packet loss rate and throughput. Futhermore, NCR employs conditional broadcasting, which avoids broadcast storm problem.PAR and NCR are implemented and evaluated in WiZiTJU testbed. Experiment results show that the PAR can provide better reliability; NCR outperforms the broadcast tree protocol in terms of the throughput, packet loss rate.