Research Of Cross-layer Optimization In Wireless Sensor Network Based On Crossbow

Wireless sensor network(WSN) has become a hotspot research in recently years. There are many applications, such as environment monitoring, medical system and robot exploration. With the different need of field, the sensor node can collect data of magnetic intensity, temperature, humidity, noise, light intensity and the velocity of mobile object.Generally there are four layers when we discuss WSN. They are application layer, network layer, medium access control (MAC) layer and physics layer. The sensor nodes are often supplied with batteries, and it's not easy for replacing the battery. So the energy consumption is considered as the most important factor in WSN, and this is the difference between other network and WSN. All of above four layers need to reduce energy consumption, and most protocols are proposed in network layer and MAC layer. In network layer, WSN is constructed with different clusters and each cluster head is responsible for converging data from other nodes in its cluster. In MAC layer, nodes are assigned with appropriate schedules and some medium access scheme for reducing collision. These two layers is our optimized target.There have been many protocols in WSN, such as LEACH, HEED in network layer and SMAC, TMAC in MAC layer. The MAC protocol can reduce the interference and collision in network, but it is not suitable for large network. The network protocol often select cluster heads randomly, and the selected cluster head may be not the suitable one in network.This paper first proposed an adaptive transmission scheme based on emergency for heterogeneous network convergence. With the assistance of cellular network, this scheme can achieve low packet loss ratio and low latency transmission to gateway. This scheme can also reduce energy consumption of sensor node and increase the lifetime of network. After emergency data transmission finished, this scheme optimized the network topology.This paper then proposed a new protocol called Ring Clustering based on above protocols. In network layer, node with the least cost value is selected as a cluster head. The cost value is determined not only by cost intra-cluster but also by cost inter-cluster. So this cost can guarantee the most suitable cluster head can be selected. All the nodes are not clustering at the same time. However, the nodes are clustering from inner board to outboard in ring, just like a water wave. In MAC layer, we adopt suitable schedule based on CSMA/CA, and make intra-cluster communication and inter-cluster communication through different channels. These scheme can reduce the interference between nodes. The good simulation results validate the efficiency of Ring Clustering protocol.