Research On The Self-adaptive Routing Strategy Based On Node Mobility In ZigBee Networks

With the rapid development of wireless network technique, manifold standards for short-range wireless communication emerge as the times require. Thereinto, the ZigBee specification, which has the virtue of low consumption, low cost and high reliability, arouses wide concern in the field of industry, agriculture, military, building automation, security system, remote control, smart home, health care and etc.The routing protocol is one of the most important components of short-range wireless network system. It is of great significance to reduce the node power dissipation and expand the lifetime of network for improving the routing performance, especially in ZigBee specification whose goal is low energy cost. The hierarchical tree routing and the Z-AODV routing are both available in the ZigBee specification to meet the requirements such as routing efficiency and network robustness in different applications. However, due to the extensive application of ZigBee technique and the complicated environmental situation, the research on routing methods so far could not completely meet the requirements of practical applications. For example, the analysis of the performances of the two routing methods is still not sufficient and the performances of routing algorithms which may fit the change of node mobility remain to be improved. To solve above problems, based on the analysis of ZigBee networks and existing routing algorithms, this thesis focused on the study of routing performance improvement in the aspects of the performance analysis of different routing methods and routing selection. The major contribution of this dissertation is specifically stated as follows:(1) Based on the research on routing performances of different routing algorithms in different network stability in ZigBee networks, the routing selection strategy based on node mobility (BNM) was proposed. The strategy is based on the idea of utilizing the most efficient routing method in the networks. Firstly, the routing performance of different routing methods in different network conditions was analized, based on which, the strategies of self-adaptive routing selection and the setting of threshold were proposed. The node mobility information was acquired without extra data communications by inspecting the data command and the change of node parameters caused by node movement. On that basis, the routing method was chosen adaptively. The simulation results showed that the strategy had better performances on network load and data transmission efficiency than traditional single routing method schemes. Finally, the hardware requirement was analyzed and results showed that the strategy had no extra requirements for memory cache or computing capacity for ZigBee devices.(2) With the extension of ZigBee application, the ZigBee routing method which adapts to complex environment is becoming the research hotspot. The enhanced hierarchical routing protocol (EHRP) was studied in detail and the effect of the change of node mobility on its performance was analyzed in this paper. Based on this, the EHRP was introduced into routing selection scheme, and an enhanced routing strategy based on node mobility (EBNM) was proposed to fit for advanced ZigBee devices (with powerful caculating capacity and abundant peripherals on chip). The node moving estimation and routing selection method without extra data communications were designed. The data transmission efficiencies of different routing strategies and algorithms were simulated and compared. The results showed that, compared with orginal routing selection strategy and single routing schemes, EBNM may improve routing performance and data transmission efficiency.(3) Aimed at recognizing node movement in routing selection strategy based on node mobility, the methods of judging node movement based on node information for suppressed routing discovery, enabled routing discovery and forced routing discovery schemes were proposed respectively. The methods only need to inspect the local command and the change of neighbour node information, while the extra data communications between nodes were not necessary. In this way, the bandwidth was saved and it provided essential technical support for the routing selection strategy based on node mobility.(4) The routing performance of hierarchical routing and Z-AODV routing in different network environments was studied in ZigBee networks. The effect which the node number and mobility have on the performances of ZigBee routing algorithms was analized. The simulation results showed that the forced routing discovery method always have the worst performance due to its network overhead; the suppressed routing discovery method performed better than the enable routing discovery method in stable network; while the latter gradually beats the former as the node mobility increased. It may conclude as the suppressed routing discovery method is fit for the stable networks; while in the network where the node mobility is higher, the enabled routing discovery method may lead to better data transmission efficiency. The conclusion laid a foundation for the research on routing selection strategy.