Research On UWB-based Localization Technologies For Wireless Sensor Networks

UWB technology and the perfect combination of wireless sensor networks,is changing the science and technology,changing the way of human life,work.Its application prospect is very broad,and it is widely used in national defense,military,industrial production,smart home,medical and health and so on.If the sensor nodes carry on the location information,then its application will be more broad.Therefore,the localization of sensor nodes has become a hot and difficult problem in this field.As a new type of non-carrier communication technology,UWB can support high-precision positioning of wireless sensor networks.This paper introduces the PHY signal modulation,channel combination,PHY frame structure,MAC function and MAC frame structure of UWB in IEEE 802.15.4-2011 standard,which lays a theoretical foundation for the design of positioning system in this paper.This paper mainly solves the problem of clock synchronization and NLOS communication in the localization of sensor nodes.TDOA clock synchronization algorithm using anchor nodes record TOA information to construct a relative clock bias and relative clock frequency offset of the relationship between anchor nodes,and least square is used to estimate the relative clock offset and the relative clock frequency offset.Finally,the estimated results compensation to label nodes and anchor nodes in TDOA location estimation and eliminate clock synchronization error.TDOA non-line-of-sight differential correction algorithm using reference TDOA LOS between anchor nodes were TDOA variance and the actual measurement of the mean variance comparison methods to identify NLOS anchor nodes and be removed,only the LOS anchor nodes to locate,to suppress the influence of NLOS on the positioning accuracy.At the same time,in the positioning of the anchor node is insufficient,this paper also provides a modified NLOS anchor node ideas,NLOS anchor node NLOS error estimation,correction,so that it can act as a LOS anchor nodes to participate in positioning.Based on the proposed algorithm,this paper designs a positioning system based on DW1000 wireless transceiver chip,which is provided by deacWave company,and follows the 802.15.4-2011 IEEE standard.First,completed the selection of hardware and design of the tag nodes and anchor nodes,followed by the design of the containing simple interrupt program of embedded software to capture the TOA information of sensor nodes.And then the design of the upper machine software interface and upload TOA information data packet protocol,finally through the design of the PC software call the algorithm to achieve the positioning of node labels,display.It can be seen from the experimental data that the positioning accuracy of the system can reach the order of decimeter,and the result of location validates the practicability of the system and the validity of the algorithm.