Study And Realization On Localization Technology Based On Wireless Sensor Network

In recent years, wireless sensor network (WSN) has been widely researched in the field of communications. From the practical standpoint of WSN, the location information of the WSN node is the foundation of any application. This paper focuses on the particular MC-CDMA-based WSN nodes to provide location reference to other unknown nodes in the situation that the satellite location information is missed or the satellite location system can't be used.Assuming that numerous normal sensor nodes and few MC-CDMA ones are cast in the sensing target area, once the amount of close anchor nodes is insufficient, the MC-CDMA node can perform the far distance ranging and the function of accurate self-location with the help of other nodes which is equipped with MC-CDMA module. After that it upgrades to an anchor node and can provide location reference to other unknown nodes in this network. The main ideas of this paper are as followings:First of all, the ranging algorithm based on spread spectrum code is provided which is suitable for this ranging location system, and the basic protocol of ranging is introduced. The different error which has influence on ranging is also analyzed and how to control the NLOS error is emphasized. Then two ways of classifying the NLOS controlling algorithm, which based on cost and application occasion respectively, are introduced and their own comprehensive application is provided under the guidance of the classification.Secondly, the overall design plan and the concrete work flow of WSN node based on TOA two-way ranging is stressed. The sensor node is comprised of two parts, which are ranging module and location module. The ranging module is implemented using MC-CDMA ranging scheme based on spread spectrum code and the location module is analyzed from the viewpoints of hardware and software. The hardware platform of the node is built on the development board with S3C2440A microprocessor as its center controlling chip and the software is based on the simplified embedded Linux operating system. Since the ranging module and the location module are connected by serial interface, the setting method of interface is also introduced. The location process and the location message format are correspondingly stated as well.At last, a node location algorithm suited for three-dimension space is proposed. Since most of the existing location schemes are based on two-dimension space, the available location technology of WSN nodes based on three-dimension space is studied. After that a three-dimension static location algorithm based on spherical coordinates is proposed. This algorithm makes use of which four spherical coordinates are already known and realize self-location according to calculating the spherical center coordinate. According to the problem of how to choose the suitable four spherical coordinates, this paper calculates and ranges the optimal four spherical coordinates in the range of communication radius by analyzing and comparing in the base of PIT. The simulation results and performance analysis demonstrate that when the density of neighbor nodes satisfies the location requirements, the algorithm can achieve relatively high location precision compare to the situation that don't use the PIT.