Transceiver Optimization for ToA-Based Localization of Mobile WSN

Abstract

One of the main parameters in wireless sensor networks (WSNs) is the design of energy-e±cient protocols. And accuracy is another central goal of localization. Since sensor nodes run on battery power, any WSN application and accurate localization needs to be energy-e±cient. In this paper, the accuracy of localization is increased by accurate measurement of the distance between the mobile sensors. Limit error in multiple-input multiple-output (MIMO) has been calculated by CRB method. Virtual MIMO (VMIMO) technique can obtain better localization precision and the localization is energy-e±cient. Optimum selection of the number of the transceiver nodes is obtained by the lowest possible energy consumption, the existent localization error, and speed of nodes. Mathematical relation between energy consumption and localization of mobile nodes is presented and then veri¯ed by simulation. VMIMO decreases power of transmitters and this in turn will result in decreasing destructive e®ects of electromagnetic sensitivity (EMS) on body. Furthermore, optimized localization parameters will increase the e±ciency of the system and network lifetime. and nonneighbor nodes can lead to the selection of the best route for exchange of messages. In addition, it accelerates exchange of messages and decreases energy consumption of nodes. 1 Localization is a prerequisite for nodes to achieve many of their network tasks.It is essential to measure the distance between a transmitting node and a receiving node or their angular positions in order to estimate the location of the nodes. To achieve this purpose, range-based techniques make use of distance measurements like time of arrival (ToA), angle of arrival (AoA), received signal strength indicator (RSSI), and direction of arrival (DoA) to measure the distances between the nodes to¯nd geographical location of a node. 2 IEEE 802.15.4 Standard has been widely used in WSNs. Ultra-wideband (UWB) is one of the frequency bands de¯ned for the IEEE 802.15.4 Standard. 3 UWB is a major technology implemented for localization and communication because of its desirable feature in accurate ranging and reliable communication. Two design goals, lower cost and lower power consumption, are achieved by the use of UWB in physical layer. This is because it results in using simpler demodulation schemes, lower bit rates, and by that low energy consumption. This technique is a promising method for high-resolution ToA estimation. [4][5][6] The Cramer-Rao bound (CRB) provides a standard benchmark for evaluating any estimator, independent of the particular estimator's form. 7 In this paper, CRB is used to investigate the distance between a transmitter and a receiver, which is an important parameter in localization.The application of multiple-input multiple-output (MIMO) techniques is an ordinary approach in high-speed wireless networks. The quality of communications between wireless devices can be improved by the use of multiple antennas and multiple processing units. Using di®erent antennas by means of multiplexing tech...