Power Saving in Wireless LAN Localization Systems

Abstract

<p>A localization system based on the Institute of Electrical and Electronics Engineers 802.11™ wireless local area network standard enables cost-effective localization measurements. It also integrates data dissemination within the system, unlike the popular NAVSTAR global positioning system. This thesis addresses two significant deficiencies in such a system: potentially low localization accuracy and high power usage of the communication infrastructure. A design for a low-cost solar powered localization augmentation node (SPLAN) is proposed to provide accuracy-increasing localization assistance service to localization tags-small battery powered units equipped with an IEEE 802.11 transceiver. Power saving network protocols for the SPLAN/ tag architecture are developed to extend the tag battery lifetime and allow the SPLAN to be cost-effectively supplied by renewable energy sources such as solar energy.<br />A comprehensive power consumption model is developed for two complementary communication systems: plain tag and smart tag. Through its use, significant SPLAN energy conservation for low tag densities was demonstrated in the plain tag system, while preserving legacy compatibility. In the smart tag system even greater energy gains were obtained for both the SPLAN and the smart tag, up to maximum supportable tag densities. This was possible through the use of a custom communication protocol designed specifically for smart tag system power saving. Two innovative aspects of the protocol include timing-assisted scanning of management beacon packets and an optimized procedure for dissemination of raw localization data.</p>