Communications protocol for RF-based wireless indoor localization networks.

摘要

This research presents a new novel communications scheme for application-specific RF-based wireless indoor localization systems. In such a system, wireless badges attached to people or devices send periodical Received Signal Strength Indicator (RSSI) bytes at several selected frequencies to wireless router units. Routers measure RSSI and route collected badge information hop-by-hop toward a Central Management Station (CMS). In this many-to-one data communications network, CMS receives data entries of a badge and calculates positions at a desired level of accuracy.; The new Wireless Indoor Localization System Protocol (WILSP) specifies a mixed time and frequency division (TDMA/FDMA) for medium access. The system has a fixed EPOCH time divided into three consecutive phases. Management time and frequency are reserved for management messages originated from CMS. During Badge-Router (B-R) time at selected frequencies, badges occupy time slots at associated routers and periodically report RSSI bytes to routers. The third phase time and frequencies are reserved for Router-Router (R-R) communications.; WILSP specify rules both for B-R and R-R communications. A router shows up as a badge first. CMS authorizes its switch to router operations, and lets it know about the UPLINK reference neighbor, EPOCH start offset relative to the schedule of the UPLINK neighbor, UPLINK and DOWNLINK communications frequencies and times. These data are derived from an optimal or near-optimal routing spanning tree for routing built by CMS using heuristics. Assuming the limited capabilities of Chipcon CC1010EM chips, simulator results indicate that WILSP performs well in both grid- and linear-structure scenarios and the multi-hop scheme introduced meets the specified requirements. Statistics show that initialization time of routers depends mainly on two factors: the number of hops the information takes toward CMS and the fixed size of EPOCH time. Simulation results on the Cafeteria scenario prove that the protocol can handle situations at a high reliability.; For different EPOCH times in linear structures, the choice of positive relative EPOCH start offsets resulted in significantly less router initialization times than in the other scenarios. As the total EPOCH time decreases, the EPOCH start time offset assignment has more of an effect on the overall initialization time.