LOCATION SYSTEM USING ULTRASOUND

摘要

A transmitter device transmits an ultrasonic signal encoding a binary identifier. Each bit position in the identifier is associated with a pair of frequencies and with first and second time positions in the signal. The bit value determines which of the pair of frequencies is transmitted at the first time position, with the other being transmitted at the second time position. A receiver device receives the signal. Each bit position of the identifier is decoded based on the strength of the received signal at (a) the first frequency and first time position associated with the particular bit position, (b) the associated first frequency and second time position, (c) the associated second frequency and first time position, and (d) the associated second frequency and second time position. The decoded identifier is used to determine information relating to the position of a mobile one of the devices.

主权项

1. A system for determining the position of a mobile device, the system comprising:
a transmitter device arranged to transmit an ultrasonic signal that encodes a binary identifier, wherein the encoding is such that each bit position in the identifier is associated with a respective pair of frequencies and with respective first and second time positions in the signal, with the value of the bit position in the identifier determining which frequency of the pair of frequencies is transmitted at the first respective time position in the signal, and with the other frequency of the pair of frequencies being transmitted at the second respective time position in the signal; a receiver device arranged to receive the ultrasonic signal, wherein one of the transmitter device and the receiver device is a mobile device; decoding means configured to decode the binary identifier from the received signal by determining a value for each bit position in the identifier using information relating to the strength of the received signal at (a) the first frequency and first time position in the received signal that are associated with the bit position, (b) the associated first frequency and second time position, (c) the associated second frequency and first time position, and (d) the associated second frequency and second time position; and processing means configured to use the decoded binary identifier to determine information relating to the position of the mobile device.