Abstract: A network has wireless access points, each configured for bi-directional communication, using a first radio protocol, with a communication device that has been associated with the access point by an association data exchange. Each access point is also configured to receive, at a first data rate using the first radio protocol, a multicast radio message and to forward the multicast message onto the network. A radio transmitter is configured to send data at a second data rate, using a second radio protocol different from the first radio protocol. A wireless communication unit transmits a multicast radio message at the first data rate using the first radio protocol. It also receives data from the radio transmitter at the second data rate using the second radio protocol and decodes the data.

Abstract: A position determination system is provided comprising one or more fixed base units and one or more mobile units, wherein the system is arranged to determine the horizontal position of a mobile unit based on the proximity of said mobile unit to at least one base unit and wherein the system is arranged to determine the height of said mobile unit based on the air pressure sensed at the mobile unit and the air pressure sensed at one or more of the base units. The use of pressure sensors to determine height reduces the complexity of the infrastructure required for 3D positioning. The invention finds particular benefit in patient care and monitoring environments and in object tracking and inventory systems. The invention also extends to mobile units for use in the system, intelligent buildings fitted with the system and to methods of determining the position of mobile units.

Abstract: Static transmitter stations are used to determine the position of a mobile receiver unit. Each transmitter station transmits an ultrasonic signal including a transmitter-specific phase-shifting signature. The receiver unit receives a signal and identifies a transmitter station by its signature. It uses the received signal and the identity of the source transmitter station to determine the position of the mobile receiver unit. The signature may include two patterns phase-shift-key (PSK)-encoded on respective carrier signals of the same frequency but different phase, with the patterns being offset from each other by a transmitter-specific offset. The signal from the transmitter station may also include a PSK-encoded message.