Abstract: A system for monitoring at least one tag device has at least one mobile cellular telephone. The mobile cellular telephone is capable of communicating on a WiFi network, wherein the at least one tag device transmits wireless data messages in a non-associating mode.

Abstract: A wireless network has at least one wireless unit which transmits messages in multiple channels. The messages are synchronously transmitted using a transmit clock signal. The at least one wireless unit starting transmission of the messages at intervals consisting of at least one of one or multiple periods of the transmit clock signal. A plurality of location receivers are used for receiving the messages at different channels transmitted by the wireless units within the wireless network and determining a time of arrival for the received messages. At least one master unit is used for receiving the time of arrival from each of the location units. The location of the wireless unit is to be determined on the Time Difference Of Arrival (TDOA) of the transmitted messages at the location units.

Abstract: A location system and method operable to locate mobile units has a mobile unit operable to transmit wireless signals. A wireless network is used to receive the wireless signals and to report data used to estimate the location of the mobile unit. A location server is used to process the data reported by the wireless network. The location server generates a plurality of location reports for the mobile unit. A preprocessing component is operable to communicate with the location server. The location reports generated by the location server are transferred to the preprocessing component. A location application is operable to communicate with the preprocessing component, and interfaced to a database operable to store data records related to the mobile unit. The preprocessing component processes the location report and stores the data records only if the data in the data records meets a specified criteria.

Abstract: A wireless local area network (WLAN) method and system for presence detection provide a low-cost and WLAN-compatible means for detecting the presence of an asset without requiring full location-finding support within a WLAN environment. The presence of a transmitter is detected by examining the signal strength of a presence signal. The presence signal is WLAN-compatible, but does not require association of the transmitter with the WLAN and does not require a response from the WLAN. The presence signal may be transmitted on multiple WLAN channels for presence detection by multiple WLAN APs. The presence signals transmissions may be periodic or may be stimulated by a stimulus from the WLAN or external device that may or may not be coupled to the WLAN. Location finding can also be performed in combination with the signal strength presence detection.

Abstract: A radio-frequency identification (RFID) tag employing a unique reception window and method for operating the tag system provides low-power operation for enhanced tag battery life, while providing addressable tags that can receive commands and data from the system, which can be a wireless local area network (WLAN) incorporating location finding for locating the tags. Interference with other tags and other transmitters is prevented by either using a sniffer circuit to determine that no network transmission is in progress, or by using a special non-interfering coding sequence. A receiver within the tag is operated for a predetermined period of time after a periodic transmission is made from the tag, and an address decoder determines if the tag is being addressed. The receiver can receive data and/or commands after being addressed and is shutdown if the window time elapses, the tag is not addressed, or at the completion of data/command transfer.

Abstract: A method and system for synchronizing location finding measurements in a wireless local area network (WLAN) provides a low cost mechanism for correcting location measurements within a WLAN location finding system. Multiple location receivers compute the time-of-arrival (TOA) of a reference transmitter signal, which is generally a beacon signal. The TOAs are collected and reported to a master unit that contains stored predetermined position information for the location receivers. The master unit computes the time-differences-of-arrival (TDOA) between multiple receivers and computes differences between the measured TDOAs and theoretical TDOAs computed in conformity with the predetermined position of each location receiver. The deviations between theoretical and measured TDOAs are collected in a statistical sample set and Kalman filters are used to produce a model of location receiver timebase offset and drift over multiple received beacon signals.

Abstract: A wireless local area network (WLAN) radio-frequency identification (RFID) tag system provides location finding in a wireless local area network (WLAN), using a WLAN channel. Interference with the WLAN is prevented by either using a sniffer circuit to determine that no network transmission is in progress, using a modified coding sequence or preamble to cause standard WLAN receivers to ignore the RFID tag transmissions, or transmitting a message using a standard WLAN signal addressed to an address not corresponding to a unit within the WLAN. Location units (LUs) and a master unit (MU) within the WLAN receive the RFID tag transmissions and can determine the location of a tag by triangulation based on differences between the signals received at the location units from the tag. The master unit receives the signal information from the location units and computes the location of the tag. Time-difference-of-Arrival (TDOA), received signal strength indication (RSSI) or other triangulation techniques may be used.