Abstract: A method for reducing synchronization offset errors in a TDOA location finding wireless system, comprising: receiving transmissions from at least one sync unit at multiple location transceivers, wherein the multiple location transceivers are synchronized from the sync unit; determining actual times-of-arrival of the received transmissions in response to receiving transmissions; performing a wireless distance measurement between the transceivers and the at least one sync unit, the wireless distance measurement performed by the transceivers in response to the received transmissions from the at least one sync unit; computing an actual propagation time between the sync unit to the transceivers; computing differences between the actual propagation time and theoretical propagation time determined in conformity with the predetermined locations; estimating synchronization offset error of the transceivers in conformity with the computed differences; and correcting the synchronization offset error.

Abstract: A method and system for distance measurement in a low or zero intermediate frequency (IF) half-duplex communications loop measures the distance between two transceivers without synchronizing the local oscillators of the two transceivers. Transceiver distance may be measured in systems that use direct conversion (zero IF) or intermediate frequencies that are so low that phase noise significantly reduces the accuracy of the distance measurement. The communications loop demodulates, re-modulates and retransmits a received signal to provide a re-transmitted signal that has the same carrier and modulation frequency as the received signal. A phase-hold circuit provides an analog system for half-duplex operation that retains the frequency and phase information of the received signal for retransmission in a subsequent time slot.

Abstract: A method and apparatus for enhancing security in a wireless network using distance measurement techniques provides an additional layer of security and privacy in wireless communications. A distance measurement or location-finding is performed between two devices by transmitting and receiving one or more signals and computing a distance between the two devices or a location of a connecting device. The resulting computed distance or location is used to determine whether or not to permit pairing, secure connection or secure transactions between the two devices. The computed distance or location can be further used in combination with a signal strength measurement to link to locate and measure nearby devices first, reducing the time required to initialize network communications.

Abstract: A system and method is capable of identifying multipath wireless signals, their relative strength, and their position. The system and method may be used in wireless distance measurement to generate a distance measurement free of multipath distortion. First and second wireless devices transmit and receive signals to generate multipath information. For distance measurements, this information may be used to calculate the true distance between two wireless devices that is compensated for multipath. The system and method may be used in a mobile wireless communications system to discriminate between various mobile wireless communications devices located in a region, for example, to conduct a commercial transaction or transmit or receive other information.