Cambridge Positioning Systems Limited

Malcolm David MacNaughtan

Peter James Duffett-Smith

Robert Willem Rowe

Christopher R Drane

John Christopher Clarke

Craig A Scott

James Brice

Christopher John Clarke

Craig Andrew Scott

Guy Albert Graube

A method of calculating the position or state of motion of one or more terminals is proposed in which each has a receiver capable of making measurements of signals received from one or more transmission sources for use in calculating the unknown position or state of motion of the or each terminal. At least one transmission source has a known directional transmission pattern, and the bearing from one of the receivers of the or each of the transmission source having a known directional transmission pattern is estimated. Weights are assigned to the measurements made by the one receiver, the weights being calculated from the bearing or bearings and the known directional transmission pattern of the transmission sources.

Location systems and methods

The present invention sets out to overcome the hearability problem in CDMA communications networks in which positioning services are provided, by using a separate sampling devicefor each transmitter, which sends to the computing devicea representation of the signals transmitted only by that transmitter. A cross-correlation of the representation sent back by the mobile terminalwith the representation sent back by the sampling device in the brightest transmitter is performed in the computing device, and a blurred estimate of that brightest signal is subtracted from a blurred version of the representation sent back by the mobile terminalin order to reduce its effect on the remaining signals as far as possible. The cross-correlation and subtraction steps are iterated until no useful signals remain to be extracted.

Radio positioning systems

The invention provides a method of estimating the time offsets between signals transmitted by plural transmitters of a communications network and received by a receiver attached to a terminal. In the method a section of a representation of the signals from the plural transmitters received by the receiver at the terminal (a 'terminal section') is created as are a first section of a representation of the signal transmitted by a first of said transmitters and a second section of a representation of the signal transmitted by a second of said transmitters. Each of the first and second sections overlaps in time with the terminal section. Using the first section, the second section and a set of signal parameters, including initial estimates of the time offsets between the first section and the terminal section and between the second section and the terminal section, a model of a section of a representation of the composite signal received by the receiver from the first and second transmitters is created. Thereafter, the model is compared with the terminal section and the set of signal parameters including the time offset estimates is refined to minimize the difference between the model and the terminal section. The time offsets in the refined parameter set used to minimize the difference between said model and the terminal section, are adopted as the estimated time offsets between the first section and the terminal section and between the second section and the terminal section.

The present invention sets out to overcome the hearability problem in CDMA communications networks in which positioning services are provided, by using a separate sampling device () for each transmitter (), which sends to the computing device () a representation of the signals transmitted only by that transmitter. A cross-correlation of the representation sent back by the mobile terminal () with the representation sent back by the sampling device in the brightest transmitter is performed in the computing device (), and an estimate of that brightest signal is subtracted from the representation sent back by the mobile terminal () in order to reduce its effect on the remaining signals as far as possible. The cross-correlation and subtraction steps are iterated until no useful signals remain to be extracted.

A method is disclosed for finding the position of a mobile radio-frequency transceiver in a communication system. A network of at least two unsynchronized base stations is arranged to transmit and receive signals to and from at least one mobile radio frequency transceiver. A reference receiver located at a known distance from the base stations measures the times of arrival of signals transmitted from the base stations. Using the known distances and measured times, a determination is made of the relative time offsets of transmission from each base station. The determined relative time offsets are used to calculate the position of the mobile transceiver in the network area using hyperbolic positioning techniques. A number of other enhancements including the use of Doppler, carrier information, and direction of arrival to improve the performance of mobile telephone-based positioning systems are also described.

Location and tracking system

The invention concerns a method of finding the position of a mobile radio-frequency transceiver in a communications system. A network of at least two unsynchronized base stations arranged to transmit/receive signals to at least one mobile-radio frequency transceiver; a reference receiver located at a known distance from the base stations and including measuring means to measure the times of arrival of signals transmitted from the base stations; determination means to use the known distances and measured times to determine the relative time offsets of transmissions from each base station; and location means to use the determined relative time offsets to calculate the position of a mobile transceiver in the network area using hyperbolic positioning techniques. A number of other enhancements to positioning systems relating to the usage of Doppler, carrier information, direction of arrival to improve the performance of mobile telephone-based positioning systems are also described.

Growing community of inventors

Sydney, Australia

Malcolm David MacNaughtan