Nortel Networks Corporation

Northern Telecom Limited

Stc, Inc

Francis Giles Overbury

Simon John Gale

John Edward Hudson

David Damian Nicholas Bevan

Christopher John Reed

Jeffrey G Searle

Christopher R Ward

Jonathan Fraser Page

In a cellular mobile telecommunications system the position of a mobile station can be estimated in terms of its bearing and range from a cell site. A multi-element direction finding antenna at the cell site receives signals from the mobile station and a receiver circuit estimates the bearing using the relative phase of signals received at different antenna elements and estimates the range by measuring round trip delay of signals to and from the mobile station. Motion of the mobile station can introduce errors into the bearing estimate due to frequency offset and frequency spread when element sampling is non-simultaneous. Compensation for these errors is introduced by using signal samples successively received at the same antenna element to estimate Doppler frequency offset and spread. It is necessary to ensure accurate calibration of the direction finding antenna and the receiver circuit. This is done by injecting calibration signals into the circuit near the antenna or into the antenna itself from a near field probe. Other aspects of calibration, such as antenna position, are calibrated using a remote beacon. A beacon emulating a mobile station but at a fixed, known location, or a beacon at an adjacent cell site may be used.

Position location method and apparatus for a mobile telecommunications system

A phase array antenna is monitored by applying to each element of the array in turn a signal known characteristics, detecting the signal output from the selected element as a result of the applied known signal, and comparing the detected signal with the applied signal whereby to monitor changes in the applied signal due to the signal path. The detection is preferably carried out using a single monitoring unit in the near-field of each antenna element. Alternatively the detection is carried out using a single source of applied signals a number of individual monitoring units one for each element of the array, and a switching device for selecting the element of the array to be monitored.

Phase control of transmission antennas

Interference on a differential signal received at a first input to a digital data system processor is minimised or cancelled by summing a weighted portion of a local field signal with the differential signal. The local field signal may be a common-mode signal from the same line as the differential signal received at a second input. Weight may be a complex weight which shifts the local field signal in amplitude and phase. A weight control signal is derived from a comparison processor which compares the processed outputs of signal processors. Signal processors are preferably Discrete Multi-tone processors. Several iterations of this technique may be performed to establish an accurate weighting value.

Interference reduction in telecommunications systems

A steered adaptive antenna arrangement including an adaptive beamforming network 10 to which the output signals of an array of antenna elements are applied, the network having a feedback wherein the summed output of the network is correlated with each element signal, applied to a limiter and added to the steering component whereby the derived value is used to drive the associated weight coefficient, characterized in that the summed output of the beamformer network 10 is further applied to a desired signal estimator 11 the output of which is subtracted from the summed output to provide the feedback input 12 to be correlated with each element signal.

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Great Dunmow, United Kingdom

Francis Giles Overbury