Industrial Research Limited

Alan James Coulson

Chaturanga Pilans Lokuge

Derek Bernard Richardson

A method of detecting interference in a received sample vector using hidden Markov modelling by first estimating noise variance, where estimating noise variance comprises the steps of receiving a sample vector of noise and interference, sorting the sample vector in the frequency domain by order of increasing magnitude to produce an ordered vector, finding a sub-vector of the ordered vector that minimizes the distance from a noise measure, and estimating the noise variance.

Detection of wideband interference

A method for reducing interference from at least one narrowband interferer in a pilot symbol assisted receiver () includes the steps of; receiving a stream of received data, passing the stream of received data through an adaptive filter that reduces interference from any narrowband interferer, passing the filtered data through a correlator () arranged to detect pilot symbols, when a pilot symbol is detected passing the stream of received data to a receiving apparatus without first passing the received data through the adaptive filter (), and wherein the pilot symbol includes one or more repetitions of known data or pseudo noise.

Method and apparatus for improving the performance of pilot symbol assisted receivers in the presence of narrowband interference

A method for suppressing narrowband interference in OFDM receivers is provided including the steps of acquiring a sample of received data, estimating parameters of each of a number of narrowband interferers from the acquired sample of data, forming an excision filter using the estimated parameters and inserting the excision filter into an OFDM receiver.

Narrowband interference suppression for OFDM systems

A method and apparatus for detecting and synchronizing packets of data with a repeated sequence as a pilot symbol received by a communications system are provided. The method and apparatus include receiving data, detecting a packet within the received data, producing an estimate of the time-varying frequency offset of the received data, estimating the start of the packet of the received data, estimating the time-varying phase offset of the received data and estimating the time-varying time offset of the received data. Methods for assessing each one of the time-varying frequency offset, the time-varying phase offset, the time-varying time offset and the start of packet are also provided.

Maximum likelihood synchronization for a communications system using a pilot symbol

The OFDM communications system for wireless networks includes at least one transmitter and at least one receiver. Each transmitter includes a signal source, a transmit modulator that arranges the data into packets and appends a pilot symbol of a repeated pseudo random binary sequence to the start of each packet, a multiplexer, an inverse fast Fourier transform, an up-sampler, a digital low pass filter, a digital to analogue converter, and an RF module. Each receiver includes an RF module, an analogue to digital converter, a digital low pass filter, a down-sampler, a frame detector to search for significant pilot symbol correlations and make initial estimates of at least one signal parameter, a digital phase locked loop to remove estimated frequency- and phase-offsets, a fast Fourier transform operator, a linear phase corrector to remove estimated sub-sample timing errors, a decision block, and a demultiplexer.

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Lower Hutt, New Zealand

Alan James Coulson