patents

Alan James Coulson, Lower Hutt (NZ)

A method of detecting interference in a received sample vec­ tor 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.

Alan James Coulson, Waterloo (NZ); Chaturanga Pilane Lokuge, Tawa (NZ); Derek Bernard Richaedson, Belmot(NZ)

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.

Alan James Coulson, Lower Hutt (NZ)

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.

Industrial Research Limited, Lower Hutt (NZ)

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.

Alan James Coulson, Lower Hutt (NZ)

A method for reducing interference from at least one narrowband interferer in a pilot symbol assisted receiver (10) 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 (7, 8) 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 (3), and wherein the pilot symbol includes one or more repetitions of known data or pseudo noise.

Mark Poletti, Lower Hutt (NZ)

A circular transducer array is provided for use in recording a sound field. The array comprises a plurality of microphones, a digital processor, frequency compensation filters and a sum and difference network. The digital signal processor calculates the Fourier transform of sampled output signals from the transducers to produce a plurality of sound wave components specifying the sound field. The frequency compensation network equalises each component using Bassel functions to flatten the apparent response of the array and the sum difference network then combines the equalised components to provide a plurality of audio signals which represent the sound field.