Communication system and methods of estimating channel impulse responses therein

A method of determining channel impulse responses of channels incident to a communication device, the method comprising:

• transmitting multiple quasi-orthogonal pseudo-noise sequences as bursts from multiple base stations each having at least one transmit element, successive bursts providing an extended training sequence for use in channel estimation at the communication device;
• and
• applying a Wiener frequency domain MMSE deconvolution with frequency domain spatial decoupling matrices to generate channel impulse response estimates for the channels:
• wherein the quasi-orthogonal pseudo-noise sequences are Steiner codes.

A method of determining channel impulse responses of a plurality of channels established between a plurality of transmitting elements and a communication device in a communication system, the method comprising:

• substantially simultaneously transmitting different training bursts from each of the plurality of transmitting elements, each burst having a length at least as long as a maximum channel duration in the communication system multiplied by a number corresponding to the plurality of transmitting elements;
• recovering at the communication device a signal sequence Sn from the different training bursts Yn;
• and
• resolving the plurality of channels to recover associated channel impulse responses H for each channel by solving an algebraic matrix operation expressed in matrix-vector form as Y=SH, where:
• S is a matrix of partial training bursts for each channel, each training burst segmented into N pieces in the time domain;
• Y is a vector of a received signal sequence;
• and H is a concatenation of different channel impulse response vectors;
• wherein multiple Steiner codes are transmitted as training sequences, the multiple Steiner codes sent from multiple transmit elements in multiple training bursts.

A computer program product residing in a computer readable medium and for a processor within a receiver device, the computer program product comprising:

• code that performs transform operations an both a replica of a signal sequence sn and a received training sequence yn received by a communication device in at least one burst, the received training sequence yn being one of multiple Steiner codes, the multiple Steiner codes sent from multiple transmit elements in multiple training bursts and being the signal sequence as received through a channel, the transform operations arranged to generate a multiplicity of signal sequence frequency bins and a multiplicity of training sequence frequency bins;
• code that performs paint-by-point operations between corresponding signal sequence frequency bins and training sequence frequency bins;
• and
• code that concatenates the point-by-point operations associated with the channel to provide a composite frequency response for the channel, the composite frequency response allowing, in the time domain, generation of the channel impulse response for the channel.

A communication device having a receiver coupled, in use, to receive a plurality of channels supporting a signal sequence sn and training sequence yn bursts, the communication device having:

• a signal processing platform to perform transform operations on both a replica of a signal sequence sn and a received training sequence yn received by the communication device in at least one burst, the received training sequence yn being the signal sequence as received through a channel, the transform operations arranged to generate a multiplicity of signal sequence frequency bins and a multiplicity of training sequence frequency bins;
• the signal processing platform arranged to perform point-by-point operations between corresponding signal sequence frequency bins and training sequence frequency bins;
• and
• the signal processing platform further arranged to concatenate the point-by-point operations associated with the channel to provide a composite frequency response for the channel, the composite frequency response allowing, in the time domain, generation of a channel impulse response for the channel;
• whereby multiple Steiner codes are transmitted as the training sequences, the multiple Steiner codes sent to the receiver through multiple channels in multiple training bursts.

A communication receiver comprising:

• means for receiving, in use, multiple quasi-orthogonal pseudo-noise sequences as bursts from multiple base stations each having at least one transmit element, successive bursts providing an extended training sequence for use in channel estimation at the communication receiver;
• and
• means for applying a Wiener frequency domain MMSE deconvolution with frequency domain spatial decoupling matrices to generate channel impulse response estimates for the channels;
• wherein the quasi-orthogonal pseudo-noise sequences are Steiner codes.

A communication device operational to receive a plurality of training sequences on a plurality of channels and a signal sequence Sn, the communication device comprising:

• a receiver for substantially simultaneously receiving, in use, different training bursts from each of the plurality of channels emanating from a plurality of transmit elements, each burst having a length at least as long as a maximum channel duration multiplied by a number corresponding to the plurality of transmit elements;
• recovery circuitry for recovering, in use, the signal sequence Sn from the different training bursts Yn;
• and
• a processor arranged to resolve the plurality of channels to recover associated channel impulse responses H for each channel by solving an algebraic matrix operation expressed in matrix-vector form as Y=SH, where:
• S is a matrix of partial training bursts for each channel, each training burst segmented into N pieces in the time domain;
• Y is a vector of a received signal sequence;
• and H is a concatenation of different channel impulse response vectors;
• wherein multiple Steiner codes are transmitted as training bursts, the multiple Steiner codes sent from multiple transmit elements in multiple training bursts.

A base station of a communication system, the base station comprising:

• a transmitter chain arranged to transmit multiple quasi-orthogonal pseudo-noise sequences as training bursts Yn from at least one transmit element and further arranged to transmit a signal sequence Sn, successive training bursts providing an extended training sequence for use in channel estimation at a communication device of the communication system, the transmitter chain substantially simultaneously transmitting, in use, different training bursts from each of the at least one transmit element, each training burst having a length at least as long as a maximum channel duration in the communication system multiplied by a number corresponding to a plurality of channels to the communication device, the extended training sequence and the signal sequence Sn providing a resolution mechanism to the communication device allowing the communication device to resolving the plurality of channels to recover associated channel impulse responses H for each channel by solving an algebraic matrix operation expressed in matrix-vector form as Y=SH, where:
• S is a matrix of partial training bursts for each channel, each training burst segmented into N pieces in the time domain;
• Y is a vector of a received signal sequence;
• and H is a concatenation of different channel impulse response vectors;
• multiple Steiner codes are transmitted as training bursts, the multiple Steiner codes sent from multiple transmit elements in multiple training bursts.

A method of estimating a channel impulse response comprising:

• (a) receiving a signal including a training sequence of predetermined training symbols,
• (b) passing the received signal through a channel equaliser to substantially remove distortion of the signal caused by transmission over a channel,
• (c) demodulating at least one of the training symbols,
• (d) calculating a non quadratic, non linear error metric of the demodulated training symbol against a locally stored record of a known correct value of the demodulated training symbol
• (a) adjusting the estimated channel impulse response to substantially minimise a mean square error, and
• (f) feeding the adjusted estimated channel impulse response back to the channel equaliser for use in subsequent equalisation operations;
• whereby channel estimates used in the channel equaliser are iteratively refined;
• and multiple transmissions are received over a plurality of channels each including a training sequence and wherein a summed mean square error of all training sequences is minimised by adjusting the estimated channel response h for each tap of each channel impulse response in turn according to the equation
• θ(h)=(h−hOPT)HM(h−hOPT)+c
• where h is a vector of channel impulse responses for all channels, hOPT is an optimum channel impulse response, M is a matrix representing cross-coupling between channel components and a is the minimum error.

A method of estimating a channel impulse response comprising:

• (a) obtaining a long-term averaged power delay profile for the channel,
• (b) setting a predetermined variance threshold,
• (c) estimating a channel impulse response having a plurality of taps, and
• d) removing taps from the channel impulse response estimate equivalent to those which in the long-term averaged power delay profile, have a variance below the predetermined variance thresholds;
• wherein the channel impulse response estimate is combined with an accuracy of the channel impulse response estimate as predicted point-by-point from a combined power delay profile end interference level, whereby a modified short term, channel estimate is produced in which points likely to have poor accuracy are deweighted and those likely to have good accuracy are retained such that a final equalise performance is optimised.

A computer program product residing in a computer readable medium which when executed by a computer causes the computer to carry out the steps of:

• (a) receiving a signal including a training sequence of predetermined training symbols,
• (b) passing the received signal through a channel equaliser to substantially remove distortion of the signal caused by transmission over a channel,
• (c) demodulating at least one of the training symbols,
• (d) calculating a non quadratic, non linear error metric of the demodulated training symbol against a locally stored record of a known correct value of the demodulated training symbol,
• (e) adjusting an estimated channel impulse response to substantially minimise the mean square error, and
• (f) feeding the adjusted estimated channel impulse response back to the channel equaliser for use in subsequent equalisation operations
• whereby channel estimates used in the channel equaliser are iteratively refined;
• and wherein multiple transmissions are received over a plurality of channels each including a training sequence and wherein a summed mean square error of all training sequences is minimised by adjusting the estimated channel response h for each tap of each channel impulse response in turn according to the equation
• θ(h)=(h−hOPT)HM(h−hOPT)+c
• where h is the vector of channel impulse responses for all channels, hOPT is the optimum channel impulse response, M is a matrix representing cross-coupling between channel components and c is the minimum error.

A computer program product residing in a computer readable medium which when executed by a computer causes the computer to carry out the steps of:

• (a) obtaining a long-term averaged power delay profile for the channel,
• (b) setting a predetermined variance threshold,
• (c) estimating a channel impulse response having a plurality of taps, and
• (d) removing taps from the channel impulse response estimate equivalent to those which in the long-term averaged power delay profile, have a variance below the predetermined variance threshold;
• wherein the channel impulse response estimate is combined with the accuracy of the channel impulse response as predicted point-by-point from the combined power delay profile and interference level, whereby a modified short tern channel estimate is produced in which points likely to have poor accuracy are deweighted and those likely to have good accuracy are retained such that final equalise performance is optimised.

A communications receiver arranged to receive signals from a plurality of sources and arranged to estimate a channel impulse response for a channel between the receiver and each source by:

• (a) receiving a signal including a training sequence of predetermined training symbols,
• (b) passing the received signal through a channel equaliser to substantially remove distortion of the signal caused by transmission over a channel,
• (c) demodulating at least one of the training symbols,
• (d) calculating a non quadratic, non linear error metric of the demodulated training symbol against a locally stored record of its known correct value,
• (e) adjusting an estimated channel impulse response to substantially minimise the mean square error, and
• (f) feeding the adjusted estimated channel impulse response back to the channel equaliser for use in subsequent equalisation operations;
• whereby the channel estimates used in the channel equaliser are iteratively refined;
• and multiple transmissions are received over a plurality of channels each including a training sequence and wherein a summed mean square error of all training sequences is minimised by adjusting the estimated channel response h for each tap of each channel impulse response in turn according to the equation
• θ(h)=(h−hOPT)HM(h−hOPT)+c
• where h is a vector of channel impulse responses for all channels, hOPT is an optimum channel impulse response, M is a matrix representing cross-coupling between channel components and c is the minimum error.

A communications receiver arranged to receive signals from a plurality of sources and arranged to estimate a channel impulse response for the channel between the receiver and each source by:

• (a) obtaining a long-term averaged power delay profile for the channel,
• (b) setting a predetermined variance threshold,
• (c) estimating a channel impulse response having a plurality of taps, and
• (d) removing taps from the channel impulse response estimate equivalent to those which in the long-term averaged power delay profile, have a variance below the predetermined variance threshold;
• wherein the channel impulse response estimate is combined with the accuracy of the channel impulse response as predicted point-by-point from a combined power delay profile and interference level, whereby a modified short term channel estimate is produced in which points likely to have poor accuracy are deweighted and those likely to have good accuracy are retained such that final equalise performance is optimised.