Communication system and methods of estimating channel impulse responses therein
First Claim
1. A method of determining channel impulse responses of a plurality of channels to a communication device, the method comprising:
- performing 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;
performing point-by-point operations between corresponding signal sequence frequency bins and training sequence frequency bins; and
concatenating 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.
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Accused Products
Abstract
Multiple Steiner codes are transmitted as bursts (s11, s12, . . . s33, 560, 524) from multiple base stations (182, 184, 186) having one or more transmit elements (174, 176, 178, 180), with successive bursts providing an extended training sequence for use in channel estimation at an addressed unit (172), such as a mobile handset. Accurate channel estimation is possible through the use of Wiener frequency domain MMSE deconvolution (518) combined with frequency domain spatial decoupling matrices, with quasi-orthogonal pseudo-noise sequences (502, 504, 520, 522) allocated to base stations and their antenna elements. The use of Steiner codes to supplement Wiener frequency domain MMSE deconvolution and frequency domain spatial decoupling results in the possibility of allocating only a single training sequence to each base station provided that the training sequence is of sufficient length to encompass all multiple time-translated channel impulse responses (H). Estimates may be refined iteratively by minimizing the MS error of demodulated pilot symbols. Estimates may also be refined by removing taps from the impulse response which are insignificant based on a relatively long-term power-delay profile for the channel.
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Citations
59 Claims
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1. A method of determining channel impulse responses of a plurality of channels to a communication device, the method comprising:
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performing 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;
performing point-by-point operations between corresponding signal sequence frequency bins and training sequence frequency bins; and
concatenating 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. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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10. A method of determining channel impulse responses of channels incident to a communication device, the method comprising:
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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;
applying a Wiener frequency domain MMSE deconvolution with frequency domain spatial decoupling matrices to generate channel impulse response estimates for the channels. - View Dependent Claims (11, 12)
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13. 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:
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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 yn from the different training bursts sn; 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.
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14. A computer program product for a processor within a receiver device, the computer program product comprising:
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code that performs transform operations on both a replica of a signal sequence s, 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;
code that performs point-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;
wherein the codes reside in a computer readable medium.
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15. A communication device having a receiver coupled, in use, to receive a plurality of channels supporting a signal sequence yn and training sequence bursts, the communication device having:
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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 the channel impulse response for the channel. - View Dependent Claims (16, 17, 18, 19)
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20. A communication receiver comprising:
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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. - View Dependent Claims (21)
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22. A communication device operational to receive a plurality of training sequences on a plurality of channels and a signal sequence yn, the communication device comprising:
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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 yn from the different training bursts sn; 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.
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23. 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 sn from at least one transmit element and further arranged to transmit a signal sequence yn, 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 yn 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.- View Dependent Claims (24, 25, 26)
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27. A method of estimating a channel impulse response comprising:
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(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 the non quadratic, non linear error metric of the demodulated training symbol against a locally stored record of its known correct value, (e) adjusting the 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. - View Dependent Claims (8, 9, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. A method of estimating a channel impulse response comprising;
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(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 power delay profile, have a variance below the predetermined variance threshold. - View Dependent Claims (39, 40, 41, 42, 43, 44, 46, 48, 49)
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45. A method according to claim 447 wherein the short term channel estimate is produced using a Bayesian method.
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47. A method of estimating a channel impulse response comprising:
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(a) taking long-term measurements to build a database of where in time, multipath interference is located in the channel to generate an incoherent power delay profile for the channel, and (b) modelling a relatively short term channel impulse response by allocating variable complex amplitudes and phases to the taps at the locations in the short term model which have the multipath power in the incoherent power delay profile which is above a predetermined threshold.
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50. A computer program product which when executed by a computer causes the computer to carry out the steps of:
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(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 the 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. - View Dependent Claims (51, 52)
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53. A computer program product which when executed by a computer causes the computer to carry out the steps of:
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(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 power delay profile, have a variance below the predetermined variance threshold. - View Dependent Claims (54)
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55. 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:
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(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 the 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. - View Dependent Claims (56, 57)
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58. 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:
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(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 power delay profile, have a variance below the predetermined variance threshold. - View Dependent Claims (59)
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Specification