Channels estimation for multiple input—multiple output, orthogonal frequency division multiplexing (OFDM) system
First Claim
1. A method of estimating distortion in the sub-carrier channels of signals received by a respective receiver from a plurality of transmitters, each of said signals including a portion that represented a plurality of known values when said signal was transmitted, said method comprising:
- extracting said portion of said signal to obtain a frequency domain data vector;
multiplying each element of said frequency domain data vector by a respective element of a known vector to obtain a channel response vector, each element in said known vector being a function of a respective one of said plurality of known values, each element in said channel response vector being indicative of a distortion value;
selecting respective ones of said channel response vector to form a plurality of further channel response vectors, each of said further channel response vectors corresponding to a respective one of said plurality of transmitters, and inserting, within said each of said further channel response vectors, at least one zero value before or after each non-zero valued element therein such that said elements of said each of said further channel response vectors correspond to a transmission pattern of said corresponding one of said plurality of transmitters;
interpolating said elements of said further channel response vectors to obtain a plurality of distortion values each corresponding to a respective zero value element of said further channel response vectors, and substituting said plurality of distortion values in place of said corresponding zero value element;
performing an inverse fast Fourier transform (IFFT) on each of said further channel response vectors to obtain a plurality of time domain further channel response vectors;
substituting a zero value in place of any element of said time domain further channel response vectors that has a value indicative of signal noise; and
performing a fast Fourier transform (FFT) on said time domain further channel response vectors to obtain a plurality of frequency response vectors.
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0 Petitions
Accused Products
Abstract
The distortion in the sub-carrier signals is determined by transmitting known values that are incorporated into the preamble portion of the frame and/or are incorporated into pilot symbols that are inserted into the data portion of the frame. The receiver typically receives these known values in a distorted form and then processes the distorted values together with the original known values to obtain a channel response. The channel response is then used to estimate the frequencies at which the channels are received.
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Citations
59 Claims
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1. A method of estimating distortion in the sub-carrier channels of signals received by a respective receiver from a plurality of transmitters, each of said signals including a portion that represented a plurality of known values when said signal was transmitted, said method comprising:
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extracting said portion of said signal to obtain a frequency domain data vector;
multiplying each element of said frequency domain data vector by a respective element of a known vector to obtain a channel response vector, each element in said known vector being a function of a respective one of said plurality of known values, each element in said channel response vector being indicative of a distortion value;
selecting respective ones of said channel response vector to form a plurality of further channel response vectors, each of said further channel response vectors corresponding to a respective one of said plurality of transmitters, and inserting, within said each of said further channel response vectors, at least one zero value before or after each non-zero valued element therein such that said elements of said each of said further channel response vectors correspond to a transmission pattern of said corresponding one of said plurality of transmitters;
interpolating said elements of said further channel response vectors to obtain a plurality of distortion values each corresponding to a respective zero value element of said further channel response vectors, and substituting said plurality of distortion values in place of said corresponding zero value element;
performing an inverse fast Fourier transform (IFFT) on each of said further channel response vectors to obtain a plurality of time domain further channel response vectors;
substituting a zero value in place of any element of said time domain further channel response vectors that has a value indicative of signal noise; and
performing a fast Fourier transform (FFT) on said time domain further channel response vectors to obtain a plurality of frequency response vectors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of estimating distortion in the sub-carrier channels of signals received by a respective receiver from a plurality of transmitters, each of said signals including a portion that represented a plurality of known values when said signal was transmitted, said method comprising:
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extracting said portion of said signal to obtain a frequency domain data vector;
multiplying said frequency domain data vector by a known array to obtain a channel response vector, each element in said known array being a function of a respective one of said plurality of known values, each element in said channel response vector being indicative of a distortion value;
interpolating said elements of said channel response vector to obtain at least one distortion value corresponding to a respective zero value element of said further channel response vectors, and substituting said plurality of distortion values in place of said corresponding zero value element;
performing an inverse fast Fourier transform (IFFT) on said channel response vector to obtain a frequency domain channel response vector;
substituting a zero value in place of any element of said time domain further channel response vectors that has a value indicative of signal noise; and
performing a fast Fourier transform (FFT) on said time domain further channel response vectors to obtain a plurality of frequency response vectors. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of estimating distortion in the sub-carrier channels of signals received by a respective receiver from a plurality of transmitters, each of said signals including a portion that represented a plurality of known values when said signal was transmitted, said method comprising:
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extracting said portion of said signal during at least portion of a plurality of times nT, to obtain a plurality of sample values ri(nT), wherein i is an index of said respective receiver;
defining each of said plurality of sample values ri(nT) as a function of a plurality of time domain channel response values chmi(kT) according to the relation;
wherein m is an index of a respective one of said plurality of transmitters that is transmitting a non-zero value at time nT, Tn−
k is a corresponding one of said plurality of known values, and Ni(nT) is noise value for receiver i, thereby obtaining a plurality of equations;solving said plurality of equations to obtain a plurality of solutions; and
averaging said plurality of solutions to obtain said plurality of time domain channel response values chmi(kT). - View Dependent Claims (23, 24, 25, 26, 27, 28)
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29. An apparatus for estimating distortion in the sub-carrier channels of signals received by a respective receiver from a plurality of transmitters, each of said signals including a portion that represented a plurality of known values when said signal was transmitted, said apparatus being configured to:
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extract said portion of said signal to obtain a frequency domain data vector;
multiply each element of said frequency domain data vector by a respective element of a known vector to obtain a channel response vector, each element in said known vector being a function of a respective one of said plurality of known values, each element in said channel response vector being indicative of a distortion value;
select respective ones of said channel response vector to form a plurality of further channel response vectors, each of said further channel response vectors corresponding to a respective one of said plurality of transmitters, and inserting, within said each of said further channel response vectors, at least one zero value before or after each non-zero valued element therein such that said elements of said each of said further channel response vectors correspond to a transmission pattern of said corresponding one of said plurality of transmitters;
interpolate said elements of said further channel response vectors to obtain a plurality of distortion values each corresponding to a respective zero value element of said further channel response vectors, and substitute said plurality of distortion values in place of said corresponding zero value element;
perform an inverse fast Fourier transform (IFFT) on each of said further channel response vectors to obtain a plurality of time domain further channel response vectors substitute a zero value in place of any element of said time domain further channel response vectors that has a value indicative of signal noise; and
perform a fast Fourier transform (FFT) on said time domain further channel response vectors to obtain a plurality of frequency response vectors. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38)
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39. An apparatus for estimating distortion in the sub-carrier channels of signals received by a respective receiver from a plurality of transmitters, each of said signals including a portion that represented a plurality of known values when said signal was transmitted, said apparatus being configured to:
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extract said portion of said signal to obtain a frequency domain data vector;
multiply said frequency domain data vector by a known array to obtain a channel response vector, each element in said known array being a function of a respective one of said plurality of known values, each element in said channel response vector being indicative of a distortion value;
interpolate said elements of said channel response vector to obtain at least one distortion value corresponding to a respective zero value element of said further channel response vectors, and substitute said plurality of distortion values in place of said corresponding zero value element;
perform an inverse fast Fourier transform (IFFT) on said channel response vector to obtain a frequency domain channel response vector;
substitute a zero value in place of any element of said time domain further channel response vectors that has a value indicative of signal noise; and
perform an FFT on said time domain further channel response vectors to obtain a plurality of frequency response vectors. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49)
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50. An apparatus for estimating distortion in the sub-carrier channels of signals received by a respective receiver from a plurality of transmitters, each of said signals including a portion that represented a plurality of known values when said signal was transmitted, said apparatus being configured to:
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extract said portion of said signal during at least portion of a plurality of times nT, wherein n=0, 1, . . . , 1023, to obtain a plurality of sample values ri(nT), wherein i is an index of said respective receiver;
define each of said plurality of sample values ri(nT) as a function of a plurality of time domain channel response values chmi(kT) according to the relation;
wherein m is an index of a respective one of said plurality of transmitters that is transmitting a non-zero value at time nT, Tn−
k is a corresponding one of said plurality of known values, and Ni(nT) is noise value for receiver i, thereby obtaining a plurality of equations; andsolve said plurality of equations to obtain a plurality of solutions; and
average said plurality of solutions to obtain said plurality of time domain channel response values chmi(kT). - View Dependent Claims (51, 52, 53, 54, 55, 56)
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57. An apparatus for estimating distortion in the sub-carrier channels of signals received by a respective receiver from a plurality of transmitters, each of said signals including a portion that represented a plurality of known values when said signal was transmitted, said apparatus comprising:
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means for extracting said portion of said signal to obtain a frequency domain data vector;
means for multiply each element of said frequency domain data vector by a respective element of a known vector to obtain a channel response vector, each element in said known vector being a function of a respective one of said plurality of known values, each element in said channel response vector being indicative of a distortion value;
means for selecting respective ones of said channel response vector to form a plurality of further channel response vectors, each of said further channel response vectors corresponding to a respective one of said plurality of transmitters, and inserting, within said each of said further channel response vectors, at least one zero value before or after each non-zero valued element therein such that said elements of said each of said further channel response vectors correspond to a transmission pattern of said corresponding one of said plurality of transmitters;
means for interpolating said elements of said further channel response vectors to obtain a plurality of distortion values each corresponding to a respective zero value element of said further channel response vectors, and for substituting said plurality of distortion values in place of said corresponding zero value element;
means for performing an inverse fast Fourier transform (IFFT) on each of said further channel response vectors to obtain a plurality of time domain further channel response vectors;
means for substituting a zero value in place of any element of said time domain further channel response vectors that has a value indicative of signal noise; and
means for performing an fast Fourier transform (FFT) on said time domain further channel response vectors to obtain a plurality of frequency response vectors.
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58. An apparatus for estimating distortion in the sub-carrier channels of signals received by a respective receiver from a plurality of transmitters, each of said signals including a portion that represented a plurality of known values when said signal was transmitted, said apparatus comprising:
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means for sampling said portion of said signal to obtain a frequency domain data vector;
means for multiplying said frequency domain data vector by a known array to obtain a channel response vector, each element in said known array being a function of a respective one of said plurality of known values, each element in said channel response vector being indicative of a distortion value;
means for interpolating said elements of said channel response vector to obtain a least one distortion value corresponding to a respective zero value element of said further channel response vectors, and for substituting said plurality of distortion values in place of said corresponding zero value element;
means for performing an inverse fast Fourier transform (IFFT) on said channel response vector to obtain a frequency domain channel response vector;
means for substituting a zero value in place of any element of said time domain further channel response vectors that has a value indicative of signal noise; and
means for performing an fast Fourier transform (FFT) on said time domain further channel response vectors to obtain a plurality of frequency response vectors.
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59. An apparatus for estimating distortion in the sub-carrier channels of signals received by a respective receiver from a plurality of transmitters, each of said signals including a portion that represented a plurality of known values when said signal was transmitted, said apparatus comprising:
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means for sampling said portion of said signal during at least portion of plurality of times nT, wherein n=0, 1, . . . , 1023, to obtain a plurality of sample values ri(nT), wherein i is an index of said respective receiver;
means for defining each of said plurality of sample values ri(nT) as a function of a plurality of time domain channel response values chmi(kT)according to the relation;
wherein m is an index of a respective one of said plurality of transmitters that is transmitting a non-zero value at time nT, Tn−
k is a corresponding one of said plurality of known values, and Ni(nT) is noise value for receiver i, thereby obtaining a plurality of equations;means for solving said plurality of equations to obtain a plurality of solutions; and
means for averaging said plurality of solutions to obtain said plurality of time domain channel response values chmi(kT).
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Specification