Pilot-aided channel estimation for OFDM in wireless systems
AssigneeAT&T Corp.
InventorYe Li
Life of this patent
Estimating the term…
Abstract
A method and apparatus for pilot-symbol aided channel estimation in a wireless digital communication system which transmits packets of N OFDM data blocks, each data block comprising a set of K orthogonal carrier frequencies. At the transmitter, pilot symbols are inserted into each data packet at known positions so as to occupy predetermined positions in the time-frequency space. At the receiver, the received signal is subject to a two-dimensional inverse Fourier transform, two-dimensional filtering and a two-dimensional Fourier transform to recover the pilot symbols so as to estimate the channel response.
Claims20
A method for processing an OFDM signal received over a wireless communication channel, said OFDM signal comprising a packet of a number N of OFDM blocks, each OFDM block comprising a number K of signal tones, the method comprising the steps of:
- sequentially receiving N channel-impaired OFDM blocks;
- computing noisy channel estimates, based on said channel-impaired blocks;
- arranging the noisy channel estimates into a first array having a first axis representative of a frequency index of the noisy channel estimates and a second axis representative of a time index of the noisy channel estimates;
- performing a first two-dimensional Fourier transform on said first array;
- multiplying the Fourier transformed first array with a second array representing a two-dimensional filter to thereby form a third array;
- and
- performing a second two-dimensional Fourier transform on said third array to thereby form a fourth array comprising elements representative of an estimate of channel parameters for said wireless communication channel.
A method of estimating channel parameters for a wireless communication channel by transmitting a signal from a transmitter to a receiver, the method comprising the steps of:
- inserting pilot symbols at predetermined positions in a plurality of blocks, each block comprising a plurality of data symbols representative of a signal being transmitted;
- sequentially transmitting each of said plurality of blocks over a finite number of tones, said finite number of tones being broadcast substantially simultaneously for each block;
- sequentially receiving a corresponding plurality of channel-impaired blocks at the receiver;
- computing a corresponding plurality of noisy channel estimates from said plurality of channel-impaired blocks;
- arranging the plurality of noisy channel estimates into a first array having a first axis representative of a frequency index of the noisy channel estimates and a second axis representative of a time index of the noisy channel estimates;
- performing a first two-dimensional Fourier transform on said first array;
- multiplying the Fourier transformed first array with a second array representing a two-dimensional filter to thereby form a third array;
- and
- performing a second two-dimensional Fourier transform on said third array to thereby form a fourth array comprising elements representative of the channel parameters.
An apparatus for processing an OFDM signal received over a wireless communication channel, said OFDM signal comprising a packet of a number N of OFDM blocks, each OFDM block comprising a number K of signal tones, said apparatus comprising:
- at least one antenna arranged to sequentially receive N channel-impaired OFDM blocks;
- a first multiplier configured to compute K noisy channel estimates for each of said N channel-impaired blocks, based on said channel-impaired blocks;
- a first two-dimensional transformer arranged to perform a first two-dimensional transform on the K noisy channel estimates for each of the N blocks, wherein said noisy channel estimates are arranged into a first array having a first axis representative of a frequency index of the noisy channel estimates and a second axis representative of a time index of the noisy channel estimates;
- a second multiplier configured to multiply the two-dimensional transformed first array with a second array representing a two-dimensional filter to thereby form a third array;
- and
- a second two-dimensional transformer arranged to perform a second two-dimensional transform on said third array to thereby form a fourth array comprising elements representative of an estimate of channel parameters for said wireless communication channel.
A diversity receiver for receiving an OFDM signal over a wireless communication channel, said OFDM signal comprising a packet of a number N of OFDM blocks, each OFDM block comprising a number K of signal tones, said receiver comprising:
- a plurality of antennas, each antenna configured to sequentially receive N channel-impaired OFDM blocks which have been transmitted over said wireless communication channel;
- a channel estimator configured to estimate channel parameters for the wireless communication channel based on the N channel-impaired OFDM blocks received by each antenna, said channel estimator comprising:
- a first two-dimensional transformer arranged to perform a first two-dimensional transform on a two-dimensional array of noisy channel estimates;
- a second multiplier configured to multiply the output of the first two-dimensional transformer with a second array representing a two-dimensional filter to thereby form a third array;
- and
- a second two-dimensional transformer arranged to perform a second two-dimensional transform on said third array to thereby form a fourth array comprising elements representative of an estimate of channel parameters for said wireless communication channel;
- and
- a diversity combiner arranged to estimate a transmitted signal based on said elements representative of an estimate of channel parameters produced by said channel estimator and said N channel-impaired OFDM blocks received at each antenna.
Dependencies are inferred from the claim text.