US 8,559,546 B2 · Methods and an apparatus for estimating a residual frequency error in a comunications system

Abstract

The present invention relates to methods and an apparatus for estimating a residual frequency error. According to an embodiment, an expected vector for selected subcarriers of a received symbol is estimated using a channel estimate vector and a reference vector; a sampling frequency mismatch is removed and a dot product is calculated using the expected and a received vector. An angle of the product is estimated and a change in angle from a previous symbol is calculated. The residual frequency is estimated using the calculated change in angle. In another embodiment, an expected subcarrier is estimated based on a channel estimate and on a reference subcarrier, an angle and magnitude of the multiplication between the expected and a received subcarrier are estimated; a phase offset is removed; a weighted mean value of the angles is calculated and the residual frequency error is estimated using a change in weighted mean angle.

Claims25

Dependent claims

A method for estimating a residual frequency error in a Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) receiver, the method comprising:

(1) estimating, for selected subcarriers of a current symbol of a received signal, an expected vector based on a channel estimate vector and on a reference vector;
(2) removing, by phase rotation, a sampling frequency mismatch of the reference vector from the expected vector;
(3) calculating a dot product of the estimated expected vector and a received vector;
(4) estimating, by an angle estimator, an angle of the calculated dot product;
(5) calculating a change in angle from an accumulated phase of a previous symbol, based on the estimated angle of the calculated dot product of the current symbol and an estimated angle of a calculated dot product of the previous symbol;
and
(6) estimating the residual frequency error based on the calculated change in angle.

4 more elements

A method for estimating a residual frequency error in a Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) receiver, the method comprising:

(1) estimating, for each subcarrier of a current symbol of a received signal, an expected subcarrier based on a channel estimation of a subcarrier and on a reference subcarrier;
(2) multiplying in a complex plane, for each subcarrier of the current symbol, the estimated expected subcarrier and a received subcarrier;
(3) estimating, by an angle and magnitude estimator, for each subcarrier of the current symbol, an angle and magnitude of the multiplication performed in the multiplying step;
(4) removing, for each subcarrier of the current symbol, a phase offset caused by a sampling frequency mismatch;
(5) calculating a weighted mean value of the estimated angles and magnitudes from the estimating step;
(6) calculating a change in a weighted mean angle from a previous symbol, based on the calculated weighted mean value of the estimate angles and magnitudes of the current symbol and a calculated weighted mean value of estimate angles and magnitudes of the previous symbol;
and
(7) estimating the residual frequency error based on the change in the weighted mean angle.

5 more elements

Dependencies are inferred from the claim text.

Methods and an apparatus for estimating a residual frequency error in a comunications system

Life of this patent

Methods and an apparatus for estimating a residual frequency error in a comunications system

Life of this patent

Abstract

Claims25