Compensation of sampling frequency offset and local oscillator frequency offset in a ofdm receiver
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsSteve Duncan, Rob Heaton
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Abstract
A partial Fourier Transform is performed, using Goertzel's algorithm, to calculate two frequency bins. A phase variation is calculated for each bin, the phase variation preferably representing the phase difference between the bin calculated by a Fourier Transform performed on samples in a guard interal and the bin calculated by a Fourier Transform performed on matching samples within the useful part of the symbol. The local oscillator frequency offset is compensated by summing the phase variations, and the sampling frequency offset is compensated by taking the difference between the phase variations.
Claims27
A method of compensating for sampling frequency offset in an OFDM receiver which samples a received multicarrier signal and performs a Fourier Transform on the sampled signal to extract data therefrom, the method comprising
- performing a separate Fourier Transform on the sampled signal, the separate Fourier Transform being a partial and/or reduced Fourier Transform to derive phase values for at least two points thereof, and
- compensating for the sampling frequency offset in dependence on the phase values.
A method as claimed in any preceding claim, wherein the separate Fourier Transform is a reduced Fourier Transform.
A method as claimed in any preceding claim, including performing the compensation for the sampling frequency offset in dependence on phase values measured over a plurality of OFDM symbols.
A method as claimed in any preceding claim, wherein the separate Fourier Transform is a partial Fourier Transform.
A method as claimed in any preceding claim, wherein the phase values for said points are calculated only in response to selected samples of the received signal.
A method as claimed in any preceding claim, wherein the compensation for the sampling frequency offset is performed by adjusting the sampling frequency.
A method of synchronising an OFDM receiver, the method comprising
- compensating the sampling frequency offset of the OFDM receiver using a method as claimed in any preceding claim, and
- compensating for a local oscillator-frequency offset in dependence upon one of the phase values for at least one of said points.
A method of compensating for a local oscillator frequency offset in an OFDM receiver which samples a received multicarrier signal and performs a Fourier Transform on the sampled signal to extract data therefrom, the method comprising
- performing a separate Fourier Transform on the sampled signal, the separate Fourier Transform being a partial and/or reduced Fourier Transform to derive a phase value for at least one point thereof, and
- compensating for the local oscillator frequency offset in dependence on the phase value.
A method of synchronising an OFDM receiver which samples a received multicarrier signal and performs a Fourier Transform on the sampled signal to extract data therefrom, the method comprising
- performing a separate Fourier Transform on the sampled signal, the separate Fourier Transform comprising a partial and/or reduced Fourier Transform to derive phase values for at least two points thereof,
- determining, for each point, a phase variation corresponding to the difference between the phase values at different parts of an OFDM symbol separated by the useful part of the symbol,
- compensating for an offset of the sampling frequency in dependence on the difference between the phase variations and
- compensating for an offset of a local oscillator frequency in dependence on at least one of the phase variations.
An OFDM receiver operable to perform a synchronising operation using a method as claimed in any preceding claim.
Dependencies are inferred from the claim text.