Frequency-offset estimation
View Patent ↗A device for calculating an overall frequency-offset estimate from a plurality of frequency-offset estimates includes a receiver unit configured to receive a plurality of data streams, a phase shift estimation unit configured to generate a phase shift quantity representative of a phase shift over a number of consecutive data samples in the respective data stream, and a phase shift processing unit coupled to the phase shift estimation unit and configured to calculate a quantity related to the signal-to-noise ratio associated with a data stream on the basis of the respective phase shift quantity. Further, the device includes a frequency-offset estimation unit configured to generate frequency-offset estimates associated with the respective data streams, and a combiner configured to calculate an overall frequency-offset estimate on the basis of the frequency-offset estimates and on the basis of the quantities related to the signal-to-noise ratios.
1. A device for calculating an overall frequency-offset estimate from a plurality of frequency-offset estimates, comprising:
a receiver unit configured to receive a plurality of complex-valued data streams;
a phase shift estimation unit configured to generate a phase shift quantity representative of a phase shift over a number of consecutive data samples in the respective data stream;
a phase shift processing unit coupled to the phase shift estimation unit and configured to calculate a quantity related to the signal-to-noise ratio associated with a data stream on the basis of the respective phase shift quantity;
a frequency-offset estimation unit configured to generate frequency-offset estimates associated with the respective data streams; and
a combiner configured to calculate the overall frequency-offset estimate based on the frequency-offset estimates and the quantities related to the signal-to-noise ratios.
2. The device according to claim 1 , wherein an input of the frequency-offset estimation unit is coupled to an output of the phase shift estimation unit.
3. The device according to claim 1 , wherein the phase shift estimation unit comprises a multiplier for multiplying a data sample with a conjugate complex of a preceding data sample in the received data stream.
4. The device according to claim 3 , wherein the phase shift estimation unit comprises an averaging unit having an input coupled to an output of the multiplier.
5. The device according to claim 1 , wherein the combiner comprises a comparator configured to compare the quantities related to the signal-to-noise ratios with a threshold value.
6. The device according to claim 1 , wherein the combiner comprises a first weighting stage configured to weight the quantities related to the signal-to-noise ratios with a first weight factor dependent on a signal content of the data stream associated with the respective signal-to-noise ratio.
7. The device according to claim 6 , wherein the first weight factor is dependent on a service indicator transmitted by a signal source with respect to the respective data stream.
8. The device according to claim 1 , wherein the combiner comprises a second weighting stage configured to weight the frequency-offset estimates with a second weight factor dependent on the signal-to-noise ratio associated with the respective frequency-offset estimate.
9. The device according to claim 8 , wherein the combiner comprises an averaging stage configured to average the weighted frequency-offset estimates to generate the overall frequency-offset estimate.
10. A device for calculating an overall frequency-offset estimate from a plurality of frequency-offset estimates, comprising:
a receiver unit configured to receive a plurality of complex-valued data streams;
a frequency-offset estimation unit configured to generate frequency-offset estimates associated with the respective data streams;
a weighting stage configured to weight the frequency-offset estimates with a respective weight factor that is dependent on an importance of the associated data stream for signal demodulation; and
an averaging stage configured to average the weighted frequency-offset estimates to generate the overall frequency-offset estimate.
11. The device of claim 10 , wherein the weight factor is dependent on whether or not a specific service is supported by a signal source transmitting the respective signal.
12. A device for calculating an overall frequency-offset estimate from a plurality of frequency-offset estimates, comprising:
a weighting stage configured to weight the frequency-offset estimates with a respective weight factor that is dependent on a signal content of the signal from which the respective frequency-offset estimate was derived;
an averaging stage configured to average the weighted frequency-offset estimates to generate the overall frequency-offset estimate; and
a calculation unit configured to calculate a plurality of quantities which are each related to a signal-to-noise ratio associated with a signal from which the respective frequency-offset estimate was derived,
wherein the weighting stage is further configured to weight the frequency-offset estimates with the quantities which are each related to a signal-to-noise ratio.
13. A device for calculating a quantity related to a signal-to-noise ratio of a complex-valued data stream, comprising:
a phase shift estimation unit configured to generate a phase shift quantity representative of a phase shift occurred over a number of consecutive samples in the data stream, and
a phase shift processing unit coupled to the phase shift estimation unit and configured to calculate a quantity related to the signal-to-noise ratio associated with the complex-valued data stream on the basis of the respective phase shift quantity.
14. The device of claim 13 , wherein the phase shift processing unit comprises a squaring element.
15. The device of claim 13 , wherein the phase shift processing unit comprises a dividing stage.
16. The device of claim 15 , wherein the divisor used in the dividing stage comprises a factor representative of a power level of the complex-valued data stream.
17. A method for calculating an overall frequency-offset estimate from a plurality of frequency-offset estimates, comprising:
receiving a plurality of complex-valued data streams;
estimating for each data stream a phase shift quantity representative of a phase shift occurring over a number of consecutive data samples in the respective data stream;
calculating for each data stream a quantity related to the signal-to-noise ratio in the respective data stream on the basis of the phase shift quantity associated with the respective data stream;
generating frequency-offset estimates associated with the respective data streams using the estimated phase shift quantities and the quantities related to the signal-to-noise ratio; and
combining the frequency-offset estimates on the basis of the quantities related to the signal-to-noise ratios to yield the overall frequency-offset estimate.
18. The method of claim 17 , wherein estimating the phase shift quantity comprises multiplying a data sample by a complex conjugate of a preceding data sample in the respective data stream.
19. The method of claim 18 , wherein estimating the phase shift quantity comprises summing a plurality of multiplication results.
20. The method of claim 17 , wherein calculating the quantity related to the signal-to-noise ratio comprises squaring the respective phase shift quantity.
21. The method of claim 17 , wherein combining the frequency-offset estimates comprises weighting the quantities related to the signal-to-noise ratios with a first weight factor that is dependent on a signal content of the data stream associated with the respective signal-to-noise ratio.
22. A method for calculating an overall frequency-offset estimate from a plurality of frequency-offset estimates, comprising:
receiving a plurality of complex-valued data streams;
generating frequency-offset estimates associated with the respective data streams;
weighting the frequency-offset estimates with a respective weight factor that is dependent on an importance of the associated data stream for signal demodulation; and
averaging the weighted frequency-offset estimates to generate the overall frequency-offset estimate.
23. The method of claim 22 , wherein the weight factor is adjusted dependent on whether or not a specific service is supported by a signal source transmitting the respective signal.
24. A method for calculating an overall frequency-offset estimate from a plurality of frequency-offset estimates, comprising:
weighting the frequency-offset estimates with a respective weight factor that is dependent on the signal content of the signal from which the respective frequency-offset estimate was derived; and
averaging the weighted frequency-offset estimates to generate the overall frequency-offset estimate;
calculating a plurality of quantities that are each related to a signal-to-noise ratio associated with a signal from which the respective frequency-offset estimate was derived; and
weighting the frequency-offset estimates with the quantities that are each related to a signal-to-noise ratio.
25. A method for calculating a quantity related to a signal-to-noise ratio of a complex-valued data stream, comprising:
generating a phase shift quantity representative of a phase shift that occurred over a number of consecutive samples in the data stream; and
calculating a quantity related to the signal-to-noise ratio associated with a the complex-valued data stream based on the respective phase shift quantity.
26. The method of claim 25 , wherein calculating a quantity related to the signal-to-noise ratio comprises calculating the absolute value of the phase shift quantity.
27. The method of claim 26 , wherein calculating a quantity related to the signal-to-noise ratio comprises dividing the calculated absolute value of the phase shift quantity by a factor representative of a power level of the complex-valued data stream.