Phase tracking in communications systems
The present invention includes a method of determining a phase estimate for an input signal having pilot symbols. The method includes receiving a plurality of pilot symbols, and then multiplying two or more pilot symbol slots by corresponding correlator coefficients to correct a phase estimate of the input signal.
1. A method comprising:
receiving a first set of pilot symbols and a second set of pilot symbols in a data stream, wherein the data stream comprises data symbols positioned between the first set of pilot symbols and the second set of pilot symbols, and wherein the first set of pilot symbols and the second set of pilot symbols each comprise one or more pilot symbols;
generating a first phase estimate and a second phase estimate based on the first set of pilot symbols and the second set of pilot symbols respectively;
determining a phase difference between the second phase estimate and the first phase estimate; and
correcting phases associated with the data symbols in the data stream based on the phase difference, wherein correcting phases associated with the data symbols includes:
generating a phase ramp signal representative of respective beginning and ending points associated with the first set of pilot symbols and the second set of pilot symbols;
converting the phase ramp signal to a complex sinusoidal value; and
multiplying the complex sinusoidal value with the data symbols to correct phases of the data symbols,
wherein the receiving, generating, determining and correcting are performed by one or more circuits.
2. The method of claim 1 , wherein determining the phase difference includes:
delaying the first phase estimate by a delay unit to form a delayed first phase estimate; and
subtracting the delayed first phase estimate from the second phase estimate to form the phase difference.
3. The method of claim 1 , wherein generating the first phase estimate includes:
forming a first correlator output by multiplying the first set of pilot symbols with respective pilot symbol coefficients;
forming a second correlator output by multiplying the second set of pilot symbols with respective pilot symbol coefficients;
delaying the first correlator output by a delay unit to output a delayed first correlator output; and
forming a weighted sum of the delayed first correlator output and the second correlator output to generate the first phase estimate.
4. The method of claim 3 , wherein forming the weighted sum of the delayed first correlator output and the second correlator output includes:
multiplying the delayed first correlator output and the second correlator output with a first weighting coefficient and a second weighting coefficient respectively.
5. The method of claim 4 , wherein the first weighting coefficient and the second weighting coefficient are precalculated based on characteristics of a communication system that uses the data stream.
6. The method of claim 3 , wherein the pilot symbol coefficients comprise conjugates of corresponding pilot symbols.
7. The method of claim 1 , wherein correcting phases of the data symbols includes:
forming a complex sinusoid using a scalar value and a direct digital frequency synthesizer.
8. The method of claim 7 , wherein the scalar value is derived from a number of the data symbols.
9. The method of claim 1 , wherein the first weighting coefficient and the second weighting coefficient are precalculated based on characteristics of a channel associated with a communication system that uses the data stream.
10. A method comprising:
receiving first set of pilot symbols and a second set of pilot symbols in a data stream, wherein the data stream comprises data symbols positioned between the first set of pilot symbols and the second set of pilot symbols, and wherein the first set of pilot symbols and the second set of pilot symbols each comprise one or more pilot symbols;
generating a first phase estimate and a second phase estimate based on the first set of pilot symbols and the second set of pilot symbols respectively, where generating the first phase estimate and the second phase estimate includes being triggered based on sensing a presence of the first set of pilot symbols and the second set of pilot symbols respectively;
determining a phase difference between the second phase estimate and the first phase estimate; and
correcting phases associated with the data symbols in the data stream based on the phase difference,
wherein the receiving, generating, determining and correcting are performed by one or more circuits.
11. A system comprising:
one or more circuits configured to:
receive a first set of pilot symbols and a second set of pilot symbols in a data stream, wherein the data stream comprises data symbols positioned between the first set of pilot symbols and the second set of pilot symbols, and wherein the first set of pilot symbols and the second set of pilot symbols each comprise one or more pilot symbols;
generate a first phase estimate and a second phase estimate based on the first set of pilot symbols and the second set of pilot symbols respectively;
determine a phase difference between the second phase estimate and the first phase estimate; and
correct phases associated with the data symbols in the data stream based on the phase difference, wherein the one or more circuits are further configured to correct phases associated with the data symbols by:
generating a phase ramp signal representative of respective beginning and ending points associated with the first set of pilot symbols and the second set of pilot symbols;
converting the phase ramp signal to a complex sinusoidal value; and
multiplying the complex sinusoidal value with the data symbols to correct the phases associated with the data symbols.
12. The system of claim 11 , wherein the one or more circuits are farther configured to determine the phase difference by:
delaying the first phase estimate by a delay unit to form a delayed first phase estimate; and
subtracting the delayed first phase estimate from the second phase estimate to form the phase difference.
13. The system of claim 11 , wherein the one or more circuits are further configured to generate the first phase estimate by:
forming a first correlator output by multiplying the first set of pilot symbols with respective pilot symbol coefficients;
forming a second correlator output by multiplying the second set of pilot symbols with respective pilot symbol coefficients;
delaying the first correlator output by a delay unit to output a delayed first correlator output; and
forming a weighted sum of the delayed first correlator output and the second correlator output to generate the first phase estimate.
14. The system of claim 13 , wherein the one or more circuits are further configured to form the weighted sum of the delayed first correlator output and the second correlator output by:
multiplying the delayed first correlator output and the second correlator output with a first weighting coefficient and a second weighting coefficient respectively.
15. The system of claim 14 , wherein the first weighting coefficient and the second weighting coefficient are precalculated based on characteristics of a communication system that uses the data stream.
16. The system of claim 13 , wherein the pilot symbol coefficients comprise conjugates of corresponding pilot symbols.
17. The system of claim 11 , wherein the one or more circuits are further configured to correct the phases associated with the data symbols by:
forming a complex sinusoid using a scalar value and a direct digital frequency synthesizer.
18. The system of claim 17 , wherein the scalar value is derived from a number of the data symbols.
19. The system of claim 11 , wherein the first weighting coefficient and the second weighting coefficient are precalculated based on characteristics of a channel associated with a communication system that uses the data stream.
20. A system comprising:
one or more circuits configured to:
receive a first set of pilot symbols and a second set of pilot symbols in a data stream, wherein the data stream comprises data symbols positioned between the first set of pilot symbols and the second set of pilot symbols, and wherein the first set of pilot symbols and the second set of pilot symbols each comprise one or more pilot symbols;
generate a first phase estimate and a second phase estimate based on the first set of pilot symbols and the second set of pilot symbols respectively;
determine a phase difference between the second phase estimate and the first phase estimate; and
correct phases associated with the data symbols in the data stream based on the phase difference,
wherein the one or more circuits are further configured to generate the first phase estimate and the second phase estimate by being triggered based on sensing a presence of the first set of pilot symbols and the second set of pilot symbols respectively.