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 system for aligning a phase of data symbols positioned between at least two pilot symbol slots in a received data stream, one of the slots being currently received and the other slot being previously received, the system comprising:
a flag module configured to produce an enable signal when at least one of the pilot symbol slots is sensed;
an estimator configured to estimate a phase of a first pilot symbol in the currently received slot, and to produce a current phase estimate value based upon the enable signal; and
a comparator configured to compare the current phase estimate value with a phase estimate value from a second pilot symbol of the previously received slot to produce a difference phase estimate value;
wherein the phase of the data symbols is corrected based upon the difference phase estimate value.
2. The system of claim 1 , further comprising a delay module configured to delay the phase estimate value of the first pilot symbol.
3. The system of claim 2 , wherein the delay module includes a memory configured to store the delayed phase estimate value.
4. The system of claim 3 , wherein the difference phase estimate value is representative of a phase difference between the at least two pilot symbol slots.
5. The system of claim 4 , further comprising a processing module configured to produce a phase ramp representative of respective beginning and ending points of the first and second pilot symbols.
6. The system of claim 5 , wherein the processing module includes a scalar and a frequency synthesizer.
7. The system of claim 6 , wherein the phase ramp is converted to a complex sinusoidal value.
8. The system of claim 7 , further comprising a multiplier coupled to a second delay module and the processing module, the second delay module configured to store the data symbols.
9. The system of claim 8 , wherein the multiplier is configured to multiply the complex sinusoidal value with the data symbols.
10. The system of claim 9 , wherein the multiplying corrects the phase of the data symbols.
11. The system of claim 6 , wherein the scalar divides the difference phase estimate value by a number of data symbols between the first pilot symbol and the second pilot symbol.
12. The system of claim 11 , wherein the frequency synthesizer produces the phase ramp based on the divided difference phase estimate.
13. The system of claim 9 , wherein the complex sinusoidal value includes a real part that corresponds to a sine of the phase ramp, and an imaginary part that corresponds to a cosine of the phase ramp.
14. A non-transitory tangible computer readable medium having stored thereon computer executable instructions that, if executed by a computing device, cause the computing device to perform a method for aligning a phase of data symbols positioned between at least two pilot symbol slots in a received data stream, one of the slots being currently received and the other slot being previously received, the method comprising:
generating an enable signal when at least one of the pilot symbol slots is sensed;
estimating via a phase estimator a phase of a first pilot symbol in the currently received slot to produce a current phase estimate value based upon the enable signal;
comparing the current phase estimate value with a phase estimate value from a second pilot symbol of the previously received slot to produce a difference phase estimate value; and
correcting the phase of the data symbols based upon the difference phase estimate value.
15. The non-transitory tangible computer readable medium of claim 14 , wherein the comparing includes storing and delaying the phase estimate value of the first pilot symbol.
16. The non-transitory tangible computer readable medium of claim 15 , wherein the difference phase estimate value is representative of a phase difference between the at least two pilot symbol slots.
17. The non-transitory tangible computer readable medium of claim 16 , wherein the correcting includes producing a phase ramp representative of respective beginning and ending points of the first and second pilot symbols.
18. The non-transitory tangible computer readable medium of claim 17 , wherein the phase ramp is converted to a complex sinusoidal value.
19. The non-transitory tangible computer readable medium of claim 18 , wherein the correcting includes multiplying the complex sinusoidal value with the data symbols.
20. A system for aligning a phase of data symbols positioned between at least two pilot symbol slots in a received data stream, one of the slots being currently received and the other slot being previously received, the system comprising:
a flag module configured to produce an enable signal when at least one of the pilot symbol slots is sensed;
an estimator configured to estimate a phase of a first pilot symbol in the currently received slot and to produce a current phase estimate value based upon the enable signal;
a comparator configured to compare the current phase estimate value with a phase estimate value from a second pilot symbol of the previously received slot to produce a difference phase estimate value;
a processing module configured to produce a phase ramp representative of respective beginning and ending points of the first and second pilot symbols; and
a multiplier configured to multiply the data symbols with a complex sinusoidal value that is based on the phase ramp.