System and method for mitigating frequency offsets in wireless systems
Exemplary communication apparatus can comprise a receiver; a computer arrangement; and a non-transitory medium comprising computer-executable instructions that cause the apparatus to: receive a signal comprising a plurality of symbols in a first domain; store a portion of the signal comprising at least one symbol in a buffer; determine a frequency offset parameter relating to the buffered portion; apply a correction signal based on the offset parameter to the buffered portion to generate an at least partially corrected signal in the first domain; and transform the at least partially corrected signal into a second domain. In some embodiments, the first domain is a time domain, the second domain is a frequency domain, and the symbols are OFDM symbols. The corrected signal can be further transformed into a third domain. Further, exemplary methods and computer-readable media can be provided embodying one or more procedures the apparatus is configured to perform.
1. A communication apparatus, comprising:
a receiver;
a computer arrangement; and
a non-transitory, computer-readable medium comprising computer-executable instructions that, when executed by the computer arrangement, cause the apparatus to:
receive a signal comprising a plurality of symbols in a first domain;
store a portion of the signal comprising no more than one symbol in a buffer;
determine a frequency offset parameter relating to the buffered portion;
apply a correction signal to the buffered portion to generate an at least partially corrected signal in the first domain, wherein the correction signal is based on the frequency offset parameter; and
transform the at least partially corrected signal into a second domain.
2. The communication apparatus of claim 1 , wherein the first domain is a time domain, and the second domain is a frequency domain.
3. The communication apparatus of claim 1 , wherein each of the plurality of symbols is an OFDM symbol comprising a cyclic prefix, and the frequency offset parameter is determined based on a cyclic prefix comprising the buffered portion.
4. The communication apparatus of claim 1 , wherein the instructions that cause the apparatus to determine the frequency offset parameter further cause the apparatus to:
compute a representation of the buffered portion in the second domain; and
determine the frequency offset parameter based on a plurality of reference elements comprising the representation of the buffered portion in the second domain.
5. The communication apparatus of claim 4 , wherein the second domain is a frequency domain and the plurality of reference elements comprise at least one of pilot symbols and reference subcarriers.
6. The communication apparatus of claim 1 , wherein the medium further comprises instructions that, when executed by the computer arrangement, cause the apparatus to estimate a residual frequency offset corresponding to the at least partially corrected signal in the second domain.
7. The communication apparatus of claim 1 , wherein the medium further comprises instructions that, when executed by the computer arrangement, cause the apparatus to further transform the at least partially corrected signal from the second domain into a third domain.
8. The communication apparatus of claim 7 , wherein the medium further comprises instructions that, when executed by the computer arrangement, cause the apparatus to estimate a residual frequency offset corresponding to the at least partially corrected signal in at least one of the second and third domains.
9. The communication apparatus of claim 1 , wherein:
the frequency offset parameter comprises an average frequency offset of the buffered portion; and
the correction signal comprises a complex sinusoid having a frequency substantially equal to the negative of the average frequency offset.
10. The communication apparatus of claim 1 , wherein the instructions that cause the apparatus to apply the correction signal further configure:
one of a numerically controlled oscillator (NCO), a voltage controlled oscillator (VCO), and a frequency modulator to generate the correction signal; and
one of a complex multiplier and a digital mixer to perform a complex multiplication of the buffered portion with the correction signal in the first domain.
11. A non-transitory, computer-readable medium comprising computer-executable instructions that, when executed by a communications apparatus, cause the apparatus to:
receive a signal comprising a plurality of symbols in a first domain;
store a portion of the signal comprising at least no more than one symbol in a buffer;
determine a frequency offset parameter relating to the buffered portion;
apply a correction signal to the buffered portion to generate an at least partially corrected signal in the first domain, wherein the correction signal is based on the frequency offset parameter; and
transform the at least partially corrected signal into a second domain.
12. The non-transitory, computer-readable medium of claim 11 , wherein the first domain is a time domain, and the second domain is a frequency domain.
13. The non-transitory, computer-readable medium of claim 11 , wherein each of the plurality of symbols is an OFDM symbol comprising a cyclic prefix, and the frequency offset parameter is determined based on a cyclic prefix comprising the buffered portion.
14. The non-transitory, computer-readable medium of claim 11 , wherein the instructions that cause the apparatus to determine the frequency offset parameter further cause the apparatus to:
compute a representation of the buffered portion in the second domain; and
determine the frequency offset parameter based on a plurality of reference elements comprising the representation of the buffered portion in the second domain.
15. The non-transitory, computer-readable medium of claim 14 , wherein the second domain is a frequency domain and the plurality of reference elements comprise at least one of pilot symbols and reference subcarriers.
16. The non-transitory, computer-readable medium of claim 11 , wherein the medium further comprises instructions that, when executed by the apparatus, cause the apparatus to estimate a residual frequency offset corresponding to the at least partially corrected signal in the second domain.
17. The non-transitory, computer-readable medium of claim 11 , wherein the medium further comprises instructions that, when executed by the apparatus, cause the apparatus to further transform the at least partially corrected signal from the second domain into a third domain.
18. The non-transitory, computer-readable medium of claim 17 , wherein the medium further comprises instructions that, when executed by the apparatus, cause the apparatus to estimate a residual frequency offset corresponding to the at least partially corrected signal in at least one of the second and third domains.
19. The non-transitory, computer-readable medium of claim 11 , wherein:
the frequency offset parameter comprises an average frequency offset of the buffered portion; and
the correction signal comprises a complex sinusoid having a frequency substantially equal to the negative of the average frequency offset.
20. The non-transitory, computer-readable medium of claim 11 , wherein the instructions that cause the apparatus to apply the correction signal further configure:
one of a numerically controlled oscillator (NCO), a voltage controlled oscillator (VCO), and a frequency modulator to generate the correction signal; and
one of a complex multiplier and a digital mixer to perform a complex multiplication of the buffered portion with the correction signal in the first domain.
21. A computerized method for improving the performance of a communication apparatus that can be subjected to received signals having frequency offsets, comprising:
receiving a signal comprising a plurality of symbols in a first domain;
storing a portion of the signal comprising at least no more than one symbol in a buffer;
determining a frequency offset parameter relating to the buffered portion;
applying a correction signal to the buffered portion to generate an at least partially corrected signal in the first domain, wherein the correction signal is based on the frequency offset parameter; and
transforming the at least partially corrected signal into a second domain.
22. The method of claim 21 , wherein the first domain is a time domain, and the second domain is a frequency domain.
23. The method of claim 21 , wherein each of the plurality of symbols is an OFDM symbol comprising a cyclic prefix, and the frequency offset parameter is determined based on a cyclic prefix comprising the buffered portion.
24. The method of claim 21 , wherein determining the frequency offset parameter further comprises:
computing a representation of the buffered portion in the second domain; and
determining the frequency offset parameter based on a plurality of reference elements comprising the representation of the buffered portion in the second domain.
25. The method of claim 24 , wherein the second domain is a frequency domain and the plurality of reference elements comprise at least one of pilot symbols and reference subcarriers.
26. The method of claim 21 , further comprising estimating a residual frequency offset corresponding to the at least partially corrected signal in the second domain.
27. The method of claim 21 , further comprising transforming the at least partially corrected signal from the second domain into a third domain.
28. The method of claim 27 , further comprising estimating a residual frequency offset corresponding to the at least partially corrected signal in at least one of the second and third domains.
29. The method of claim 21 , wherein:
the frequency offset parameter comprises an average frequency offset of the buffered portion; and
the correction signal comprises a complex sinusoid having a frequency substantially equal to the negative of the average frequency offset.
30. The method of claim 21 , wherein applying the correction signal further comprises:
configuring one of a numerically controlled oscillator (NCO), a voltage controlled oscillator (VCO), and a frequency modulator to generate the correction signal; and
configuring one of a complex multiplier and a digital mixer to perform a complex multiplication of the buffered portion with the correction signal in the first domain.