Joint estimation of channel and preamble sequence for orthogonal frequency division multiplexing systems
View Patent ↗A system includes an estimation module, a processing module, and a control module. The estimation module receives a signal having N sub-carriers and generates N first estimates for channel gains of the N sub-carriers, where N is an integer greater than 1. The processing module generates N second estimates based on the N first estimates. The control module generates N differences between each of the N first estimates and corresponding ones of the N second estimates and estimates (i) a channel gain of the signal and (ii) a preamble sequence in the signal based on the N differences.
1. A system, comprising:
an estimation module configured to
receive a signal having N sub-carriers, and
generate N first estimates for channel gains of the N sub-carriers, where N is an integer greater than 1;
a processing module configured to generate N second estimates based on the N first estimates; and
a control module configured to
generate N differences between each of the N first estimates and corresponding ones of the N second estimates, and
estimate (i) a channel gain of the signal and (ii) a preamble sequence in the signal based on the N differences.
2. The system of claim 1 , wherein the estimation module generates the N first estimates by dividing the signal by one of i preamble sequences, where i is an integer greater than or equal to 1.
3. The system of claim 1 , wherein the processing module generates each of the N second estimates by generating weighted averages of the N first estimates.
4. The system of claim 1 , wherein the processing module generates each of the N second estimates by processing the N first estimates using a maximum likelihood (ML) estimator or a minimum mean square error (MMSE) estimator.
5. The system of claim 2 , wherein the estimation module generates i sets of the N first estimates, where each of the i sets is generated by dividing the signal by each of the i preamble sequences.
6. The system of claim 5 , wherein the processing module generates i sets of the N second estimates based on the i sets of the N first estimates.
7. The system of claim 6 , wherein the control module generates i sums, where each of the i sums is a sum of squares of the N differences in one of the i sets of the N differences.
8. The system of claim 7 , wherein the control module determines a value of i that generates a smallest of the i sums, estimates the preamble sequence present in the signal based on the value of i, and estimates the channel gain based on one of the N second estimates that generates the smallest of the i sums.
9. The system of claim 1 , wherein the N sub-carriers are modulated using orthogonal frequency domain multiplexing (OFDM).
10. The system of claim 9 , wherein every P th one of the N sub-carriers is modulated with a preamble symbol from one of i preamble sequences, where P and i are integers greater than or equal to 1.
11. The system of claim 10 , wherein the every P th one of the N sub-carriers has substantially the same channel phase or substantially the same differential channel phase.
12. The system of claim 10 , wherein each of the i preamble sequences is different from others of the i preamble sequences, the i preamble sequences have a cross-correlation value that is less than or equal to a predetermined threshold, and the i preamble sequences are stored in the estimation or the control modules.
13. The system of claim 12 , wherein the predetermined threshold is less than approximately 0.2 for an orthogonal frequency domain multiplexing (OFDM) system using a 1024 fast Fourier transform (FFT) mode.
14. The system of claim 1 , wherein the control module identifies a segment of a base station that transmitted the signal based on the preamble sequence present in the signal.
15. A physical layer module (PHY) comprising:
the system of claim 1 ; and
a transceiver module configured to communicate with the estimation module and receive the signal.
16. A network device comprising:
the PHY of claim 15 ; and
at least one antenna configured to communicate with the transceiver module.
17. A method for a physical layer (PHY) of a mobile station for estimating channel gain and preamble sequence, the method comprising:
receiving a signal having N sub-carriers at the PHY of the mobile station, where N is an integer greater than 1;
generating N first estimates for channel gains of the N sub-carriers;
generating N second estimates based on the N first estimates;
generating N differences between each of the N first estimates and corresponding ones of the N second estimates; and
estimating in the PHY (i) a channel gain of the signal and (ii) a preamble sequence in the signal based on the N differences.
18. The method of claim 17 , further comprising generating the N first estimates by dividing the signal by one of i preamble sequences, where i is an integer greater than or equal to 1.
19. The method of claim 17 , further comprising generating each of the N second estimates by generating weighted averages of the N first estimates.
20. The method of claim 17 , further comprising generating each of the N second estimates by processing the N first estimates using a maximum likelihood (ML) estimator or a minimum mean square error (MMSE) estimator.
21. The method of claim 18 , further comprising generating i sets of the N first estimates, where each of the i sets is generated by dividing the signal by each of the i preamble sequences.
22. The method of claim 21 , further comprising generating i sets of the N second estimates based on the i sets of the N first estimates.
23. The method of claim 22 , further comprising generating i sums, where each of the i sums is a sum of squares of the N differences in one of the i sets of the N differences.
24. The method of claim 23 , further comprising determining a value of i that generates a smallest of the i sums, estimating the preamble sequence present in the signal based on the value of i, and estimating the channel gain based on one of the N second estimates that generates the smallest of the i sums.
25. The method of claim 17 , wherein the N sub-carriers are modulated using orthogonal frequency domain multiplexing (OFDM).
26. The method of claim 25 , wherein every P th one of the N sub-carriers is modulated with a preamble symbol from one of i preamble sequences, where P and i are integers greater than or equal to 1.
27. The method of claim 26 , wherein the every P th one of the N sub-carriers has substantially the same channel phase or substantially the same differential channel phase.
28. The method of claim 26 , further comprising storing the i preamble sequences, wherein each of the i preamble sequences is different from others of the i preamble sequences, and wherein the i preamble sequences have a cross-correlation value that is less than or equal to a predetermined threshold.
29. The method of claim 28 , wherein the predetermined threshold is less than approximately 0.2 for an orthogonal frequency domain multiplexing (OFDM) system using a 1024 fast Fourier transform (FFT) mode.
30. The method of claim 17 , further comprising identifying a segment of a base station that transmitted the signal based on the preamble sequence present in the signal.
31. The method of claim 17 , further comprising communicating with a transceiver module in a physical layer module (PHY) and receiving the signal from the transceiver module.
32. The method of claim 31 , further comprising communicating with at least one antenna of a network device comprising the PHY and receiving the signal via the at least one antenna.
33. A system, comprising:
estimation means for receiving a signal having N sub-carriers and generating N first estimates for channel gains of the N sub-carriers, where N is an integer greater than 1;
processing means for generating N second estimates based on the N first estimates; and
control means for generating N differences between each of the N first estimates and corresponding ones of the N second estimates, and estimating (i) a channel gain of the signal and (ii) a preamble sequence in the signal based on the N differences.
34. The system of claim 33 , wherein the estimation means generates the N first estimates by dividing the signal by one of i preamble sequences, where i is an integer greater than or equal to 1.
35. The system of claim 33 , wherein the processing means generates each of the N second estimates by generating weighted averages of the N first estimates.
36. The system of claim 33 , wherein the processing means generates each of the N second estimates by processing the N first estimates using a maximum likelihood (ML) estimator or a minimum mean square error (MMSE) estimator.
37. The system of claim 34 , wherein the estimation means generates i sets of the N first estimates, where each of the i sets is generated by dividing the signal by each of the i preamble sequences.
38. The system of claim 37 , wherein the processing means generates i sets of the N second estimates based on the i sets of the N first estimates.
39. The system of claim 38 , wherein the control means generates i sums, where each of the i sums is a sum of squares of the N differences in one of the i sets of the N differences.
40. The system of claim 39 , wherein the control means determines a value of i that generates a smallest of the i sums, estimates the preamble sequence present in the signal based on the value of i, and estimates the channel gain based on one of the N second estimates that generates the smallest of the i sums.
41. The system of claim 33 , wherein the N sub-carriers are modulated using orthogonal frequency domain multiplexing (OFDM).
42. The system of claim 41 , wherein every P th one of the N sub-carriers is modulated with a preamble symbol from one of i preamble sequences, where P and i are integers greater than or equal to 1.
43. The system of claim 42 , wherein the every P th one of the N sub-carriers has substantially the same channel phase or substantially the same differential channel phase.
44. The system of claim 42 , wherein each of the i preamble sequences is different from others of the i preamble sequences, the i preamble sequences have a cross-correlation value that is less than or equal to a predetermined threshold, and the i preamble sequences are stored in the estimation or the control means.
45. The system of claim 44 , wherein the predetermined threshold is less than approximately 0.2 for an orthogonal frequency domain multiplexing (OFDM) system using a 1024 fast Fourier transform (FFT) mode.
46. The system of claim 33 , wherein the control means identifies a segment of a base station that transmitted the signal based on the preamble sequence present in the signal.
47. A physical layer module (PHY) comprising:
the system of claim 33 ; and
transceiver means for communicating with a medium, wherein the transceiver means communicates with the estimation means and receives the signal.
48. A network device comprising:
the PHY of claim 47 ; and
antenna means for receiving signals, wherein the antenna means communicates with the transceiver means.