OFDM/OFDMA channel estimation
View Patent ↗Systems and methods which introduce a variable shift with respect to pilot symbols in providing a data subcarrier channel estimation are shown. Use of pilot symbol shifts may be useful, for example, when path delay is long and/or when non-consecutive, non-uniformly distributed pilot subcarriers are used. The foregoing shift may be introduced in the time or frequency domains according to embodiments of the invention. For example, a shift of a particular number of samples may be introduced with respect to the symbols of the pilot subcarriers in the measured pilot subcarrier channel response for use in data subcarrier channel estimation.
1. A method comprising:
determining a shift factor from a pilot subcarrier channel response associated with a received pilot signal using a shift factor estimator; and
estimating a data subcarrier channel as a function of said shift factor and said received pilot signal
wherein said determining said shift factor comprises:
determining an average sample delay associated with a portion of said pilot signal.
2. The method of claim 1 , wherein said portion of said pilot signal comprises a cyclic preamble.
3. A method comprising:
determining a shift factor from a pilot subcarrier channel response associated with a received pilot signal; and
estimating a data subcarrier channel as a function of said shift factor and said received pilot signal,
wherein said determining said shift factor comprises:
determining a plurality of shift factors, wherein said plurality of shift factors are associated with different symbols of a plurality of symbols in said pilot signal; and filtering said plurality of shift factors to provide said shift factor.
4. The method of claim 3 , wherein said filtering comprises:
averaging said plurality of putative shift factors.
5. A method comprising:
determining a shift factor from a pilot subcarrier channel response associated with a received pilot signal using a shift factor estimator; and
estimating a data subcarrier channel as a function of said shift factor and said received pilot signal,
wherein said estimating said data subcarrier channel comprises:
applying a cyclic shift of samples of symbols of a payload portion of a frame of said pilot signal without altering a cyclic prefix portion of said frame of said pilot signal.
6. A method comprising:
determining a shift factor from a pilot subcarrier channel response associated with a received pilot signal using a shift factor estimator; and
estimating a data subcarrier channel as a function of said shift factor and said received pilot signal,
wherein said estimating said data subcarrier channel comprises:
applying a cyclic shift of samples of symbols of said pilot signal, wherein said cyclic shift corresponds to said shift factor;
determining a pilot subcarrier channel response from said shifted pilot signal symbols; and
filtering said pilot subcarrier channel response to provide said data subcarrier channel estimation.
7. A method comprising:
determining a shift factor from a pilot subcarrier channel response associated with a received pilot signal using a shift factor estimator; and
estimating a data subcarrier channel as a function of said shift factor and said received pilot signal,
wherein said estimating said data subcarrier channel comprises:
determining a pilot subcarrier channel response from said pilot signal;
applying a phase shift to said pilot subcarrier channel response, wherein said phase shift corresponds to said shift factor; and
filtering said shifted pilot subcarrier channel response to provide said data subcarrier channel estimation.
8. A system for providing a data subcarrier channel estimate, said system comprising:
a pilot subcarrier channel response estimator operable to provide a pilot subcarrier channel response from a pilot signal provided thereto;
a shift factor estimator coupled to said pilot subcarrier channel response estimator and operable to compute a shift factor as a function of said pilot subcarrier channel response;
a cyclic shifter coupled to said shift factor estimator and operable to introduce a cyclic shift of pilot signal samples, wherein an amount of said cyclic shift corresponds to said shift factor; and
a filter coupled to said pilot subcarrier channel response estimator and operable to provide a data subcarrier channel estimate from said pilot subcarrier channel response.
9. The system of claim 8 , wherein said pilot signal is transmitted using a non-consecutive pilot subcarrier assignment.
10. The system of claim 8 , wherein said shift factor estimator comprises logic to determine an average sample delay with respect to a portion of a pilot signal symbol.
11. The system of claim 10 , wherein said portion of said pilot signal symbol comprises a cyclic preamble.
12. The system of claim 8 , further comprising:
a shift factor filter coupled to said shift factor estimator and operable to provide a filtered shift factor to said cyclic shifter for introducing a cyclic shift corresponding to said filtered shift factor.
13. The system of claim 11 , wherein said shift factor filter provides averaging with respect to a plurality of shift factors, wherein said plurality of shift factors are determined from a plurality of symbols of said pilot signal.
14. A system for providing a data subcarrier channel estimate, said system comprising:
a pilot subcarrier channel response estimator operable to provide a pilot subcarrier channel response from a pilot signal provided thereto;
a shift factor estimator coupled to said pilot subcarrier channel response estimator and operable to compute a shift factor as a function of said pilot subcarrier channel response;
a phase shifter coupled to said shift factor estimator and operable to introduce a phase shift to said pilot subcarrier channel response, wherein an amount of said phase shift corresponds to said shift factor; and
a filter coupled to said phase shifter and operable to provide a data subcarrier channel estimate from said phase shifted pilot subcarrier channel response.
15. The system of claim 14 , wherein said pilot signal is transmitted using a non-consecutive pilot subcarrier assignment.
16. The system of claim 14 , wherein said shift factor estimator comprises logic to determine an average sample delay with respect to a portion of a pilot signal symbol.
17. The system of claim 16 , wherein said portion of said pilot signal symbol comprises a cyclic preamble.
18. The system of claim 14 , further comprising:
a shift factor filter coupled to said shift factor estimator and operable to provide a filtered shift factor to said cyclic shifter for introducing a cyclic shift corresponding to said filtered shift factor.
19. The system of claim 18 , wherein said shift factor filter provides averaging with respect to a plurality of shift factors, wherein said plurality of shift factors are determined from a plurality of symbols of said pilot signal.