Channel estimator with high noise suppression and low interpolation error for OFDM systems
First Claim
1. A method of operating a receiver, said method comprising:
- transforming a received signal into a frequency domain signal, said received signal having a number of subcarrier channel locations;
determining a time-domain vector from a set of pilot subcarriers of said received signal, wherein determining a time-domain vector, further comprises;
determining a spectral window size, said spectral window size based upon said number of subcarriers;
computing a first channel estimate vector from said set of pilot subcarriers, said pilot subcarriers having a given spacing in the frequency domain;
inserting a first set of padding values, said first set of padding values corresponding to a set of subcarriers at both edges of said window, into said first channel estimate vector;
determining a time-domain vector from said first channel estimate vector having said padding values; and
weighting said time-domain vector according to a set of weighting factors to obtain a weighted time-domain vector;
providing compensation for time domain aliasing in said time-domain vector, wherein providing compensation for time domain aliasing further comprises;
inserting a set of padding zeros into said weighted time-domain vector, starting from a position based on a maximum channel spread and channel characteristics; and
obtaining a second time-domain vector;
transforming said second time-domain vector into a frequency-domain channel estimate vector;
mapping said frequency-domain channel estimate vector to said subcarriers of said spectral window; and
providing compensation for irregularity in said spacing of said pilot subcarriers; and
obtaining a channel estimate vector.
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Accused Products
Abstract
A receiver with DFT based channel estimation having good noise suppression for both high and low signal-to-noise ratios providing advantages over conventional DFT estimators and Minimum-Mean-Square-Error (MMSE) estimators. The use of MMSE may be incorporated for estimation at the band edges providing further improvements. The received signal in the time domain, is transformed to the frequency-domain received signal via an N-point FFT (501). The frequency-domain received signal at the pilot locations is then used to obtain a “noisy” channel estimates at the pilot subcarriers by dividing the known pilot symbols in (503). Uniformly spaced pilots are assumed over a window of usable subcarriers. Padding is applied to the initial channel estimates at both sides of the band to account for unused subcarriers such as guard spacing. Weighting factors during power estimation may take into account various noise characteristics such as combinations of known and time-limited noise power characteristics.
6 Citations
12 Claims
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1. A method of operating a receiver, said method comprising:
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transforming a received signal into a frequency domain signal, said received signal having a number of subcarrier channel locations; determining a time-domain vector from a set of pilot subcarriers of said received signal, wherein determining a time-domain vector, further comprises; determining a spectral window size, said spectral window size based upon said number of subcarriers; computing a first channel estimate vector from said set of pilot subcarriers, said pilot subcarriers having a given spacing in the frequency domain; inserting a first set of padding values, said first set of padding values corresponding to a set of subcarriers at both edges of said window, into said first channel estimate vector; determining a time-domain vector from said first channel estimate vector having said padding values; and weighting said time-domain vector according to a set of weighting factors to obtain a weighted time-domain vector; providing compensation for time domain aliasing in said time-domain vector, wherein providing compensation for time domain aliasing further comprises; inserting a set of padding zeros into said weighted time-domain vector, starting from a position based on a maximum channel spread and channel characteristics; and obtaining a second time-domain vector; transforming said second time-domain vector into a frequency-domain channel estimate vector; mapping said frequency-domain channel estimate vector to said subcarriers of said spectral window; and providing compensation for irregularity in said spacing of said pilot subcarriers; and obtaining a channel estimate vector. - View Dependent Claims (2, 3, 4, 5)
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6. A method of operating a receiver, said method comprising:
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transforming a received signal into a frequency domain signal, said received signal having a number of subcarrier channel locations; determining a time-domain vector from a set of pilot subcarriers of said received signal, wherein determining a time-domain vector, further comprises; determining a spectral window size, said spectral window size based upon said number of subcarriers; computing a first channel estimate vector from said set of pilot subcarriers, said pilot subcarriers having a given spacing in the frequency domain; inserting a first set of padding values, said first set of padding values corresponding to a set of subcarriers at both edges of said window, into said first channel estimate vector; determining a time-domain vector from said first channel estimate vector having said padding values; and weighting said time-domain vector according to a set of weighting factors to obtain a weighted time-domain vector, wherein weighting said time-domain vector according to a set of weighting factors, further comprises; performing power estimation on each element of said time-domain vector; and computing said weighting factors based upon a noise and interference characteristic and said power estimation; providing compensation for time domain aliasing in said time-domain vector; and obtaining a channel estimate vector. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A receiver unit comprising:
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a receiver component; a channel estimation component coupled to said receiver component; a noise determination and weighting component coupled to said channel estimation component; a window adjustment component coupled to said channel estimation component, said window adjustment component being configured to determine a spectral window size, said spectral window size based upon said number of subcarriers, said subcarrier further comprising a set of pilots having a given frequency domain spacing; an aliasing compensation component, coupled to said channel estimation component, said aliasing compensation component being configured to insert a set of padding zeros into a weighted estimation vector, starting from a position based on a maximum channel spread and a channel characteristic; a pilot spacing compensator component, coupled to said channel estimation component and to said window adjustment component, said pilot spacing compensator configured to insert a set of insertions/omissions corresponding to a set of irregularities in pilot spacing; and a channel decoding component coupled to said channel estimation component.
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Specification