Methods and apparatus for spectral filtering channel estimates
First Claim
1. A method of processing an initial channel estimate including a plurality of initial channel estimate values, the initial channel estimate corresponding to a multi-tone communications channel, the method comprising:
- filtering the initial channel estimate using a real filter to produce a filtered channel estimate including a set of filtered channel estimate values;
identifying regions of said initial channel estimate corresponding to multi-path interference;
performing a channel compensation operation using at least one initial channel estimate value corresponding to a channel estimate region where multi-path interference is identified and using at least one filtered channel estimate value in another channel estimate region;
wherein said communications channel is a communications channel through which an orthogonal frequency division multiplexed signal is transmitted;
wherein each of said initial communications channel estimate values corresponds to the frequency of a tone of said orthogonal frequency division multiplexed signal; and
wherein said step of identifying regions of said initial channel estimate corresponding to multi-path interference includes identifying regions where said multi-path interference is sufficient to cause said filtering to produce filtered channel estimate values which are less accurate than the unfiltered channel estimate values corresponding to the same regions.
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Abstract
Methods and apparatus for performing spectral filtering of channel estimates corresponding to a communications channel used to transmit a multi-tone signal are described. A channel estimate is examined to identify portions where significant multi-path interference is present. Real, as opposed to complex, low pass filters are used to perform spectral filtering on the channel estimate to produce a filtered channel estimate. Values corresponding to portions of the channel estimate determined to correspond to areas where significant multi-path interference is present are replaced with the original unfiltered channel estimate values to generate a selectively filtered channel estimate. By using unfiltered channel estimate values in areas of multi-path interference, the errors introduced in such areas by real filtering are avoided without the need to resort to complex filtering.
46 Citations
18 Claims
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1. A method of processing an initial channel estimate including a plurality of initial channel estimate values, the initial channel estimate corresponding to a multi-tone communications channel, the method comprising:
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filtering the initial channel estimate using a real filter to produce a filtered channel estimate including a set of filtered channel estimate values; identifying regions of said initial channel estimate corresponding to multi-path interference; performing a channel compensation operation using at least one initial channel estimate value corresponding to a channel estimate region where multi-path interference is identified and using at least one filtered channel estimate value in another channel estimate region; wherein said communications channel is a communications channel through which an orthogonal frequency division multiplexed signal is transmitted; wherein each of said initial communications channel estimate values corresponds to the frequency of a tone of said orthogonal frequency division multiplexed signal; and wherein said step of identifying regions of said initial channel estimate corresponding to multi-path interference includes identifying regions where said multi-path interference is sufficient to cause said filtering to produce filtered channel estimate values which are less accurate than the unfiltered channel estimate values corresponding to the same regions. - View Dependent Claims (9)
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2. A method of processing an initial channel estimate including a plurality of initial channel estimate values, the initial channel estimate corresponding to a multi-tone communications channel, the method comprising:
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filtering the initial channel estimate using a real filter to produce a filtered channel estimate including a set of filtered channel estimate values; identifying regions of said initial channel estimate corresponding to multi-path interference; performing a channel compensation operation using at least one initial channel estimate value corresponding to a channel estimate region where multi-path interference is identified and using at least one filtered channel estimate value in another channel estimate region; and wherein channel estimate regions of multi-path interference are regions where the channel estimate values are degraded by performing said filtering using a real filter.
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3. A method of processing an initial channel estimate including a plurality of initial channel estimate values, the initial channel estimate corresponding to a multi-tone communications channel, the method comprising:
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filtering the initial channel estimate using a real filter to produce a filtered channel estimate including a set of filtered channel estimate values; identifying regions of said initial channel estimate corresponding to multi-path interference; performing a channel compensation operation using at least one initial channel estimate value corresponding to a channel estimate region where multi-path interference is identified and using at least one filtered channel estimate value in another channel estimate region; and replacing filtered channel estimate values in said filtered channel estimate corresponding to regions of multi-path interference with unfiltered channel estimate values corresponding to said regions of multi-path interference to thereby produce a selectively filtered channel estimate. - View Dependent Claims (4, 5, 6, 7, 8)
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10. A multi-tone communications apparatus, comprising:
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a real low pass filter circuit for performing a real low pass filtering operation on a set of initial channel estimate values to generate a filtered channel estimate including filtered channel estimate values; a channel state confidence computation module for identifying at least one initial channel estimate value resulting from multi-path interference; and a selective replacement module being coupled to said real low pass filter module to receive said filtered channel estimate and being coupled to said channel state confidence computation module, said selective replacement module generating a selectively filtered channel estimate by replacing at least one filtered channel estimate value with an identified initial channel estimate value. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. An apparatus for processing an initial channel estimate including a plurality of initial channel estimate values, the initial channel estimate corresponding to a multi-tone communications channel, the apparatus comprising:
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means for filtering the initial channel estimate using a real filter to produce a filtered channel estimate including a set of filtered channel estimate values; means for identifying at least one region of said initial channel estimate corresponding to multi-path interference; means for performing a channel compensation operation using an initial channel estimate value corresponding to said at least one region of said initial channel estimate where multi-path interference is identified and using at least one filtered channel estimate value in another channel estimate region; and means for replacing filtered channel estimate values in said filtered channel estimate corresponding to regions of multi-path interference with unfiltered channel estimate values corresponding to regions of multi-path interference to thereby produce a selectively filtered channel estimate.
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Specification