Ch Frequency Response (802.16 OFDM)
shows the frequency response for the channel for which the equalizer is correcting. is computed as the reciprocal of the equalizer frequency response. The contains one complex value for each subcarrier plus an interpolated value for the middle unused subcarrier (a total of 201 values). The equalizer frequency response is normally estimated from the Channel Estimation Sequence portion of the OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. preamble. When the Equalization Training parameter is set to , the equalizer frequency response is estimated using both the Channel Estimation Sequence and the payload data.
This is similar to, but not the same as, the Digital Demod Ch Frequency Response. The differences are:
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Digital Demod computes this by comparing the and data, while 802.16 OFDM demodulation computes it from the preamble/data of the burst.
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typically uses a running average to average multiple scans when computing the equalizer frequency response.demodulation does not average, but computes a new equalizer response for each burst.
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The equalization filter is inherent to demodulation, it cannot be enabled/disabled like in .
See Also
