57 lines
2.1 KiB
Matlab
57 lines
2.1 KiB
Matlab
function [y,cpe] = preHECommonPhaseErrorTracking(x,chanEst,fieldName,chanBW)
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%preHECommonPhaseErrorTracking Estimate and correct common phase error
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%
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% [Y,CPE] = preHECommonPhaseErrorTracking(X,CHANEST,FIELDNAME,CHANBW)
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% returns the phase corrected OFDM symbols and common phase error per
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% OFDM symbols using the input X, channel estimates, CHANEST, field name,
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% FIELDNAME and channel bandwidth CHANBW.
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%
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% Y are the phase corrected OFDM symbols and is of same size as X. CPE is
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% of size 1-by-Nsym, contains common phase error for each OFDM symbol.
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%
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% X is a complex Nst-by-Nsym-by-Nr array containing the received OFDM
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% symbols. Nst is the number of subcarriers and Nr is the number of
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% receive antennas.
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%
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% CHANEST is a real or complex array containing the channel estimates for
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% each carrier. It is of size Nst-by-1-by-Nr.
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%
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% FIELDNAME is a character vector or string specifying the field of
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% interest. The allowed field names are 'L-SIG', 'RL-SIG', 'HE-SIG-A',
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% and 'HE-SIG-B'.
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%
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% CHANBW is a character vector or string. The allowed channel bandwidth
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% are 'CBW20', 'CBW40', 'CBW80', and 'CBW160'.
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% Copyright 2018-2019 The MathWorks, Inc.
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%#codegen
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numOFDMSym = size(x,2);
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switch fieldName
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case {'L-SIG','RL-SIG'}
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z = 0; % Pilot symbol offset
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ofdmInfo = wlanHEOFDMInfo('L-LTF',chanBW);
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case 'HE-SIG-A'
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z = 2;
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ofdmInfo = wlanHEOFDMInfo('HE-SIG-A',chanBW);
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case 'HE-SIG-B'
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z = 2;
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ofdmInfo = wlanHEOFDMInfo('HE-SIG-B',chanBW);
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end
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refPilots = wlan.internal.nonHTPilots(numOFDMSym,z);
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refPilots = repmat(refPilots,ofdmInfo.NumSubchannels,1);
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% Estimate CPE and phase correct symbols
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[~,~,fieldPilotInd] = wlan.internal.hePreHEOFDMConfig(chanBW,fieldName);
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if numel(ofdmInfo.PilotIndices)==size(chanEst,1)
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% Assume channel estimate is only for pilots
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chanEstPilots = chanEst;
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else
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chanEstPilots = chanEst(ofdmInfo.PilotIndices,:,:);
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end
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cpe = wlan.internal.commonPhaseErrorEstimate(x(fieldPilotInd,:,:),chanEstPilots,refPilots);
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y = wlan.internal.commonPhaseErrorCorrect(x,cpe);
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end |