gusucode.com > wlan工具箱matlab源码程序 > wlan/wlan/wlanNonHTDataRecover.m
function [bits, eqDataSym, varargout] = wlanNonHTDataRecover( ...
rxNonHTData, chanEst, noiseVarEst, cfgNonHT, varargin)
%wlanNonHTDataRecover Recover information bits from Non-HT Data field signal
%
% BITS = wlanNonHTDataRecover(RXNONHTDATA, CHANEST, NOISEVAREST,
% CFGNONHT) recovers the information bits in the Non-HT Data field for a
% Non-HT OFDM format transmission.
%
% BITS is an int8 column vector of length 8*CFGNONHT.PSDULength
% containing the recovered information bits.
%
% RXNONHTDATA is the received time-domain NonHT-Data field signal. It is
% a Ns-by-Nr matrix of real or complex values, where Ns represents the
% number of time-domain samples in the NonHT-Data field and Nr represents
% the number of receive antennas. Ns can be greater than the NonHT-Data
% field length; in this case redundant samples at the end of RXNONHTDATA
% are not used.
%
% CHANEST is the estimated channel at data and pilot subcarriers based on
% the L-LTF. It is a real or complex array of size Nst-by-1-by-Nr, where
% Nst represents the total number of occupied subcarriers. The singleton
% dimension corresponds to the single transmitted stream in the L-LTF
% which includes the combined cyclic shifts if multiple transmit antennas
% are used.
%
% NOISEVAREST is the noise variance estimate. It is a real, nonnegative
% scalar.
%
% CFGNONHT is the format configuration object of type <a href="matlab:help('wlanNonHTConfig')">wlanNonHTConfig</a>
% that specifies the Non-HT format parameters. Only OFDM modulation is
% supported.
%
% BITS = wlanNonHTDataRecover(..., CFGREC) allows different algorithm
% options for data recovery via the input CFGREC, which is a
% <a href="matlab:help('wlanRecoveryConfig')">wlanRecoveryConfig</a> configuration object. When the CFGREC input is not
% specified, the default property values of the <a href="matlab:help('wlanRecoveryConfig')">wlanRecoveryConfig</a> object
% are adopted in the recovery.
%
% [..., EQDATASYM, CPE] = wlanNonHTDataRecover(...) also returns the
% equalized subcarriers and common phase error.
%
% EQDATASYM is a complex 48-by-Nsym matrix containing the equalized
% symbols at data carrying subcarriers. There are 48 data carrying
% subcarriers in the Non-HT Data field. Nsym represents the number of
% OFDM symbols in the NonHT-Data field.
%
% CPE is a column vector of length Nsym containing the common phase error
% between each received and expected OFDM symbol.
%
% Example:
% % Recover a NONHT-Data field signal through a SISO AWGN channel
% % using ZF equalization.
%
% cfgNonHT = wlanNonHTConfig('PSDULength', 1024); % NonHT OFDM
% txBits = randi([0 1], 8*cfgNonHT.PSDULength, 1); % PSDU bits
% tx = wlanNonHTData(txBits, cfgNonHT); % NonHT-Data field signal
%
% % Add AWGN, with noise variance of 1
% rx = awgn(tx, 1, 1);
%
% % Configure recovery object
% cfgRec = wlanRecoveryConfig('EqualizationMethod', 'ZF');
% % Recover PSDU bits
% rxBits = wlanNonHTDataRecover(rx, ones(52,1), 1, cfgNonHT, cfgRec);
%
% [numerr, ber] = biterr(rxBits, txBits); % Compare bits
% disp(ber)
%
% See also wlanNonHTConfig, wlanRecoveryConfig, wlanLLTFChannelEstimate,
% wlanNonHTData.
% Copyright 2015-2016 The MathWorks, Inc.
%#codegen
narginchk(4,5);
nargoutchk(0,3);
% Calculate CPE if requested
if nargout>2
calculateCPE = true;
else
calculateCPE = false;
end
% NonHT configuration input self-validation
validateattributes(cfgNonHT, {'wlanNonHTConfig'}, ...
{'scalar'}, mfilename, 'format configuration object');
% Only applicable for OFDM and DUP-OFDM modulations
coder.internal.errorIf( ~strcmp(cfgNonHT.Modulation, 'OFDM'), ...
'wlan:wlanNonHTDataRecover:InvalidModulation');
s = validateConfig(cfgNonHT);
% Validate rxNonHTData
validateattributes(rxNonHTData, {'double'}, {'2d','finite'}, ...
'rxHTData', 'Non-HT OFDM Data field signal');
% Validate chanEst
validateattributes(chanEst, {'double'}, {'3d','finite'}, ...
'chanEst', 'channel estimates');
% Validate noiseVarEst
validateattributes(noiseVarEst, {'double'}, ...
{'real','scalar','nonnegative','finite'}, ...
'noiseVarEst', 'noise variance estimate');
% Optional recovery configuration input validation
if nargin == 5
validateattributes(varargin{1}, {'wlanRecoveryConfig'}, ...
{'scalar'}, mfilename, 'recovery configuration object');
symOffset = varargin{1}.OFDMSymbolOffset;
eqMethod = varargin{1}.EqualizationMethod;
pilotPhaseTracking = varargin{1}.PilotPhaseTracking;
else % use defaults
symOffset = 0.75;
eqMethod = 'MMSE';
pilotPhaseTracking = 'PreEQ';
end
numRx = size(rxNonHTData, 2);
mcsTable = wlan.internal.getRateTable(cfgNonHT);
pNcbpssi = mcsTable.NCBPS;
numOFDMSym = s.NumDataSymbols;
% Get OFDM configuration
[cfgOFDM,dataInd,pilotInd] = wlan.internal.wlanGetOFDMConfig( ...
cfgNonHT.ChannelBandwidth, 'Long', 'Legacy');
% Cross validate inputs
numST = numel([dataInd; pilotInd]); % Total number of occupied subcarriers
coder.internal.errorIf(size(chanEst, 1) ~= numST, ...
'wlan:wlanNonHTDataRecover:InvalidNHTChanEst1D', numST);
coder.internal.errorIf(size(chanEst, 2) ~= 1, ...
'wlan:wlanNonHTDataRecover:InvalidNHTChanEst2D');
coder.internal.errorIf(size(chanEst, 3) ~= numRx, ...
'wlan:wlanNonHTDataRecover:InvalidNHTChanEst3D');
% Extract data and pilot subcarriers from channel estimate
chanEstData = chanEst(dataInd,:,:);
chanEstPilots = chanEst(pilotInd,:,:);
% Cross-validation between inputs
minInputLen = numOFDMSym*(cfgOFDM.FFTLength+cfgOFDM.CyclicPrefixLength);
coder.internal.errorIf(size(rxNonHTData, 1) < minInputLen, ...
'wlan:wlanNonHTDataRecover:ShortNHTDataInput', minInputLen);
% Processing
% OFDM Demodulation
[ofdmDemodData,ofdmDemodPilots] = wlan.internal.wlanOFDMDemodulate( ...
rxNonHTData(1:minInputLen, :), cfgOFDM, symOffset);
% Pilot phase tracking
if calculateCPE==true || strcmp(pilotPhaseTracking, 'PreEQ')
% Get reference pilots, from IEEE Std 802.11-2012, Eqn 18-22
z = 1; % Offset by 1 to account for L-SIG pilot symbol
refPilots = wlan.internal.nonHTPilots(numOFDMSym, z);
% Estimate CPE and phase correct symbols
cpe = wlan.internal.commonPhaseErrorEstimate(ofdmDemodPilots, ...
chanEstPilots, refPilots);
if strcmp(pilotPhaseTracking, 'PreEQ')
ofdmDemodData = wlan.internal.commonPhaseErrorCorrect(ofdmDemodData, cpe);
end
if calculateCPE==true
varargout{1} = cpe.'; % Permute to Nsym-by-1
end
end
% Equalization
[eqDataSym, csiData] = wlan.internal.wlanEqualize(ofdmDemodData, ...
chanEstData, eqMethod, noiseVarEst);
% LLR Demodulation
qamDemodOut = wlan.internal.wlanConstellationDemodulate(eqDataSym, ...
mcsTable.NBPSCS, noiseVarEst);
% Apply bit-wise CSI
qamDemodOut = bsxfun(@times, ...
reshape(qamDemodOut, mcsTable.NBPSCS, [], numOFDMSym), ...
reshape(csiData, 1, [])); % [Nbpscs Nsd Nsym]
% Deinterleave per OFDM symbol
deintlvrOut = zeros(pNcbpssi*numOFDMSym, 1);
for symIdx = 1:numOFDMSym
deintlvrOut((symIdx-1)*pNcbpssi+(1:pNcbpssi), 1) = ...
wlan.internal.wlanBCCDeinterleave(reshape( ...
qamDemodOut(:,:,symIdx), [], 1), 'NON_HT', pNcbpssi, mcsTable.NBPSCS);
end
% Channel decoding
nhtDecBits = wlan.internal.wlanBCCDecode(deintlvrOut, mcsTable.Rate);
% Combine bits and Descramble with derived initial State
iniY = nhtDecBits(1:7,1); % Take the first 7 bits for scrambler init
scramInit = [iniY(3)+iniY(7) iniY(2)+iniY(6) iniY(1)+iniY(5) ...
iniY(4)+iniY(3)+iniY(7) iniY(3)+iniY(2)+iniY(6) ...
iniY(2)+iniY(1)+iniY(5) iniY(1)+iniY(4)+iniY(3)+iniY(7)];
scramInit = mod(scramInit, 2);
% Remove the padded and tail bits to output only the data bits
descramDataOut = wlan.internal.wlanScramble( ...
nhtDecBits(1:(16+8*cfgNonHT.PSDULength),:), scramInit);
% Remove the 16 service bits
bits = descramDataOut(17:end);
end