gusucode.com > wlan工具箱matlab源码程序 > wlan/wlan/wlanFieldIndices.m
function indices = wlanFieldIndices(cfgFormat, varargin)
%WLANFIELDINDICES Generate field indices for WLAN packet
%
% INDICES = wlanFieldIndices(CFGFORMAT) returns the start and end
% time-domain sample indices for all fields in a packet relative to the
% first sample in a packet.
%
% INDICES is a structure array of field names for the specified
% configuration and contains the start and end indices of all fields in a
% packet.
%
% CFGFORMAT is a format configuration object of type <a href="matlab:help('wlanVHTConfig')">wlanVHTConfig</a>,
% <a href="matlab:help('wlanHTConfig')">wlanHTConfig</a>, or <a href="matlab:help('wlanNonHTConfig')">wlanNonHTConfig</a>.
%
% INDICES = wlanFieldIndices(CFGFORMAT, FIELDNAME) returns the start and
% end time-domain sample indices for the specified FIELDNAME in a packet.
% INDICES is a row vector of size two representing the start and end
% sample indices of the specified field.
%
% FIELDNAME is a string specifying the field of interest and depends on
% the type of CFGFORMAT. FIELDNAME must be one of 'VHT-SIG-A', 'VHT-STF',
% 'VHT-LTF', 'VHT-SIG-B' or 'VHT-Data' for a CFGFORMAT specified as a
% <a href="matlab:help('wlanVHTConfig')">wlanVHTConfig</a> object. For <a href="matlab:help('wlanHTConfig')">wlanHTConfig</a>, the field of interest must be
% 'HT-SIG', 'HT-STF', 'HT-LTF or 'HT-Data'. FIELDNAME 'NonHT-Data' is
% valid for <a href="matlab:help('wlanNonHTConfig')">wlanNonHTConfig</a> object, only OFDM modulation is supported.
% FIELDNAME 'L-STF', 'L-LTF' and 'L-SIG' are common for all formats.
%
% Example 1:
% % Extract the necessary fields to decode VHT data for a received
% % 802.11ac VHT transmission.
%
% cfgVHT = wlanVHTConfig; % Create packet configuration
% cfgVHT.MCS = 1; % Modulation: QPSK, Rate: 1/2
% cfgVHT.APEPLength = 1024; % A-MPDU length in bytes
%
% % Generate transmit waveform
% txWaveform = wlanWaveformGenerator([1;0;0;1],cfgVHT);
%
% rxWaveform = awgn(txWaveform, 1, 1); % Add noise
%
% % Recover transmitted bits, assuming synchronization
% ind = wlanFieldIndices(cfgVHT);
% symVHTLTF = wlanVHTLTFDemodulate(...
% rxWaveform(ind.VHTLTF(1):ind.VHTLTF(2),:),cfgVHT);
% chanEst = wlanVHTLTFChannelEstimate(symVHTLTF,cfgVHT);
% rxBits = wlanVHTDataRecover(rxWaveform(ind.VHTData(1): ...
% ind.VHTData(2),:),chanEst,1,cfgVHT);
%
% % Example 2:
% % Extract and demodulate L-LTF field from a NonHT OFDM packet.
%
% % Create packet configuration
% cfgNonHT = wlanNonHTConfig('Modulation','OFDM');
%
% % Generate transmit waveform
% txWaveform = wlanWaveformGenerator([1;0;0;1],cfgNonHT);
% rxWaveform = awgn(txWaveform,1,1); % Add noise
% indLLTF = wlanFieldIndices(cfgNonHT,'L-LTF');
% y = wlanLLTFDemodulate(rxWaveform(indLLTF(1):indLLTF(2)),cfgNonHT);
%
% See also wlanVHTDataRecover, wlanHTDataRecover, wlanNonHTDataRecover.
% Copyright 2015-2016 The MathWorks, Inc.
%#codegen
% Validate input is a class object
validateattributes(cfgFormat, {'wlanVHTConfig', ...
'wlanHTConfig','wlanNonHTConfig'}, ...
{'scalar'}, mfilename, 'format configuration object');
% DSSS modulation in NonHT format is not supported
coder.internal.errorIf(isa(cfgFormat, 'wlanNonHTConfig') &&...
strcmp(cfgFormat.Modulation, 'DSSS'), ...
'wlan:wlanFieldIndices:InvalidModulation');
narginchk(1,2)
if nargin == 1
if isa(cfgFormat, 'wlanVHTConfig')
[numVHTLTF, symLength, N20] = getVHTParams(cfgFormat);
indLSTF = getIndices(cfgFormat,'L-STF',N20);
indLLTF = getIndices(cfgFormat,'L-LTF',N20);
indLSIG = getIndices(cfgFormat,'L-SIG',N20);
indVHTSIGA = getIndices(cfgFormat,'VHT-SIG-A',N20);
indVHTSTF = getIndices(cfgFormat,'VHT-STF',N20);
indVHTLTF = getIndices(cfgFormat,'VHT-LTF',N20,numVHTLTF);
indVHTSIGB = getIndices(cfgFormat,'VHT-SIG-B',N20,numVHTLTF);
if isscalar(cfgFormat.APEPLength) && (cfgFormat.APEPLength == 0)
indVHTData = zeros(0,2,'uint32');
else
indVHTData = getIndices(cfgFormat,'VHT-Data',N20, ...
numVHTLTF,symLength);
end
indices = struct('LSTF', indLSTF, ...
'LLTF', indLLTF, ...
'LSIG', indLSIG, ...
'VHTSIGA', indVHTSIGA, ...
'VHTSTF', indVHTSTF, ...
'VHTLTF', indVHTLTF, ...
'VHTSIGB', indVHTSIGB, ...
'VHTData', indVHTData);
elseif isa(cfgFormat,'wlanHTConfig')
[numHTLTF, symLength, N20] = getHTParams(cfgFormat);
indLSTF = getIndices(cfgFormat,'L-STF',N20);
indLLTF = getIndices(cfgFormat,'L-LTF',N20);
indLSIG = getIndices(cfgFormat,'L-SIG',N20);
indHTSIG = getIndices(cfgFormat,'HT-SIG',N20);
indHTSTF = getIndices(cfgFormat,'HT-STF',N20);
indHTLTF = getIndices(cfgFormat,'HT-LTF',N20,numHTLTF);
if (cfgFormat.PSDULength ==0)
indHTData = zeros(0,2,'uint32');
else
indHTData = getIndices(cfgFormat,'HT-Data',N20, ...
numHTLTF,symLength);
end
indices = struct('LSTF', indLSTF, ...
'LLTF', indLLTF, ...
'LSIG', indLSIG, ...
'HTSIG', indHTSIG,...
'HTSTF', indHTSTF,...
'HTLTF', indHTLTF,...
'HTData',indHTData);
else
indLSTF = getIndices(cfgFormat,'L-STF',1);
indLLTF = getIndices(cfgFormat,'L-LTF',1);
indLSIG = getIndices(cfgFormat,'L-SIG',1);
indNonHTData = getIndices(cfgFormat,'NonHT-Data',1);
indices = struct('LSTF', indLSTF, ...
'LLTF', indLLTF, ...
'LSIG', indLSIG, ...
'NonHTData',indNonHTData);
end
else
fieldType = varargin{1};
if isa(cfgFormat, 'wlanVHTConfig')
coder.internal.errorIf(~ischar(fieldType) || ...
~any(strcmp(fieldType, ...
{'L-STF','L-LTF','L-SIG','VHT-SIG-A','VHT-STF','VHT-LTF', ...
'VHT-SIG-B','VHT-Data'})), ...
'wlan:wlanFieldIndices:InvalidFieldTypeVHT');
if strcmp(fieldType, 'VHT-Data') && ...
isscalar(cfgFormat.APEPLength) && (cfgFormat.APEPLength == 0)
indices = zeros(0,2,'uint32'); % NDP
else
[numVHTLTF, symLength, N20] = getVHTParams(cfgFormat);
indices = getIndices(cfgFormat, fieldType, N20, numVHTLTF, ...
symLength);
end
elseif isa(cfgFormat,'wlanHTConfig')
coder.internal.errorIf(~ischar(fieldType) || ...
~any(strcmp(fieldType, ...
{'L-STF','L-LTF','L-SIG','HT-SIG','HT-STF','HT-LTF', ...
'HT-Data'})), ...
'wlan:wlanFieldIndices:InvalidFieldTypeHT');
if strcmp(fieldType, 'HT-Data') && (cfgFormat.PSDULength == 0)
indices = zeros(0,2,'uint32'); % NDP
else
[numHTLTF, symLength, N20] = getHTParams(cfgFormat);
indices = getIndices(cfgFormat, fieldType ,N20, numHTLTF, ...
symLength);
end
else
coder.internal.errorIf(~ischar(fieldType) || ...
~any(strcmp(fieldType, ...
{'L-STF','L-LTF','L-SIG', 'NonHT-Data'})), ...
'wlan:wlanFieldIndices:InvalidFieldTypeNonHT');
indices = getIndices(cfgFormat, fieldType, 1);
end
end
end
function out = getIndices(format, fieldType, N20, varargin)
% Start and end sample indices are relative to the field length in samples
% for 20MHz bandwidth.
if strcmp(fieldType, 'L-STF')
indStart = 1; % Start of L-STF field
indEnd = 160*N20; % End of L-STF field
elseif strcmp(fieldType, 'L-LTF')
indStart = 160*N20+1; % Start of L-LTF field
indEnd = 320*N20; % End of L-LTF field
elseif strcmp(fieldType, 'L-SIG')
indStart = 320*N20+1; % Start of L-SIG field
indEnd = indStart+80*N20-1; % End of L-SIG field
elseif strcmp(fieldType, 'VHT-SIG-A')
indStart = 400*N20+1; % Start of VHT-SIG-A field
indEnd = indStart+160*N20-1; % End of VHT-SIG-A field
elseif strcmp(fieldType, 'HT-SIG')
indStart = 400*N20+1; % Start of HT-SIG field
indEnd = indStart+160*N20-1; % End of HT-SIG field
elseif strcmp(fieldType, 'VHT-STF')
indStart = 560*N20+1; % Start of VHT-STF field
indEnd = indStart+80*N20-1; % End of VHT-STF field
elseif strcmp(fieldType, 'HT-STF')
indStart = 560*N20+1; % Start of HT-STF field
indEnd = indStart+80*N20-1; % End of HT-STF field
elseif strcmp(fieldType, 'VHT-LTF')
numVHTLTF = varargin{1};
indStart = 640*N20+1; % Start of VHT-LTF field
indEnd = indStart+numVHTLTF*80*N20-1; % End of VHT-LTF field
elseif strcmp(fieldType, 'HT-LTF')
numHTLTF = varargin{1};
validateConfig(format, 'EssSTS');
validateConfig(format, 'STSTx');
indStart = 640*N20+1; % Start of HT-LTF field
indEnd = indStart+numHTLTF*80*N20-1; % End of HT-LTF field
elseif strcmp(fieldType, 'VHT-SIG-B')
numVHTLTF = varargin{1};
indStart = (640+numVHTLTF*80)*N20+1; % Start of VHT-SIG-B field
indEnd = indStart+80*N20-1; % End of VHT-SIG-B field
elseif strcmp(fieldType, 'VHT-Data')
S = validateConfig(format, 'MCS');
numVHTLTF = varargin{1};
symLength = varargin{2};
indStart = (720+numVHTLTF*80)*N20+1; % Start of VHT-Data field
indEnd = indStart+S.NumDataSymbols*symLength-1; % End of VHT-Data field
elseif strcmp(fieldType, 'HT-Data')
numHTLTF = varargin{1};
symLength = varargin{2};
validateConfig(format, 'EssSTS');
validateConfig(format, 'MCSSTSTx');
S = validateConfig(format, 'MCS');
indStart = (640+numHTLTF*80)*N20+1; % Start of HT-Data field
indEnd = indStart+S.NumDataSymbols*symLength-1; % End of HT-Data field
elseif strcmp(fieldType, 'NonHT-Data')
symLength = 80;
S = validateConfig(format, 'Full');
indStart = 400*N20+1; % Start of NonHT-Data field
% End of NonHT-Data field
indEnd = indStart+S.NumDataSymbols*symLength-1;
end
out = uint32([indStart, indEnd]);
end
function [numLTF, symLength, N20MHz] = getVHTParams(format)
NVHTLTFVec = [1 2 4 4 6 6 8 8]; % Number of VHT-LTF symbols
numLTF = NVHTLTFVec(sum(format.NumSpaceTimeStreams));
channelBandwidth = format.ChannelBandwidth;
N20MHz = real(str2double(channelBandwidth(4:end)))/20;
FFTLen = 64 * N20MHz; % FFT length for 20MHz bandwidth
if strcmp(format.GuardInterval,'Short')
% Short symbol length for 20MHz bandwidth
symLength = FFTLen * 9/8;
else
% Long symbol length for 20MHz bandwidth
symLength = FFTLen * 5/4;
end
end
function [numLTF, symLength, N20MHz] = getHTParams(format)
chanBW = format.ChannelBandwidth;
if wlan.internal.inESSMode(format)
numESS = format.NumExtensionStreams;
else
numESS = 0;
end
[~, ~, Ndltf, Neltf] = wlan.internal.vhtltfSequence(chanBW, ...
format.NumSpaceTimeStreams, numESS);
numLTF = Ndltf + Neltf;
N20MHz = real(str2double(chanBW(4:end)))/20;
FFTLen = 64 * N20MHz; % FFT length for 20MHz bandwidth
if strcmp(format.GuardInterval,'Short')
% Short symbol length for 20MHz bandwidth
symLength = FFTLen * 9/8;
else
% Long symbol length for 20MHz bandwidth
symLength = FFTLen * 5/4;
end
end
% [EOF]