www.gusucode.com > wlan工具箱matlab源码程序 > wlan/wlanexamples/helperVHTConfigRecover.m
function [cfgVHTRx, numDataSym, crcBits, apepLen] = ...
helperVHTConfigRecover(LSIGBits, VHTSIGABits, varargin)
%helperVHTConfigRecover Recover VHT transmission configuration
%
% CFGVHT = helperVHTConfigRecover(LSIGBITS,VHTSIGABITS) returns a VHT
% configuration object of type <a href="matlab:help('wlanVHTConfig')">wlanVHTConfig</a> given recovered
% bits from L-SIG and VHT-SIG-A fields for a single-user or multi-user
% transmission.
%
% CFGVHT = helperVHTConfigRecover(LSIGBITS,VHTSIGABITS,VHTSIGBBITS)
% returns a VHT configuration object of type <a href="matlab:help('wlanVHTConfig')">wlanVHTConfig</a> given recovered
% bits from L-SIG, VHT-SIG-A, and VHT-SIG-B fields for a single-user
% transmission only.
%
% CFGVHT = helperVHTConfigRecover(LSIGBITS,VHTSIGABITS,VHTSIGBBITS, ...
% USERNUMBER) returns a VHT configuration object of type <a href="matlab:help('wlanVHTConfig')">wlanVHTConfig</a>
% given recovered bits from L-SIG, VHT-SIG-A, and VHT-SIG-B fields for a
% user specified by USERNUMBER for a multi-user transmission.
%
% See also wlanVHTDataRecover, wlanVHTConfig.
% Copyright 2015-2016 The MathWorks, Inc.
%#codegen
% Note: Best effort processing implies offering as much configuration
% detail as possible based on inputs:
% LSIG + VHTSIGA : for Single-user Tx
% LSIG + VHTSIGA + VHTSIGB : for Single-user Tx
% LSIG + VHTSIGA + VHTSIGB + UserNum : for Multi-user Tx
narginchk(2,4);
if nargin==3
VHTSIGBBits = varargin{1}; % For single-user transmission
userNum = 1;
elseif nargin==4
VHTSIGBBits = varargin{1}; % For multi-user transmission
userNum = varargin{2};
else % two inputs
VHTSIGBBits = []; % For single-user transmission
userNum = 1;
end
% Retrieve information from VHT-SIG-A bits
VHTSIGABits = double(reshape(VHTSIGABits, 24, 2)');
if all(VHTSIGABits(1,1:2) == [0 0])
chanBW = 'CBW20';
numSD = 52;
elseif all(VHTSIGABits(1,1:2) == [1 0])
chanBW = 'CBW40';
numSD = 108;
elseif all(VHTSIGABits(1,1:2) == [0 1])
chanBW = 'CBW80';
numSD = 234;
else
chanBW = 'CBW160';
numSD = 468;
end
stbc = logical(VHTSIGABits(1, 4));
groupID = bi2de(VHTSIGABits(1, 5:10));
if groupID == 0 || groupID == 63
isSUTx = true;
else
isSUTx = false; % is MU transmission
end
% Get extra OFDM symbol information from VHTSIG-A bits
if VHTSIGABits(2,4)==1
LDPCextraOFDMsymbol = 1;
else
LDPCextraOFDMsymbol = 0;
end
% Retrieve rxTime from L-SIG bits
rxTime = getRxTime(LSIGBits);
% default assignments
crcBits = zeros(8, 1, 'int8');
apepLen = 0;
if isSUTx
% SINGLE-USER Transmission
numSpaceTimeStreams = bi2de(VHTSIGABits(1, 11:13)) + 1;
partialAID = bi2de(VHTSIGABits(1, 14:22));
mcs = bi2de(VHTSIGABits(2, 5:8));
beamforming = logical(VHTSIGABits(2, 9));
channelCodingBit = bi2de(VHTSIGABits(2, 3));
if channelCodingBit==1
% Channel coding is LDPC
channelCoding = {'LDPC'};
else
% Channel coding is BCC
channelCoding = {'BCC'};
end
% Get number of OFDM Data symbols
[numDataSym, guardInterval] = getDataSym(VHTSIGABits, ...
numSpaceTimeStreams, rxTime);
% Calculate received PSDULength and set it to be the APEPLength
[numDBPS, numES] = getMCSTable(mcs, numSD, ...
numSpaceTimeStreams/(1+stbc), channelCoding{1});
if strcmp(channelCoding{1}, 'BCC')
numTailBits = 6;
psduLength = floor((numDataSym*numDBPS - numTailBits*numES - 16)/8);
else % LDPC
psduLength = floor(((numDataSym-LDPCextraOFDMsymbol*(1+stbc))*numDBPS - 16)/8);
end
% Create the returned object from individual parameters
cfgVHTRx = wlanVHTConfig('ChannelBandwidth', chanBW, ...
'NumSpaceTimeStreams', numSpaceTimeStreams, ...
'GroupID', groupID, ...
'STBC', stbc, ...
'Beamforming', beamforming, ...
'PartialAID', partialAID, ...
'MCS', mcs, ...
'ChannelCoding', channelCoding, ...
'GuardInterval', guardInterval, ...
'APEPLength', psduLength);
% Dont necessarily need the SIGB bits for SU recovery.
% If passed in, confirm the actual lengths are appropriate
if ~isempty(VHTSIGBBits)
[crcBits, apepLen] = helperInterpretSIGB(VHTSIGBBits, chanBW, true);
% Confirm APEP lengths and PSDU length are commensurate
if psduLength < apepLen
coder.internal.error('wlan:helperVHTConfigRecover:InvalidLengths');
end
end
else
% MULTI-USER Transmission
% Get coded NSTS per user
numSTS = [bi2de(VHTSIGABits(1, 11:13)) ...
bi2de(VHTSIGABits(1, 14:16)) bi2de(VHTSIGABits(1, 17:19)) ...
bi2de(VHTSIGABits(1, 20:22))];
% Derive other properties from numSTS: numUsers, UserPositions,
% NumSpaceTimeStreams, channelCodingBits
maxUsers = 4; % Maximum allowed
uPositions = 0:3; % correspond to max. users
channelCodingBits = ones(1, maxUsers); % corresponding to max. users
for userIdx = 1:maxUsers
% Read off the received channelCoding bits
if userIdx == 1
% Read B2 for 1 user
channelCodingBits(1) = bi2de(VHTSIGABits(2, 3));
else
% Read B4:B6 for 2:4 users
channelCodingBits(userIdx) = bi2de(VHTSIGABits(2, 3+userIdx));
end
end
% Check numSTS values and revise properties
uPositions = uPositions(numSTS~=0);
channelCodingBits = channelCodingBits(numSTS~=0);
numUsers = length(uPositions);
numSpaceTimeStreams = numSTS(numSTS~=0);
% Per-user coding information
% 0 indicates BCC, 1 indicates LDPC for present users.
channelCoding = cell(1, numUsers);
for userIdx = 1:numUsers
if channelCodingBits(userIdx) == 1
% Channel coding is LDPC
channelCoding{userIdx} = 'LDPC';
else
% Channel coding is BCC
channelCoding{userIdx} = 'BCC';
end
end
% Get number of OFDM Data symbols
[numDataSym, guardInterval] = getDataSym(VHTSIGABits, ...
sum(numSpaceTimeStreams), rxTime);
if ~isempty(VHTSIGBBits)
% Individual user processing (based on userNum)
% apepLen Rounded to 4-byte multiple
[crcBits, apepLen, mcs] = helperInterpretSIGB(VHTSIGBBits, chanBW, false);
% Calculate received PSDULength and set it to be the APEPLength
[numDBPS, numES] = getMCSTable(mcs, numSD, ...
numSpaceTimeStreams(userNum)/(1+stbc), channelCoding{userNum});
if strcmp(channelCoding{userNum}, 'BCC')
numTailBits = 6;
psduLength = floor((numDataSym*numDBPS - numTailBits*numES - 16)/8);
else % LDPC
psduLength = floor(((numDataSym-LDPCextraOFDMsymbol*(1+stbc))*numDBPS - 16)/8);
end
% Confirm APEP lengths and PSDU length are commensurate
if psduLength < apepLen
coder.internal.error('wlan:helperVHTConfigRecover:InvalidLengths');
end
% Create the returned object from individual parameters
% Set this to be a single-user config.
cfgVHTRx = wlanVHTConfig('ChannelBandwidth', chanBW, ...
'NumUsers', 1, ...
'NumSpaceTimeStreams', numSpaceTimeStreams(userNum), ...
'GroupID', groupID, ...
'STBC', stbc, ...
'MCS', mcs, ...
'ChannelCoding', {channelCoding{userNum}}, ...
'GuardInterval', guardInterval, ...
'APEPLength', psduLength ); %#ok<CCAT1> % Required for codegen
else
% Create the returned object from individual parameters
% Set this to be a MULTI-USER configuration
% But with no length information (only the default)
cfgVHTRx = wlanVHTConfig('ChannelBandwidth', chanBW, ...
'NumUsers', numUsers, ...
'UserPositions', uPositions, ...
'NumSpaceTimeStreams', numSpaceTimeStreams, ...
'GroupID', groupID, ...
'STBC', stbc, ...
'ChannelCoding', channelCoding, ...
'GuardInterval', guardInterval);
end
end
end
%--------------------------------------------------------------------------
function rxTime = getRxTime(LSIGBits)
% Retrieve RXTime from L-SIG for VHT transmission
% 4 symbol range, [RXTime - 3: RXTime]
rxTime = (bi2de(double(LSIGBits(6:17)')) + 3)/3*4 + 20;
end
%--------------------------------------------------------------------------
function [numDataSym, giType] = getDataSym(VHTSIGABits, numSTSTotal, rxTime)
% Recover number of OFDM symbols and guard interval type
NVHTLTFVec = [1 2 4 4 6 6 8 8];
numPreambSym = 9 + NVHTLTFVec(numSTSTotal);
if VHTSIGABits(2, 1)
giType = 'Short';
numDataSym = floor((rxTime/4 - numPreambSym)*10.0/9.0) - VHTSIGABits(2, 2);
else
giType = 'Long';
numDataSym = rxTime/4 - numPreambSym; % Precise
end
end
%--------------------------------------------------------------------------
function [Ndbps, Nes] = getMCSTable(MCS, Nsd, Nss, channelCoding)
% Similar to wlan.internal.getRateTable, but with modified inputs
switch MCS
case 0
Nbpscs = 1; % 'BPSK'
rate = 1/2;
case 1
Nbpscs = 2; % 'QPSK'
rate = 1/2;
case 2
Nbpscs = 2;
rate = 3/4;
case 3
Nbpscs = 4; % '16QAM'
rate = 1/2;
case 4
Nbpscs = 4;
rate = 3/4;
case 5
Nbpscs = 6; % '64QAM'
rate = 2/3;
case 6
Nbpscs = 6;
rate = 3/4;
case 7
Nbpscs = 6;
rate = 5/6;
case 8
Nbpscs = 8; % 256QAM
rate = 3/4;
otherwise % MCS == 9
Nbpscs = 8;
rate = 5/6;
end
Ndbps = Nsd * Nbpscs * Nss * rate;
if strcmp(channelCoding, 'LDPC')
Nes = 1; % always the case
else % BCC
% Handle exceptions to Nes generic rule - Table 7.13 [2].
% For each case listed, work off the Ndbps value and create a look-up
% table for the Nes value.
% Only 9360 has a valid value from the generic rule also,
% all others are exceptions
NdbpsVec = [2457 8190 9828 9360 14040 9828 16380 19656 21840 14976 22464];
expNes = [ 3 6 6 6 8 6 9 12 12 8 12];
exceptIdx = find(Ndbps == NdbpsVec);
if ~isempty(exceptIdx)
if (Ndbps == 9360) && (Nss == 5) % One valid case for 160, 80+80
Nes = 5;
else % Two exception cases
Nes = expNes(exceptIdx(1));
end
else % Generic rule: 3.6*600 - for a net 600Mbps per encoder
Nes = ceil(Ndbps/2160);
end
end
end
% [EOF]