gusucode.com > wlan工具箱matlab源码程序 > wlan/wlanexamples/nonHTBeaconRxMPDUDecode.m
function [validBeacon, mpdu] = nonHTBeaconRxMPDUDecode(payload)
% nonHTBeaconRxMPDUDecode Checks if the payload input is from a beacon
% packet and returns its MPDU information. This is a helper function for
% the Non-HT beacon receiver example.
%
% [VALIDBEACON, MPDU] = nonHTBeaconRxMPDUDecode(PAYLOAD) checks the
% PAYLOAD binary input and sets VALIDBEACON to be true if PAYLOAD is from
% a beacon packet. The MPDU information is also returned, but it is
% meaningful only when VALIDBEACON is true.
% Copyright 2015-2016 The MathWorks, Inc.
%#codegen
coder.extrinsic('warning')
persistent crcDetector defaultMPDU
% Frame check sequence (FCS)
if isempty(crcDetector)
crcDetector = comm.CRCDetector( ...
[32 26 23 22 16 12 11 10 8 7 5 4 2 1 0], ...
'InitialConditions', 1, ...
'DirectMethod', true, ...
'FinalXOR', 1);
defaultMPDU.Header = parseMPDUHeader(zeros(64,1), 1);
defaultMPDU.FrameBody = unknownMPDU();
end
% Predefine output
validBeacon = false;
mpdu = defaultMPDU;
% If the CRC for the header decodes correctly (i.e. CRC flag is 0) and the
% received MPDU payload length is greater than or equal to the expected
% length, then turn on the MPDU decoder
if (length(payload) >= 32+16)
% Compute CRC based on IEEE Std 802.11(TM)-2007 section 7.1.3.7.
[frame, mpduCRCd] = crcDetector(double(payload));
mpduCRC = mpduCRCd > 0; % Convert to logical
% Extract header information
[mpdu.Header, mpduHeaderLen] = parseMPDUHeader(frame, mpduCRC);
% Evaluate frame body
if (mpduCRC == 1) || ((mpdu.Header.FrameCtrl.Type ~= 0) ...
|| (mpdu.Header.FrameCtrl.Subtype ~= 8))
mpdu.FrameBody = unknownMPDU();
else
validBeacon = true;
mpdu.FrameBody = parseBeaconMPDU(frame(mpduHeaderLen+1:end, 1), mpduCRC);
end
end
end
function [mpduHeader, len] = parseMPDUHeader(frame, mpduCRC)
% Based on IEEE Std 802.11-2007 chapter 7.
mpduHeader.FrameCtrl = parseFrameControl(frame(1:16,1), mpduCRC);
mpduHeader.DurationID = zeros(1,2,'uint8');
mpduHeader.Address1 = zeros(1,6,'uint8');
mpduHeader.Address2 = zeros(1,6,'uint8');
mpduHeader.Address3 = zeros(1,6,'uint8');
mpduHeader.SequenceControl = zeros(1,2,'uint8');
mpduHeader.Address4 = zeros(1,6,'uint8');
len = (2+6+6+6+2+6)*8 + 16;
if (mpduCRC == 0)
p = 1;
mpduHeader.FrameCtrl = parseFrameControl(frame(p:p+15,1), mpduCRC);
p = p+16;
mpduHeader.DurationID = bit2Octet(frame(p:p+15,1),2);
p = p+16;
mpduHeader.Address1 = bit2Octet(frame(p:p+47,1),6);
p = p+48;
isManagementFrame = (mpduHeader.FrameCtrl.Type == 0);
isControlFrame = (mpduHeader.FrameCtrl.Type == 1);
isDataFrame = (mpduHeader.FrameCtrl.Type == 2);
isCTSFrame = isControlFrame && (mpduHeader.FrameCtrl.Subtype == 12);
isACKFrame = isControlFrame && (mpduHeader.FrameCtrl.Subtype == 13);
if ~(isCTSFrame || isACKFrame)
mpduHeader.Address2 = bit2Octet(frame(p:p+47,1),6);
p = p+48;
end
if isManagementFrame
mpduHeader.Address3 = bit2Octet(frame(p:p+47,1),6);
p = p+48;
end
if ~isControlFrame
mpduHeader.SequenceControl = bit2Octet(frame(p:p+15,1),2);
p = p+16;
end
if isDataFrame
mpduHeader.Address4 = bit2Octet(frame(p:p+47,1),6);
p = p+48;
end
len = p-1;
end
end
function frameCtrl = parseFrameControl(fcBits, mpduCRC)
if (mpduCRC == 0)
frameCtrl.ProtocolVersion = uint8(bi2de(fcBits(1:2,1)'));
frameCtrl.Type = uint8(bi2de(fcBits(3:4,1)'));
frameCtrl.Subtype = uint8(bi2de(fcBits(5:8,1)'));
frameCtrl.ToDS = uint8(bi2de(fcBits(9,1)'));
frameCtrl.FromDS = uint8(bi2de(fcBits(10,1)'));
frameCtrl.MoreFragments = uint8(bi2de(fcBits(11,1)'));
frameCtrl.Retry = uint8(bi2de(fcBits(12,1)'));
frameCtrl.PowerManagement = uint8(bi2de(fcBits(13,1)'));
frameCtrl.MoreData = uint8(bi2de(fcBits(14,1)'));
frameCtrl.ProtectedFrame = uint8(bi2de(fcBits(15,1)'));
frameCtrl.Order = uint8(bi2de(fcBits(16,1)'));
else
frameCtrl.ProtocolVersion = uint8(0);
frameCtrl.Type = uint8(0);
frameCtrl.Subtype = uint8(0);
frameCtrl.ToDS = uint8(0);
frameCtrl.FromDS = uint8(0);
frameCtrl.MoreFragments = uint8(0);
frameCtrl.Retry = uint8(0);
frameCtrl.PowerManagement = uint8(0);
frameCtrl.MoreData = uint8(0);
frameCtrl.ProtectedFrame = uint8(0);
frameCtrl.Order = uint8(0);
end
end
function frameBody = parseBeaconMPDU(frame, mpduCRC)
if (mpduCRC == 0)
bitCount = uint32(1);
frameBody.TimeStamp = bit2Octet(frame(bitCount:bitCount+63,1),8);
bitCount = bitCount + 64;
frameBody.BeaconInterval = bit2Octet(frame(bitCount:bitCount+15,1),2);
bitCount = bitCount + 16;
frameBody.Capability = parseCapabilities(frame(81:96), mpduCRC);
bitCount = bitCount + 16;
else
frameBody.TimeStamp = zeros(1,8,'uint8');
frameBody.BeaconInterval = zeros(1,2,'uint8');
frameBody.Capability = parseCapabilities(frame(81:96), mpduCRC);
bitCount = uint32(97);
end
frameLength = length(frame);
frameBody.NumInfoElements = uint8(0);
macElementStruct = struct('ID', uint8(255), ...
'Length', uint8(0), ...
'Value', zeros(1,257,'uint8'));
frameBody.InfoElements = repmat(macElementStruct, 1, 60);
if (mpduCRC == 0)
while bitCount < frameLength
frameBody.NumInfoElements = frameBody.NumInfoElements + 1;
frameBody.InfoElements(frameBody.NumInfoElements).ID = ...
bit2Octet(frame(bitCount:bitCount+7,1), 1);
bitCount = bitCount + 8;
elemLength = bit2Octet(frame(bitCount:bitCount+7,1), 1);
frameBody.InfoElements(frameBody.NumInfoElements).Length = elemLength;
bitCount = bitCount + 8;
for p=1:elemLength
frameBody.InfoElements(frameBody.NumInfoElements).Value(p) = ...
bit2Octet(frame(bitCount:bitCount+7),1);
bitCount = bitCount+8;
end
end
end
end
function capability = parseCapabilities(frame, mpduCRC)
if (mpduCRC == 0)
capability.ESS = frame(1,1);
capability.IBSS = frame(2,1);
capability.CFPollable = frame(3,1);
capability.CFPollRequest = frame(4,1);
capability.Privacy = frame(5,1);
capability.ShortPreamble = frame(6,1);
capability.PBCC = frame(7,1);
capability.ChannelAgility = frame(8,1);
capability.SpectrumManagement = frame(9,1);
capability.QoS = frame(10,1);
capability.ShortSlotTime = frame(11,1);
capability.APSD = frame(12,1);
capability.Reserved = frame(13,1);
capability.DSSOFDM = frame(14,1);
capability.DelayedBlockAck = frame(15,1);
capability.ImmediateBlockAck = frame(16,1);
else
capability.ESS = double(false);
capability.IBSS = double(false);
capability.CFPollable = double(false);
capability.CFPollRequest = double(false);
capability.Privacy = double(false);
capability.ShortPreamble = double(false);
capability.PBCC = double(false);
capability.ChannelAgility = double(false);
capability.SpectrumManagement = double(false);
capability.QoS = double(false);
capability.ShortSlotTime = double(false);
capability.APSD = double(false);
capability.Reserved = double(false);
capability.DSSOFDM = double(false);
capability.DelayedBlockAck = double(false);
capability.ImmediateBlockAck = double(false);
end
end
function frameBody = unknownMPDU()
frameBody.TimeStamp = zeros(1,8,'uint8');
frameBody.BeaconInterval = zeros(1,2,'uint8');
frameBody.Capability = parseCapabilities(zeros(16,1), 1);
frameBody.NumInfoElements = uint8(0);
macElementStruct = struct('ID', uint8(255), ...
'Length', uint8(0), ...
'Value', zeros(1,257,'uint8'));
frameBody.InfoElements = repmat(macElementStruct, 1, 60);
end
function octets = bit2Octet(bits,numOctets)
octets = zeros(1, numOctets, 'uint8');
for p=1:numOctets
octets(1,p) = (bits((p-1)*8+1:p*8)')*2.^(0:7)';
end
end
% [EOF]