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Impl task1 some part of task2

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ti_mo
2026-05-19 21:56:06 +02:00
parent fca31532d1
commit 1561016689
8 changed files with 849 additions and 187 deletions
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lab_3/from_matlab_example/hWLANPacketDetector.m
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classdef hWLANPacketDetector < handle & comm.internal.ConfigBase
%hWLANPacketDetector OFDM packet detection using the L-STF
%
% WPD = hWLANPacketDetector(X,CBW) creates an hWLANPacketDetector object,
% WPD, that sets the Waveform property to X and ChannelBandwidth to CBW.
%
% WPD = hWLANPacketDetector(...,Name,Value) creates an
% hWLANPacketDetector object, WPD, with the specified property Name set
% to the specified Value. You can specify additional name-value pair
% arguments in any order as (Name1,Value1,...,NameN,ValueN).
%
% hWLANPacketDetector methods:
%
% findPacketStart - Returns the offset to the start of a detected
% packet in Waveform
%
% hWLANPacketDetector properties:
%
% Waveform - A time-domain signal specified as a Ns-by-Nr
% matrix of real or complex float values where Ns
% represents the number of time domain samples and
% Nr represents the number of receive antennas.
% ChannelBandwidth - A text scalar describing the channel bandwidth of
% WAVEFORM. The value must be 'CBW5', 'CBW10',
% 'CBW20', 'CBW40', 'CBW80', 'CBW160', or 'CBW320'.
% OversamplingFactor - The oversampling factor of WAVEFORM. The value
% must be greater than or equal to 1. The default is
% 1.
% Threshold - The threshold which the decision statistic must
% meet or exceed to detect a packet in WAVEFORM when
% calling FINDPACKETSTART. The value must be a real
% scalar that is greater than 0 and less than or
% equal to 1. The default is 0.5.
% SearchOffset - The index from which FINDPACKETSTART looks for a
% packet. The value must be a real scalar integer
% that is greater than or equal to 0 and less than
% Ns in WAVEFORM. The default is 0.
%
%
% % Example 1:
% % Detect a received 802.11a packet
% cfgNonHT = wlanNonHTConfig; % Create packet configuration
%
% % Generate transmit waveform
% txWaveform = wlanWaveformGenerator([1;0;0;1],cfgNonHT, ...
% 'WindowTransitionTime',0);
%
% % Delay the signal by appending zeros at the start
% rxWaveform = [zeros(20,1);txWaveform];
%
% wpd = hWLANPacketDetector(rxWaveform,cfgNonHT.ChannelBandwidth);
% wpd.SearchOffset = 5;
% wpd.Threshold = 0.99;
%
% startOffset = findPacketStart(wpd);
%
% disp("Packet start offset: " + startOffset)
% Copyright 2024 The MathWorks, Inc.
properties
Waveform {mustBeFloat,mustBeFinite} = [];
ChannelBandwidth {mustBeTextScalar} = 'CBW20';
OversamplingFactor (1,1) {mustBeNumeric, mustBeFinite, mustBeGreaterThanOrEqual(OversamplingFactor, 1)} = 1;
Threshold (1,1) {mustBeFloat, mustBeReal, mustBeInRange(Threshold,0,1,'exclude-lower')} = 0.5;
SearchOffset (1,1) {mustBeNumeric,mustBeInteger,mustBeNonnegative} = 0;
end
properties(Access=private)
UpdateDecisionStatistic = true;
UpdatePacketOffsets = true;
FoundOffsets;
DecisionStatistic;
DetectedColumnIndicies;
end
methods
function obj = hWLANPacketDetector(wav,cbw,opts)
arguments
wav;
cbw;
opts.Threshold
opts.OversamplingFactor
opts.SearchOffset
end
nvpairs = [{'Waveform' wav 'ChannelBandwidth' cbw} namedargs2cell(opts)];
obj@comm.internal.ConfigBase(nvpairs{:});
end
function [startOffset,M] = findPacketStart(obj)
%findPacketStart Return the offset of a detected packet
%
% [STARTOFFSET,M] = findPacketStart(OBJ) returns the index of a
% detected packet in WAVEFORM. The index returned is the next
% closest index to SEARCHOFFSET. If no packet is detected an empty
% value is returned.
%
% OBJ is a hWLANPacketDetector object.
%
% STARTOFFSET is an integer scalar indicating the location of the
% start of a detected packet.
%
% M is a real vector of size N-by-1, representing the decision
% statistics based on auto-correlation of WAVEFORM. The
% length of N depends on index of a successful detection of a
% packet.
if isempty(obj.Waveform)
startOffset = [];
M = [];
return;
end
cbw = obj.ChannelBandwidth;
[fftLen,nsc] = wlan.internal.cbw2nfft(cbw);
osf = obj.OversamplingFactor;
wlan.internal.validateOFDMOSF(osf, fftLen, 0); % Validate OSF
Td = 0.8e-6; % Time period of a short training symbol for 20MHz
symbolLength = Td*osf*nsc*20e6;
lenLSTF = symbolLength*10; % Length of 10 L-STF symbols
lenHalfLSTF = lenLSTF/2; % Length of 5 L-STF symbols
if obj.UpdateDecisionStatistic
inpLength = size(obj.Waveform,1);
% Append zeros to make the input equal to multiple of L-STF/2
if inpLength<=lenHalfLSTF
numPadSamples = lenLSTF - inpLength;
else
numPadSamples = lenHalfLSTF*ceil(inpLength/lenHalfLSTF) - inpLength;
end
padSamples = zeros(numPadSamples,size(obj.Waveform,2),'like',obj.Waveform);
% Process the input waveform in blocks of L-STF length. The processing
% blocks are offset by half the L-STF length.
numBlocks = (inpLength + numPadSamples)/lenHalfLSTF;
searchBuffer = reshape([obj.Waveform;padSamples],lenHalfLSTF,numBlocks,size(obj.Waveform,2));
searchBuffer = [searchBuffer(:,1:end-1,:);searchBuffer(:,2:end,:)];
[obj.FoundOffsets,obj.DecisionStatistic,obj.DetectedColumnIndicies] = ...
wlan.internal.detectPackets(searchBuffer,symbolLength, ...
lenLSTF,obj.Threshold);
obj.UpdateDecisionStatistic = false;
obj.UpdatePacketOffsets = false;
elseif obj.UpdatePacketOffsets
% obj.Threshold was updated so update the offsets
[obj.FoundOffsets,obj.DetectedColumnIndicies] = ...
getPacketOffsets(obj.DecisionStatistic,symbolLength, ...
lenLSTF,obj.Threshold);
obj.UpdatePacketOffsets = false;
end
idx = find(obj.FoundOffsets >= obj.SearchOffset,1);
startOffset = obj.FoundOffsets(idx);
if isempty(idx)
endIdx = size(obj.DecisionStatistic,2);
else
endIdx = obj.DetectedColumnIndicies(idx);
end
M = double([reshape(obj.DecisionStatistic(1:lenHalfLSTF,1:endIdx-1),[],1); ...
reshape(obj.DecisionStatistic(:,endIdx),[],1)]);
end % function findPacketStart
% Setters
function set.Waveform(obj,value)
if ~isequal(obj.Waveform,value)
obj.Waveform = value;
obj.UpdateDecisionStatistic = true; %#ok<*MCSUP>
end
end
function set.ChannelBandwidth(obj,value)
if ~strcmpi(obj.ChannelBandwidth,value)
obj.ChannelBandwidth = wlan.internal.validateParam('NONHTEHTCHANBW', value, mfilename);
obj.UpdateDecisionStatistic = true;
end
end
function set.OversamplingFactor(obj,value)
if ~isequal(obj.OversamplingFactor,value)
obj.OversamplingFactor = value;
obj.UpdateDecisionStatistic = true;
end
end
function set.Threshold(obj,value)
if ~isequal(obj.Threshold,value)
obj.Threshold = value;
obj.UpdatePacketOffsets = true;
end
end
function set.SearchOffset(obj,value)
coder.internal.errorIf(~isempty(obj.Waveform) && value>size(obj.Waveform, 1)-1, 'wlan:shared:InvalidOffsetValue')
obj.SearchOffset = value;
end
end
end
function [packetStarts,colIdxs] = getPacketOffsets(mn,symbolLength,lenLSTF,threshold)
% mn: Decision statistic
% threshold: Decision threshold as specified by user
N = mn > threshold;
colDesc = sum(N) >= symbolLength*1.5;
N(:,~colDesc) = false;
colIdxs = find(colDesc);
% Create a matrix of indicies where each column has the value 1:corrLen
% then extract indices based on N and desc and calculate all possible
% packet start locations
corrLen = lenLSTF - (symbolLength*2) + 1;
idxs = repmat((1:corrLen)',1,size(N,2));
idxs(~N) = NaN;
idxs = idxs(:,colDesc);
packetStarts = min(idxs) + (colIdxs-1)*lenLSTF/2 - 1;
% Check relative distances between peaks for all detected packets
if ~isempty(packetStarts)
packetStarts = arrayfun(@(x)checkRelativeDist(packetStarts(x),idxs(:,x),symbolLength),1:length(packetStarts));
end
% Extract non-NaN values
colIdxs = colIdxs(~isnan(packetStarts));
packetStarts = packetStarts(~isnan(packetStarts));
end
function pS = checkRelativeDist(pS,idxs,symbolLength)
% Check the relative distance between peaks relative to the first peak. If
% this exceed three times the symbol length then the packet is not
% detected.
nonan = idxs(~isnan(idxs));
if any(nonan(2:symbolLength) - nonan(1)>symbolLength*3)
pS = NaN;
end
end