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savedradioconfigurations = radioconfigurations;

savedradioconfigurationnames = [string({savedradioconfigurations.name})];
radio = savedradioconfigurationnames(1);

if ~exist("pd","var")
    pd = preambledetector(radio);
end

captureantennaselection = hcaptureantennas(radio);
pd.antennas = captureantennaselection(1);

osf = 2;
pd.samplerate = 20e6*osf;
pd.capturedatatype = "double";
pd.thresholdmethod = "adaptive";

cbw = "cbw20";
cfg = wlannonhtconfig(channelbandwidth=cbw);
lltf = wlanlltf(cfg,oversamplingfactor=osf);

cyclicprefixlength = 1.6e-6*pd.samplerate;
trainingsymbollength = 3.2e-6*pd.samplerate;
preamble = lltf(cyclicprefixlength 1:cyclicprefixlength trainingsymbollength);

preamble = preamble/sqrt(sum(abs(preamble).^2));
pd.preamble = preamble;

lstflength = 8e-6*pd.samplerate;
pd.triggeroffset = -(lstflength   cyclicprefixlength   trainingsymbollength   5);

band = 5;
channel = 100;
pd.centerfrequency = wlanchannelfrequency(channel,band);

pd.adaptivethresholdgain = 0.3;
pd.adaptivethresholdoffset = 0.0005;
pd.radiogain = 60;

captureduration = milliseconds(120);
plotthreshold(pd,captureduration);

band = 5;
channels = [32 36 40 44 48 52 56 60 64 100 104 108 112 116 120 124 128 132 136 140 144 149 153 157 161 165 169 173 177];

centerfrequencies = wlanchannelfrequency(channels,band);

capturelength = milliseconds(100);
timeout = milliseconds(100);

aps = struct(...
    "ssid",[],"bssid",[],"vendor",[],"snr_db",[],"beacon_channel",[], ...
    "operating_channel",[],"channel_width_mhz",[],"band",[],"mode",[], ...
    "mac_config",wlanmacframeconfig,"waveform",[],"offset",[]);

retrievevendorinfo = true;
counter = 1;
ind = wlanfieldindices(cfg);
% begin scanning and decoding for specified channels.
for i = 1:length(centerfrequencies)
    pd.centerfrequency = centerfrequencies(i);
    fprintf("scanning channel %d on band %.1f.\n",channels(i),band);
    [captureddata, ~, ~, status] = capture(pd, capturelength, timeout);
    if ~status
        % if no non-ht packet is decoded, go to next channel.
        fprintf("no non-ht packet detected on channel %d in band %.1f.\n",channels(i),band);
        continue;
    else
        fprintf("non-ht packet detected on channel %d in band %.1f.\n",channels(i),band)
    end
    % resample the captured data to 20 mhz for beacon processing.
    captureddata = resample(captureddata,1,osf);
    searchoffset = 0;
    while searchoffset% recoverpreamble detects a packet and performs analysis of the non-ht preamble.
        [preamblestatus,res] = recoverpreamble(captureddata,cbw,searchoffset);
        if matches(preamblestatus,"no packet detected")
            break;
        end
        % retrieve synchronized data and scale it with lstf power as done
        % in the recoverpreamble function.
        syncdata = captureddata(res.packetoffset 1:end)./sqrt(res.lstfpower);
        syncdata = frequencyoffset(syncdata,pd.samplerate/osf,-res.cfoestimate);
        % need only 4 ofdm symbols (lsig   3 more symbols) following lltf
        % for format detection
        fmtdetect = syncdata(ind.lsig(1):(ind.lsig(2) 4e-6*pd.samplerate/osf*3));
        [lsigbits, failcheck] = wlanlsigrecover(fmtdetect(1:4e-6*pd.samplerate/osf*1), ...
            res.chanestnonht,res.noiseestnonht,cbw);
        if ~failcheck
            format = wlanformatdetect(fmtdetect,res.chanestnonht,res.noiseestnonht,cbw);
            if matches(format,"non-ht")
                % extract mcs from first 3 bits of l-sig.
                rate = double(bit2int(lsigbits(1:3),3));
                if rate <= 1
                    cfg.mcs = rate   6;
                else
                    cfg.mcs = mod(rate,6);
                end
                % determine psdu length from l-sig.
                cfg.psdulength = double(bit2int(lsigbits(6:17),12,0));
                ind.nonhtdata = wlanfieldindices(cfg,"nonht-data");
                if double(ind.nonhtdata(2)-ind.nonhtdata(1))> ...
                        length(syncdata(ind.nonhtdata(1):end))
                    % exit while loop as full packet not captured.
                    break;
                end
                nonhtdata = syncdata(ind.nonhtdata(1):ind.nonhtdata(2));
                bitsdata = wlannonhtdatarecover(nonhtdata,res.chanestnonht, ...
                    res.noiseestnonht,cfg);
                [cfgmac, ~, decodestatus] = wlanmpdudecode(bitsdata,cfg, ...
                    suppresswarnings=true);
                % extract information about channel from the beacon.
                if ~decodestatus && matches(cfgmac.frametype,"beacon")
                    fprintf("beacon detected on channel %d in band %.1f.\n",channels(i),band);
                    % populate the table with information about the beacon.
                    if isempty(cfgmac.managementconfig.ssid)
                        aps(counter).ssid = "hidden";
                    else
                        aps(counter).ssid = string(cfgmac.managementconfig.ssid);
                    end
                    aps(counter).bssid = string(cfgmac.address3);
                    if retrievevendorinfo
                        aps(counter).vendor = determinevendor(cfgmac.address3);
                    else
                        aps(counter).vendor = "skipped"; %#ok
                    end
                    [aps(counter).mode, aps(counter).channel_width_mhz, operatingchannel] = ...
                        determinemode(cfgmac.managementconfig.informationelements);
                    if isempty(operatingchannel)
                        % default to scanning channel if operating channel
                        % cannot be determined.
                        operatingchannel = channels(i);
                    end
                    aps(counter).beacon_channel = channels(i);
                    aps(counter).operating_channel = operatingchannel;
                    aps(counter).snr_db = res.lltfsnr;
                    aps(counter).mac_config = cfgmac;
                    aps(counter).offset = res.packetoffset;
                    aps(counter).waveform = captureddata;
                    counter = counter   1;
                end
                % shift packet search offset for next iteration of while loop.
                searchoffset = res.packetoffset   double(ind.nonhtdata(2));
            else
                % packet is not non-ht; shift packet search offset by 10 ofdm symbols (minimum
                % packet length of non-ht) for next iteration of while loop.
                searchoffset = res.packetoffset   4e-6*pd.samplerate/osf*10;
            end
        else
            % l-sig recovery failed; shift packet search offset by 10 ofdm symbols (minimum
            % packet length of non-ht) for next iteration of while loop.
            searchoffset = res.packetoffset   4e-6*pd.samplerate/osf*10;
        end
    end
end

detectedbeaconsinfo = generatebeacontable(aps,band)

function vendor = determinevendor(mac)
% determinevendor returns the vendor name of the ap by extracting the
% organizationally unique identifier (oui) from the specified mac address.
persistent ouis
vendor = strings(0);
try
    if isempty(ouis)
        if ~exist("oui.csv","file")
            disp("downloading oui.csv from ieee registration authority...")
            % increase websave timeout if necessary
            options = weboptions("timeout",5);
            websave("oui.csv","http://standards-oui.ieee.org/oui/oui.csv",options);
        end
        ouis = readtable("oui.csv",variablenamingrule="preserve");
    end
    % extract oui from mac address.
    oui = mac(1:6);
    % extract vendors name based on oui.
    vendor = string(cell2mat(ouis.("organization name")(matches(ouis.assignment,oui))));
catch me
    % rethrow caught error as warning.
    warning(me.message "\nto skip the determinevendor function call, set retrievevendorinfo to false.",[]);
end
if isempty(vendor)
    vendor = "unknown";
end
end
function [mode,bw,operatingchannel] = determinemode(informationelements)
% determinemode determines the 802.11 standard that the ap uses.
% the function checks for the presence of ht, vht, and he capability
% elements and determines the 802.11 standard that the ap uses. the element
% ids are defined in ieee std 802.11-2020 and ieee std 802.11ax-2021.
elementids = cell2mat(informationelements(:,1));
ids = elementids(:,1);
if any(ids==255)
    if any(elementids(ids==255,2)==35)
        % he packet format
        mode = "802.11ax";
    else
        mode = "unknown";
    end
    vhtelement = informationelements{ids==192,2};
    htelement = informationelements{ids==61,2};
    [bw,operatingchannel] = determinechannelwidth(htelement,vhtelement);
elseif any(ids==191)
    % vht packet format
    mode = "802.11ac";
    vhtelement = informationelements{ids==192,2};
    htelement = informationelements{ids==61,2};
    [bw,operatingchannel] = determinechannelwidth(htelement,vhtelement);
elseif any(ids==45)
    % ht packet format
    mode = "802.11n";
    htelement = informationelements{ids==61,2};
    [bw,operatingchannel] = determinechannelwidth(htelement);
else
    % non-ht packet format
    % exclude b as only dsss is supported
    mode ="802.11a/g/j/p";
    bw = "unknown";
    operatingchannel = [];
end
end
function [bw,operatingchannel] = determinechannelwidth(htelement,varargin)
% determinechannelwidth returns the bandwidth of the channel from the
% beacons ht/vht operation information elements as defined in ieee std 802.11-2020
% section 9.4.2.56 and section 9.4.2.158.
msbfirst = false;
% ieee std 802.11-2020 figure 9-382 and table 9-190 define each bit in
% htoperationinfobits
% convert to bits to get sta channel width value in 3rd bit.
htoperationinfobits = int2bit(htelement(2),5*8,msbfirst);
operatingchannel = 0;
if nargin == 2
    % ieee std 802.11-2020 figure 9-163 and table 9-274 define each octet
    % in vhtelement
    vhtelement = varargin{1};
    % vht operation channel width field
    cw = vhtelement(1);
    % channel center frequency segment 0
    ccfs0 = vhtelement(2);
    % channel center frequency segment 1
    ccfs1 = vhtelement(3);
    % ieee std 802.11-2020 table 11-23 defines the logic below
    if htoperationinfobits(3) == 0
        bw = "20";
        operatingchannel = ccfs0;
    elseif cw == 0
        % ht operation channel width field is 1
        bw = "40";
        operatingchannel = ccfs0;
    elseif ccfs1 == 0
        % ht operation channel width field is 1 and
        % vht operation channel width field is 1
        bw = "80";
        operatingchannel = ccfs0;
    elseif abs(ccfs1 - ccfs0) == 8
        % ht operation channel width field is 1 and
        % vht operation channel width field is 1 and
        % ccfs1 is greater than 0
        bw = "160";
        operatingchannel = ccfs1;
    else
        % ht operation channel width field is 1 and
        % vht operation channel width field is 1 and
        % ccfs1 is greater than 0 and
        % |ccfs1 - ccfs0| is greater than 16
        bw = "80 80";
    end
end
if operatingchannel == 0
    if htoperationinfobits(3) == 1
        bw = "40";
        secondarychanneloffset = bit2int(htoperationinfobits(1:2),2,false);
        if secondarychanneloffset == 1
            % secondary channel is above the primary channel.
            operatingchannel = htelement(1)   2;
        elseif secondarychanneloffset == 3
            % secondary channel is below the primary channel.
            operatingchannel = htelement(1) - 2;
        else
            warning("could not determine operating channel.")
        end
    else
        bw = "20";
        operatingchannel = htelement(1);
    end
end
end
function tbl = generatebeacontable(aps,band)
% generatebeacontable converts the access point structure to a table and
% cleans up the variable names.
tbl = struct2table(aps,"asarray",true);
tbl.band = repmat(band,length(tbl.ssid),1);
tbl = renamevars(tbl,["snr_db","beacon_channel","operating_channel","channel_width_mhz"], ...
    ["snr (db)","primary 20 mhz channel","current channel center frequency index", ...
    "channel width (mhz)"]);
tbl = tbl(:,1:9);
end