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wlanFieldIndices

Generate PPDU field indices

Syntax

ind = wlanFieldIndices(cfg)
ind = wlanFieldIndices(cfg,field)

Description

example

ind = wlanFieldIndices(cfg) returns ind, a structure containing the start and stop indices of the individual component fields that comprise the baseband physical layer convergence procedure protocol data unit (PPDU) waveform.

Note

For non-high-throughput (non-HT) format, this function supports generation of field indices only for OFDM modulation.

example

ind = wlanFieldIndices(cfg,field) returns the start and stop indices for the specified field type in the rows of a matrix ind.

Examples

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Extract the very-high-throughput short training field (VHT-STF) from a VHT waveform.

Create a VHT-format configuration object for a multiple-input/multiple-output (MIMO) transmission using a 160-MHz channel bandwidth. Generate the corresponding VHT waveform.

cfg = wlanVHTConfig('MCS',8,'ChannelBandwidth','CBW160', ... 
    'NumTransmitAntennas',2,'NumSpaceTimeStreams',2);
txSig = wlanWaveformGenerator([1;0;0;1],cfg);

Determine the component PPDU field indices for the VHT format.

ind = wlanFieldIndices(cfg)
ind = struct with fields:
       LSTF: [1 1280]
       LLTF: [1281 2560]
       LSIG: [2561 3200]
    VHTSIGA: [3201 4480]
     VHTSTF: [4481 5120]
     VHTLTF: [5121 6400]
    VHTSIGB: [6401 7040]
    VHTData: [7041 8320]

The VHT PPDU waveform is comprised of eight fields, including seven preamble fields and one data field.

Extract the VHT-STF from the transmitted waveform.

stf = txSig(ind.VHTSTF(1):ind.VHTSTF(2),:);

Verify that the VHT-STF has dimension 640-by-2, corresponding to the number of samples (80 for each 20-MHz bandwidth segment) and the number of transmit antennas.

disp(size(stf))
   640     2

Generate a VHT waveform. Extract and demodulate the VHT long training field (VHT-LTF) to estimate the channel coefficients. Recover the data field by using the channel estimate and use this field to determine the number of bit errors.

Configure a VHT-format configuration object with two paths.

vht = wlanVHTConfig('NumTransmitAntennas',2,'NumSpaceTimeStreams',2);

Generate a random PSDU and create the corresponding VHT waveform.

txPSDU = randi([0 1],8*vht.PSDULength,1);
txSig = wlanWaveformGenerator(txPSDU,vht);

Pass the signal through a TGac 2x2 MIMO channel.

tgacChan = wlanTGacChannel('NumTransmitAntennas',2,'NumReceiveAntennas',2, ...
    'LargeScaleFadingEffect','Pathloss and shadowing');
rxSigNoNoise = tgacChan(txSig);

Add AWGN to the received signal. Set the noise variance for the case in which the receiver has a 9-dB noise figure.

nVar = 10^((-228.6+10*log10(290)+10*log10(80e6)+9)/10);
awgnChan = comm.AWGNChannel('NoiseMethod','Variance','Variance',nVar);
rxSig = awgnChan(rxSigNoNoise);

Determine the indices for the VHT-LTF and extract the field from the received signal.

indVHT = wlanFieldIndices(vht,'VHT-LTF');
rxLTF = rxSig(indVHT(1):indVHT(2),:);

Demodulate the VHT-LTF and estimate the channel coefficients.

dLTF = wlanVHTLTFDemodulate(rxLTF,vht);
chEst = wlanVHTLTFChannelEstimate(dLTF,vht);

Extract the VHT-Data field and recover the information bits.

indData = wlanFieldIndices(vht,'VHT-Data');
rxData = rxSig(indData(1):indData(2),:);
rxPSDU = wlanVHTDataRecover(rxData,chEst,nVar,vht);

Determine the number of bit errors.

numErrs = biterr(txPSDU,rxPSDU)
numErrs = 0

Input Arguments

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Transmission format, specified as one of these configuration objects: wlanHESUConfig, wlanHEMUConfig, wlanHERecoveryConfig wlanDMGConfig, wlanS1GConfig, wlanVHTConfig, wlanHTConfig, or wlanNonHTConfig.

Example: cfg = wlanVHTConfig

PPDU field name, specified as a character vector. The valid set of field values depends on the transmission format specified in the cfg input.

Transmission Format (cfg)Valid Field Name Values (field)
wlanHESUConfig, wlanHEMUConfig, or wlanHERecoveryConfig

'L-STF', 'L-LTF', 'L-SIG', 'RL-SIG', 'HE-SIG-A', 'HE-SIG-B', 'HE-STF', 'HE-LTF', or 'HE-Data'

wlanDMGConfig

'DMG-STF', 'DMG-CE', 'DMG-Header', and 'DMG-Data' are common for all directional multi-gigabit (DMG) physical layer (PHY) configurations.

When the wlanDMGConfig property TrainingLength is positive, additional valid fields include: 'DMG-AGC', 'DMG-AGCSubfields', 'DMG-TRN', 'DMG-TRNCE', and 'DMG-TRNSubfields'.

  • 'DMG-AGCSubfields' is returned in a matrix with TrainingLength rows.

  • 'DMG-TRNCE' is returned in a matrix with TrainingLength/4 rows.

  • 'DMG-TRNSubfields' is returned in a matrix with TrainingLength rows.

wlanS1GConfig

'S1G-STF', 'S1G-LTF1', and 'S1G-Data' are common for all sub-one-gigahertz (S1G) configurations.

For a 1-MHz or greater than 2-MHz short preamble configuration, additional valid fields include 'S1G-SIG' and 'S1G-LTF2N'.

For a greater than 2-MHz long preamble configuration, additional valid fields include 'S1G-SIG-A', 'S1G-DSTF', 'S1G-DLTF', and 'S1G-SIG-B'.

wlanVHTConfig

'L-STF', 'L-LTF', 'L-SIG', 'VHT-SIG-A', 'VHT-STF', 'VHT-LTF', 'VHT-SIG-B', or 'VHT-Data'

wlanHTConfig

'L-STF', 'L-LTF', 'L-SIG', 'HT-SIG', 'HT-STF', 'HT-LTF', or 'HT-Data'

wlanNonHTConfig

'L-STF', 'L-LTF', 'L-SIG', or 'NonHT-Data'

Data Types: char | string

Output Arguments

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Start and stop indices, returned as a structure matrix. The indices correspond to the start and stop indices of fields included in the baseband waveform defined by the cfg input.

If you specify the field input, the function returns ind as an N-by-2 matrix of uint32 values, consisting of the start and stop indices of the PPDU field. This table outlines the N dimension of the N-by-2 matrix that is returned based on the specific format and configuration.

FormatConfigurationind or Specific Field Dimension

non-HT

1-by-2 matrix for each field

HT

1-by-2 matrix for each field

Null data packet (NDP) mode, if the PSDULength property of wlanHTConfig object is 0Empty matrix

VHT and S1G

1-by-2 matrix for each field

When null data packet (NDP) mode, if the APEPLength property of wlanVHTConfig or wlanS1GConfig object is 0Empty matrix

HE(1)

1-by-2 matrix for each field

Null data packet (NDP) mode, if the APEPLength property of wlanHESUConfig or wlanHESUConfig object is 0Empty matrix
When a midamble is added to the HE-Data field to improve channel estimates for high Doppler scenarios.

'HE Data' is an R-by-2 matrix, where R is the number of data blocks separated by midamble periods.

DMG(2)

1-by-2 matrix for each field

When the TrainingLength property of wlanDMGConfig object is positive'DMG-AGC' is a 1-by-2 matrix.
'DMG-TRN' is a 1-by-2 matrix
'DMG-AGCSubfields' is a TrainingLength-by-2 matrix.
'DMG-TRNSubfields' is a TrainingLength-by-2 matrix.
'DMG-TRNCE' is a (TrainingLength/4)-by-2 matrix.
When the TrainingLength property of wlanDMGConfig object is 0'DMG-AGC' is an empty matrix.
'DMG-TRN' is an empty matrix.
'DMG-AGCSubfields' is an empty matrix.
'DMG-TRNSubfields' is an empty matrix.
'DMG-TRNCE' is an empty matrix.
  1. As described in Section 28.3.11.16 of [1], you can add a midamble to the HE Data field to improve the channel estimates for high Doppler scenarios.

  2. For DMG, the 'DMG-AGC' field contains NTrainingLength subfields, where NTrainingLength is 0–64 subfields. The 'DMG-TRN' field contains NTrainingLength + (NTrainingLength/4) subfields. As shown in this figure, the indices for 'DMG-AGC' and 'DMG-TRN' overlap with the indices of their respective subfields, 'DMG-AGCSubfields' and 'DMG-TRNSubfields'.

References

[1] IEEE P802.11ax™/D3.1 “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Amendment 6: Enhancements for High Efficiency WLAN." Draft Standard for Information technology – Telecommunications and information exchange between systems – Local and metropolitan area networks – Specific requirements.

[2] IEEE Std 802.11™-2016 IEEE Standard for Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Specific requirements — Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.

[3] IEEE Std 802.11™-2012 IEEE Standard for Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Specific requirements — Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.

[4] IEEE Std 802.11ac™-2013 IEEE Standard for Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Specific requirements — Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications — Amendment 4: Enhancements for Very High Throughput for Operation in Bands below 6 GHz.

[5] IEEE Std 802.11ad™-2012 IEEE Standard for Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Specific requirements — Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications — Amendment 3: Enhancements for Very High Throughput in the 60 GHz Band.

Extended Capabilities

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Introduced in R2015b