wlanHESIGABitRecover

Recover information bits in HE-SIG-A field

Syntax

[bits,failCRC] = wlanHESIGABitRecover(siga,noiseVarEst)

[bits,failCRC] = wlanHESIGABitRecover(siga,noiseVarEst,csi)

Description

[bits,failCRC] = wlanHESIGABitRecover(siga,noiseVarEst) recovers bits, the information bits contained in siga, the HE-SIG-A field of an IEEE^® 802.11™ high-efficiency transmission subject to channel noise with estimated variance noiseVarEst. The function also returns failCRC, the result of the cyclic redundancy check (CRC) on bits.

For more information on 802.11ax™ signal recovery, see Recovery Procedure for an 802.11ax Packet.

[bits,failCRC] = wlanHESIGABitRecover(siga,noiseVarEst,csi) also enhances the demapping of orthogonal frequency-division multiplexing (OFDM) subcarriers by using channel state information csi.

Examples

Recover Information Bits in HE-SIG-A Field

Create a WLAN HE SU configuration object with default settings and use it to generate a waveform.

cfgHE = wlanHESUConfig;
cbw = cfgHE.ChannelBandwidth;
waveform = wlanWaveformGenerator(1,cfgHE);

Get the WLAN field indices. Use them to isolate the HE-SIG-A field.

ind = wlanFieldIndices(cfgHE);
rxSIGA = waveform(ind.HESIGA(1):ind.HESIGA(2),:);

Perform OFDM demodulation to extract the HE-SIG-A field.

sigaDemod = wlanHEDemodulate(rxSIGA,'HE-SIG-A',cbw);

Return the pre-HE OFDM information and use it to extract the demodulated HE-SIG-A data symbols.

preHEInfo = wlanHEOFDMInfo('HE-SIG-A',cbw);
siga = sigaDemod(preHEInfo.DataIndices,:);

Recover the HE-SIG-A information bits and other information, assuming no channel noise. Display the parity check result.

noiseVarEst = 0;
[bits,failCRC] = wlanHESIGABitRecover(siga,noiseVarEst);
disp(failCRC);

   0

Recover HE-SIG-A Information Bits with Channel State Information

Recover the information bits in the HE-SIG-A field of a WLAN HE multiuser (HE-MU) waveform with specified channel state information.

Create a WLAN HE-MU-format configuration object with default settings and use it to generate an HE-MU waveform.

cfgHE = wlanHEMUConfig(0);
cbw = cfgHE.ChannelBandwidth;
waveform = wlanWaveformGenerator(1,cfgHE);

Obtain the WLAN field indices, which contain the modulated HE-SIG-A symbols.

ind = wlanFieldIndices(cfgHE);
rxSIGA = waveform(ind.HESIGA(1):ind.HESIGA(2),:);

Perform OFDM demodulation to extract the HE-SIG-A field.

sigaDemod = wlanHEDemodulate(rxSIGA,'HE-SIG-A',cbw);

Return the pre-HE OFDM information and extract the demodulated HE-SIG-A symbols.

preHEInfo = wlanHEOFDMInfo('HE-SIG-A',cbw);
siga = sigaDemod(preHEInfo.DataIndices,:);

Specify the channel state information and assume no channel noise.

csi = ones(52,1);
noiseVarEst = 0;

Recover the HE-SIG-A information bits and other information. Display the CRC result.

[bits,failCRC] = wlanHESIGABitRecover(siga,noiseVarEst,csi);
disp(failCRC);

   0

Update HE MU Recovery Configuration Object

Update a WLAN HE recovery configuration object by interpreting recovered HE-SIG-A and HE-SIG-B information bits.

Generate HE MU Waveform

Create a WLAN HE MU configuration object, setting the allocation index to 0.

cfgHEMU = wlanHEMUConfig(0);

Generate a WLAN waveform and PPDU field indices for the specified configuration.

waveform = wlanWaveformGenerator(1,cfgHEMU);
ind = wlanFieldIndices(cfgHEMU);

Recover L-SIG Bits

Create a WLAN recovery configuration object, specifying an HE MU packet format and the length of the L-SIG field.

cfg = wlanHERecoveryConfig('PacketFormat','HE-MU','ChannelBandwidth','CBW20');

Decode the L-SIG field and obtain the orthogonal frequency-division multiplexing (OFDM) information. The recovery configuration object requires this information to obtain the L-SIG length.

lsig = waveform(ind.LSIG(1):ind.LSIG(2));
lsigDemod = wlanHEDemodulate(lsig,'L-SIG',cfg.ChannelBandwidth);
info = wlanHEOFDMInfo('L-SIG',cfg.ChannelBandwidth);
lsigDemod = lsigDemod(info.DataIndices,:);

Recover the L-SIG bits and related information, making sure that the bits pass the parity check, and update the recovery configuration object with the L-SIG length. For this example we assume a noiseless channel. For more realistic results you can pass the waveform through an 802.11ax™ channel model by using the wlanTGaxChannel System object™ and work with the received waveform.

csi = ones(52,1);
[lsigBits,failCheck,lsigInfo] = wlanLSIGBitRecover(lsigDemod,0,csi);
cfg.LSIGLength = lsigInfo.Length;

Update Recovery Configuration Object with HE-SIG-A Bits

Decode the HE-SIG-A field and recover the HE-SIG-A bits, ensuring that the bits pass the cyclic redundancy check (CRC).

siga = waveform(ind.HESIGA(1):ind.HESIGA(2));
sigaDemod = wlanHEDemodulate(siga,'HE-SIG-A',cfg.ChannelBandwidth);
sigaDemod = sigaDemod(info.DataIndices,:);
[sigaBits,failCRC] = wlanHESIGABitRecover(sigaDemod,0,csi);
disp(failCRC)

   0

Update the recovery configuration object with the recovered HE-SIG-A bits. Display the updated object. A property value of -1 or 'Unknown' indicates an unknown or undefined property, which can be updated after decoding the HE-SIG-B common and user fields of the HE MU packet.

[cfg,failInterpretation] = interpretHESIGABits(cfg,sigaBits)

cfg = 
  wlanHERecoveryConfig with properties:

                    PacketFormat: 'HE-MU'
                ChannelBandwidth: 'CBW20'
                      LSIGLength: 878
                 SIGBCompression: 0
                         SIGBMCS: 0
                         SIGBDCM: 0
          NumSIGBSymbolsSignaled: 10
                            STBC: 0
                 LDPCExtraSymbol: 1
             PreFECPaddingFactor: 1
                  PEDisambiguity: 0
                   GuardInterval: 3.2000
                       HELTFType: 4
                 NumHELTFSymbols: 1
                UplinkIndication: 0
                        BSSColor: 0
                    SpatialReuse: 0
                    TXOPDuration: 127
                     HighDoppler: 0
                 AllocationIndex: -1
       NumUsersPerContentChannel: -1
         RUTotalSpaceTimeStreams: -1
                          RUSize: -1
                         RUIndex: -1
                           STAID: -1
                             MCS: -1
                             DCM: -1
                   ChannelCoding: 'Unknown'
                     Beamforming: -1
             NumSpaceTimeStreams: -1
    SpaceTimeStreamStartingIndex: -1

failInterpretation = logical
   0

Update Recovery Configuration Object with HE-SIG-B Common Field Bits

Decode the HE-SIG-B common field, ensuring that all content channels pass the CRC.

len = getSIGBLength(cfg);
sigbCommon = waveform(double(ind.HESIGA(2))+(1:len.NumSIGBCommonFieldSamples),:);
sigbCommonDemod = wlanHEDemodulate(sigbCommon,'HE-SIG-B',cfgHEMU.ChannelBandwidth);
sigbCommonDemod = sigbCommonDemod(info.DataIndices);
[sigbCommonBits,status,~] = wlanHESIGBCommonBitRecover(sigbCommonDemod,0,csi,cfg);
disp(status)

Success

Update the recovery configuration object with the recovered HE-SIG-B common field bits and display the updated object. A field returned as -1 or 'Unknown' indicates an unknown or undefined property value, which can be updated after decoding the HE-SIG-B user field of the HE MU packet.

[cfg,failInterpretation] = interpretHESIGBCommonBits(cfg,sigbCommonBits,status)

cfg = 
  wlanHERecoveryConfig with properties:

                    PacketFormat: 'HE-MU'
                ChannelBandwidth: 'CBW20'
                      LSIGLength: 878
                 SIGBCompression: 0
                         SIGBMCS: 0
                         SIGBDCM: 0
          NumSIGBSymbolsSignaled: 10
                            STBC: 0
                 LDPCExtraSymbol: 1
             PreFECPaddingFactor: 1
                  PEDisambiguity: 0
                   GuardInterval: 3.2000
                       HELTFType: 4
                 NumHELTFSymbols: 1
                UplinkIndication: 0
                        BSSColor: 0
                    SpatialReuse: 0
                    TXOPDuration: 127
                     HighDoppler: 0
                 AllocationIndex: 0
       NumUsersPerContentChannel: 9
         RUTotalSpaceTimeStreams: -1
                          RUSize: -1
                         RUIndex: -1
                           STAID: -1
                             MCS: -1
                             DCM: -1
                   ChannelCoding: 'Unknown'
                     Beamforming: -1
             NumSpaceTimeStreams: -1
    SpaceTimeStreamStartingIndex: -1

failInterpretation = logical
   0

Update Recovery Configuration Object with HE-SIG-B User Field Bits

Decode the HE-SIG-B user field, ensuring that all users pass the CRC.

sigbUser = waveform(ind.HESIGB(1):ind.HESIGB(2));
sigbUserDemod = wlanHEDemodulate(sigbUser,'HE-SIG-B',cfgHEMU.ChannelBandwidth);
sigbUserDemod = sigbUserDemod(info.DataIndices,:);
[sigbUserBits,failCRC,~] = wlanHESIGBUserBitRecover(sigbUserDemod,0,csi,cfg);
disp(failCRC)

   0   0   0   0   0   0   0   0   0

Update the recovery configuration object with the recovered HE-SIG-B user field bits.

[user,failInterpretation] = interpretHESIGBUserBits(cfg,sigbUserBits,failCRC);

Display the results of interpretation and the third element of the user output.

disp(failInterpretation)

   0   0   0   0   0   0   0   0   0

disp(user{3})

  wlanHERecoveryConfig with properties:

                    PacketFormat: 'HE-MU'
                ChannelBandwidth: 'CBW20'
                      LSIGLength: 878
                 SIGBCompression: 0
                         SIGBMCS: 0
                         SIGBDCM: 0
          NumSIGBSymbolsSignaled: 10
                            STBC: 0
                 LDPCExtraSymbol: 1
             PreFECPaddingFactor: 1
                  PEDisambiguity: 0
                   GuardInterval: 3.2000
                       HELTFType: 4
                 NumHELTFSymbols: 1
                UplinkIndication: 0
                        BSSColor: 0
                    SpatialReuse: 0
                    TXOPDuration: 127
                     HighDoppler: 0
                 AllocationIndex: 0
       NumUsersPerContentChannel: 9
         RUTotalSpaceTimeStreams: 1
                          RUSize: 26
                         RUIndex: 3
                           STAID: 0
                             MCS: 0
                             DCM: 0
                   ChannelCoding: 'LDPC'
                     Beamforming: 0
             NumSpaceTimeStreams: 1
    SpaceTimeStreamStartingIndex: 1

Input Arguments

siga — Demodulated HE-SIG-A symbols

complex-valued matrix

Demodulated HE-SIG-A symbols, specified as a complex-valued matrix. The size of siga depends on the packet format.

• For high-efficiency single-user (HE SU) or high-efficiency multiuser (HE MU) packets, specify a 52-by-2 matrix.

• For high-efficiency extended-range single-user (HE ER SU) packets, specify a 52-by-4 matrix.

Data Types: single | double
Complex Number Support: Yes

noiseVarEst — Channel noise variance estimate

nonnegative scalar

Channel noise variance estimate, specified as a nonnegative scalar.

Data Types: single | double

csi — Channel state information

52-by-1 real-valued vector

Channel state information, specified as a 52-by-1 real-valued vector. To use the channel state information for enhanced demapping of the orthogonal frequency-division multiplexing (OFDM) symbols, specify this argument.

Data Types: single | double

Output Arguments

bits — Information bits recovered from HE-SIG-A field

52-by-1 binary column vector

Information bits recovered from HE-SIG-A field, returned as a 52-by-1 binary column vector.

Data Types: int8

failCRC — CRC result

1 (true) | 0 (false)

CRC result, returned as a logical value of 1 (true) or 0 (false). The function returns this argument as 1 (true) if the recovered bits fail the CRC. The function returns this argument as 0 (false) if the recovered bits pass the CRC.

Data Types: logical

References

[1] IEEE Std 802.11-2020 (Revision of IEEE Std 802.11-2016). “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.” IEEE Standard for Information Technology — Telecommunications and Information Exchange between Systems — Local and Metropolitan Area Networks — Specific Requirements.

[2] IEEE Std 802.11ax-2021 (Amendment to IEEE Std 802.11-2020). “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Amendment 1: Enhancements for High Efficiency WLAN.” IEEE Standard for Information Technology — Telecommunications and Information Exchange between Systems. Local and Metropolitan Area Networks — Specific Requirements.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2019a