wlanVHTSIGABitRecover

Recover bits from equalized VHT-SIG-A OFDM symbols

Since R2026a

Syntax

[bits,failCRC] = wlanVHTSIGABitRecover(sym,noiseEst,csi)

Description

[bits,failCRC] = wlanVHTSIGABitRecover(sym,noiseEst,csi) recovers bits from the equalized very high-throughput signal A (VHT-SIG-A) OFDM symbols sym.

Examples

Recover Bits from VHT-SIG-A Field

Create a VHT configuration object with default parameters. Generate a time-domain waveform for the configuration.

cfg = wlanVHTConfig;
tx = wlanWaveformGenerator([1;0;0;1],cfg);

Pass the waveform through an AWGN channel with a signal-to-noise ratio of 10 dB.

rx = awgn(tx,10);

Get indices for the legacy long training field (L-LTF). Use the indices to isolate the part of the received waveform that corresponds to the L-LTF.

indLLTF = wlanFieldIndices(cfg,"L-LTF");
rxLLTF = rx(indLLTF(1):indLLTF(2),:);

Demodulate the L-LTF. Use the demodulated symbols to estimate the channel and noise at the L-LTF.

demodLLTF = wlanVHTDemodulate(rxLLTF,"L-LTF",cfg);
chEst = wlanLLTFChannelEstimate(demodLLTF,cfg);
noiseEst = wlanLLTFNoiseEstimate(demodLLTF);

Isolate the part of the received waveform that corresponds to the VHT-SIG-A field.

field = "VHT-SIG-A";
indSIGA = wlanFieldIndices(cfg,field);
rxSIGA = rx(indSIGA(1):indSIGA(2),:);

Demodulate and equalize the VHT-SIG-A field, returning channel state information.

sym = wlanVHTDemodulate(rxSIGA,field,cfg);
[sym,csi] = wlanVHTEqualize(sym,chEst,noiseEst,cfg,field);

Use the noise estimate and channel state information to recover the VHT-SIG-A bits.

[bits,failCRC] = wlanVHTSIGABitRecover(sym,noiseEst,csi);

Display the result of the cyclic redundancy check.

failCRC

failCRC = logical
   0

Input Arguments

sym — Equalized VHT-SIG-A OFDM symbols

complex matrix

Equalized VHT-SIG-A OFDM symbols, specified as a complex matrix. The size of the matrix must be 52-by-2 or 48-by-2. The first option incorporates data and pilot subcarriers. The second option incorporates only data subcarriers. The matrix has two columns because the VHT-SIG-A field consists of two OFDM symbols.

Data Types: double | single
Complex Number Support: Yes

noiseEst — Noise estimate

nonnegative real scalar

Noise estimate, specified as a nonnegative real scalar.

csi — Channel state information

real column vector

Channel state information (CSI), specified as a real column vector. The vector length is 52 or 48 and must be equal to the first dimension of the sym input. When the length is 52, the CSI is for the data and pilot subcarriers. When the length is 48, the CSI is for only the data subcarriers.

Data Types: double | single

Output Arguments

bits — Recovered VHT-SIG-A bits

binary column vector

Recovered VHT-SIG-A bits, returned as a binary column vector. The length of the vector is 48.

Data Types: int8

failCRC — CRC result

logical scalar

Cyclic redundancy check (CRC) result, returned as a logical scalar. A value of 1 indicates a CRC failure.

Data Types: logical

More About

VHT-SIG-A

The very high throughput signal A (VHT-SIG-A) field contains information required to interpret VHT format packets. Similar to the non-HT signal (L-SIG) field for the non-HT OFDM format, this field stores the actual rate value, channel coding, guard interval, MIMO scheme, and other configuration details for the VHT format packet. Unlike the HT-SIG field, this field does not store the packet length information. Packet length information is derived from L-SIG and is captured in the VHT-SIG-B field for the VHT format.

For a detailed description of the VHT-SIG-A field, see Section 21.3.8.3.3 of IEEE^® Std 802.11™-2020. The VHT-SIG-A field consists of two symbols: VHT-SIG-A1 and VHT-SIG-A2. These symbols are located between the L-SIG and the VHT-STF portion of the VHT format PPDU. This diagram¹ shows the VHT-SIG-A field in a VHT packet.

This diagram² shows the structure of the VHT-SIG-A1 symbol.

This diagram³ shows the structure of the VHT-SIG-A2 symbol.

The VHT-SIG-A field includes the following components. The bit field structures for VHT-SIG-A1 and VHT-SIG-A2 vary for single-user or multi-user transmissions.

• BW — A two-bit field that indicates 0 for 20 MHz, 1 for 40 MHz, 2 for 80 MHz, or 3 for 160 MHz.

• STBC — A bit that indicates the presence of space-time block coding.

• Group ID — A six-bit field that indicates the group and user position assigned to a STA.

• N_STS — A three-bit field for a single user or 4 three-bit fields for a multi-user scenario that indicates the number of space-time streams per user.

• Partial AID — An identifier that combines the association ID and the basic service set (BSS) ID.

• TXOP_PS_NOT_ALLOWED — An indicator bit that shows whether client devices are allowed to enter the doze state. This bit is set to false when the VHT-SIG-A structure is populated, indicating that the client device is allowed to enter the doze state.

• Short GI — A bit that indicates use of the 400 ns guard interval.

• Short GI NSYM Disambiguation — A bit that indicates if an extra symbol is required when the short GI is used.

• SU/MU[0] Coding — A bit field that indicates if convolutional or LDPC coding is used for a single user or for user MU[0] in a multi-user scenario.

• LDPC Extra OFDM Symbol — A bit that indicates if an extra OFDM symbol is required to transmit the data field.

• MCS — A four-bit field.

  • For a single-user scenario, this field indicates the modulation and coding scheme used.

  • For a multi-user scenario, this field indicates the use of convolutional or LDPC coding and the MCS setting is conveyed in the VHT-SIG-B field.

• Beamformed — An indicator bit set to 1 when a beamforming matrix is applied to the transmission.

• CRC — An eight-bit field used to detect errors in the VHT-SIG-A transmission.

• Tail — A six-bit field used to terminate the convolutional code.

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.

Extended Capabilities

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

Version History

Introduced in R2026a