wlanVHTSIGBBitRecover

Recover bits from equalized VHT-SIG-B OFDM symbols

Since R2026a

Syntax

bits = wlanVHTSIGBBitRecover(sym,noiseEst,csi,cfg)

Description

bits = wlanVHTSIGBBitRecover(sym,noiseEst,csi,cfg) recovers bits from the equalized very high-throughput signal B (VHT-SIG-B) OFDM symbols sym.

Examples

Recover Bits from VHT-SIG-B 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 15 dB.

rx = awgn(tx,15);

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 legacy long training field (L-LTF). Use the demodulated symbols to estimate the noise at the L-LTF.

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

Demodulate the very high-throughput long training field (VHT-LTF). Use the demodulated symbols to estimate the channel at the VHT-LTF.

indVHTLTF = wlanFieldIndices(cfg,"VHT-LTF");
rxVHTLTF = rx(indVHTLTF(1):indVHTLTF(2),:);
demodVHTLTF = wlanVHTDemodulate(rxVHTLTF,"VHT-LTF",cfg);
chEst = wlanVHTLTFChannelEstimate(demodVHTLTF,cfg);

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

field = "VHT-SIG-B";
indSIGB = wlanFieldIndices(cfg,field);
rxSIGB = rx(indSIGB(1):indSIGB(2),:);

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

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

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

bits = wlanVHTSIGBBitRecover(sym,noiseEst,csi,cfg);

Recover the transmitted bits from the configuration. Verify that the recovered bits match the transmitted bits.

[~,txBits] = wlanVHTSIGB(cfg);
disp(isequal(bits,txBits))

   1

Input Arguments

sym — Equalized VHT-SIG-B OFDM symbols

complex column vector

Equalized VHT-SIG-B OFDM symbols, specified as a complex column vector. The length of the vector is N_SC, where N_SC is the number of subcarriers. N_SC can be the number of data subcarriers, or the combined total of data and pilot subcarriers. The values depend on the channel bandwidth you specify in cfg.

Channel Bandwidth (MHz)	Number of Data Subcarriers	Combined Total of Data and Pilot Subcarriers
20	52	56
40	108	114
80	234	242
160	468	484

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 must be equal to the length of the sym input.

Data Types: double | single

cfg — Format configuration

wlanVHTConfig object

Format configuration, specified as a wlanVHTConfig object.

Output Arguments

bits — Recovered VHT-SIG-B bits

binary column vector

Recovered VHT-SIG-B bits, returned as a binary column vector. The length of the vector depends on the channel bandwidth you specify in cfg.

Data Types: int8

More About

VHT-SIG-B

Receivers use the very high throughput signal B (VHT-SIG-B) field in multi-user scenarios to set up the data rate and to fine-tune MIMO reception. The field uses MCS 0 and consists of a single OFDM symbol.

The VHT-SIG-B field is located between the VHT-LTF and the data portion of the VHT format PPDU. This diagram¹ shows the VHT-SIG-B field in a VHT packet.

The VHT-SIG-B field contains the actual rate and A-MPDU length value per user. For a detailed description of the VHT-SIG-B field, see Section 21.3.8.3.6 of IEEE^® Std 802.11™-2020. The number of bits in the VHT-SIG-B field varies with the channel bandwidth. The assignment of the bits depends on whether the transmission has a single user or multiple users. For single-user configurations, the same information is available in the L-SIG field, but the VHT-SIG-B field is included for continuity purposes.

Field	VHT MU PPDU Allocation (bits)			VHT SU PPDU Allocation (bits)			Description
	20 MHz	40 MHz	80 MHz, 160 MHz	20 MHz	40 MHz	80 MHz, 160 MHz
VHT-SIG-B	B0–15 (16)	B0–16 (17)	B0–18 (19)	B0–16 (17)	B0–18 (19)	B0–20 (21)	This variable-length field indicates the size of the data payload in four-byte units. The length of the field depends on the channel bandwidth.
VHT-MCS	B16–19 (4)	B17–20 (4)	B19–22 (4)	N/A	N/A	N/A	This four-bit field is for multi-user scenarios only.
Reserved	N/A	N/A	N/A	B17–19 (3)	B19–20 (2)	B21–22 (2)	All ones
Tail	B20–25 (6)	B21–26 (6)	B23–28 (6)	B20–25 (6)	B21–26 (6)	B23–28 (6)	This six-bit field contains all zeros to terminate the convolutional code.
Total number of bits	26	27	29	26	27	29	N/A
Bit field repetition	1	2	4	1	2	4	For 160 MHz, the 80 MHz channel repeats twice.

For a null data packet (NDP), the VHT-SIG-B bits are set according to Table 21-15 of IEEE Std 802.11-2020.

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