wlanVHTDataNoiseEstimate

R2026b

Estimate noise using VHT-Data field

Since R2026b

Syntax

nVar = wlanVHTDataNoiseEstimate(sym,chanEstSSPilots,cfg)

Description

nVar = wlanVHTDataNoiseEstimate(sym,chanEstSSPilots,cfg) estimates the variance of additive white Gaussian noise in a very high-throughput (VHT) transmission configured by cfg. For the estimate, the function uses the demodulated pilot symbols in the VHT-Data field, sym, and the single-stream channel estimates at pilot subcarriers, chanEstSSPilots. The noise estimate is averaged over the number of OFDM symbols and receive antennas.

Examples

Estimate Noise Power Using VHT-Data Field

Create a VHT configuration object with default parameters. Specify an initial signal-to-noise ratio (SNR) of 15 dB.

cfg = wlanVHTConfig;
snr = 15;

Extract the field indices that correspond to the VHT-LTF and the VHT-Data field.

indVHTLTF = wlanFieldIndices(cfg,"VHT-LTF");
indData = wlanFieldIndices(cfg,"VHT-Data");

Generate a time-domain waveform for the configuration. Pass the waveform through an AWGN channel.

tx = wlanWaveformGenerator([1;0;0;1],cfg);
rx = awgn(tx,snr);

Extract the indices of the received waveform that correspond to the VHT-LTF. Demodulate the VHT-LTF and perform channel estimation at the single-stream pilots.

rxVHTLTF = rx(indVHTLTF(1):indVHTLTF(2),:);
demodVHTLTF = wlanVHTDemodulate(rxVHTLTF,"VHT-LTF",cfg);
[~,chanEstSSPilots] = wlanVHTLTFChannelEstimate(demodVHTLTF,cfg);

Extract the indices of the received waveform that correspond to the VHT-Data field. Demodulate the VHT-Data field.

rxData = rx(indData(1):indData(2),:);
sym = wlanVHTDemodulate(rxData,"VHT-Data",cfg);

Estimate the noise power from the demodulated symbols and the channel estimate.

nVar = wlanVHTDataNoiseEstimate(sym,chanEstSSPilots,cfg);

Input Arguments

sym — Demodulated VHT-Data symbols

3-D array

Demodulated VHT-Data symbols, specified as an N_SC-by-N_SYM-by-N_R array.

• N_SC is the number of pilot subcarriers, or the combined total of data and pilot subcarriers, in the VHT-Data field. The numbers of subcarriers are determined by the ChannelBandwidth property of the cfg input.

• N_SYM is the number of OFDM symbols.

• N_R is the number of receive antennas.

Data Types: double | single
Complex Number Support: Yes

chanEstSSPilots — Channel estimate for pilot subcarriers

3-D array

Channel estimate at each pilot subcarrier location for the VHT-LTF, specified as an N_SP-by-N_LTF-by-N_R array.

• N_SP is the number of pilot subcarriers.

• N_LTF is the number of demodulated VHT-LTF OFDM symbols.

• N_R is the number of receive antennas.

The function assumes that the pilot sequence is the same across all space-time streams at the transmitter.

Data Types: double | single
Complex Number Support: Yes

cfg — PHY format configuration

wlanVHTConfig object

Physical layer (PHY) format configuration, specified as a wlanVHTConfig object.

Output Arguments

nVar — Noise variance estimate

positive real scalar

Noise variance estimate, returned as a positive real scalar.

Data Types: double | single

More About

VHT-Data

The VHT-Data field carries one or more frames from the medium access control (MAC) layer. This field follows the VHT-SIG-B field in a VHT PPDU. This diagram¹ shows the VHT-Data field in a VHT PPDU:

For a detailed description of the VHT-Data field, see section 21.3.10 of IEEE^® Std 802.11™-2020. The VHT-Data field consists of four subfields, shown in this diagram:²

• Service — 16-bit field that contains a seven-bit scrambler initialization state, one bit reserved for future considerations, and eight bits for the VHT-SIG-B cyclic redundancy check (CRC) field

• PSDU — Variable-length field containing a PLCP service data unit

• PHY Pad — Variable number of bits passed to the transmitter to create a complete OFDM symbol

• Tail — Bits required to terminate a convolutional code (not required when the transmission uses LDPC channel coding)

Extended Capabilities

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

Version History

Introduced in R2026b