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wlanNonHTDataBitRecover

Recover PSDU from non-HT Data field

Since R2020b

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Syntax

psdu = wlanNonHTDataBitRecover(sym,noiseVarEst,cfg)
psdu = wlanNonHTDataBitRecover(sym,noiseVarEst,csi,cfg)
[psdu,scramInit] = wlanNonHTDataBitRecover(___,'OFDMSymbolOffset',symOffset)

Description

psdu = wlanNonHTDataBitRecover(sym,noiseVarEst,cfg) recovers psdu, a vector of physical layer service data unit (PSDU) bits, from sym, the demodulated and equalized OFDM symbols that make up the non-HT Data field of a non-high-throughput (non-HT) waveform. The function recovers the PSDU by using noise variance estimate noiseVarEst and non-HT transmission parameters cfg.

example

psdu = wlanNonHTDataBitRecover(sym,noiseVarEst,csi,cfg) enhances the demapping of OFDM subcarriers by using channel state information csi.

[psdu,scramInit] = wlanNonHTDataBitRecover(___,'OFDMSymbolOffset',symOffset) recovers initial scrambler state scramInit for any combination of input arguments from previous syntaxes.

example

Examples

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Open Live Script

Configure and generate a non-HT time-domain waveform.

cfg = wlanNonHTConfig(MCS=4);
bits = randi([0 1],8*cfg.PSDULength,1,'int8');
waveform = wlanWaveformGenerator(bits,cfg);

Transmit the waveform through an additive white Gaussian noise (AWGN) channel with a signal-to-noise ratio (SNR) of 30.

snr = 30;
rxWaveform = awgn(waveform,snr);

Extract the non-HT Data field from the received waveform.

field = 'NonHT-Data';
ind = wlanFieldIndices(cfg,field);
rx = rxWaveform(ind(1):ind(2),:);

Recover the frequency-domain signal by OFDM demodulating the time-domain data signal.

sym = wlanNonHTOFDMDemodulate(rx,field,cfg);

Extract the data subcarriers from the demodulated signal.

info = wlanNonHTOFDMInfo(field,cfg);
sym = sym(info.DataIndices,:,:);

Recover the PSDU and confirm that it matches the transmitted PSDU.

noiseVarEst = 10^(-snr/10);
psdu = wlanNonHTDataBitRecover(sym,noiseVarEst,cfg);
isequal(bits,psdu)
ans = logical
   1
Open Live Script

Configure and generate a non-HT Data signal with a channel bandwidth of 160 MHz and dynamic bandwidth operation.

bandwidth = 'CBW160';
cfg = wlanNonHTConfig(ChannelBandwidth=bandwidth,PSDULength=1, ...
    SignalChannelBandwidth=true,BandwidthOperation='Dynamic');
bits = randi([0 1],8*cfg.PSDULength,1,'int8');
[range,~] = scramblerRange(cfg);
scramInit = randi(range);
y = wlanNonHTData(bits,cfg,scramInit);

Transmit the waveform through an AWGN channel with an SNR of 50.

snr = 50;
noiseVarEst = 10^(-snr/10);
rx = awgn(y,snr);

Recover the frequency-domain signal by OFDM-demodulating the non-HT Data signal, specifying an OFDM symbol sampling offset.

field = 'NonHT-Data';
symOffset = 0.5;
sym = wlanNonHTOFDMDemodulate(rx,field,bandwidth,OFDMSymbolOffset=symOffset);

Extract the data subcarriers.

info = wlanNonHTOFDMInfo(field,bandwidth);
sym = sym(info.DataIndices,:);

Recover the first 20 MHz subchannel of the PSDU, enhancing the demapping of the OFDM subcarriers by specifying channel state information. Confirm that the received and transmitted PSDUs match.

csi = ones(48,1);
[psdu,scramInit] = wlanNonHTDataBitRecover(sym(1:48,:),noiseVarEst,csi,cfg);
isequal(bits,psdu)
ans = logical
   1

Recover and display bandwidth signaling by interpreting the scrambler state.

[bandwidth,dyn] = wlanInterpretScramblerState(scramInit)
bandwidth = 
'CBW160'

dyn = logical
   1

Input Arguments

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Demodulated and equalized OFDM symbols comprising the non-HT Data field, specified as a complex-valued matrix of size 48-by-Nsym, where Nsym is the number of OFDM symbols.

Data Types: single | double
Complex Number Support: Yes

Noise variance estimate, specified as a nonnegative scalar.

Data Types: single | double

Non-HT transmission parameters, specified as a wlanNonHTConfig object.

Channel state information, specified as a real-valued column vector of length 48.

Data Types: single | double

OFDM symbol sampling offset, as a fraction of the cyclic prefix length, specified as a scalar in the interval [0, 1].

The value that you specify indicates the start location for OFDM demodulation relative to the beginning of the cyclic prefix.

Different values of OFDM symbol sampling offset

Example: 0.45

Data Types: double

Output Arguments

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Recovered PSDU bits, returned as a binary-valued column vector of length 8 × L, where L is the PSDU length in bytes. To specify L, set the PSDULength property of the cfg input.

Data Types: int8

Initial scrambler state, returned as an integer in the interval [1, 127].

Section 17.3.5.5 of [1] specifies the scrambling and descrambling process applied to the transmitted data. The header and data fields that follow the scrambler initialization field (including data padding bits) are scrambled by XORing each bit with a length-127 periodic sequence generated by the polynomial S(x) = x7 + x4 + 1. The octets of the PSDU are placed into a bit stream, and, within each octet, bit 0 (LSB) is first and bit 7 (MSB) is last. This figure demonstrates the sequence generation and XOR operation.

Generate a periodic sequence of length 127 by using an XOR operation

Conversion from integer to bits uses left-MSB orientation. For example, initializing the scrambler with decimal 1, the bits map to these elements.

ElementX7X6X5X4X3X2X1
Bit Value0000001

To generate the bit stream equivalent to a decimal, use the int2bit function. For example, for decimal 1:

int2bit(1,7)'
ans =

     0     0     0     0     0     0     1

Data Types: int8

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 R2020b

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See Also

Functions

Objects