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wlanNonHTDataBitRecover

Recover PSDU from non-HT Data field

Description

example

psdu = wlanNonHTDataBitRecover(sym,noiseVarEst,cfg) recovers psdu, a column vector of physical layer service data unit (PSDU) bits, from sym, the demodulated and equalized orthogonal frequency-division multiplexing (OFDM) symbols comprising 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.

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

example

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

Examples

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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

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: double
Complex Number Support: Yes

Noise variance estimate, specified as a nonnegative scalar.

Data Types: 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: 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.

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], or the corresponding binary-valued column vector of length 7.

Section 17.3.5.5 [1]of 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.

Conversion from integer to bits uses left-MSB orientation. For the initialization of the scrambler with decimal 1, the bits are mapped to the elements shown.

ElementX7X6X5X4X3X2X1
Bit value0000001

To generate the bit stream equivalent to a decimal, use the de2bi function. For example, for the decimal 1:

de2bi(1,7,'left-msb')
ans =

     0     0     0     0     0     0     1

Example: [1; 0; 1; 1; 1; 0; 1] conveys the scrambler initialization state of 93 as a binary-valued column vector.

Data Types: double

References

[1] IEEE Std 802.11™-2016 (Revision of IEEE Std 802.11-2012). “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™.

Introduced in R2020b