Generate non-HT-Data field waveform
Generate Non-HT-Data Waveform
Generate the waveform for a 20MHz non-HT-Data field for 36 Mbps.
Create a non-HT configuration object and assign
MCS to 5.
cfg = wlanNonHTConfig('MCS',5);
Assign random data to the PSDU and generate the data field waveform.
psdu = randi([0 1],cfg.PSDULength*8,1); y = wlanNonHTData(psdu,cfg); size(y)
ans = 1×2 4480 1
Generate Data Field Signal of Non-HT Transmission
Configure transmission parameters by creating a
wlanNonHTConfig object, specifying a channel bandwidth of 80 MHz and static bandwidth operation.
cfg = wlanNonHTConfig('ChannelBandwidth','CBW80','SignalChannelBandwidth',true, ... 'BandwidthOperation','Static');
Generate a random PSDU of the appropriate length.
psdu = randi([0 1],8*cfg.PSDULength,1,'int8');
Generate the initial pseudorandom scrambler sequence.
[range,numBits] = scramblerRange(cfg); scramInit = randi(range);
Generate the non-HT Data field signal.
y = wlanNonHTData(psdu,cfg,scramInit);
cfg — Non-HT transmission parameters
Non-HT transmission parameters, specified as a
scramInit — Initial scrambler state or initial pseudorandom scrambler sequence
93 (default) | integer in the interval [1, 127] | binary-valued column vector
Initial scrambler state or initial pseudorandom scrambler sequence for each generated packet.
When you disable bandwidth signaling by setting the
SignalchannelBandwidth property of the
cfg input to
false), this input represents the initial scrambler
state. In this case, this input must be an integer in the interval [1, 127],
or as the corresponding binary-valued column vector of length seven. The
93, is the example state in section
I.1.5.2 of .
When you enable bandwidth signaling by setting the
SignalchannelBandwidth property of the
cfg input to
true), this input represents the pseudorandom
scrambler sequence described in Table 17-7 of . In this case,
this input must be an integer in the interval [min,
max], or the corresponding binary-valued column
vector of length NB. The values of
min, max, and
NB depend on the values of the
ChannelBandwidth properties of the
cfg input according to this table.
||Value of min||Value of max||Value of NB|
If you do not specify this input, the function uses the
NB most significant bits of
the default value,
Section 22.214.171.124 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 example, initializing the scrambler with decimal
the bits map to these elements.
To generate the bit stream equivalent to a decimal, use the
int2bit function. For example, for decimal
int2bit(1,7)' ans = 0 0 0 0 0 0 1
[1; 0; 1; 1; 1; 0; 1] conveys the scrambler
initialization state of 93 as a binary vector.
osf — Oversampling factor
1 (default) | scalar greater than or equal to 1
Oversampling factor, specified as a scalar greater than or equal to 1. The oversampled cyclic prefix length must be an integer number of samples.
y — Non-HT Data field time-domain waveform
Non-HT Data field time-domain waveform, returned as a complex-valued matrix of size NS-by-NT.
NS is the number of time domain samples
NT is the number of transmit antennas.
Complex Number Support: Yes
Physical layer (PHY) service data unit (PSDU). This field is composed of a variable number of octets. The minimum is 0 (zero) and the maximum is 2500. For more information, see IEEE Std 802.11™-2012, Section 126.96.36.199.
Non-HT Data field
The non-high throughput Data (non-HT Data) field is used to transmit MAC frames and is composed of a service field, a PSDU, tail bits, and pad bits.
Service field — Contains 16 zeros to initialize the data scrambler.
PSDU — Variable-length field containing the PLCP service data unit (PSDU).
Tail — Tail bits required to terminate a convolutional code. The field uses six zeros for the single encoding stream.
Pad Bits — Variable-length field required to ensure that the non-HT data field contains an integer number of symbols.
Non-HT Data Field Processing
The non-HT Data field follows the L-SIG in the packet. For algorithm details, refer to section 17.3.5 of . The non-HT Data includes the user payload in the PSDU plus 16 service bits, six tail bits, and additional padding bits as required to fill out the last OFDM symbol. The function performs transmitter processing on the non-HT Data field and generates the time-domain waveform.
An oversampled signal is a signal sampled at a frequency that is higher than the Nyquist rate. WLAN signals maximize occupied bandwidth by using small guardbands, which can pose problems for anti-imaging and anti-aliasing filters. Oversampling increases the guardband width relative to the total signal bandwidth, thereby increasing the number of samples in the signal.
This function performs oversampling by using a larger IFFT and zero pad when generating an OFDM waveform. This diagram shows the oversampling process for an OFDM waveform with NFFT subcarriers comprising Ng guardband subcarriers on either side of Nst occupied bandwidth subcarriers.
 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.
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