wlanVHTSIGA

Generate VHT-SIG-A waveform

Description

example

y= wlanVHTSIGA(cfg) generates a VHT-SIG-A[1] time-domain waveform for the specified configuration object. See VHT-SIG-A Processing for waveform generation details.

[y,bits] = wlanVHTSIGA(cfg) also outputs VHT-SIG-A information bits.

Examples

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Generate the VHT-SIG-A waveform for an 80 MHz transmission packet.

Create a VHT configuration object, assign an 80 MHz channel bandwidth, and generate the waveform.

cfgVHT = wlanVHTConfig;
cfgVHT.ChannelBandwidth = 'CBW80';
y = wlanVHTSIGA(cfgVHT);
size(y)
ans = 1×2

   640     1

The 80 MHz waveform has two OFDM symbols and is a total of 640 samples long. Each symbol contains 320 samples.

Generate the VHT-SIG-A waveform for a 40 MHz transmission packet.

Create a VHT configuration object, and assign a 40 MHz channel bandwidth.

cfgVHT = wlanVHTConfig;
cfgVHT.ChannelBandwidth = 'CBW40';

Generate the VHT-SIG-A waveform and information bits.

[y,bits] = wlanVHTSIGA(cfgVHT);

Extract the bandwidth from the returned bits and analyze. The bandwidth information is contained in the first two bits.

bwBits = bits(1:2);
bi2de(bwBits)
ans = 2x1 int8 column vector

   1
   0

As defined in IEEE Std 802.11ac-2013, Table 22-12, a value of '1' corresponds to 40 MHz bandwidth.

Input Arguments

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Format configuration, specified as a wlanVHTConfig object.

Output Arguments

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VHT-SIG-A time-domain waveform, returned as an NS-by-NT matrix. NS is the number of time-domain samples, and NT is the number of transmit antennas.

NS is proportional to the channel bandwidth. The time-domain waveform consists of two symbols.

ChannelBandwidthNS
'CBW20'160
'CBW40'320
'CBW80'640
'CBW160'1280

See VHT-SIG-A Processing for waveform generation details.

Data Types: double
Complex Number Support: Yes

Signaling bits used for the VHT-SIG-A, returned as a 48-bit column vector.

Data Types: int8

More About

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VHT-SIG-A

The very high throughput signal A (VHT-SIG-A) field contains information required to interpret VHT format packets. Similar to the non-HT signal (L-SIG) field for the non-HT OFDM format, this field stores the actual rate value, channel coding, guard interval, MIMO scheme, and other configuration details for the VHT format packet. Unlike the HT-SIG field, this field does not store the packet length information. Packet length information is derived from L-SIG and is captured in the VHT-SIG-B field for the VHT format.

For a detailed description of the VHT-SIG-A field, see section 21.3.8.3.3 of IEEE® Std 802.11™-2016. The VHT-SIG-A field consists of two symbols: VHT-SIG-A1 and VHT-SIG-A2. These symbols are located between the L-SIG and the VHT-STF portion of the VHT format PPDU.

The VHT-SIG-A field includes these components. The bit field structures for VHT-SIG-A1 and VHT-SIG-A2 vary for single user or multiuser transmissions.

  • BW — A two-bit field that indicates 0 for 20 MHz, 1 for 40 MHz, 2 for 80 MHz, or 3 for 160 MHz.

  • STBC — A bit that indicates the presence of space-time block coding.

  • Group ID — A six-bit field that indicates the group and user position assigned to a STA.

  • NSTS — A three-bit field for a single user or 4 three-bit fields for a multiuser scenario, that indicates the number of space-time streams per user.

  • Partial AID — An identifier that combines the association ID and the BSSID.

  • TXOP_PS_NOT_ALLOWED — An indicator bit that shows if client devices are allowed to enter dose state. This bit is set to false when the VHT-SIG-A structure is populated, indicating that the client device is allowed to enter dose state.

  • Short GI — A bit that indicates use of the 400 ns guard interval.

  • Short GI NSYM Disambiguation — A bit that indicates if an extra symbol is required when the short GI is used.

  • SU/MU[0] Coding — A bit field that indicates if convolutional or LDPC coding is used for a single user or for user MU[0] in a multiuser scenario.

  • LDPC Extra OFDM Symbol — A bit that indicates if an extra OFDM symbol is required to transmit the data field.

  • MCS — A four-bit field.

    • For a single user scenario, it indicates the modulation and coding scheme used.

    • For a multiuser scenario, it indicates use of convolutional or LDPC coding and the MCS setting is conveyed in the VHT-SIG-B field.

  • Beamformed — An indicator bit set to 1 when a beamforming matrix is applied to the transmission.

  • CRC — An eight-bit field used to detect errors in the VHT-SIG-A transmission.

  • Tail — A six-bit field used to terminate the convolutional code.

Algorithms

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VHT-SIG-A Processing

The VHT-SIG-A field includes information required to process VHT format packets.

For algorithm details, refer to IEEE Std 802.11ac™-2013 [1], Section 22.3.4.5. The wlanVHTSIGA function performs transmitter processing on the VHT-SIG-A field and outputs the time-domain waveform.

References

[1] IEEE Std 802.11ac™-2013 IEEE Standard for Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Specific requirements — Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications — Amendment 4: Enhancements for Very High Throughput for Operation in Bands below 6 GHz.

Extended Capabilities

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

Introduced in R2015b


[1] IEEE Std 802.11ac-2013 Adapted and reprinted with permission from IEEE. Copyright IEEE 2013. All rights reserved.