Documentation

This is machine translation

Translated by Microsoft
Mouseover text to see original. Click the button below to return to the English verison of the page.

Note: This page has been translated by MathWorks. Please click here
To view all translated materals including this page, select Japan from the country navigator on the bottom of this page.

wlanHTSIG

Generate HT-SIG waveform

Syntax

y = wlanHTSIG(cfg)
[y,bits] = wlanHTSIG(cfg)

Description

example

y = wlanHTSIG(cfg) generates an HT-SIG[1] time-domain waveform for HT-mixed format transmissions given the parameters specified in cfg.

example

[y,bits] = wlanHTSIG(cfg) returns the information bits, bits, that comprise the HT-SIG field.

Examples

collapse all

Generate an HT-SIG waveform for a single transmit antenna.

Create an HT configuration object. Specify a 40 MHz channel bandwidth.

cfg = wlanHTConfig;
cfg.ChannelBandwidth = 'CBW40'
cfg = 

  wlanHTConfig with properties:

       ChannelBandwidth: 'CBW40'
    NumTransmitAntennas: 1
    NumSpaceTimeStreams: 1
         SpatialMapping: 'Direct'
                    MCS: 0
          GuardInterval: 'Long'
          ChannelCoding: 'BCC'
             PSDULength: 1024
         AggregatedMPDU: 0
     RecommendSmoothing: 1

Generate the HT-SIG waveform. Determine the size of the waveform.

y = wlanHTSIG(cfg);
size(y)
ans =

   320     1

The function returns a waveform having a complex output of 320 samples corresponding to two 160-sample OFDM symbols.

Generate an HT-SIG waveform and display the MCS information. Change the MCS and display the updated information.

Create a wlanHTConfig object having two spatial streams and two transmit antennas. Specify an MCS value of 8, corresponding to BPSK modulation and a coding rate of 1/2.

cfg = wlanHTConfig('NumSpaceTimeStreams',2,'NumTransmitAntennas',2,'MCS',8);

Generate the information bits from the HT-SIG waveform.

[~,sigBits] = wlanHTSIG(cfg);

Extract the MCS field from sigBits and convert it to its decimal equivalent. The MCS information is contained in bits 1-7.

 mcsBits = sigBits(1:7);
 bi2de(mcsBits')
ans =

  int8

   8

The MCS matches the specified value.

Change the MCS to 13, which corresponds to 64-QAM modulation with a 2/3 coding rate. Generate the HT-SIG waveform.

cfg.MCS = 13;
[~,sigBits] = wlanHTSIG(cfg);

Verify that the MCS bits are the binary equivalent of 13.

mcsBits = sigBits(1:7);
bi2de(mcsBits')
ans =

  int8

   13

Input Arguments

collapse all

Format configuration, specified as a wlanHTConfig object. The wlanHTSIG function uses these properties.

Modulation and coding scheme to use for transmitting the current packet, specified as an integer from 0 to 31. The MCS setting identifies which modulation and coding rate combination is used, and the number of spatial streams (NSS).

MCS(Note 1)NSS(Note 1)ModulationCoding Rate

0, 8, 16, or 24

1, 2, 3, or 4

BPSK1/2

1, 9, 17, or 25

1, 2, 3, or 4

QPSK1/2

2, 10, 18, or 26

1, 2, 3, or 4

QPSK3/4

3, 11, 19, or 27

1, 2, 3, or 4

16QAM1/2

4, 12, 20, or 28

1, 2, 3, or 4

16QAM3/4

5, 13, 21, or 29

1, 2, 3, or 4

64QAM2/3

6, 14, 22, or 30

1, 2, 3, or 4

64QAM3/4

7, 15, 23, or 31

1, 2, 3, or 4

64QAM5/6
Note-1 MCS from 0 to 7 have one spatial stream. MCS from 8 to 15 have two spatial streams. MCS from 16 to 23 have three spatial streams. MCS from 24 to 31 have four spatial streams.

See IEEE® 802.11™-2012, Section 20.6 for further description of MCS dependent parameters.

When working with the HT-Data field, if the number of space-time streams is equal to the number of spatial streams, no space-time block coding (STBC) is used. See IEEE 802.11-2012, Section 20.3.11.9.2 for further description of STBC mapping.

Example: 22 indicates an MCS with three spatial streams, 64-QAM modulation, and a 3/4 coding rate.

Data Types: double

Channel bandwidth in MHz, specified as 'CBW20' or 'CBW40'.

Data Types: char | string

Number of bytes carried in the user payload, specified as an integer from 0 to 65,535. A PSDULength of 0 implies a sounding packet for which there are no data bits to recover.

Example: 512

Data Types: double

Recommend smoothing for channel estimation, specified as a logical.

  • If the frequency profile is nonvarying across the channel , the receiver sets this property to true. In this case, frequency-domain smoothing is recommended as part of channel estimation.

  • If the frequency profile varies across the channel, the receiver sets this property to false. In this case, frequency-domain smoothing is not recommended as part of channel estimation.

Data Types: logical

Number of space-time streams in the transmission, specified as 1, 2, 3, or 4.

Data Types: double

Type of forward error correction coding for the data field, specified as 'BCC' (default) or 'LDPC'. 'BCC' indicates binary convolutional coding and 'LDPC' indicates low density parity check coding. Providing a character vector or a single cell character vector defines the channel coding type for a single user or all users in a multiuser transmission. By providing a cell array different channel coding types can be specified per user for a multiuser transmission.

Data Types: char | cell | string

Cyclic prefix length for the data field within a packet, specified as 'Long' or 'Short'.

  • The long guard interval length is 800 ns.

  • The short guard interval length is 400 ns.

Data Types: char | string

Number of extension spatial streams in the transmission, specified as 0, 1, 2, or 3. When NumExtensionStreams is greater than 0, SpatialMapping must be 'Custom'.

Data Types: double

Output Arguments

collapse all

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

Data Types: double
Complex Number Support: Yes

HT-SIG information bits, returned as a 48-by-1 vector.

Data Types: int8

More About

collapse all

HT-SIG

The high throughput signal (HT-SIG) field is located between the L-SIG field and HT-STF and is part of the HT-mixed format preamble. It is composed of two symbols, HT-SIG1 and HT-SIG2.

HT-SIG carries information used to decode the HT packet, including the MCS, packet length, FEC coding type, guard interval, number of extension spatial streams, and whether there is payload aggregation. The HT-SIG symbols are also used for auto-detection between HT-mixed format and legacy OFDM packets.

Refer to IEEE Std 802.11-2012, Section 20.3.9.4.3 for a detailed description of the HT-SIG field.

HT-mixed

As described in IEEE Std 802.11-2012, Section 20.1.4, high throughput mixed (HT-mixed) format packets contain a preamble compatible with IEEE Std 802.11-2012, Section 18 and Section 19 receivers. Non-HT (Section 18 and Section19) STAs can decode the non-HT fields (L-STF, L-LTF, and L-SIG). The remaining preamble fields (HT-SIG, HT-STF, and HT-LTF) are for HT transmission, so the Section 18 and Section 19 STAs cannot decode them. The HT portion of the packet is described in IEEE Std 802.11-2012, Section 20.3.9.4. Support for the HT-mixed format is mandatory.

References

[1] IEEE Std 802.11™-2012 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.

Extended Capabilities

Introduced in R2015b


[1] IEEE Std 802.11-2012 Adapted and reprinted with permission from IEEE. Copyright IEEE 2012. All rights reserved.

Was this topic helpful?