wlanHTConfig

Configure HT transmission

Description

The wlanHTConfig object is a configuration object for the WLAN high throughput (HT) packet format.

Creation

Syntax

cfgHT = wlanHTConfig

cfgHT = wlanHTConfig(Name,Value)

Description

cfgHT = wlanHTConfig creates a configuration object that initializes parameters for an IEEE^® 802.11™ HT PPDU.

cfgHT = wlanHTConfig(Name,Value) sets properties using one or more name-value pairs. Enclose each property name in quotation marks. For example, wlanHTConfig('GuardInterval','Short') specifies a 400 nanosecond guard interval (cyclic prefix) duration.

At runtime, the calling function validates object settings for properties relevant to the operation of the function.

Properties

ChannelBandwidth — Channel bandwidth of PPDU transmission

'CBW20' (default) | 'CBW40'

Channel bandwidth of PPDU transmission, specified as one of these values:

• 'CBW20' – Channel bandwidth of 20 MHz

• 'CBW40' – Channel bandwidth of 40 MHz

Data Types: char | string

NumTransmitAntennas — Number of transmit antennas

1 (default) | positive integer

Number of transmit antennas, specified as a positive integer.

Data Types: double

PreHTCyclicShifts — Cyclic shift values of additional transmit antennas

-75 (default) | integer in the interval [–200, 0] | row vector

Cyclic shift values, in nanoseconds, of additional transmit antennas for the pre-HT fields of the waveform. The first four antennas use the cyclic shift values specified in Table 19-9 of [1]. The remaining L antennas use the values you specify in this property, where L = NumTransmitAntennas – 4. Specify this property as one of these values:

• An integer in the interval [–200, 0] – the wlanHTConfig object uses this cyclic shift value for each of the L additional antennas.

• A row vector of length L of integers in the interval [–200, 0] – the wlanHTConfig object uses the kth element as the cyclic shift value for the (k + 4)th transmit antenna.

  Note

  If you specify this property as a row vector of length greater than L, the wlanHTConfig object uses only the first L elements. For example, if you set the NumTransmitAntennas property to 16, the wlanHTConfig object uses only the first L= 16 – 4 = 12 elements of this vector.

Dependencies

To enable this property, set the NumTransmitAntennas property to a value greater than 4.

Data Types: double

NumSpaceTimeStreams — Number of space-time streams

1 (default) | 2 | 3 | 4

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

Data Types: double

NumExtensionStreams — Number of extension spatial streams

0 (default) | 1 | 2 | 3

Number of extension spatial streams in the transmission, specified as 0, 1, 2, or 3.

Data Types: double

SpatialMapping — Spatial mapping scheme

'Direct' (default) | 'Hadamard' | 'Fourier' | 'Custom'

Spatial mapping scheme, specified as 'Direct', 'Hadamard', 'Fourier', or 'Custom'.

Dependencies

The default value, 'Direct', applies only when you set the NumTransmitAntennas and NumSpaceTimeStreams properties to the same value. This property must be set to 'Custom' when the NumExtensionStreams property is greater than zero.

SpatialMappingMatrix — Spatial mapping matrix

1 (default) | complex-valued scalar | complex-valued matrix | complex-valued 3-D array

Spatial mapping matrix, specified as one of these values:

• A complex-valued scalar. This value applies to all the subcarriers.

• A complex-valued matrix of size (N_STS+N_ESS) -by-N_T, where:

  • N_STS is the number of space-time streams;

  • N_ESS is the number of extension spatial streams;

  • N_T is the number of transmit antennas.

  In this case, the spatial mapping matrix applies to all the subcarriers.

• A complex-valued 3-D array of size N_ST-by-(N_STS + N_ESS)-by-N_T, where N_ST is the number of occupied subcarriers. The value of N_ST is the sum of the occupied data and pilot subcarriers. The ChannelBandwidth property determines the value of N_ST. In this case, each occupied subcarrier has its own spatial mapping matrix.

  This table shows the ChannelBandwidth setting and the corresponding N_ST:

  ChannelBandwidth	Number of Occupied Subcarriers, NST	Number of Data Subcarriers	Number of Pilot Subcarriers
  'CBW20'	56	52	4
  'CBW40'	114	108	6

Use this property to rotate and scale the output vector of the constellation mapper. The spatial mapping matrix is used for beamforming and mixing space-time streams over the transmit antennas. For more information, see Section 19.3.11.11.2 of [1]. The calling function normalizes the spatial mapping matrix for each subcarrier.

Example: [0.5 0.3; 0.4 0.4; 0.5 0.8] represents a spatial mapping matrix with three space-time streams and two transmit antennas.

Dependencies

This property applies only when you set the SpatialMapping property to 'Custom'.

Data Types: double
Complex Number Support: Yes

MCS — MCS used for transmission

0 (default) | integer in the interval [0, 31]

Modulation and coding scheme (MCS) used for transmission, specified as an integer in the interval [0, 31]. Each value of this property corresponds to a modulation type and coding rate in accordance with this table.

MCS	Modulation	Coding Rate
0, 8, 16, or 24	Binary phase-shift keying (BPSK)	1/2
1, 9, 17, or 25	Quadrature phase-shift keying (QPSK)	1/2
2, 10, 18, or 26	QPSK	3/4
3, 11, 19, or 27	16-point quadrature amplitude modulation (16-QAM)	3/4
4, 12, 20, or 28	16-QAM	3/4
5, 13, 21, or 29	64-QAM	2/3
6, 14, 22, or 30	64-QAM	3/4
7, 15, 23, or 31	64-QAM	5/6

Values of this property in the interval [0, 7] specify one spatial stream. Values in the interval [8, 15] specify two spatial streams. Values in the interval [16, 23] specify three spatial streams. Values in the interval [24, 31] specify four spatial streams.

For more information on MCS-dependent transmission parameters, see Section 19.5 of [1]. If the number of space-time streams is equal to the number of spatial streams, no space-time block coding (STBC) is applied to the HT-Data field. For a description of STBC, see Section 19.3.11.9.2 of [1].

Example: A value of 22 specifies an MCS with three spatial streams, 64-QAM, and a coding rate of ¾.

Data Types: double

GuardInterval — Guard interval (cyclic prefix) duration

'Long' (default) | 'Short'

Guard interval (cyclic prefix) duration for the data field within a packet, specified as one of these values:

• 'Long' – Guard interval duration of 800 ns

• 'Short' – Guard interval duration of 400 ns

Data Types: char | string

ChannelCoding — FEC coding type

'BCC' (default) | 'LDPC'

Forward-error-correction (FEC) coding type for the HT-Data field, specified as 'BCC' for binary convolutional coding (BCC) or 'LDPC' for low-density parity-check (LDPC) coding.

Data Types: char | string

PSDULength — PSDU length

1024 (default) | integer in the interval [0, 2¹⁶ – 1]

Physical layer convergence procedure (PLCP) service data unit (PSDU) length, in bytes, specified as an integer in the interval [0, 2¹⁶ – 1]. To indicate a sounding packet for which there are no data bits to recover, set this property to 0.

Data Types: double

AggregatedMPDU — MPDU aggregation indicator

false or 0 (default) | true or 1

MAC protocol data unit (MPDU) aggregation indicator, specified as a numeric or logical 1 (true) or 0 (false). To specify that the generated packet uses MPDU aggregation, set this property to 1 (true).

Dependencies

This property does not apply when you set the MCS property to 0

Data Types: logical

RecommendSmoothing — Recommend smoothing for channel estimation

true or 1 (default) | false or 0

Recommend smoothing for channel estimation, specified as a numeric or logical 1 (true) or 0 (false).

• If the frequency profile does not vary across the channel, the receiver sets this property to 1 (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 0 (false). In this case, frequency-domain smoothing is not recommended as part of channel estimation.

Data Types: logical

Object Functions

transmitTime

Packet transmission time

Examples

Create HT Configuration Object with Default Settings

Create an HT configuration object. After creating the object update the number of transmit antennas and space-time streams.

cfgHT = wlanHTConfig

cfgHT = 
  wlanHTConfig with properties:

       ChannelBandwidth: 'CBW20'
    NumTransmitAntennas: 1
    NumSpaceTimeStreams: 1
         SpatialMapping: 'Direct'
                    MCS: 0
          GuardInterval: 'Long'
          ChannelCoding: 'BCC'
             PSDULength: 1024
         AggregatedMPDU: 0
     RecommendSmoothing: 1

Update the number of antennas to two, and number of space-time streams to four.

cfgHT.NumTransmitAntennas = 2;
cfgHT.NumSpaceTimeStreams = 4

cfgHT = 
  wlanHTConfig with properties:

       ChannelBandwidth: 'CBW20'
    NumTransmitAntennas: 2
    NumSpaceTimeStreams: 4
         SpatialMapping: 'Direct'
                    MCS: 0
          GuardInterval: 'Long'
          ChannelCoding: 'BCC'
             PSDULength: 1024
         AggregatedMPDU: 0
     RecommendSmoothing: 1

Create wlanHTConfig Object

Create a wlanHTConfig object with a PSDU length of 2048 bytes, and using BCC forward error correction.

cfgHT = wlanHTConfig('PSDULength',2048);
cfgHT.ChannelBandwidth = 'CBW20'

cfgHT = 
  wlanHTConfig with properties:

       ChannelBandwidth: 'CBW20'
    NumTransmitAntennas: 1
    NumSpaceTimeStreams: 1
         SpatialMapping: 'Direct'
                    MCS: 0
          GuardInterval: 'Long'
          ChannelCoding: 'BCC'
             PSDULength: 2048
         AggregatedMPDU: 0
     RecommendSmoothing: 1

More About

PPDU

The physical layer (PHY) protocol data unit (PPDU) is the complete physical layer convergence procedure (PLCP) frame, including PLCP headers, MAC headers, the MAC data field, and the MAC and PLCP trailers.

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 R2015b