# wlanTGaxChannel

Filter signal through 802.11ax multipath fading channel

## Description

The `wlanTGaxChannel`

System object™ filters an input signal through an 802.11ax™ (TGax) indoor MIMO channel as specified in [1], following the MIMO modeling approach described in [4].

The fading processing assumes the same parameters for all
*N*_{T}-by-*N*_{R}
links of the TGax channel, where *N*_{T} is the
number of transmit antennas and *N*_{R} is the
number of receive antennas. Each link comprises all multipaths for that link.

To filter an input signal using a TGax multipath fading channel:

Create the

`wlanTGaxChannel`

object and set its properties.Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?

## Creation

### Description

creates a
TGax channel System object, `tgax`

= wlanTGaxChannel`tgax`

. This object filters a real or complex
input signal through the TGax channel to obtain the channel-impaired
signal.

creates a TGax channel object, `tgax`

= wlanTGaxChannel(`Name`

,`Value`

)`tgax`

, and sets properties
using one or more name-value pairs. Enclose each property name in quotes. For
example,
`wlanTGaxChannel('NumReceiveAntennas',2,'SampleRate',10e6)`

creates a TGax channel with two receive antennas and a 10 MHz sample
rate.

## Properties

Unless otherwise indicated, properties are *nontunable*, which means you cannot change their
values after calling the object. Objects lock when you call them, and the
`release`

function unlocks them.

If a property is *tunable*, you can change its value at
any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

`SampleRate`

— Sample rate of the input signal

`80e6`

(default) | positive scalar

Sample rate of the input signal in Hz, specified as a positive scalar.

**Data Types: **`double`

`DelayProfile`

— Delay profile model

`'Model-B'`

(default) | `'Model-A'`

| `'Model-C'`

| `'Model-D'`

| `'Model-E'`

| `'Model-F'`

Delay profile model, specified as `'Model-A'`

,
`'Model-B'`

, `'Model-C'`

,
`'Model-D'`

, `'Model-E'`

, or
`'Model-F'`

.

The table summarizes the properties of the models before the bandwidth reduction factor. For more information, see Increased Bandwidth.

Property | Model | |||||
---|---|---|---|---|---|---|

A | B | C | D | E | F | |

Breakpoint distance (m) | 5 | 5 | 5 | 10 | 20 | 30 |

RMS delay spread (ns) | 0 | 15 | 30 | 50 | 100 | 150 |

Maximum delay (ns) | 0 | 80 | 200 | 390 | 730 | 1050 |

Rician K-factor (dB) | 0 | 0 | 0 | 3 | 6 | 6 |

Number of taps | 1 | 9 | 14 | 18 | 18 | 18 |

Number of clusters | 1 | 2 | 2 | 3 | 4 | 6 |

Propagation scenario | Flat fading | Indoor residential | Indoor residential or small office | Office | Large office/warehouse | Large space indoor (pseudo-outdoor) |

The number of clusters represents the number of independently modeled propagation paths.

**Data Types: **`char`

| `string`

`ChannelBandwidth`

— Channel bandwidth

`'CBW80'`

(default) | `'CBW20'`

| `'CBW40'`

| `'CBW160'`

| `'CBW320'`

Channel bandwidth, specified as one of these values.

`'CBW20'`

— Channel bandwidth of 20 MHz`'CBW40'`

— Channel bandwidth of 40 MHz`'CBW80'`

— Channel bandwidth of 80 MHz`'CBW160'`

— Channel bandwidth of 160 MHz`'CBW320'`

— Channel bandwidth of 320 MHz

**Data Types: **`char`

| `string`

`CarrierFrequency`

— RF carrier frequency

`5.25e9`

(default) | positive scalar

RF carrier frequency, in Hz, specified as a positive scalar.

**Data Types: **`double`

`EnvironmentalSpeed`

— Speed of the scatterers

`0.089`

(default) | positive scalar

Speed of the scatterers in km/h, specified as a positive scalar.

**Data Types: **`double`

`TransmitReceiveDistance`

— Distance between transmitter and receiver

`3`

(default) | positive scalar

Distance between the transmitter and receiver in meters, specified as a positive scalar.

`TransmitReceiveDistance`

is used to compute the path
loss, and to determine whether the channel has a line of sight (LOS) or non
line of sight (NLOS) condition. The path loss and standard deviation of
shadow fading loss depend on the separation between the transmitter and the
receiver.

**Data Types: **`double`

`NormalizePathGains`

— Normalize path gains

`true`

or `1`

(default) | `false`

or `0`

Normalize path gains, specified as a numeric or logical
`1`

(`true`

) or `0`

(`false`

). To normalize the fading processes such that
the total power of the path gains, averaged over time, is 0 dB, set this
property to `1`

(`true`

). Otherwise, set
this property to `false`

.

**Data Types: **`logical`

`UserIndex`

— User index for single or multi-user scenario

`0`

(default) | positive integer

User index, specified as a nonnegative integer. If the property is set to
`0`

, the angles of arrival and departure from the TGn
channel model are used in the calculation of the spatial correlation matrix.
If the property is set to a positive integer, pseudorandom offsets are
applied to the TGn angles of arrival and departure before the calculation of
the spatial correlation matrix. For more details, see the section on MIMO Enhancements.

**Data Types: **`double`

`TransmissionDirection`

— Transmission direction

`'Downlink'`

(default) | `'Uplink'`

Transmission direction of the active link, specified as either
`'Downlink'`

or `'Uplink'`

. The
default value, `'Downlink'`

, specifies transmission from an
access point to a user station.

**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`

`TransmitAntennaSpacing`

— Distance between transmit antenna elements

`0.5`

(default) | positive scalar

Distance between transmit antenna elements, specified as a positive scalar expressed in wavelengths.

`TransmitAntennaSpacing`

supports uniform linear arrays
only.

#### Dependencies

To enable this property, set the
`NumTransmitAntennas`

property to a value greater
than `1`

.

**Data Types: **`double`

`NumReceiveAntennas`

— Number of receive antennas

`1`

(default) | positive integer

Number of receive antennas, specified as a positive integer.

**Data Types: **`double`

`ReceiveAntennaSpacing`

— Distance between receive antenna elements

`0.5`

(default) | positive scalar

Distance between receive antenna elements, specified as a positive scalar expressed in wavelengths.

`ReceiveAntennaSpacing`

supports uniform linear arrays
only.

#### Dependencies

To enable this property, set the
`NumReceiveAntennas`

property to a value greater
than `1`

.

**Data Types: **`double`

`LargeScaleFadingEffect`

— Large-scale fading effects

`'None'`

(default) | `'Pathloss'`

| `'Shadowing'`

| `'Pathloss and shadowing'`

Large-scale fading effects applied in the channel, specified as
`'None'`

, `'Pathloss'`

,
`'Shadowing'`

, or ```
'Pathloss and
shadowing'
```

.

**Data Types: **`char`

| `string`

`NumPenetratedFloors`

— Number of building floors

`0`

(default) | positive integer

Number of building floors between the transmitter and the receiver,
specified as a positive integer. Use this property in multiple floor
scenarios to account for the floor attenuation loss in the path loss
calculation. The default is `0`

, which represents a
communication link between a transmitter and a receiver located on the same
floor.

#### Dependencies

The `NumPenetratedFloors`

property applies only
when `DelayProfile`

is `'Model-A'`

or `'Model-B'`

.

**Data Types: **`double`

`NumPenetratedWalls`

— Number of walls

`0`

(default) | positive integer

Number of walls between the transmitter and receiver, specified as a positive integer. Use this property to account for the wall penetration loss in the path loss calculation.

The default is `0`

, which represents a communication link
between a transmitter and a receiver without wall penetration loss.

**Data Types: **`double`

`WallPenetrationLoss`

— Penetration loss of a single wall

`5`

(default) | real scalar

Penetration loss of a single wall in dB, specified as a real scalar.

#### Dependencies

The `WallPenetrationLoss`

property applies only
when `NumPenetratedWalls`

is greater than 0.

**Data Types: **`double`

`FluorescentEffect`

— Fluorescent effect

`true`

or `1`

(default) | `false`

or `0`

Fluorescent effect, specified as a numeric or logical `1`

(`true`

) or `0`

(`false`

). To include Doppler effects from fluorescent
lighting, set this property to `1`

(`true`

).

#### Dependencies

To enable this property, set the `DelayProfile`

property to `'Model-D'`

or
`'Model-E'`

.

**Data Types: **`logical`

`PowerLineFrequency`

— Power line frequency

`'60Hz'`

(default) | `'50Hz'`

Power line frequency in Hz, specified as `'50Hz'`

or
`'60Hz'`

.

The power line frequency is 60 Hz in the United States and 50 Hz in Europe.

#### Dependencies

To enable this property, set the
`FluorescentEffect`

property to
`1`

(`true`

) and the
`DelayProfile`

property to
`'Model-D'`

or `'Model-E'`

.

**Data Types: **`char`

| `string`

`NormalizeChannelOutputs`

— Normalize channel outputs

`true`

or `1`

(default) | `false`

or `0`

Normalize channel outputs by the number of receive antennas, specified as
a numeric or logical `1`

(`true`

) or
`0`

(`false`

).

**Data Types: **`logical`

`ChannelFiltering`

— Enable channel filtering

`true`

or `1`

(default) | `false`

or `0`

Enable channel filtering, specified as a numeric or logical
`1`

(`true`

) or `0`

(`false`

). To enable channel filtering, set this
property to `1`

(`true`

). To disable
channel filtering, set this property to `0`

(`false`

).

**Note**

If you set this property to `0`

(`false`

), the `step`

object
function does not accept an input signal. In this case, the
`NumSamples`

and `SampleRate`

properties determine the duration of the
fading process realization. The object acts as a source of path
gains without filtering an input signal.

**Data Types: **`logical`

`NumSamples`

— Number of time-domain samples

`1280`

(default) | positive integer

Number of time-domain samples used to get path gain samples, specified as a positive integer.

#### Dependencies

To enable this property, set the `ChannelFiltering`

property to `0`

(`false`

).

**Data Types: **`double`

`OutputDataType`

— Data type of impaired signal

`'double'`

(default) | `'single'`

Data type of impaired signal, specified as one of these values:

`'double'`

– Return the`pathGains`

output as a double-precision matrix`'single'`

– Return the`pathGains`

output as a single-precision matrix

#### Dependencies

To enable this property, set the `ChannelFiltering`

property to
`0`

(`false`

).

**Data Types: **`char`

| `string`

`RandomStream`

— Source of random number stream

`'Global stream'`

(default) | `'mt19937ar with seed'`

Source of random number stream, specified as `'Global stream'`

or
`'mt19937ar with seed'`

.

If you set this property to `'Global stream'`

, the System object uses the current global random number stream to generate random numbers.
In this case, the `reset`

function resets the filters and creates a new
channel realization.

If you set this property to `'mt19937ar with seed'`

, the mt19937ar
algorithm generates random numbers. In this case, the `reset`

function
not only resets the filters, but also reinitializes the random number stream to the
value of the `Seed`

property. This results in the same channel
realization.

**Note**

The random numbers of the channel components are distributed as follows:

The random phase of the Doppler component due to fluorescent lights is uniformly distributed. See equation 27 of

*TGn Channel Models*for more information.In multi-user scenarios using the TGac, TGah, or TGax channel models, the per-user angle-of-arrival (AoA) and angle-of-departure (AoD) rotations discussed in the MIMO Enhancements section are uniformly distributed.

The fading samples are generated by a normally-distributed complex uncorrelated Gaussian process with zero mean and unit variance in discrete time.

**Data Types: **`char`

| `string`

`Seed`

— Initial seed of mt19937ar random number stream

`73`

(default) | nonnegative integer

Initial seed of an mt19937ar random number stream, specified as a
nonnegative integer. The `Seed`

property reinitializes
the mt19937ar random number stream in the `reset`

function.

#### Dependencies

To enable this property, set the `RandomStream`

property to `'mt19937ar with seed'`

.

**Data Types: **`double`

`PathGainsOutputPort`

— Enable path gain output

`false`

or `0`

(default) | `true`

or `1`

Enable path gain output computation, specified as a numeric or logical
`1`

(`true`

) or `0`

(`false`

).

**Data Types: **`logical`

## Usage

### Description

`[`

also returns in `y`

,`pathGains`

] = tgax(`x`

)`pathGains`

the TGax channel path gains of
the underlying fading process.

This syntax applies when you set the `PathGainsOutputPort`

property of `tgax`

to
`1`

(`true`

).

### Input Arguments

`x`

— Input signal

complex matrix

Input signal, specified as a real or complex
*N*_{S}-by-*N*_{T}
matrix, where:

*N*_{S}is the number of samples.*N*_{T}is the number of transmit antennas and must be equal to the`NumTransmitAntennas`

property value of`tgax`

.

**Data Types: **`single`

| `double`

**Complex Number Support: **Yes

### Output Arguments

`y`

— Output signal

complex matrix

Output signal, returned as an
*N*_{S}-by-*N*_{R}
complex matrix, where:

*N*_{S}is the number of samples.*N*_{R}is the number of receive antennas and is equal to the`NumReceiveAntennas`

property value of`tgax`

.

**Data Types: **`single`

| `double`

`pathGains`

— Path gains of the fading process

complex array

Path gains of the fading process, returned as an
*N*_{S}-by-*N*_{P}-by-*N*_{T}-by-*N*_{R}
complex array, where:

*N*_{S}is the number of samples.*N*_{P}is the number of resolvable paths, that is, the number of paths defined for the case specified by the`DelayProfile`

property.*N*_{T}is the number of transmit antennas and is equal to the`NumTransmitAntennas`

property value of`tgax`

.*N*_{R}is the number of receive antennas and is equal to the`NumReceiveAntennas`

property value of`tgax`

.

**Data Types: **`single`

| `double`

## Object Functions

To use an object function, specify the
System object as the first input argument. For
example, to release system resources of a System object named `obj`

, use
this syntax:

release(obj)

**Note**

`reset`

: If the
`RandomStream`

property of the System object is set to `'Global stream'`

, the `reset`

function resets the filters only. If you set
`RandomStream`

to `'mt19937ar with seed'`

,
the `reset`

function not only resets the filters,
but also reinitializes the random number stream to the value of the
`Seed`

property. This results in the same channel
realization.

## Examples

### TGax Channel Impulse Response

Obtain a channel impulse response by filtering an impulse through a TGax channel.

Create an impulse.

input = zeros(100,1); input(10) = 1;

Create the TGax channel System Object with path loss and shadowing, two penetrated floors, and a sampling rate of 1 GHz.

tgax = wlanTGaxChannel; tgax.LargeScaleFadingEffect = 'Pathloss and shadowing'; tgax.NumPenetratedFloors = 2; tgax.RandomStream = 'mt19937ar with seed'; tgax.Seed = 10; tgax.SampleRate = 1e9;

Plot the output impulse response of the channel.

figure time = (1/tgax.SampleRate)*(0:length(input)-1); stem(time,abs(tgax(input))) xlabel('Time (s)') ylabel('Amplitude') title('Channel Impulse Response')

### TGax Channel Delay Profile and Path Gains

Plot the delay profile and path gains of a TGax channel.

Create an impulse.

input = zeros(100,4); input(10) = 1;

Create the TGax channel System Object. Enable path gains at the output, and specify path loss, 20 MHz of channel bandwidth, a 4x2 MIMO channel, four penetrated floors, and a sampling rate of 1 GHz.

tgax = wlanTGaxChannel; tgax.LargeScaleFadingEffect = 'Pathloss'; tgax.ChannelBandwidth = 'CBW20'; tgax.NumTransmitAntennas = 4; tgax.NumReceiveAntennas = 2; tgax.NumPenetratedFloors = 4; tgax.RandomStream = 'mt19937ar with seed'; tgax.Seed = 10; tgax.SampleRate = 1e9; tgax.PathGainsOutputPort = true;

Filter the input impulse. Use the TGax channel object to generate the output response and the path gains.

[out,pathgains]= tgax(input);

Plot the output impulse response of the channel. The channel has two delay profiles, one per each receive antenna.

figure time = (1/tgax.SampleRate)*(0:length(input)-1); stem(time,abs(out)) xlabel('Time (s)') ylabel('Amplitude') title('Delay Profile')

The path gains of the channel are contained in a four dimensional array since the channel has nine resolvable paths, four transmit antennas and two receive antennas.

size(pathgains)

`ans = `*1×4*
100 9 4 2

### Compare Random Number Sources for TGn Channel

Create a non-HT configuration object with default parameters. Generate a waveform for the configuration.

cfg = wlanNonHTConfig; tx = wlanWaveformGenerator([1;0;0;1],cfg);

Create a TGn channel System object with default parameters. Display the value of the `RandomStream`

property.

tgnChan = wlanTGnChannel; disp(tgnChan.RandomStream)

Global stream

Pass the waveform through the channel twice, resetting the System object between the two iterations.

for i = 1:2 rx(:,i) = tgnChan(tx); reset(tgnChan); end

Compare the two received waveforms. They are different because the `reset`

object function resets the filters and the channel object takes new random numbers from the global stream. This causes it to generate a different channel realization.

isequal(rx(:,1),rx(:,2))

`ans = `*logical*
0

Now release the System object and set the `RandomStream`

property to `"mt19937ar with seed"`

.

```
release(tgnChan);
tgnChan.RandomStream = "mt19937ar with seed";
```

Pass the waveform through the channel twice, resetting the System object between the two iterations.

for i = 1:2 rx(:,i) = tgnChan(tx); reset(tgnChan); end

Compare the two received waveforms. They are equal because the channel realization is the same for both iterations. This happens because the `reset`

function reinitializes the random number stream to the value of the `Seed`

property, so the channel object uses the same random numbers for both channel realizations.

isequal(rx(:,1),rx(:,2))

`ans = `*logical*
1

## Algorithms

The algorithms used to model the TGax channel are based on those used for the TGn
channel (as described in `wlanTGnChannel`

and *TGn Channel
Models*
[2]) and the TGac channel (as
described in `wlanTGacChannel`

and *TGac Channel
Model Addendum*
[3]). Complete information on
the changes required to support TGax channels can be found in *TGax Channel
Model*
[1]. The changes to support the
TGax channel include lower bandwidths, floor separation attenuation, wall separation
attenuation, and path loss and shadowing.

### Floor Separation Attenuation

In the TGax channel, the path loss model used to compute the spatial correlation accounts for floor separation attenuation effects. The floor separation loss depends on the number of floors penetrated, as shown in the equation:

*PEL*_{floor}=
18.3*n*^{(n +
2)/(n + 1) -0.46},

where *n* is the number of floors, represented by the
`NumPenetratedFloors`

property of the System object. For more information, see *TGax Channel Model*
[1].

### Wall Separation Attenuation

In the TGax channel, the path loss model used to compute the spatial correlation accounts for wall separation attenuation effects. The wall separation loss is defined by the following equation:

*PEL*_{wall}=
*m*×*L*_{iw}.

Where *m* is the number of walls penetrated, and
*L*_{iw} is the penetration loss for a
single wall. The variables *m* and
*L*_{iw} are represented by the
`NumPenetratedWalls`

and
`WallPenetrationLoss`

properties of the System object, respectively. For more information, see *TGax Channel
Model*
[1].

### MIMO Enhancements

The TGn channel model supports no more than 4x4 MIMO, while the TGax model supports 8x8 MIMO.

The TGax model uses per-user angle diversity to support simultaneous communication
between multiple user stations and an access point. For each channel realization,
the model achieves this by adding pseudorandom offsets to the angles of arrival and
departure of each cluster before the calculation of the spatial correlation matrix.
Different offsets are chosen for each positive value of the
`UserIndex`

property. This causes the angles of arrival and
departure for each cluster to differ between users.

Changing the `TransmissionDirection`

property swaps the angle
of arrival of each cluster with its corresponding angle of departure. For more
details, see the Appendix of [3].

To see how the `UserIndex`

property can be used in an
application, see this example: 802.11ax Packet Error Rate Simulation for Uplink Trigger-Based Format.

### Path Loss and Shadowing

In *TGax Channel Model*
[1], Table 3 defines path
loss parameters that are slightly modified from those defined for TGn. The floor
penetration loss and wall penetration loss are added to this path loss.

The path loss exponent and the standard deviation of the shadow fading loss
characterize each model. The two parameters depend on the presence of a line of
sight (LOS) between the transmitter and receiver. For paths with a
transmitter-to-receiver distance, *d*, less than the breakpoint
distance, *d*_{BP}, the LOS parameters apply.
For *d* > *d*_{BP}, the non line of sight (NLOS) parameters apply. The table
summarizes the path loss and shadow fading parameters.

Parameter | Model | |||||
---|---|---|---|---|---|---|

A | B | C | D | E | F | |

Breakpoint distance,
d_{BP} (m) | 5 | 5 | 5 | 10 | 20 | 30 |

Path loss exponent for d ≤
d_{BP} | 2 | 2 | 2 | 2 | 2 | 2 |

Path loss exponent for d
>d_{BP} | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 | 3.5 |

Shadow fading σ (dB) for d ≤
d_{BP} | 3 | 3 | 3 | 3 | 3 | 3 |

Shadow fading σ (dB) for d
>d_{BP} | 4 | 4 | 5 | 5 | 6 | 6 |

### Increased Bandwidth

TGax channels support bandwidths of up to 320 MHz whereas TGn channels have a
maximum bandwidth of 40 MHz. By increasing the sampling rate and decreasing the tap
spacing of the power delay profile (PDP), the TGn model is used as the basis for
TGax. The channel sampling rate is increased by a factor of $${2}^{\lceil {\mathrm{log}}_{2}\left(W/40\right)\rceil}$$, where *W* is the bandwidth. The PDP tap spacing
is reduced by the same factor. This is shown in the table, which is adapted from
Table 1 in [3].

Bandwidth, W | Sampling Rate Expansion Factor | PDP Tap Spacing (ns) |
---|---|---|

W ≤ 40 MHz | 1 | 10 |

40 MHz < W ≤ 80 MHz | 2 | 5 |

80 MHz < W ≤ 160 MHz | 4 | 2.5 |

160 MHz < W ≤ 320 MHz | 8 | 1.25 |

320 MHz < W ≤ 640 MHz | 16 | 0.625 |

640 MHz < W ≤ 1280 MHz | 32 | 0.3125 |

## References

[1] Jianhan, L., Ron, P.
*et al.*
*TGax Channel Model*. IEEE 802.11-14/0882r4, September
2014.

[2] Erceg, V., Schumacher, L.,
Kyritsi, P. *et al.*
*TGn Channel Models*. Version 4. IEEE 802.11-03/940r4, May
2004.

[3] Breit, G., Sampath, H.,
Vermani, S. *et al.*
*TGac Channel Model Addendum*. Version 12. IEEE 802.11-09/0308r12,
March 2010.

[4] Kermoal, J. P., L. Schumacher,
K. I. Pedersen, P. E. Mogensen, and F. Frederiksen. “A Stochastic MIMO Radio
Channel Model with Experimental Validation.” *IEEE Journal on Selected
Areas in Communications*. Vol. 20, No. 6, August 2002, pp.
1211–1226.

## Extended Capabilities

### C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

See System Objects in MATLAB Code Generation (MATLAB Coder).

## Version History

**Introduced in R2018a**

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