nrTDLChannel

Send signal through TDL channel model

Description

The nrTDLChannel System object™ sends an input signal through a tapped delay line (TDL) multi-input multi-output (MIMO) link-level fading channel to obtain the channel-impaired signal. The object implements the following aspects of TR 38.901 [1]:

• Section 7.7.2: TDL models

• Section 7.7.3: Scaling of delays

• Section 7.7.5.2 TDL extension: Applying a correlation matrix

• Section 7.7.6: K-factor for LOS channel models

To send a signal through the TDL MIMO channel model:

1. Create the nrTDLChannel object and set its properties.

2. 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

Syntax

tdl = nrTDLChannel

tdl = nrTDLChannel(Name,Value)

Description

tdl = nrTDLChannel creates a TDL MIMO channel System object.

tdl = nrTDLChannel(Name,Value) creates the object with properties set by using one or more name-value pairs. Enclose the property name inside quotes, followed by the specified value. Unspecified properties take default values.

Example: tdl = nrTDLChannel('DelayProfile','TDL-D','DelaySpread',2e-6) creates a TDL channel model with TDL-D delay profile and a 2-microseconds delay spread.

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.

Configurable Channel Properties

DelayProfile — TDL delay profile

'TDL-A' (default) | 'TDL-B' | 'TDL-C' | 'TDL-D' | 'TDL-E' | 'Custom'

TDL delay profile, specified as one of 'TDL-A', 'TDL-B', 'TDL-C', 'TDL-D', 'TDL-E', or 'Custom'. See TR 38.901 Section 7.7.2, Tables 7.7.2-1 to 7.7.2-5.

When you set this property to 'Custom', configure the delay profile using properties PathDelays, AveragePathGains, FadingDistribution, and KFactorFirstTap.

Data Types: char | string

PathDelays — Discrete path delays in seconds

0.0 (default) | numeric scalar | row vector

Discrete path delays in seconds, specified as a numeric scalar or row vector. AveragePathGains and PathDelays must have the same size.

Dependencies

To enable this property, set DelayProfile to 'Custom'.

Data Types: double

AveragePathGains — Average path gains in dB

0.0 (default) | numeric scalar | row vector

Average path gains in dB, specified as a numeric scalar or row vector. AveragePathGains and PathDelays must have the same size.

Dependencies

To enable this property, set DelayProfile to 'Custom'.

Data Types: double

FadingDistribution — Fading process statistical distribution

'Rayleigh' (default) | 'Rician'

Fading process statistical distribution, specified as 'Rayleigh' or 'Rician'.

Dependencies

To enable this property, set DelayProfile to 'Custom'.

Data Types: char | string

KFactorFirstTap — K-factor of first tap of delay profile in dB

13.3 (default) | numeric scalar

K-factor of first tap of delay profile in dB, specified as a numerical scalar. The default value corresponds to the K-factor of the first tap of TDL-D as defined in TR 38.901 Section 7.7.2, Table 7.7.2-4.

Dependencies

To enable this property, set DelayProfile to 'Custom' and FadingDistribution to 'Rician'.

Data Types: double

DelaySpread — Desired RMS delay spread in seconds

30e-9 (default) | numeric scalar

Desired root mean square (RMS) delay spread in seconds, specified as a numeric scalar. For examples of desired RMS delay spreads, DSdesired, see TR 38.901 Section 7.7.3 and Tables 7.7.3-1 and 7.7.3-2.

Dependencies

To enable this property, set DelayProfile to 'TDL-A', 'TDL-B', 'TDL-C', 'TDL-D', or 'TDL-E'. This property does not apply for custom delay profile.

Data Types: double

MaximumDopplerShift — Maximum Doppler shift in Hz

5 (default) | nonnegative numeric scalar

Maximum Doppler shift in Hz, specified as a nonnegative numeric scalar. This property applies to all channel paths. When the maximum Doppler shift is set to 0, the channel remains static for the entire input. To generate a new channel realization, reset the object by calling the reset function.

Data Types: double

KFactorScaling — K-factor scaling

false (default) | true

K-factor scaling, specified as false or true. When set to true, the KFactor property specifies the desired K-factor, and the object applies K-factor scaling as described in TR 38.901 Section 7.7.6.

Note

K-factor scaling modifies both the path delays and path powers.

Dependencies

To enable this property, set DelayProfile to 'TDL-D' or 'TDL-E'.

Data Types: double

KFactor — Desired K-factor for scaling in dB

9.0 (default) | numeric scalar

Desired K-factor for scaling in dB, specified as a numeric scalar. For typical K-factor values, see TR 38.901 Section 7.7.6 and Table 7.5-6.

Note

• K-factor scaling modifies both the path delays and path powers.

• K-factor applies to the overall delay profile. Specifically, the K-factor after the scaling is Kmodel as described in TR 38.901 Section 7.7.6. Kmodel is the ratio of the power of the first path LOS to the total power of all the Rayleigh paths, including the Rayleigh part of the first path.

Dependencies

To enable this property, set KFactorScaling to true.

Data Types: double

SampleRate — Sample rate of input signal in Hz

30.72e6 (default) | positive numeric scalar

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

Data Types: double

MIMOCorrelation — Correlation between UE and BS antennas

'Low' (default) | 'Medium' | 'Medium-A' | 'UplinkMedium' | 'High' | 'Custom'

Correlation between user equipment (UE) and base station (BS) antennas, specified as one of these values:

• 'Low' or 'High' — Applies to both uplink and downlink. 'Low' is equivalent to no correlation between antennas.

• 'Medium' or 'Medium-A' — For downlink, see TS 36.101 Annex B.2.3.2. For uplink, see TS 36.104 Annex B.5.2. The TransmissionDirection property controls the transmission direction.

• 'UplinkMedium' — See TS 36.104, Annex B.5.2.

• 'Custom' — The ReceiveCorrelationMatrix property specifies the correlation between UE antennas, and the TransmitCorrelationMatrix property specifies the correlation between BS antennas. See TR 38.901 Section 7.7.5.2.

For more details on correlation between UE and BS antennas, see TS 36.101 [2] and TS 36.104 [3]

Data Types: char | string

Polarization — Antenna polarization arrangement

'Co-Polar' (default) | 'Cross-Polar' | 'Custom'

Antenna polarization arrangement, specified as 'Co-Polar', 'Cross-Polar', 'Custom'.

Data Types: char | string

TransmissionDirection — Transmission direction

'Downlink' (default) | 'Uplink'

Transmission direction, specified as 'Downlink' or 'Uplink'.

Dependencies

To enable this property, set MIMOCorrelation to 'Low', 'Medium', 'Medium-A', 'UplinkMedium', or 'High'.

Note

This property describes the transmission direction corresponding to the channel status in which the role of the transmit and receive antennas are not swapped. If the antennas are swapped, the opposite transmission direction applies to this property. To determine the current link direction of the channel, inspect the TransmitAndReceiveSwapped property value.

Data Types: char | string

NumTransmitAntennas — Number of transmit antennas

1 (default) | positive integer

Number of transmit antennas, specified as a positive integer.

Dependencies

To enable this property, set MIMOCorrelation to 'Low', 'Medium', 'Medium-A', 'UplinkMedium', or 'High', or set both MIMOCorrelation and Polarization to 'Custom'.

Data Types: double

NumReceiveAntennas — Number of receive antennas

2 (default) | positive integer

Number of receive antennas, specified as a positive integer.

Dependencies

To enable this property, set MIMOCorrelation to 'Low', 'Medium', 'Medium-A', 'UplinkMedium', or 'High'.

Data Types: double

TransmitCorrelationMatrix — Spatial correlation of transmitter

[1] (default) | 2-D matrix | 3-D array

Spatial correlation of transmitter, specified as a 2-D matrix or 3-D array.

• If the channel is frequency-flat (PathDelays is a scalar), specify TransmitCorrelationMatrix as a 2-D Hermitian matrix of size N_T-by-N_T. N_T is the number of transmit antennas. The main diagonal elements must be all ones, and the off-diagonal elements must have a magnitude smaller than or equal to one.

• If the channel is frequency-selective (PathDelays is a row vector of length N_P), specify TransmitCorrelationMatrix as one of these arrays:

  • 2-D Hermitian matrix of size N_T-by-N_T with element properties as previously described. Each path has the same transmit correlation matrix.

  • 3-D array of size N_T-by-N_T-by-N_P, where each submatrix of size N_T-by-N_T is a Hermitian matrix with element properties as previously described. Each path has its own transmit correlation matrix.

Dependencies

To enable this property, set MIMOCorrelation to 'Custom' and Polarization to either 'Co-Polar' or 'Cross-Polar'.

Data Types: double
Complex Number Support: Yes

ReceiveCorrelationMatrix — Spatial correlation of receiver

[1 0; 0 1] (default) | 2-D matrix | 3-D array

Spatial correlation of receiver, specified as a 2-D matrix or 3-D array.

• If the channel is frequency-flat (PathDelays is a scalar), specify ReceiveCorrelationMatrix as a 2-D Hermitian matrix of size N_R-by-N_R. N_R is the number of receive antennas. The main diagonal elements must be all ones, and the off-diagonal elements must have a magnitude smaller than or equal to one.

• If the channel is frequency-selective (PathDelays is a row vector of length N_P), specify ReceiveCorrelationMatrix as one of these arrays:

  • 2-D Hermitian matrix of size N_R-by-N_R with element properties as previously described. Each path has the same receive correlation matrix.

  • 3-D array of size N_R-by-N_R-by-N_P, where each submatrix of size N_R-by-N_R is a Hermitian matrix with element properties as previously described. Each path has its own receive correlation matrix.

Dependencies

To enable this property, set MIMOCorrelation to 'Custom' and Polarization to either 'Co-Polar' or 'Cross-Polar'.

Data Types: double
Complex Number Support: Yes

TransmitPolarizationAngles — Transmit polarization slant angles in degrees

[45 -45] (default) | row vector

Transmit polarization slant angles in degrees, specified as a row vector.

Dependencies

To enable this property, set MIMOCorrelation to 'Custom' and Polarization to 'Cross-Polar'.

Data Types: double

ReceivePolarizationAngles — Receive polarization slant angles in degrees

[90 0] (default) | row vector

Receive polarization slant angles in degrees, specified as a row vector.

Dependencies

To enable this property, set MIMOCorrelation to 'Custom' and Polarization to 'Cross-Polar'.

Data Types: double

XPR — Cross-polarization power ratio in dB

10.0 (default) | numeric scalar | row vector

Cross-polarization power ratio in dB, specified as a numeric scalar or a row vector. This property corresponds to the ratio between the vertical-to-vertical (P_VV) and vertical-to-horizontal (P_VH) polarizations defined for the clustered delay line (CDL) models in TR 38.901 Section 7.7.1.

• If the channel is frequency-flat (PathDelays is a scalar), specify XPR as a scalar.

• If the channel is frequency-selective (PathDelays is a row vector of length N_P), specify XPR as one of these values:

  • Scalar — Each path has the same cross-polarization power ratio.

  • Row vector of size 1-by-N_P — Each path has its own cross-polarization power ratio.

The default value corresponds to the cluster-wise cross-polarization power ratio of CDL-A as defined in TR 38.901 Section 7.7.1, Table 7.7.1-1.

Dependencies

To enable this property, set MIMOCorrelation to 'Custom' and Polarization to 'Cross-Polar'.

Data Types: double

SpatialCorrelationMatrix — Combined correlation for channel

[1 0; 0 1] (default) | 2-D matrix | 3-D array

Combined correlation for the channel, specified as 2-D matrix or 3-D array. The matrix determines the product of the number of transmit antennas (N_T) and the number of receive antennas (N_R).

• If the channel is frequency-flat (PathDelays is a scalar), specify SpatialCorrelationMatrix as a 2-D Hermitian matrix of size (N_T ⨉ N_R)-by-(N_T ⨉ N_R).The magnitude of any off-diagonal element must be no larger than the geometric mean of the two corresponding diagonal elements.

• If the channel is frequency-selective (PathDelays is a row vector of length N_P), specify SpatialCorrelationMatrix as one of these arrays:

  • 2-D Hermitian matrix of size (N_T ⨉ N_R)-by-(N_T ⨉ N_R) with off-diagonal element properties as previously described. Each path has the same spatial correlation matrix.

  • 3-D array of size (N_T ⨉ N_R)-by-(N_T ⨉ N_R)-by-N_P array — where each matrix of size (N_T ⨉ N_R)-by-(N_T ⨉ N_R) is a Hermitian matrix with off-diagonal element properties as previously described. Each path has its own spatial correlation matrix.

Dependencies

To enable this property, set MIMOCorrelation to 'Custom' and Polarization to 'Custom'.

Data Types: double

NormalizePathGains — Normalize path gains

true (default) | false

Normalize path gains, specified as true or false. Use this property to normalize the fading processes. When this property is set to true, the total power of the path gains, averaged over time, is 0 dB. When this property is set to false, the path gains are not normalized. The average powers of the path gains are specified by the selected delay profile, or if DelayProfile is set to 'Custom', by the AveragePathGains property.

Data Types: logical

InitialTime — Time offset of fading process in seconds

0.0 (default) | numeric scalar

Time offset of fading process in seconds, specified as a numeric scalar.

Data Types: double

NumSinusoids — Number of modeling sinusoids

48 (default) | positive integer

Number of modeling sinusoids, specified as a positive integer. These sinusoids model the fading process.

Data Types: double

RandomStream — Source of random number stream

'mt19937ar with seed' (default) | 'Global stream'

Source of random number stream, specified as one of the following:

• 'mt19937ar with seed' — The object uses the mt19937ar algorithm for normally distributed random number generation. Calling the reset function resets the filters and reinitializes the random number stream to the value of the Seed property.

• 'Global stream' — The object uses the current global random number stream for normally distributed random number generation. Calling the reset function resets only the filters.

Seed — Initial seed of mt19937ar random number stream

73 (default) | nonnegative numeric scalar

Initial seed of mt19937ar random number stream, specified as a nonnegative numeric scalar.

Dependencies

To enable this property, set RandomStream to 'mt19937ar with seed'. When calling the reset function, the seed reinitializes the mt19937ar random number stream.

Data Types: double

NormalizeChannelOutputs — Normalize channel outputs

true (default) | false

Normalize channel outputs, specified as true or false. When this property is set to true, the channel outputs are normalized by the number of receive antenna elements.

Note

When you call the swapTransmitAndReceive function to reverse the role of the transmit and receive antennas within the channel, the function also swaps the NumTransmitAntennas and NumReceiveAntennas properties. Hence the normalization is always by the number of receive antenna elements, specified by the NumReceiveAntennas property.

Data Types: logical

Nonconfigurable Channel Properties

TransmitAndReceiveSwapped — Reversed channel link direction

false (default) | true

This property is read-only.

Reversed channel link direction, returned as one of these values.

• false — The role of the transmit and receive antennas within the channel model corresponds to the original channel link direction. Calling the swapTransmitAndReceive function on the nrTDLChannel object reverses the link direction of the channel and toggles this property value from false to true.

• true — The role of the transmit and receive antennas within the channel model are swapped. Calling the swapTransmitAndReceive function on the nrTDLChannel object restores the original link direction of the channel and toggles this property value from true to false.

Data Types: logical

Usage

Syntax

signalOut = tdl(signalIn)

[signalOut,pathGains] = tdl(signalIn)

[signalOut,pathGains,sampleTimes] = tdl(signalIn)

Description

signalOut = tdl(signalIn) sends the input signal through a TDL MIMO fading channel and returns the channel-impaired signal.

[signalOut,pathGains] = tdl(signalIn) also returns the MIMO channel path gains of the underlying fading process.

[signalOut,pathGains,sampleTimes] = tdl(signalIn) also returns the sample times of the channel snapshots of the path gains.

Input Arguments

signalIn — Input signal

complex scalar | vector | N_S-by-N_T matrix

Input signal, specified as a complex scalar, vector, or N_S-by-N_T matrix, where:

• N_S is the number of samples.

• N_T is the number of transmit antennas.

Data Types: single | double
Complex Number Support: Yes

Output Arguments

signalOut — Output signal

complex scalar | vector | N_S-by-N_R matrix

Output signal, returned as a complex scalar, vector, or N_S-by-N_R matrix, where:

• N_S is the number of samples.

• N_R is the number of receive antennas.

The output signal data type is of the same precision as the input signal data type.

Data Types: single | double
Complex Number Support: Yes

pathGains — MIMO channel path gains of fading process

N_S-by-N_P-by-N_T-by-N_R complex matrix

MIMO channel path gains of the fading process, returned as an N_S-by-N_P-by-N_T-by-N_R complex matrix, where:

• N_S is the number of samples.

• N_P is the number of paths, specified by the length of the PathDelays property of tdl.

• N_T is the number of transmit antennas.

• N_R is the number of receive antennas.

The path gains data type is of the same precision as the input signal data type.

Data Types: single | double
Complex Number Support: Yes

sampleTimes — Sample times of channel snapshots

N_S-by-1 column vector of real numbers

Sample times of the channel snapshots of the path gains, returned as an N_S-by-1 column vector of real numbers. N_S is the first dimension of pathGains that corresponds to the number of samples.

Data Types: 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)

Specific to nrTDLChannel

info	Get characteristic information about link-level MIMO fading channel
getPathFilters	Get path filter impulse response for link-level MIMO fading channel
swapTransmitAndReceive	Reverse link direction in TDL channel model

Common to All System Objects

step	Run System object algorithm
clone	Create duplicate System object
isLocked	Determine if System object is in use
release	Release resources and allow changes to System object property values and input characteristics
reset	Reset internal states of System object

Examples

Transmission Over MIMO Channel Model with Delay Profile TDL

Display the waveform spectrum received through a tapped delay line (TDL) multi-input/multi-output (MIMO) channel model from TR 38.901 Section 7.7.2 using an nrTDLChannel System object.

Define the channel configuration structure using an nrTDLChannel System object. Use delay profile TDL-C from TR 38.901 Section 7.7.2, a delay spread of 300 ns, and UE velocity of 30 km/h:

v = 30.0;                    % UE velocity in km/h
fc = 4e9;                    % carrier frequency in Hz
c = physconst('lightspeed'); % speed of light in m/s
fd = (v*1000/3600)/c*fc;     % UE max Doppler frequency in Hz

tdl = nrTDLChannel;
tdl.DelayProfile = 'TDL-C';
tdl.DelaySpread = 300e-9;
tdl.MaximumDopplerShift = fd;

Create a random waveform of 1 subframe duration with 1 antenna.

SR = 30.72e6;
T = SR * 1e-3;
tdl.SampleRate = SR;
tdlinfo = info(tdl);
Nt = tdlinfo.NumTransmitAntennas;
 
txWaveform = complex(randn(T,Nt),randn(T,Nt));

Transmit the input waveform through the channel.

rxWaveform = tdl(txWaveform);

Plot the received waveform spectrum.

analyzer = dsp.SpectrumAnalyzer('SampleRate',tdl.SampleRate,...
    'AveragingMethod','Exponential','ForgettingFactor',0.99 );
analyzer.Title = ['Received Signal Spectrum ' tdl.DelayProfile];
analyzer(rxWaveform);

Plot Path Gains for TDL-E Delay Profile with SISO

Plot the path gains of a tapped delay line (TDL) single-input/single-output (SISO) channel using an nrTDLChannel System object.

Configure a channel with delay profile TDL-E from TR 38.901 Section 7.7.2. Set the maximum Doppler shift to 70 Hz and enable path gain output.

tdl = nrTDLChannel;
tdl.SampleRate = 500e3;
tdl.MaximumDopplerShift = 70;
tdl.DelayProfile = 'TDL-E';

Configure the transmit and receive antenna arrays for SISO operation.

tdl.NumTransmitAntennas = 1;
tdl.NumReceiveAntennas = 1;

Create a dummy input signal. The length of the input determines the time samples of the generated path gain.

in = zeros(1000,tdl.NumTransmitAntennas);

To generate the path gains, call the channel on the input. Plot the results.

[~, pathGains] = tdl(in);
mesh(10*log10(abs(pathGains)));
view(26,17); xlabel('Channel Path');
ylabel('Sample (time)'); zlabel('Magnitude (dB)');

Transmission Over TDL-D Channel Model with Cross-Polar Antennas

Display the waveform spectrum received through a tapped delay line (TDL) channel model using delay profile TDL-D from TR 38.901 Section 7.7.2.

Configure 4-by-2, high-correlation, cross-polar antennas as specified in TS 36.101 Annex B.2.3A.3.

tdl = nrTDLChannel;
tdl.NumTransmitAntennas = 4;
tdl.DelayProfile = 'TDL-D';
tdl.DelaySpread = 10e-9;
tdl.KFactorScaling = true;
tdl.KFactor = 7.0;
tdl.MIMOCorrelation = 'High';
tdl.Polarization = 'Cross-Polar';

Create a random waveform of 1 subframe duration with 4 antennas.

SR = 1.92e6;
T = SR * 1e-3;
tdl.SampleRate = SR;
tdlinfo = info(tdl);
Nt = tdlinfo.NumTransmitAntennas;
 
txWaveform = complex(randn(T,Nt),randn(T,Nt));

Transmit the input waveform through the channel.

rxWaveform = tdl(txWaveform);

Plot the received waveform spectrum.

analyzer = dsp.SpectrumAnalyzer('SampleRate',tdl.SampleRate);
analyzer.Title = ['Received Signal Spectrum ' tdl.DelayProfile];
analyzer(rxWaveform);

Transmission Over TDL Channel Model with Custom Delay Profile

Transmit waveform through a tapped delay line (TDL) channel model from TR 38.901 Section 7.7.2 with customized delay profile.

Define the channel configuration structure using an nrTDLChannel System object. Customize the delay profile with two taps.

• First tap: Rician with average power 0 dB, K-factor 10 dB, and zero delay.

• Second tap: Rayleigh with average power $-$5 dB, and 45 ns path delay using TDL-D.

tdl = nrTDLChannel;
tdl.NumTransmitAntennas = 1;
tdl.DelayProfile = 'Custom';
tdl.FadingDistribution = 'Rician';
tdl.KFactorFirstTap = 10.0;
tdl.PathDelays = [0.0 45e-9];
tdl.AveragePathGains = [0.0 -5.0];

Create a random waveform of 1 subframe duration with 1 antenna.

SR = 30.72e6;
T = SR * 1e-3;
tdl.SampleRate = SR;
tdlinfo = info(tdl);
Nt = tdlinfo.NumTransmitAntennas;
 
txWaveform = complex(randn(T,Nt),randn(T,Nt));

Transmit the input waveform through the channel.

rxWaveform = tdl(txWaveform);

References

[1] 3GPP TR 38.901. “Study on channel model for frequencies from 0.5 to 100 GHz.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.

[2] 3GPP TS 36.101. “Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) radio transmission and reception.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.

[3] 3GPP TS 36.104. “Evolved Universal Terrestrial Radio Access (E-UTRA); Base Station (BS) radio transmission and reception.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.

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).