nrCDLChannel

Send signal through CDL channel model

Description

The nrCDLChannel System object™ sends an input signal through a clustered delay line (CDL) 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 7.7.1: CDL models

  • Section 7.7.3: Scaling of delays

  • Section 7.7.5.1: Scaling of angles

  • Section 7.7.6: K-factor for LOS channel models

To send a signal through the CDL MIMO channel model:

  1. Create the nrCDLChannel 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? (MATLAB).

Creation

Description

cdl = nrCDLChannel creates a CDL MIMO channel System object.

example

cdl = nrCDLChannel(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: cdl = nrCDLChannel('DelayProfile','CDL-D','DelaySpread',2e-6) creates the channel object with CDL-D delay profile and 2 microseconds delay spread.

Properties

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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 (MATLAB).

CDL delay profile, specified as 'CDL-A', 'CDL-B', 'CDL-C', 'CDL-D', 'CDL-E', or 'Custom'. See TR 38.901 Section 7.7.1, Tables 7.7.1-1 to 7.7.1-5.

When you set this property to 'Custom', configure the delay profile using properties PathDelays, AveragePathGains, AnglesAoA, AnglesAoD, AnglesZoA, AnglesZoD, HasLOSCluster, KFactorFirstCluster, AngleSpreads, XPR, and NumStrongestClusters.

Data Types: char | string

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

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

Azimuth of arrival angle in degrees, specified as a numeric scalar or row vector. The vector elements specify the angles for each cluster.

Dependencies

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

Data Types: double

Azimuth of departure angle in degrees, specified as a numeric scalar or row vector. The vector elements specify the angles for each cluster.

Dependencies

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

Data Types: double

Zenith of arrival angle in degrees, specified as a numeric scalar or row vector. The vector elements specify the angles for each cluster.

Dependencies

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

Data Types: double

Zenith of departure angle in degrees, specified as a numeric scalar or row vector. The vector elements specify the angles for each cluster.

Dependencies

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

Data Types: double

Line of sight (LOS) cluster of the delay profile, specified as false or true. The PathDelays, AveragePathGains, AnglesAoA, AnglesAoD, AnglesZoA, and AnglesZoD properties define the delay profile. To enable the LOS cluster of the delay profile, set HasLOSCluster to true.

Dependencies

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

Data Types: logical

K-factor in the first cluster of the delay profile in dB, specified as a numeric scalar. The default value corresponds to the K-factor in the first cluster of CDL-D as defined in TR 38.901 Section 7.7.1, Table 7.7.1-4.

Dependencies

To enable this property, set DelayProfile to 'Custom' and HasLOSCluster to true.

Data Types: double

Apply scaling of angles, specified as false or true according to TR 38.901 Section 7.7.5.1. When set to true, the AngleSpreads and MeanAngles properties define the scaling of angles.

Dependencies

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

Data Types: logical

Desired scaled angle spreads in degrees, specified as a four-element row vector in one of these forms:

  • [CASD CASA CZSD CZSA] row vector for scaling ray offset angles as described in TR 38.901 Section 7.7.1, Step1, where:

    • CASD is the cluster-wise azimuth spread of departure angles

    • CASA is the cluster-wise azimuth spread of arrival angles

    • CZSD is the cluster-wise zenith spread of departure angles

    • CZSA is the cluster-wise zenith spread of arrival angles

    To use this form, set DelayProfile to 'Custom'.

  • [ASD ASA ZSD ZSA] row vector for angle scaling, ASdesired, as described in TR 38.901 Section 7.7.5.1, where:

    • ASD is the azimuth spread of departure angles after scaling

    • ASA is the azimuth spread of arrival angles after scaling

    • ZSD is the zenith spread of departure angles after scaling

    • ZSA is the zenith spread of arrival angles after scaling

    To use this form, set AngleScaling to true.

The default value corresponds to the default cluster-wise angle spreads of CDL-A as defined in TR 38.901 Section 7.7.1 Table 7.7.1-1.

Dependencies

To enable this property, set DelayProfile to 'Custom' or AngleScaling to true.

Data Types: double

Desired mean angles in degrees, specified as a four-element row vector of the form [AoD AoA ZoD ZoA].

  • AoD is the mean azimuth spread of departure angles after scaling

  • AoA is the mean azimuth spread of arrival angles after scaling

  • ZoD is the mean zenith spread of departure angles after scaling

  • ZoA is the mean zenith spread of arrival angles after scaling

Use this vector for angle scaling as described in TR 38.901 Section 7.7.5.1

Dependencies

To enable this property, set AngleScaling to true.

Data Types: double

Cross-polarization power ratio in dB, specified as a numeric scalar. 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 DelayProfile to 'Custom'.

Data Types: double

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 'CDL-A', 'CDL-B', 'CDL-C', 'CDL-D', or 'CDL-E'. This property does not apply for custom delay profile.

Data Types: double

Carrier frequency in Hz, specified as a numeric scalar.

Data Types: double

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

User terminal (UT) direction of travel in degrees, specified as a two-element column vector. The vector elements specify the azimuth and the elevation components [azimuth; elevation].

Data Types: double

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 'CDL-D' or 'CDL-E'.

Data Types: double

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 Laplacian clusters, including the Laplacian part of the first cluster.

Dependencies

To enable this property, set KFactorScaling to true.

Data Types: double

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

Data Types: double

Transmit antenna array characteristics, specified as a structure that contains these fields:

Parameter FieldValuesDescription
Size

[2 2 2 1 1] (default),

row vector

Size of antenna array [M N P Mg Ng], where:

  • M and N are the number of rows and columns in the antenna array.

  • P is the number of polarizations (1 or 2).

  • Mg and Ng are the number of row and column array panels, respectively.

The antenna array elements are mapped panel-wise to the waveform channels (columns) in the order that a 5-D array of size M-by-N-by-P-by-Mg-by-Ng is linearly indexed across the first dimension to the last.

For example, an antenna array of size [4 8 2 2 2] has the first M = 4 channels mapped to the first column of the first polarization angle of the first panel. The next M = 4 antennas are mapped to the next column, and so on. Following this pattern, the first M × N = 32 channels are mapped to the first polarization angle of the complete first panel. Similarly, the remaining 32 channels are mapped to the second polarization angle of the first panel. Subsequent sets of M × N × P = 64 channels are mapped to consecutive panels, taking panel rows first, then panel columns.

ElementSpacing

[0.5 0.5 1.0 1.0] (default),

row vector

Element spacing, in wavelengths, specified as a row vector of the form [λv λh dgv dgh]. The vector elements represent the vertical and horizontal element spacing and the vertical and horizontal panel spacing, respectively.

PolarizationAngles

[45 -45] (default),

row vector

Polarization angles in degrees, specified as a row vector of the form [θ ρ]. Polarization angles apply only when the number of polarizations is 2.

Orientation

[0; 0; 0](default),

column vector

Array orientation in degrees, specified as a column vector of the form [α; β; γ]. The vector elements specify the bearing, downtilt, and slant, respectively.

Element

'38.901' (default),

'isotropic'

Antenna element radiation pattern as described in TR 38.901 Section 7.3. (Note that TR 38.901 superseded TR 38.900.)
PolarizationModel

'Model-2' (default),

'Model-1'

Model that determines the radiation field patterns based on a defined radiation power pattern. See TR 38.901 Section 7.3.2.

Data Types: struct

Receive antenna array characteristics, specified as a structure that contains these fields:

Parameter FieldValuesDescription
Size

[1 1 2 1 1] (default),

row vector

Size of antenna array [M N P Mg Ng], where:

  • M and N are the number of rows and columns in the antenna array.

  • P is the number of polarizations (1 or 2).

  • Mg and Ng are the number of row and column array panels, respectively.

The antenna array elements are mapped panel-wise to the waveform channels (columns) in the order that a 5-D array of size M-by-N-by-P-by-Mg-by-Ng is linearly indexed across the first dimension to the last.

For example, an antenna array of size [4 8 2 2 2] has the first M = 4 channels mapped to the first column of the first polarization angle of the first panel. The next M = 4 antennas are mapped to the next column, and so on. Following this pattern, the first M × N = 32 channels are mapped to the first polarization angle of the complete first panel. Similarly, the remaining 32 channels are mapped to the second polarization angle of the first panel. Subsequent sets of M × N × P = 64 channels are mapped to consecutive panels, taking panel rows first, then panel columns.

ElementSpacing

[0.5 0.5 0.5 0.5] (default),

row vector

Element spacing in wavelengths, specified as a row vector of the form [λv λh dgv dgh]. The vector values represent the vertical and horizontal element spacing, and the vertical and horizontal panel spacing, respectively.

PolarizationAngles

[0 90] (default),

row vector

Polarization angles in degrees, specified as a row vector of the form [θ ρ]. Polarization angles apply only when the number of polarizations is 2.

Orientation

[0; 0; 0](default),

column vector

Array orientation in degrees, specified as a column vector of the form [α; β; γ]. The vector elements specify the bearing, downtilt, and slant, respectively.
Element

'isotropic' (default),

'38.901'

Antenna element radiation pattern as described in TR 38.901 Section 7.3. (Note that TR 38.901 superseded TR 38.900.)

PolarizationModel

'Model-2' (default),

'Model-1'

Model that determines the radiation field patterns based on a defined radiation power pattern. See TR 38.901 Section 7.3.2.

Data Types: structure

Number of time samples per half wavelength, specified as Inf or a numeric scalar. The SampleDensity and MaximumDopplerShift properties control the coefficient generation sampling rate, Fcg, given by

Fcg = MaximumDopplerShift × 2 × SampleDensity.

Setting SampleDensity to Inf assigns Fcg the value of the SampleRate property.

Data Types: double

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

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

Tunable: Yes

Data Types: double

Number of strongest clusters to split into subclusters, specified as a numeric scalar. See TR 38.901 Section 7.5, Step 11.

Dependencies

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

Data Types: double

Cluster delay spread in seconds, specified as a nonnegative scalar. Use this property to specify the delay offset between subclusters for clusters split into subclusters. See TR 38.901 Section 7.5, Step 11.

Dependencies

To enable this property, set DelayProfile to 'Custom' and NumStrongestClusters to a value greater than zero.

Data Types: double

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.

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

Fading channel filtering, specified as true or false. When this property is set to false, the following conditions apply:

  • The object takes no input signal and returns only the path gains and sample times.

  • The SampleDensity property determines when to sample the channel coefficients.

  • The NumTimeSamples property controls the duration of the fading process realization at a sampling rate given by the SampleRate property.

Data Types: logical

Number of time samples, specified as a positive integer. Use this property to set the duration of the fading process realization.

Tunable: Yes

Dependencies

To enable this property, set ChannelFiltering to false.

Data Types: double

Normalize channel outputs by the number of receive antennas, specified as true or false.

Dependencies

To enable this property, set ChannelFiltering to true.

Data Types: logical

Usage

Description

example

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

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

example

[signalOut,pathGains,sampleTimes] = cdl(signalIn) also returns the sample times of the channel snapshots of pathGains (first-dimension elements).

[pathGains,sampleTimes] = cdl() returns only the path gains and the sample times. In this case, the NumTimeSamples property determines the duration of the fading process. The object acts as a source of the path gains and sample times without filtering an input signal.

To use this syntax, you must set the ChannelFiltering property of cdl to false.

Input Arguments

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Input signal, specified as a complex scalar, vector, or NS-by-NT matrix, where:

  • NS is the number of samples.

  • NT is the number of transmit antennas.

Data Types: single | double
Complex Number Support: Yes

Output Arguments

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Output signal, returned as a complex scalar, vector, or NS-by-NR matrix, where:

  • NS is the number of samples.

  • NR 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

MIMO channel path gains of the fading process, returned as an NCS-by-NP-by-NT-by-NR complex matrix, where:

  • NCS is the number of channel snapshots, controlled by the SampleDensity property of cdl.

  • NP is the number of paths, specified by the size of the PathDelays property of cdl.

  • NT is the number of transmit antennas.

  • NR 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

Sample times of channel snapshots, returned as an NCS-by-1 column vector, where NCS is the number of channel snapshots controlled by the SampleDensity property.

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)

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infoGet characteristic information about link-level MIMO fading channel
getPathFilters Get path filter impulse response for link-level MIMO fading channel
stepRun System object algorithm
cloneCreate duplicate System object
isLockedDetermine if System object is in use
releaseRelease resources and allow changes to System object property values and input characteristics
resetReset internal states of System object

Examples

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Transmit waveform through a Clustered Delay Line (CDL) channel model with delay profile CDL-D from TR 38.901 Section 7.7.1.

Define the channel configuration structure using an nrCDLChannel System object. Use delay profile CDL-D, a delay spread of 10 ns, and UT velocity of 15 km/h:

v = 15.0;                    % UT 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;     % UT max Doppler frequency in Hz
 
cdl = nrCDLChannel;
cdl.DelayProfile = 'CDL-D';
cdl.DelaySpread = 10e-9;
cdl.CarrierFrequency = fc;
cdl.MaximumDopplerShift = fd;

Configure the transmit array as [M N P Mg Ng] = [2 2 2 1 1], representing 1 panel (Mg=1, Ng=1) with a 2-by-2 antenna array (M=2, N=2) and P=2 polarization angles. Configure the receive antenna array as [M N P Mg Ng] = [1 1 2 1 1], representing a single pair of cross-polarized co-located antennas.

cdl.TransmitAntennaArray.Size = [2 2 2 1 1];
cdl.ReceiveAntennaArray.Size = [1 1 2 1 1];

Create a random waveform of 1 subframe duration with 8 antennas.

SR = 15.36e6;
T = SR * 1e-3;
cdl.SampleRate = SR;
cdlinfo = info(cdl);
Nt = cdlinfo.NumTransmitAntennas;
 
txWaveform = complex(randn(T,Nt),randn(T,Nt));

Transmit the input waveform through the channel.

rxWaveform = cdl(txWaveform);

Plot channel output and path gain snapshots for various sample density values while using an nrCDLChannel System object.

Configure a channel with delay profile CDL-B from TR 38.901 Section 7.7.1. Set the maximum Doppler shift to 300 Hz and the channel sampling rate to 10 kHz.

cdl = nrCDLChannel;
cdl.DelayProfile = 'CDL-B';
cdl.MaximumDopplerShift = 300.0;
cdl.SampleRate = 10e3;
cdl.Seed = 19;

Configure transmit and receive antenna arrays for single-input/single-output (SISO) operation.

cdl.TransmitAntennaArray.Size = [1 1 1 1 1];
cdl.ReceiveAntennaArray.Size = [1 1 1 1 1];

Create an input waveform with a length of 40 samples.

T = 40; 
in = ones(T,1);

Plot the step response of the channel (displayed as lines) and the corresponding path gain snapshots (displayed circles) for various values of the SampleDensity property. The sample density property controls how often the channel snapshots are taken relative to the Doppler frequency.

  • When SampleDensity = Inf, a channel snapshot is taken for every input sample.

  • When SampleDensity = X, a channel snapshot is taken at a rate of Fcs = 2*X*MaximumDopplerShift.

The nrCDLChannel object applies the channel snapshots to the input waveform by means of zero-order hold interpolation. The object takes an extra snapshot beyond the end of the input. Some of the final output samples use this extra value to minimize the interpolation error. The channel output contains a transient (and a delay) due to the filters that implement the path delays.

s = [Inf 5 2]; % sample densities

legends = {};
figure; hold on;
SR = cdl.SampleRate;
for i = 1:length(s)
    
    % call channel with chosen sample density
    release(cdl); cdl.SampleDensity = s(i);
    [out,pathgains,sampletimes] = cdl(in);
    chInfo = info(cdl); tau = chInfo.ChannelFilterDelay;
    
    % plot channel output against time
    t = cdl.InitialTime + ((0:(T-1)) - tau).' / SR;
    h = plot(t,abs(out),'o-'); h.MarkerSize = 2; h.LineWidth = 1.5;
    desc = ['Sample Density=' num2str(s(i))];
    legends = [legends ['Output, ' desc]];
    disp([desc ', Ncs=' num2str(length(sampletimes))]);
    
    % plot path gains against sample times
    h2 = plot(sampletimes-tau/SR,abs(sum(pathgains,2)),'o');
    h2.Color = h.Color; h2.MarkerFaceColor = h.Color;
    legends = [legends ['path gains, ' desc]];    
end
Sample Density=Inf, Ncs=40
Sample Density=5, Ncs=13
Sample Density=2, Ncs=6
xlabel('Time (s)');
title('Channel Output and Path Gains versus Sample Density');
ylabel('Channel Magnitude');
legend(legends,'Location','NorthWest');

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.

Extended Capabilities

Introduced in R2018b