SISO Fading Channel

Filter input signal through SISO multipath fading channel

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Libraries:
Communications Toolbox / Channels

Description

The SISO Fading Channel block filters an input signal using a single-input/single-output (SISO) multipath fading channel. This block models both Rayleigh and Rician fading. For processing details, see the Algorithms section.

Examples

Multipath Fading Channel in Simulink

Simulate multipath Rayleigh and Rician fading channels by using the SISO Fading Channel block.

Open Script

Ports

Input

in — Input data signal

vector

Input data signal, specified as an N_S-by-1 vector. N_S represents the number of samples in the input signal.

Data Types: double | single
Complex Number Support: Yes

Output

Out1 — Output data signal for fading channel

vector

Output data signal for the fading channel, returned as an N_S-by-1 vector. N_S represents the number of samples in the input signal.

Gain — Discrete path gains

matrix

Discrete path gains of the underlying fading process, returned as an N_S-by-N_P matrix.

• N_S represents the number of samples in the input signal.

• N_P represents the number of channel paths.

Dependencies

To enable this port, on the Main tab, select Output channel path gains.

Delay — Channel filter delay

scalar

Channel filter delay, returned as a scalar.

Dependencies

To enable this port, on the Main tab, select Output channel filter delay.

Parameters

Main Tab

Multipath parameters (frequency selectivity)

Inherit sample rate from input — Option to inherit the sample rate from input

on (default) | off

Select this parameter to use the sample rate of the input signal when processing. When Inherit sample rate from input is selected, the sample rate is N_S/T_S, where N_S is the number of input samples, and T_S is the model sample time.

Sample rate (Hz) — Input signal sample rate

1 (default) | positive scalar

Input signal sample rate in hertz, specified as a positive scalar. To match the model settings, set the sample rate to N_S/T_S, where N_S is the number of input samples, and T_S is the model sample time.

Dependencies

This parameter appears when Inherit sample rate from input is not selected.

Discrete path delays (s) — Delays for each discrete path

0 (default) | nonnegative scalar | row vector

Delays for each discrete path in seconds, specified as a nonnegative scalar or row vector.

• When you set Discrete path delays (s) to a scalar, the SISO channel is frequency flat.

• When you set Discrete path delays (s) to a vector, the SISO channel is frequency selective.

Average path gains (dB) — Average gain for each discrete path

0 (default) | scalar | row vector

Average gain for each discrete path in decibels, specified as a scalar or row vector. Average path gains (dB) must have the same size as Discrete path delays (s).

Normalize average path gains to 0 dB — Option to normalize average path gains to 0 dB

on (default) | off

Select this parameter to normalize the fading processes so that the total power of the path gains, averaged over time, is 0 dB.

Fading distribution — Fading distribution of channel

Rayleigh (default) | Rician

Select the fading distribution of the channel, either Rayleigh or Rician.

K-factors — K-factor of Rician fading channel

3 (default) | positive scalar | row vector of nonnegative values

K-factor of a Rician fading channel, specified as a positive scalar or a 1-by-N_P vector of nonnegative values. N_P equals the value of the Discrete path delays (s) parameter.

• If you set K-factors to a scalar, the first discrete path is a Rician fading process with a Rician K-factor of K-factors. Any remaining discrete paths are independent Rayleigh fading processes.

• If you set K-factors to a row vector, the discrete path corresponding to a positive element of the K-factors vector is a Rician fading process with a Rician K-factor specified by that element. The discrete path corresponding to any zero-valued elements of the K-factors vector are Rayleigh fading processes. At least one element value must be nonzero.

Dependencies

This parameter appears when Fading distribution is Rician.

LOS path Doppler shifts (Hz) — Doppler shifts for line-of-sight components

0 (default) | scalar | row vector

Doppler shifts for the line-of-sight components of the Rician fading channel in hertz, specified as a scalar or row vector. This parameter must have the same size as K-factors.

• If you set LOS path Doppler shifts (Hz) to a scalar, it represents the line-of-sight component Doppler shift of the first discrete path that is a Rician fading process.

• If you set LOS path Doppler shifts (Hz) to a row vector, the discrete path that is a Rician fading process has its line-of-sight component Doppler shift specified by the elements of LOS path Doppler shifts (Hz) that correspond to positive elements in the K-factors vector.

Dependencies

This parameter appears when Fading distribution is Rician.

LOS path initial phases (rad) — Initial phases for line-of-sight components

0 (default) | scalar | row vector

Initial phases for the line-of-sight component of the Rician fading channel in radians, specified as a scalar or row vector. This parameter must have the same size as K-factors.

• If you set LOS path initial phases (rad) to a scalar, it is the line-of-sight component initial phase of the first discrete path that is a Rician fading process.

• If you set LOS path initial phases (rad) to a row vector, the discrete path that is a Rician fading process has its line-of-sight component initial phase specified by the elements of LOS path initial phases (rad) that correspond to positive elements in the K-factors vector.

Dependencies

This parameter appears when Fading distribution is Rician.

Doppler parameters (time dispersion)

Maximum Doppler shift (Hz) — Maximum Doppler shift for all channel paths

0.001 (default) | nonnegative scalar

Maximum Doppler shift for all channel paths in hertz, specified as a nonnegative scalar.

Maximum Doppler shift (Hz) must be smaller than (f_s/10)/f_c for each path. f_s is the sampling rate at the input to the SISO Fading Channel block. f_c is the cutoff frequency factor of the path. For more information, see Cutoff Frequency Factor.

Doppler spectrum — Doppler spectrum shape for all channel paths

doppler('Jakes') (default) | doppler('Flat') | doppler('Rounded', ...) | doppler('Bell', ...) | doppler('Asymmetric Jakes', ...) | doppler('Restricted Jakes', ...) | doppler('Gaussian', ...) | doppler('BiGaussian', ...)

Doppler spectrum shape for all channel paths, specified as a single Doppler spectrum structure returned from the doppler function or a 1-by-N_P cell array of such structures. The default value of this parameter is the Jakes Doppler spectrum (doppler('Jakes')).

• If you assign a single call to doppler, all paths have the same specified Doppler spectrum.

• If you assign a 1-by-N_P cell array of calls to doppler using any of the specified syntaxes, each path has the Doppler spectrum specified by the corresponding Doppler spectrum structure in the array. In this case, N_P equals the value of the Discrete path delays (s) parameter.

Dependencies

This parameter applies when Maximum Doppler shift (Hz) is greater than zero.

Other parameters

Initial seed — Random number generator initial seed

73 (default) | nonnegative integer

Random number generator initial seed for this block, specified as a nonnegative integer.

Output channel path gains — Option to output channel path gains

off (default) | on

Select this parameter to add the Gain output port to the block and output the channel path gains of the underlying fading process.

Output channel filter delay — Option to output channel filter delay

off (default) | on

Select this parameter to add the Delay output port to the block and output the channel filter delay of the underlying fading process.

Simulate using — Compilation type

Interpreted execution (default) | Code generation

Compilation type, specified as Interpreted execution or Code generation.

• Interpreted execution — Simulate model using the MATLAB^® interpreter. This option shortens startup time but has slower simulation speed than Code generation.

• Code generation — Simulate model using generated C code. The first time you run a simulation, Simulink^® generates C code for the block. The C code is reused for subsequent simulations, as long as the model does not change. This option requires additional startup time but provides faster simulation speed than Interpreted execution.

Visualization Tab

Channel visualization — Select the channel visualization

Off (default) | Impulse response | Frequency response | Doppler spectrum | Impulse and frequency responses

Select the channel visualization: Off, Impulse response, Frequency response, Doppler spectrum, or Impulse and frequency responses. When visualization is on, the selected channel characteristics, such as impulse response or Doppler spectrum, display in a separate window. For more information, see Channel Visualization.

Percentage of samples to display — Percentage of samples to display

25% (default) | 10% | 50% | 100%

Select the percentage of samples to display: 10%, 25%, 50%, or 100%. Increasing the percentage improves display accuracy at the expense of simulation speed.

Dependencies

This parameter appears when Channel visualization is Impulse response, Frequency response, or Impulse and frequency responses.

Path for Doppler spectrum display — Path for which Doppler spectrum is displayed

1 (default) | positive integer

Path for which the Doppler spectrum is displayed, specified as a positive integer from 1 to N_P, where N_P equals the value of the Discrete path delays (s) parameter.

Dependencies

This parameter appears when Channel visualization is Doppler spectrum.

Block Characteristics

Data Types	double | single
Multidimensional Signals	yes
Variable-Size Signals	yes

Algorithms

The fading process for the SISO channel is described in Methodology for Simulating Multipath Fading Channels.

Cutoff Frequency Factor

The cutoff frequency factor, f_c, is dependent on the type of Doppler spectrum.

• For any Doppler spectrum type other than Gaussian and bi-Gaussian, f_c equals 1.

• For a doppler('Gaussian') spectrum type, f_c equals NormalizedStandardDeviation$$\times \sqrt{2\log 2}$$.

• For a doppler('BiGaussian') spectrum type:

  • If the PowerGains(1) and NormalizedCenterFrequencies(2) field values are both 0, then f_c equals NormalizedStandardDeviation(1)$$\times \sqrt{2\log 2}$$.

  • If the PowerGains(2) and NormalizedCenterFrequencies(1) field values are both 0, then f_c equals NormalizedStandardDeviation(2)$$\times \sqrt{2\log 2}$$.

  • If the NormalizedCenterFrequencies field value is [0,0] and the NormalizedStandardDeviation field has two identical elements, then f_c equals NormalizedStandardDeviation(1)$$\times \sqrt{2\log 2}$$.

  • In all other cases, f_c equals 1.

References

[1] Oestges, C., and B. Clerckx. MIMO Wireless Communications: From Real-World Propagation to Space-Time Code Design. Academic Press, 2007.

[2] Correira, L. M. Mobile Broadband Multimedia Networks: Techniques, Models and Tools for 4G. Academic Press, 2006.

[3] 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 of Communications. Vol. 20, Number 6, 2002, pp. 1211–1226.

[4] Jeruchim, M., P. Balaban, and K. S. Shanmugan. Simulation of Communication Systems. Second Edition. New York: Kluwer Academic/Plenum, 2000.

[5] Pätzold, Matthias, Cheng-Xiang Wang, and Bjorn Olav Hogstand. "Two New Sum-of-Sinusoids-Based Methods for the Efficient Generation of Multiple Uncorrelated Rayleigh Fading Waveforms." IEEE Transactions on Wireless Communications. Vol. 8, Number 6, 2009, pp. 3122–3131.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2017b

R2022b: Updates to channel visualization display

The channel visualization feature now presents:

• Configuration settings in the bottom toolbar on the plot window.

• Plots side-by-side in one window when you select the Impulse and frequency response channel visualization option.