MIMO Channel

Filter input signal through MIMO multipath fading channel

Library

Channels

Description

The MIMO Channel block filters an input signal using a multiple-input multiple-output (MIMO) multipath fading channel.

This block accepts up to four input ports. When you set the Antenna selection parameter to Tx, there is one additional input port. When you set the Antenna selection parameter to Rx, there is one additional input port. When you set the Antenna selection parameter to Tx and Rx, there are two additional input ports. Independent of the input ports resulting from the antenna selection parameters, when you set the Technique for generating fading samples parameter to Sum of sinusoids and the Initial time source parameter to Input port, an additional input port is created. When you check the Output channel path gains check box, there is an additional output port for the channel path gains of the underlying fading process.

The fading processing per link is described in Methodology for Simulating Multipath Fading Channels section and assumes the same parameters for all links of the MIMO channel.

Signal Dimensions

Antenna Selection ParameterSignal InputTransmit Selection InputReceive Selection InputSignal OutputOptional Channel Gain Output
OffNs-by-NtN/AN/ANs-by-NrNs-by-Np-by-Nt-by-Nr
TxNs-by-Nst1-by-NtN/ANs-by-NrNs-by-Np-by-Nt-by-Nr
RxNs-by-NtN/A1-by-NrNs-by-NsrNs-by-Np-by-Nt-by-Nr
Tx and RxNs-by-Nst1-by-Nt1-by-NrNs-by-NsrNs-by-Np-by-Nt-by-Nr

where

  • Ns represents the number of samples

  • Nt represents the number of transmit antennas determined by the Transmit spatial correlation or Number of transmit antennas

  • Nr represents the number of receive antennas determined by the Receive spatial correlation or Number of receive antennas

  • Np represents the number of paths determined by the Discrete path delays or Average path gains

  • Nst represents the number of selected transmit antennas determined by the number of ones in the Transmit Selection Input

  • Nrt represents the number of selected receive antennas determined by the number of ones in the Receive Selection Input

Dialog Box

Sample rate

Specify the sample rate of the input signal in hertz as a double-precision, real, positive scalar. The default value of this parameter is 1 Hz. To match the model settings, set the value of this parameter so it equals number of rows of the signal input divided by the model sample time.

Discrete path delays

Specify the delays of the discrete paths in seconds as a double-precision, real, scalar or row vector. The default value of this parameter is 0. When you set Discrete path delays to a scalar, the MIMO channel is frequency flat. When you set Discrete path delays to a vector, the MIMO channel is frequency selective.

Average path gains

Specify the average gains of the discrete paths in decibels as a double-precision, real, scalar or row vector. The default value of this parameter is 0. Average path gains must have the same size as Discrete path delays.

Normalize average path gains to 0 dB

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

Fading distribution

Specify the fading distribution of the channel as Rayleigh or Rician. The default selection is Rayleigh.

K-factors

Specify the K factor of a Rician fading channel. This parameter accepts a double-precision, real, positive scalar or nonnegative, non-zero row vector with the same length as Discrete path delays. The default value of this parameter is 3. This parameter applies when you set Fading distribution to Rician.

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 a zero-valued element of the K-factors vector is a Rayleigh fading process.

LOS path Doppler shifts

Specify the Doppler shift(s) for the line-of-sight component(s) of the Rician fading channel in hertz. This parameter accepts a double-precision, real scalar or row vector. This parameter appears when you set Fading distribution to Rician. The default value of this parameter is 0. This parameter must have the same size as K-factors.

If you set LOS path Doppler shift 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 shift to a row vector, the discrete path that is a Rician fading process indicated by a positive element of the K-factors vector has its line-of-sight component Doppler shift specified by the corresponding element of LOS path Doppler shift.

LOS path initial phases

Specify the initial phase(s) of the line-of-sight component(s) of a Rician fading channel in radians. This parameter accepts a double-precision, real scalar or row vector. This parameter appears when you set Fading distribution to Rician. The default value of this parameter is 0.

LOS path initial phase must have the same size as K-factors.

If you set LOS path initial phase 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 phase to a row vector, the discrete path that is a Rician fading process indicated by a positive element of the K-factors vector has its line-of-sight component initial phase specified by the corresponding element of LOS path initial phase.

Maximum Doppler shift

Specify the maximum Doppler shift for all channel paths in hertz as a double-precision, real, nonnegative scalar. The default value of this parameter is 0.001 Hz.

The Doppler shift applies to all the paths of the channel. When you set this parameter to 0, the channel remains static for the entire input.

For a Doppler spectrum type other than Gaussian and bi-Gaussian, the value of fc is 1. For these two Doppler spectrum types, fc is dependent on the Doppler spectrum structure fields. See the algorithm section for comm.MIMOChannel for more details on how the cutoff frequency is defined.

Doppler spectrum

Specify the Doppler spectrum shape for all channel paths as a single Doppler spectrum structure returned from the doppler function, or a 1-by-N cell array of such structures. The default value of this parameter is Jakes Doppler spectrum. This parameter applies when Maximum Doppler shift is greater than zero.

If you assign a single Doppler spectrum structure, all paths have the same specified Doppler spectrum. If the Technique for generating fading samples parameter is set to Sum of sinusoids, Doppler spectrum must be doppler('Jakes'); otherwise, select from the following:

  • doppler('Jakes')

  • doppler('Flat')

  • doppler('Rounded', ...)

  • doppler('Bell', ...)

  • doppler('Asymmetric Jakes', ...)

  • doppler('Restricted Jakes', ...)

  • doppler('Gaussian', ...)

  • doppler('BiGaussian', ...)

You can assign a 1-by-N cell array of Doppler spectrum structures, chosen from any items in the previous list. Each path has the Doppler spectrum specified by the corresponding Doppler spectrum structure in the array. In this case, the length of the cell array must be equal to the length of Discrete path delays.

If you run a model that contains this block in any mode except normal mode or you set Simulate using of this block to Code generation, you must specify Doppler spectrum to a single Doppler spectrum structure across different paths.

Spatially correlated antennas

Select this check box to specify the transmit and receive spatial correlation matrices from which the number of transmit and receive antennas can be derived.

Clear this check box to specify the number of transmit and receive antennas using block parameters. In this case, the transmit and receive spatial correlation matrices are both identity matrices.

Number of transmit antennas

Specify the number of transmit antennas. You can specify up to eight antennas. This parameter appears when you clear the Spatially correlated antennas check box.

Number of receive antennas

Specify the number of receive antennas. You can specify up to eight antennas. This parameter appears when you clear the Spatially correlated antennas check box.

Transmit spatial correlation

Specify the spatial correlation of the transmitter as a double-precision, real or complex, 2D matrix or 3D array. This parameter only appears when you select the Spatially correlated antennas check box. The default value of this parameter is [1 0;0 1].

The first dimension determines the number of transmit antennas, Nt, that must be between 1 and 8, inclusive. If the channel is frequency-flat, i.e., Discrete path delays is a scalar, Transmit spatial correlation is a 2D Hermitian matrix of size Nt–by–Nt. The main diagonal elements must be all ones, while the off-diagonal elements must be real or complex numbers with a magnitude smaller than or equal to one. If the channel is frequency-selective, i.e., Discrete path delays is a row vector of length Np. You can specify Transmit spatial correlation as a 2D matrix, in which case each path has the same transmit spatial correlation matrix. Alternatively, it can be specified as a 3D array of size Nt–by–Nt–by–Np, in which case each path can have its own different transmit spatial correlation matrix.

Receive spatial correlation

Specify the spatial correlation of the receiver as a double-precision, real or complex, 2D matrix or 3D array. This parameter only appears when you select the Spatially correlated antennas check box. The default value of this parameter is [1 0;0 1].

The first dimension determines the number of receive antennas, Nr, that must be between 1 and 8, inclusive. If the channel is frequency-flat, i.e., Discrete path delays is a scalar, Receive spatial correlation is a 2D Hermitian matrix of size Nr–by–Nr. The main diagonal elements must be all ones, while the off-diagonal elements must be real or complex numbers with a magnitude smaller than or equal to one. If the channel is frequency-selective, i.e., Discrete path delays is a row vector of length Np, you can specify Receive spatial correlation as a 2D matrix, in which case each path has the same receive spatial correlation matrix. Alternatively, you can specify Receive spatial correlation as a 3-D array of size Nr–by–Nr–by–Np, in which case each path can have its own different receive spatial correlation matrix.

Antenna selection

Define the antenna selection mode as one of Off, Tx, Rx, or Tx and Rx. The default selection is Off.

Antenna SelectedInput Ports Added
OffNone
TxTx Sel
RxRx Sel
Tx and RxTx Sel, Rx Sel

Normalize outputs by number of receive antennas

Select this check box to normalize the channel outputs by the number of receive antennas.

Technique for generating fading samples

Specify the channel modeling technique as either Filtered Gaussian noise or Sum of sinusoids . The default selection is Filtered Gaussian noise.

Number of sinusoids

Specify the number of oscillators used in modeling the fading process as a positive integer. This parameter is available when Technique for generating fading samples is set to Sum of sinusoids. The default value is 48.

Initial time source

Specify the source of the fading model's initial time offset as either Property or Input port. This parameter is available when Technique for generating fading samples is set to Sum of sinusoids. The default selection is Property.

Initial Time (s)

Specify the time at which the fading process begins as a real, non-negative scalar measured in seconds. This parameter is available when Technique for generating fading samples is set to Sum of sinusoids and Initial time source is set to Property. The default value is 0.

Initial seed

Specify the initial seed of the random number generator for this block as a double-precision, real, nonnegative integer scalar. The default setting for this parameter is 73.

Output channel path gains

Select this check box to output the channel path gains of the underlying fading process using a secondary block output port.

Simulation using

Select either Code generation or Interpreted execution. The default selection is Interpreted execution.

If you run a model that contains this block in any mode except normal mode or you set Simulate using to Code generation, you must specify Doppler spectrum to a single Doppler spectrum structure across different paths.

Channel visualization

Select among Off | Impulse response | Frequency response | Doppler spectrum | Impulse and frequency responses to set the channel visualization option. Visualization is available only when the Technique for generating fading samples parameter is set to Filtered Gaussian noise. The default selection is Off.

Antenna pair to display

Select the transmit-receive antenna pair to display. This parameter is available when Channel visualization is not Off. The default value is [1, 1].

Percentage of samples to display

Select the percentage of samples to display from among 10% | 25% | 50% | 100%. Increasing the percentage improves display accuracy at the expense of simulation speed. This selection is available when Channel visualization is set to Impulse response, Frequency response, or Impulse and frequency responses. The default value is 25%.

Path for Doppler spectrum display

Select the path for which the Doppler spectrum is displayed. The path number is a positive integer scalar with maximum value equal to the number of discrete paths. The default value is 1.

Supported Data Type

PortSupported Data Types
Signal input
  • Double

Optional transmit selection input
  • Binary integer

Optional receive selection input
  • Binary integer

Signal output
  • Double

Optional path gain output
  • Double

Selected Bibliography

[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.

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