Filter input signal through a Rician fading channel
The RicianChannel System object™ filters an input signal through a Rician multipath fading channel. The fading processing per link is described in Methodology for Simulating Multipath Fading Channels.
To filter an input signal using a Rician multipath fading channel:
H = comm.RicianChannel creates a frequency-selective or frequency-flat multipath Rician fading channel System object, H. This object filters a real or complex input signal through the multipath channel to obtain the channel impaired signal.
H = comm.RicianChannel(Name,Value) creates a multipath Rician fading channel object, H, with the specified property Name set to the specified Value. You can specify additional name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).
Input signal sample rate (Hertz)
Specify the sample rate of the input signal in hertz as a double-precision, real, positive scalar. The default value of this property is 1 Hz.
Discrete path delay vector (seconds)
Specify the delays of the discrete paths in seconds as a double-precision, real, scalar or row vector. The default value of this property is 0.
When you set PathDelays to a scalar, the channel is frequency flat.
When you set PathDelays to a vector, the channel is frequency selective.
Average path gain vector (decibels)
Specify the average gains of the discrete paths in decibels as a double-precision, real, scalar or row vector. The default value of this property is 0. AveragePathGains must have the same size as PathDelays.
Normalize average path gains to 0 dB
When you set this property to true, the object normalizes the fading processes so that the total power of the path gains, averaged over time, is 0dB. The default value of this property is true.
Rician K-factor scalar or vector (linear scale)
Specify the K-factor of a Rician fading channel as a double-precision, real, positive scalar or nonnegative, nonzero row vector of the same length as PathDelays. The default value of this property is 3.
If KFactor is a scalar, then the first discrete path is a Rician fading process with a Rician K-factor of KFactor. The remaining discrete paths are independent Rayleigh fading processes. If KFactor is a row vector, the discrete path corresponding to a positive element of the KFactor 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 KFactor vector is a Rayleigh fading process.
Doppler shift(s) of line-of-sight component(s) (Hertz)
Specify the Doppler shifts for the line-of-sight components of a Rician fading channel in hertz as a double-precision, real scalar or row vector. The default value of this property is 0.
DirectPathDopplerShift must have the same size as KFactor. If DirectPathDopplerShift is a scalar, this value represents the line-of-sight component Doppler shift of the first discrete path. This path exhibits a Rician fading process. If DirectPathDopplerShift is a row vector, the discrete path corresponding to a positive element of the KFactor vector is a Rician fading process. Its line-of-sight component Doppler shift is specified by the corresponding element of DirectPathDopplerShift.
Initial phase(s) of line-of-sight component(s) (radians)
Specify the initial phase(s) of the line-of-sight components of a Rician fading channel in radians as a double-precision, real scalar or row vector. The default value of this property is 0.
DirectPathInitialPhase must have the same size as KFactor. If DirectPathInitialPhase is a scalar, this value represents the line-of-sight component initial phase of the first discrete path. This path exhibits a Rician fading process. If DirectPathInitialPhase is a row vector, the discrete path corresponding to a positive element of the KFactor vector is a Rician fading process. Its line-of-sight component initial phase is specified by the corresponding element of DirectPathInitialPhase.
Maximum Doppler shift (Hertz)
Specify the maximum Doppler shift for all channel paths in hertz as a double-precision, real, nonnegative scalar. The default value of this property is 0.001 Hz.
The Doppler shift applies to all the paths of the channel. When you set the MaximumDopplerShift to 0, the channel remains static for the entire input. You can use the reset method to generate a new channel realization.
The MaximumDopplerShift must be smaller than SampleRate/10/fc for each path, where fc represents the cutoff frequency factor of the path. For a Doppler spectrum type other than Gaussian and bi-Gaussian, fc is 1. For Gaussian and bi-Gaussian Doppler spectrum types, fc is dependent on the Doppler spectrum object properties. Refer to the algorithm section of the comm.MIMOChannel for more details about how fc is defined.
Specify the Doppler spectrum shape for the path(s) of the channel. This property accepts a single Doppler spectrum structure returned from the doppler function or a row cell array of such structures. The maximum Doppler shift value necessary to specify the Doppler spectrum/spectra is given by the MaximumDopplerShift property. This property applies when the MaximumDopplerShift property value is greater than 0. The default value of this property is doppler('Jakes').
If you assign a single Doppler spectrum structure to DopplerSpectrum, all paths have the same specified Doppler spectrum. The possible Doppler spectrum structures are:
If you assign a row cell array of different Doppler spectrum structures (which can be chosen from any of those on the previous list) to DopplerSpectrum, each path has the Doppler spectrum specified by the corresponding structure in the cell array. In this case, the length of DopplerSpectrum must be equal to the length of PathDelays.
To generate C code, specify this property to a single Doppler spectrum structure.
Source of random number stream
Specify the source of random number stream as one of Global stream | mt19937ar with seed. The default value of this property is Global stream.
If you set RandomStream to Global stream, the current global random number stream is used for normally distributed random number generation. In this case, the reset method only resets the filters.
If you set RandomStream to mt19937ar with seed, the mt19937ar algorithm is used for normally distributed random number generation. In this case, the reset method not only resets the filters, but also reinitializes the random number stream to the value of the Seed property.
Initial seed of mt19937ar random number stream
Specify the initial seed of an mt19937ar random number generator algorithm as a double-precision, real, nonnegative integer scalar. The default value of this property is 73. This property applies when you set the RandomStream property to mt19937ar with seed. The Seed reinitializes the mt19937ar random number stream in the reset method.
Output channel path gains
Set this property to true to output the channel path gains of the underlying fading process. The default value of this property is false.
|clone||Create RicianChannel object with same property values|
|info||Characteristic information about Rician Channel|
|isLocked||Locked status for input attributes and nontunable properties|
|release||Allow property value and input characteristics changes|
|reset||Reset states of the RicianChannel object|
|step||Filter input signal through multipath Rician fading channel|
Produce repeatable outputs when a comm.RicianChannel System object uses the global stream for random number generation.
Create a PSK Modulator System object to modulate randomly generated data.
hMod = comm.PSKModulator; channelInput = step(hMod, randi([0 hMod.ModulationOrder-1],512,1));
Create a Rician channel System object.
hRicianChan = comm.RicianChannel(... 'SampleRate', 1e6,... 'PathDelays', [0.0 0.5 1.2]*1e-6,... 'AveragePathGains', [0.1 0.5 0.2],... 'KFactor', 2.8,... 'DirectPathDopplerShift', 5.0,... 'DirectPathInitialPhase', 0.5,... 'MaximumDopplerShift', 50,... 'DopplerSpectrum', doppler('Bell', 8),... 'PathGainsOutputPort', true);
Log current global stream state.
globalStream = RandStream.getGlobalStream; loggedState = globalStream.State;
Filter the modulated data using hRicianChan for the first time.
[RicianChanOut1, RicianPathGains1] = step(hRicianChan, channelInput);
Set global stream back to the logged state and reset hRicianChan.
globalStream.State = loggedState; reset(hRicianChan);
Filter the modulated data using hRicianChan for the second time.
[RicianChanOut2, RicianPathGains2] = step(hRicianChan, channelInput);
Verify channel and path gain outputs are the same for two step calls.
display(isequal(RicianChanOut1, RicianChanOut2)); display(isequal(RicianPathGains1, RicianPathGains2));
 Oestges, C., and B. Clerckx. MIMO Wireless Communications: From Real-World Propagation to Space-Time Code Design, Academic Press, 2007.
 Correira, L. M. Mobile Broadband Multimedia Networks: Techniques, Models and Tools for 4G, Academic Press, 2006.
 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.
 Jeruchim, M., P. Balaban, and K. S. Shanmugan. Simulation of Communication Systems, Second Edition, New York, Kluwer Academic/Plenum, 2000.