Channel_Desynchronization

 Simulates the impact of desynchronization.

 [ r_asynchr, Delta_omega, Delta_tau ] = Channel_Desynchronization( r, Para, Desynchronization_type )

 The function works for SISO and MIMO, time-invariant and time-invariant
 systems.

 Input arguments:

   s: transmit signal. Size: matrix [N_R, nFrameSamples]

   Para: structure containing the modulation parameters.

   DesynchronizationType: optional, type of synchronization error. 'CFO'
   (carrier frequency offset), 'STO' (symbol timing offset) and 'CFO_STO'
   (both effects). Set by default to 'CFO_STO'.

 Outputs arguments:

   r_asynchr: received signal impacted by synchronization errors. Size:
   matrix [N_R, nFrameSamples + Delta_tau]

   Delta_omega: CFO [angular frequency]

   Delta_tau: STO [sampling period]

0001 function [ r_asynchr, Delta_omega, Delta_tau ] = Channel_Desynchronization( r, Para, DesynchronizationType )
0002 % Simulates the impact of desynchronization.
0003 %
0004 % [ r_asynchr, Delta_omega, Delta_tau ] = Channel_Desynchronization( r, Para, Desynchronization_type )
0005 %
0006 % The function works for SISO and MIMO, time-invariant and time-invariant
0007 % systems.
0008 %
0009 % Input arguments:
0010 %
0011 %   s: transmit signal. Size: matrix [N_R, nFrameSamples]
0012 %
0013 %   Para: structure containing the modulation parameters.
0014 %
0015 %   DesynchronizationType: optional, type of synchronization error. 'CFO'
0016 %   (carrier frequency offset), 'STO' (symbol timing offset) and 'CFO_STO'
0017 %   (both effects). Set by default to 'CFO_STO'.
0018 %
0019 % Outputs arguments:
0020 %
0021 %   r_asynchr: received signal impacted by synchronization errors. Size:
0022 %   matrix [N_R, nFrameSamples + Delta_tau]
0023 %
0024 %   Delta_omega: CFO [angular frequency]
0025 %
0026 %   Delta_tau: STO [sampling period]
0027 %
0028 
0029 
0030 % This file is part of WaveComBox: www.wavecombox.com and is distributed under
0031 % the terms of the MIT license. See accompanying LICENSE file.
0032 % Original author: François Rottenberg, May 3, 2018.
0033 % Contributors:
0034 % Change log:
0035 
0036 [N_R, nFrameSamples]=size(r);
0037 r_asynchr=zeros(N_R,nFrameSamples);
0038 
0039 if exist('DesynchronizationType','var')==0
0040     DesynchronizationType='CFO_STO';
0041 end
0042 
0043 switch DesynchronizationType
0044     case 'CFO'
0045         % CFO
0046         epsilon=0.8*(rand-0.5);
0047         Delta_omega=2*pi*1/Para.T*epsilon;
0048         for index=1:N_R
0049             r_asynchr(index,:)=r(index,:).*exp(1j*Delta_omega*(0:nFrameSamples-1)*Para.T/Para.nSubcarriers);
0050         end
0051         Delta_tau=0;
0052     case 'STO'
0053         % STO
0054         Delta_tau=randi(Para.nSubcarriers*2);
0055         r_asynchr=[zeros(Para.N_R, Delta_tau) r];
0056         Delta_omega=0;
0057     case 'CFO_STO'
0058         % CFO
0059         epsilon=0.8*(rand-0.5);
0060         Delta_omega=2*pi*1/Para.T*epsilon;
0061         for index=1:N_R
0062             r_asynchr(index,:)=r(index,:).*exp(1j*Delta_omega*(0:nFrameSamples-1)*Para.T/Para.nSubcarriers);
0063         end
0064         % STO
0065         Delta_tau=randi(Para.nSubcarriers*2);
0066         r_asynchr=[zeros(Para.N_R, Delta_tau) r_asynchr];
0067     otherwise
0068         error('Desynchronization type not defined')
0069 end
0070 
0071 end
0072