Single-tap equalization of the demodulated OFDM symbols.
function [ x, B ] = OFDM_EqualizerSingleTap( z, C, criterion, Para )
function [ x, B ] = OFDM_EqualizerSingleTap( z, C, criterion, Para, B )
The function works for MIMO and SISO systems.
Input arguments:
z: demodulated OFDM symbols. Size: matrix [Para.nSubcarriers, Ns] if
Para.N_R == 1, multidimensional array [Para.N_R, Para.nSubcarriers, Ns]
if Para.N_R > 1.
C: channel impulse response. Multidimensional array [Para.N_R, Para.N_T, ~].
criterion: determines the criterion to use. Several
options are possible:
'ZF': zero forcing. Error if Para.N_R < Para.N_T.
'MMSE': minimum mean squared error. Error if Para.N_R < Para.N_T.
'MF': matched filter. Error if Para.N_R < Para.N_T.
'specific': the specific equalizing matrices given in the
function argument B should be provided and will be used for equalization.
Argument C is not regarded.
Para: structure containing the modulation parameters.
B: the equalizing matrices at each subcarrier should be provided if
'specific' equalizer type is chosen. If not chosen, the matrix B is
disregarded. Size: vector [Para.nSubcarriers ,1] if Para.N_T == 1 and multi-
dimensional array [Para.S, Para.N_R, Para.nSubcarriers] otherwise.
Ouput arguments:
x: equalized symbols. Size: matrix [Para.nSubcarriers, Ns] if Para.S == 1,
multidimensional array [para.S, Para.nSubcarriers, Ns] if Para.S > 1.
B: equalizing matrices used at each subcarrier. Size: vector
[Para.nSubcarriers ,1] if Para.N_T == 1 and multidimensional array [Para.S,
Para.N_R, Para.nSubcarriers] otherwise.0001 function [ x, B ] = OFDM_EqualizerSingleTap( z, C, criterion, Para, B ) 0002 % Single-tap equalization of the demodulated OFDM symbols. 0003 % 0004 % function [ x, B ] = OFDM_EqualizerSingleTap( z, C, criterion, Para ) 0005 % function [ x, B ] = OFDM_EqualizerSingleTap( z, C, criterion, Para, B ) 0006 % 0007 % The function works for MIMO and SISO systems. 0008 % 0009 % Input arguments: 0010 % 0011 % z: demodulated OFDM symbols. Size: matrix [Para.nSubcarriers, Ns] if 0012 % Para.N_R == 1, multidimensional array [Para.N_R, Para.nSubcarriers, Ns] 0013 % if Para.N_R > 1. 0014 % 0015 % C: channel impulse response. Multidimensional array [Para.N_R, Para.N_T, ~]. 0016 % 0017 % criterion: determines the criterion to use. Several 0018 % options are possible: 0019 % 'ZF': zero forcing. Error if Para.N_R < Para.N_T. 0020 % 0021 % 'MMSE': minimum mean squared error. Error if Para.N_R < Para.N_T. 0022 % 0023 % 'MF': matched filter. Error if Para.N_R < Para.N_T. 0024 % 0025 % 'specific': the specific equalizing matrices given in the 0026 % function argument B should be provided and will be used for equalization. 0027 % Argument C is not regarded. 0028 % 0029 % Para: structure containing the modulation parameters. 0030 % 0031 % B: the equalizing matrices at each subcarrier should be provided if 0032 % 'specific' equalizer type is chosen. If not chosen, the matrix B is 0033 % disregarded. Size: vector [Para.nSubcarriers ,1] if Para.N_T == 1 and multi- 0034 % dimensional array [Para.S, Para.N_R, Para.nSubcarriers] otherwise. 0035 % 0036 % Ouput arguments: 0037 % 0038 % x: equalized symbols. Size: matrix [Para.nSubcarriers, Ns] if Para.S == 1, 0039 % multidimensional array [para.S, Para.nSubcarriers, Ns] if Para.S > 1. 0040 % 0041 % B: equalizing matrices used at each subcarrier. Size: vector 0042 % [Para.nSubcarriers ,1] if Para.N_T == 1 and multidimensional array [Para.S, 0043 % Para.N_R, Para.nSubcarriers] otherwise. 0044 % 0045 0046 0047 % This file is part of WaveComBox: www.wavecombox.com and is distributed under the terms of the MIT license. See accompanying LICENSE file. 0048 % Original author: François Rottenberg, May 1, 2018. 0049 % Contributors: 0050 % Change log: 0051 0052 if Para.N_R==1 0053 Ns=length(z(1,:)); 0054 else 0055 Ns=length(z(1,1,:)); 0056 end 0057 0058 if Para.N_R==1 && Para.N_T==1 0059 H=fft(C,Para.nSubcarriers); 0060 x=zeros(Para.nSubcarriers,Ns); 0061 switch criterion 0062 case 'ZF' 0063 B=1./H; 0064 case 'MMSE' 0065 % Noise power 0066 Es_N0=10.^(Para.Es_N0_dB/10); 0067 B=conj(H)./(abs(H).^2+1/Es_N0); 0068 case 'MF' 0069 B=1./H; 0070 case 'Specific' 0071 if exist('B','var')==0 0072 error('Argument missing "B" for equalizer type "Specific"') 0073 end 0074 otherwise 0075 error('Equalizer type not existing') 0076 end 0077 for m=Para.ActiveSubcarriers 0078 x(m,:)=B(m).*z(m,:); 0079 end 0080 else 0081 H=zeros(Para.N_R,Para.N_T,Para.nSubcarriers); 0082 for index_N_R=1:Para.N_R 0083 for index_N_T=1:Para.N_T 0084 H(index_N_R,index_N_T,:)=fft(squeeze(C(index_N_R,index_N_T,:)),Para.nSubcarriers).'; 0085 end 0086 end 0087 x=zeros(Para.S,Para.nSubcarriers,Ns); 0088 switch criterion 0089 case 'ZF' 0090 if Para.N_T>Para.N_R 0091 error('Error: N_T>N_R') 0092 end 0093 B=zeros(Para.S, Para.N_R, Para.nSubcarriers); 0094 for m=Para.ActiveSubcarriers 0095 H_m=H(:,:,m); 0096 B(:,:,m)=(H_m'*H_m)\H(:,:,m)'; 0097 for l=1:Ns 0098 x(:,m,l)=B(:,:,m)*z(:,m,l); 0099 end 0100 end 0101 case 'MMSE' 0102 if Para.N_T>Para.N_R 0103 error('Error: N_T>N_R') 0104 end 0105 B=zeros(Para.S, Para.N_R, Para.nSubcarriers); 0106 for m=Para.ActiveSubcarriers 0107 % Noise power 0108 Es_N0=10.^(Para.Es_N0_dB/10); 0109 H_m=H(:,:,m); 0110 B(:,:,m)=eye(Para.N_T,Para.N_T)/(H_m'*H_m+1/Es_N0*Para.N_T*eye(Para.N_T,Para.N_T))*H_m'; 0111 for l=1:Ns 0112 x(:,m,l)=B(:,:,m)*z(:,m,l); 0113 end 0114 end 0115 case 'MF' 0116 if Para.N_T>Para.N_R 0117 error('Error: N_T>N_R') 0118 end 0119 B=zeros(Para.S, Para.N_R, Para.nSubcarriers); 0120 for m=Para.ActiveSubcarriers 0121 H_m=H(:,:,m); 0122 B(:,:,m)= (diag(diag(H_m'*H_m)))\H_m'; 0123 for l=1:Ns 0124 x(:,m,l)=B(:,:,m)*z(:,m,l); 0125 end 0126 end 0127 case 'Specific' 0128 if exist('B','var')==0 0129 error('Argument missing "B" for equalizer type "Specific"') 0130 end 0131 if Para.N_R==1 0132 for m=Para.ActiveSubcarriers 0133 for l=1:Ns 0134 x(:,m,l)=B(:,:,m)*z(m,l); 0135 end 0136 end 0137 else 0138 for m=Para.ActiveSubcarriers 0139 for l=1:Ns 0140 x(:,m,l)=B(:,:,m)*z(:,m,l); 0141 end 0142 end 0143 end 0144 otherwise 0145 error('Equalizer type not existing') 0146 end 0147 if Para.S==1 0148 x=squeeze(x); 0149 end 0150 end 0151 end 0152