When I run this code to depict the performance of a DCO-OFDM system, I'm getting an error with the randi function. Can you help me fix it?

clc ;

clear all ;

close all ;

m =512; % Total number of OFDM symbols

N =1024; % Length of each OFDM symbol

M =4; % Size of the Constellation ( M can be 4 , 8 , 16 ,32 , 64 , 128 , 256)

Ncp =256 ; % Length of the Cyclic Prefix

%Tx = modem.qammod ('M',M ) ; % Choosing the modulation format as M - ary Quadrature Amplitude Modulation (M- QAM )

%Rx = modem.qamdemod ('M',M) ; % Fixing up the demodulation format at the receiving end as M - ary QAM ( Note : In order to simulate the code in MATLAB R2020a version , please remove Tx and Rx instantiation and assign DataMod as DataMod = qammod( Data , M);10 % DCO - OFDM Transmitter

Data = randi ([0 M -1] ,m , N ); % Generation of Random bits Matrix of size m by N

%DataMod = modulate ( Tx , Data ); % Performing Data Modulation , for MATLAB R2020a version , assign DataMod = qammod (Data , M);

DataMod = qammod( Data , M);

DataMod_serialtoparallel = DataMod .'; % Performing Serial to Parallel Conversion

datamat = DataMod_serialtoparallel ; % Assigning the total data to a variable called datamat % Computation of Hermitian Symmetry Criteria

datamat (1 ,:) =0; % Assigning the First subcarrier to Zero

datamat (513 ,:) =0; % Assigning the Middle Subcarrier to Zero

datamat (514:1024 ,:) = flipud ( conj ( datamat (2:512 ,:) ) ) ; % Illustrating that only half of the subcarriers are exploited for data transmission as the remaining half are flipped complex conjugate versions of the previous ones .

d_ifft = ifft (( datamat ) ) ; % Computation of IFFT operation

d_ifft_paralleltoserial = d_ifft .'; % Parallel to Serial Conversion

CP_part = d_ifft_paralleltoserial (: ,end - Ncp +1: end) ; % Addition of Cyclic Prefix

DCOOFDM_CP =[ CP_part d_ifft_paralleltoserial ]; %Transmissin of DCO - OFDM signal

bdc =7; %DC BIAS

clip = sqrt ((10.^( bdc /10) ) -1) ; % clipping factor k

bdcc = clip * sqrt ( DCOOFDM_CP .* DCOOFDM_CP ) ;%Computation of DC bias

DCOOFDM_BIAS = DCOOFDM_CP + bdcc ; % Addition of DC bias to the cyclic prefix added signal

count =0;

snr_vector =0:1:80; % size of signal to noise ratio (SNR ) vector

for snr = snr_vector

SNR = snr + 10* log10 ( log2 ( M ) ) ;

count = count +1 ;

DCOOFDM_with_chann = awgn ( DCOOFDM_BIAS , SNR ,'measured '); % Addition of AWGN

% Receiver of DCO - OFDM

DCOOFDM_with_chann1 = DCOOFDM_with_chann - bdcc ; %Removal of DC bias

DCOOFDM_removal_CP = DCOOFDM_with_chann1 (: , Ncp +1: N + Ncp ) ; % Removal of Cyclic Prefix

DCOOFDM_serialtoparallel = DCOOFDM_removal_CP .'; %Serial to Parallel Conversion

DCOOFDM_parallel_fft = fft ( DCOOFDM_serialtoparallel) ; % Computation of FFT operation

DCOOFDM_Demodulation = qamdemod (DCOOFDM_parallel_fft .', M );

[~ , s_e1(count)]= symerr ( Data (: ,2:512),DCOOFDM_Demodulation (: ,2:512)) ;

end

% %%%%% With 13 dB Bias

m =512; % Total number of OFDM symbols

N =1024; % Length of each OFDM symbol

M =4; % Size of the Constellation ( M can be 4 , 8 , 16 ,32 , 64 , 128 , 256)

Ncp =256 ; % Length of the Cyclic Prefix

%Tx = modem . qammod ('M',M ) ; % Choosing the modulation format as M - ary Quadrature Amplitude Modulation (M

%Rx = modem . qamdemod ('M',M) ; % Fixing up the demodulation format at the receiving end as M - ary QAM

% DCO - OFDM Transmitter

Data1 = randi ([0 M -1] , m ,N ) ; % Generation of Random bits Matrix of size m by N

%DataMod1 = modulate ( Tx , Data1 ) ; % Performing Data Modulation , for MATLAB R2020a version , assign DataMod1 = qammod ( Data1 , M) ;

DataMod1 = qammod ( Data1 , M) ;

DataMod_serialtoparallel1 = DataMod1 .'; % Performing Serial to Parallel Conversion

datamat1 = DataMod_serialtoparallel1 ; % Assigning the total data to a variable called datamat

% Computation of Hermitian Symmetry Criteria

datamat1 (1 ,:) =0; % Assigning the First subcarrier to Zero

datamat1 (513 ,:) =0; % Assigning the Middle Subcarrier to Zero

datamat1 (514:1024 ,:) = flipud ( conj ( datamat1 (2:512 ,:) ) );

% Illustrating that only half of the subcarriers are exploited for data transmission as the remaining half are flipped complex conjugate versions of the previous ones .

d_ifft1 = ifft (( datamat1 )) ; % Computation of IFFT operation

d_ifft_paralleltoserial1 = d_ifft1 .'; % Parallel to Serial Conversion

CP_part1 = d_ifft_paralleltoserial1 (: ,end - Ncp +1: end) ; %Addition of Cyclic Prefix

DCOOFDM_CP1 =[ CP_part1 d_ifft_paralleltoserial1 ]; %Transmissin of DCO - OFDM signal

bdc1 =13; %DC BIAS

clip1 = sqrt ((10.^( bdc1 /10) ) -1) ; % clipping factor k

bdcc1 = clip1 * sqrt ( DCOOFDM_CP1 .* DCOOFDM_CP1 ) ;%Computation of DC bias

DCOOFDM_BIAS1 = DCOOFDM_CP1 + bdcc1 ; % Addition of DC bias to the cyclic prefix added signal

count =0;

snr_vector =0:1:80; % size of signal to noise ratio (SNR ) vector

for snr = snr_vector

SNR = snr + 10* log10 ( log2 ( M ) ) ;

count = count +1 ;

DCOOFDM_with_channel = awgn ( DCOOFDM_BIAS1 , SNR ,'measured ' ) ; % Addition of AWGN

% Receiver of DCO - OFDM

DCOOFDM_with_chann2 = DCOOFDM_with_channel - bdcc1 ;%Removal of DC bias

DCOOFDM_removal_CP2 = DCOOFDM_with_chann2 (: , Ncp +1: N + Ncp ) ;

% Removal of Cyclic Prefix

DCOOFDM_serialtoparallel2 = DCOOFDM_removal_CP2 .';

% Serial to Parallel Conversion

DCOOFDM_parallel_fft2 = fft (DCOOFDM_serialtoparallel2 ) ; % Computation of FFT operation

DCOOFDM_Demodulation2 = qamdemod (DCOOFDM_parallel_fft2 .', M ) ;

[~ , s_e2(count) ]= symerr ( Data1 (: ,2:512) ,DCOOFDM_Demodulation2 (: ,2:512) ) ;

end

% Plotting the BER curves

semilogy ( snr_vector , s_e1 ,'rd -','LineWidth ' ,2) ;

hold on;

semilogy ( snr_vector , s_e2 ,'gd -','LineWidth ' ,2) ;

legend (3 , 'FFT - based DCO -OFDM -7 dB of Bias ', 'FFT - based DCO -OFDM -13 dB of Bias ') ;

axis ([0 30 10^ -4 1]) ;

xlabel ('SNR in dB ') ;

ylabel ('BER ') ;

grid on ;

The error is:

Error using randi

First input must be a positive scalar integer value IMAX, or two integer values [IMIN IMAX] with IMIN less than or equal to IMAX.

Error in DCOFDM (line 13)

Data = randi ([0 M -1] ,m , N ); % Generation of Random bits Matrix of size m by N

[Marwah]

Hi,

I have question and I appreciate it if you can answer it.

why you wrote this formula (clip1 = sqrt ((10.^( bdc1 /10) ) -1) ; % clipping factor k) for clipping?

Thanks

Answer 1

[Walter Roberson]

You have [0 M -1]. Spacing is important: what you wrote is equivalent to [0, M, -1]

You should use [0, M-1]

The important part is when you have space dash value then that means "negative of the value" not subtraction. M - 1 or M-1 work but inside [] or {} then M -1 is two distinct elements, M and negative one.

[Hanojhan Rajahrajasingh]

Thank you, the issue is fixed now.

[Shahir Nawaf]

until ther is an error

[Walter Roberson]

@Shahir Nawaf

The randi() problem occurred twice.

Also, twice calls to awgn() passed an option 'measured ' with a space at the end that should not have been there.

Also, twice calls to semilogy() passed an option 'LineWidth ' with a space at the end that should not hav e been there.

Also there was a very obsolete option in the call to legend()

clc ;
clear all ;
close all ;
m =512; % Total number of OFDM symbols
N =1024; % Length of each OFDM symbol
M =4; % Size of the Constellation ( M can be 4 , 8 , 16 ,32 , 64 , 128 , 256)
Ncp =256 ; % Length of the Cyclic Prefix

%Tx = modem.qammod ('M',M ) ; % Choosing the modulation format as M - ary Quadrature Amplitude Modulation (M- QAM )
%Rx = modem.qamdemod ('M',M) ; % Fixing up the demodulation format at the receiving end as M - ary QAM ( Note : In order to simulate the code in MATLAB R2020a version , please remove Tx and Rx instantiation and assign DataMod as DataMod = qammod( Data , M);10 % DCO - OFDM Transmitter


Data = randi ([0, M-1] ,m , N ); % Generation of Random bits Matrix of size m by N

%DataMod = modulate ( Tx , Data ); % Performing Data Modulation , for MATLAB R2020a version , assign DataMod = qammod (Data , M);
DataMod = qammod( Data , M);

DataMod_serialtoparallel = DataMod .'; % Performing Serial to Parallel Conversion
datamat = DataMod_serialtoparallel ; % Assigning the total data to a variable called datamat % Computation of Hermitian Symmetry Criteria
datamat (1 ,:) =0; % Assigning the First subcarrier to Zero
datamat (513 ,:) =0; % Assigning the Middle Subcarrier to Zero
datamat (514:1024 ,:) = flipud ( conj ( datamat (2:512 ,:) ) ) ; % Illustrating that only half of the subcarriers are exploited for data transmission as the remaining half are flipped complex conjugate versions of the previous ones .
d_ifft = ifft (( datamat ) ) ; % Computation of IFFT operation
d_ifft_paralleltoserial = d_ifft .'; % Parallel to Serial Conversion
CP_part = d_ifft_paralleltoserial (: ,end - Ncp +1: end) ; % Addition of Cyclic Prefix
DCOOFDM_CP =[ CP_part d_ifft_paralleltoserial ]; %Transmissin of DCO - OFDM signal
bdc =7; %DC BIAS
clip = sqrt ((10.^( bdc /10) ) -1) ; % clipping factor k
bdcc = clip * sqrt ( DCOOFDM_CP .* DCOOFDM_CP ) ;%Computation of DC bias
DCOOFDM_BIAS = DCOOFDM_CP + bdcc ; % Addition of DC bias to the cyclic prefix added signal
count =0;
snr_vector =0:1:80; % size of signal to noise ratio (SNR ) vector
for snr = snr_vector
    SNR = snr + 10* log10 ( log2 ( M ) ) ;
    count = count +1 ;
    DCOOFDM_with_chann = awgn ( DCOOFDM_BIAS , SNR ,'measured'); % Addition of AWGN
    % Receiver of DCO - OFDM
    DCOOFDM_with_chann1 = DCOOFDM_with_chann - bdcc ; %Removal of DC bias
    DCOOFDM_removal_CP = DCOOFDM_with_chann1 (: , Ncp +1: N + Ncp ) ; % Removal of Cyclic Prefix
    DCOOFDM_serialtoparallel = DCOOFDM_removal_CP .'; %Serial to Parallel Conversion
    
    DCOOFDM_parallel_fft = fft ( DCOOFDM_serialtoparallel) ; % Computation of FFT operation
    
    DCOOFDM_Demodulation = qamdemod (DCOOFDM_parallel_fft .', M );
    [~ , s_e1(count)]= symerr ( Data (: ,2:512),DCOOFDM_Demodulation (: ,2:512)) ;
end

% %%%%% With 13 dB Bias
m =512; % Total number of OFDM symbols
N =1024; % Length of each OFDM symbol
M =4; % Size of the Constellation ( M can be 4 , 8 , 16 ,32 , 64 , 128 , 256)
Ncp =256 ; % Length of the Cyclic Prefix

%Tx = modem . qammod ('M',M ) ; % Choosing the modulation format as M - ary Quadrature Amplitude Modulation (M
%Rx = modem . qamdemod ('M',M) ; % Fixing up the demodulation format at the receiving end as M - ary QAM

% DCO - OFDM Transmitter
Data1 = randi ([0, M-1] , m ,N ) ; % Generation of Random bits Matrix of size m by N

%DataMod1 = modulate ( Tx , Data1 ) ; % Performing Data Modulation , for MATLAB R2020a version , assign DataMod1 = qammod ( Data1 , M) ;
DataMod1 = qammod ( Data1 , M) ;
DataMod_serialtoparallel1 = DataMod1 .'; % Performing Serial to Parallel Conversion
datamat1 = DataMod_serialtoparallel1 ; % Assigning the total data to a variable called datamat
% Computation of Hermitian Symmetry Criteria
datamat1 (1 ,:) =0; % Assigning the First subcarrier to Zero
datamat1 (513 ,:) =0; % Assigning the Middle Subcarrier to Zero
datamat1 (514:1024 ,:) = flipud ( conj ( datamat1 (2:512 ,:) ) );
% Illustrating that only half of the subcarriers are exploited for data transmission as the remaining half are flipped complex conjugate versions of the previous ones .
d_ifft1 = ifft (( datamat1 )) ; % Computation of IFFT operation
d_ifft_paralleltoserial1 = d_ifft1 .'; % Parallel to Serial Conversion

CP_part1 = d_ifft_paralleltoserial1 (: ,end - Ncp +1: end) ; %Addition of Cyclic Prefix
DCOOFDM_CP1 =[ CP_part1 d_ifft_paralleltoserial1 ]; %Transmissin of DCO - OFDM signal
bdc1 =13; %DC BIAS
clip1 = sqrt ((10.^( bdc1 /10) ) -1) ; % clipping factor k
bdcc1 = clip1 * sqrt ( DCOOFDM_CP1 .* DCOOFDM_CP1 ) ;%Computation of DC bias
DCOOFDM_BIAS1 = DCOOFDM_CP1 + bdcc1 ; % Addition of DC bias to the cyclic prefix added signal
count =0;

snr_vector =0:1:80; % size of signal to noise ratio (SNR ) vector
for snr = snr_vector
    SNR = snr + 10* log10 ( log2 ( M ) ) ;
    count = count +1 ;
    DCOOFDM_with_channel = awgn ( DCOOFDM_BIAS1 , SNR ,'measured' ) ; % Addition of AWGN
    % Receiver of DCO - OFDM
    DCOOFDM_with_chann2 = DCOOFDM_with_channel - bdcc1 ;%Removal of DC bias
    DCOOFDM_removal_CP2 = DCOOFDM_with_chann2 (: , Ncp +1: N + Ncp ) ; 
    % Removal of Cyclic Prefix
    DCOOFDM_serialtoparallel2 = DCOOFDM_removal_CP2 .';
    % Serial to Parallel Conversion
    DCOOFDM_parallel_fft2 = fft (DCOOFDM_serialtoparallel2 ) ; % Computation of FFT operation
    DCOOFDM_Demodulation2 = qamdemod (DCOOFDM_parallel_fft2 .', M ) ;
    [~ , s_e2(count) ]= symerr ( Data1 (: ,2:512) ,DCOOFDM_Demodulation2 (: ,2:512) ) ;
end

% Plotting the BER curves
semilogy ( snr_vector , s_e1 ,'rd -','LineWidth' ,2) ; 
hold on;
semilogy ( snr_vector , s_e2 ,'gd -','LineWidth' ,2) ;
legend ('FFT - based DCO -OFDM -7 dB of Bias ', 'FFT - based DCO -OFDM -13 dB of Bias ') ;
axis ([0 30 10^ -4 1]) ;
xlabel ('SNR in dB ') ;
ylabel ('BER ') ;
grid on ;