clear all;

close all;

file $=$ fopen$(\text{'}$TransmittedMessage$.$txt$\text{'})$; $\%$ Open the file $($should be in the same folder$)$

message $=$ fread$($file$,\text{'}*$char$\text{'})\text{'}$; $\%$ Read the text $($as a string$)$ from the file

fclose$($file$)$; $\%$ Close the file

$\%\%\%\%\%\%\%\%\%\%$ Converting the message into a bit stream $\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%$

text$2$double$\_$temp $=$ dec$2$bin$($message$,8)-\text{'}0\text{'}$; $\%$ Convert each character into binary $($minus zero is used to convert it into double instead of logical$)$

$\%$ Each character is represented by $8$ bits

bit$\_$stream $=$ reshape$($text$2$double$\_$temp.$\text{'},1,[])$; $\%$ Reshape it into an array $(.\text{'}$ is needed for proper ordering$)$

$\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%$ BPSK Modulation $\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%$

Fs $=25000$; $\%$ Sampling freq

Tb $=1$e$-3$; $\%$ Bit duration

fc $=10000$; $\%$ Carrier freq

Eb $=1$; $\%$ Energy per bit

dt $=1/$Fs; $\%$ time step

N $=$ length$($bit$\_$stream$)$; $\%$ Number of bits to be transmitted

t $=0$:dt:N$*$Tb; $\%$ Time vector

t $=$ t$(1$:length$($t$)-1)$; $\%$ the last element is discarded to adjust the size of the time vector

Stream $=$ repelem$($bit$\_$stream,Tb$/$dt$)$; $\%$ Enlarge the bit stream to match the size of the time vector

Stream$($Stream$==1)=-1$; $\%$ Replacing $1\text{'}$s with $-1($NRZ Level Encoder$).$ This arrangement fits the definition of log likelihood ratio

Stream$($Stream$==0)=1$; $\%$ Replacing $0\text{'}$s with $1($NRZ Level Encoder$).$ This arrangement fits the definition of log likelihood ratio

ModulatedSignal $=$ sqrt$((2*$Eb$)/$Tb$).*$cos$(2*$pi$*$fc$*$t$).*$Stream; $\%$ BPSK modulated signal to be transmitted