Word Transmitter

Well this a simple simulator of a word transmitter, it consists of a python script that generates a binary word using a probability of generating a 0, then simulates its transmission through a noisy channel using a probability of transmitting a 0 as a 0 and the probability of transmitting a 1 as a 1. The script gets the success of transmitting a word correctly.

The parameters that the transmitter (python script) needs are:

• Name of the .dat file that will be used
• Number of times that the word will be transmitted                  
• Frequency that a 0 will be added to the new word    
• length = max length of the words                                            
• Probability that a 0 will be transmitted as a 0                     
• Probability that a 1 will be transmitted as a 1

Next I generate a bash file to automate the simulations using different frequencies of generate a 0 and all the parameters that I mentioned above, and with this bash I generate 3 different charts using the different lengths of the words and the average of success of transmitting the word correctly.

This is the python script:

import random,sys,math

class Simulation:

    def __init__(self,frequency,length,nTimes,prob0, prob1, fileName):
        self.freq = frequency
        self.probs = ([prob0, 1-prob0],[1-prob1, prob1])
        
        self.doc = open(fileName,'w')
        
        for i in range(2, (length+1)):
            '''Gets the average of the successes of 
            transmitting a word correctly '''
            self.avrg = (self.simulator(i,nTimes))
            self.doc.write( str(i) + ' ' + str(self.avrg)+ '\n')
            

    def wordGenerator(self, length):
        '''Generate new word using a random number and comparing it
        against the frequency of producing a 0'''
        word = []
        for i in range(length):
            rand = random.uniform(0,1)
            if rand > self.freq:
                word.append(0)
            else:
                word.append(1)
        #print word
        return word
    
    def simulator(self,length, nTimes):
        '''Main function. Makes a new word and simulate its 
        transmission and compare the word against the received word'''
        success = 0
        for i in range(nTimes):
            word = self.wordGenerator(length)
            received = self.transmission(word)
            
            equal = self.comparison(word,received)
            if equal : success +=1
        #print success
        average = float(success)/nTimes
        return average

    def transmission(self,word):
        """Simulates word transmission's using the probabilities
        of transmit a 0 as a 0 and a 1 as a 1"""
        received = []
        for i in word:
            rand = random.uniform(0,1)
            
            if i is 0:
                if rand > 0 and rand < self.probs[0][0]:
                    received.append(0)
                else:
                    received.append(1)
            elif i is 1:
                if rand > 0 and rand <= self.probs[1][1] :
                    received.append(1)
                else:
                    received.append(0)
        #print received
        return received

    def comparison(self,word,received):
        '''Compare the original word against the received word '''
        wrd = ''
        rcv = ''
        for i in range(len(word)):
            wrd += str(word[i])
            rcv += str(received[i])
        #print wrd, "   ", rcv
        if wrd == rcv : return True
        else : return False


def main():
    '''
    fileName = name of the .dat file
    nTimes = number of times that the word will be transmitted 
    frequency = frequency that a 0 will be added to the new word 
    length = max length of the words
    prob0 = probability that a 0 will be transmitted as a 0 
    prob1 = probability that a 1 will be transmitted as a 1'''
    
    fileName = sys.argv[1]
    nTimes = int(sys.argv[2])
    frequency = float(sys.argv[3])
    length = int(sys.argv[4])
    prob0 = float(sys.argv[5])
    prob1 = float(sys.argv[6])
    
    sim = Simulation(frequency, length, nTimes,prob0,prob1, fileName)

if __name__ == "__main__":
    main()

And this is the bash file, here I had to thank my classmate Pedro because he helped me with the part og gnuplot because I had no idea about it.

FILENAME='data'#name of the .dats to be plot
NTIMES=10 #number of times that the word will be transmited
FREQUENCY='0.3 0.6 0.8' #frequencies that a 0 will be added to the new word
LENGTH=30 #max length of the words
PROBZERO=0.7 #probability that a 0 will be transmited as a 0
PROBONE=0.8 #probability that a 1 will be transmited as a 1

for f in $FREQUENCY
do
    for i in 1
    do
 for j in 1
 do
     python simulation.py $FILENAME$f".dat" $NTIMES $f $LENGTH $PROBZERO $PROBONE
     echo python simulation.py $FILENAME$f".dat" $NTIMES $f $LENGTH $PROBZERO $PROBONE
 done
    done
PLOTFILE="graph"$f".plot" #name of the .plot file 
>$PLOTFILE #access to the .plot file
echo set term png >>$PLOTFILE
echo set xlabel \""Length"\" >>$PLOTFILE
echo set ylabel \""Average"\">>$PLOTFILE
echo set output \""chart"$f".png"\">>$PLOTFILE
echo plot \"$FILENAME$f".dat"\" with lines>>$PLOTFILE

gnuplot *.plot
rm *.plot
done

Here some examples that the simulation gives me