Communication Plays A Vital Role Computer Science Essay

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In todays world communication plays a vital role , main aim of the communication is to transmit the data or information from source to destination. The main aim of this project is to design a basic telecommunication system .There are many methods to communicate such as wired communication and wireless communication systems. This basic telecommunication system designed by using binary phase shift keying and the code is simulated in matrix lab. The resulted values such as snr (signal to noise ratio) and ber (bit error rate) used to plot the graph to analyse the performance of the basic telecommunication system. The performance of the telecommunication system is good when the bit error rate is low.

the basic telecommunication system is designed by using BPSK(binary phase shift keying) ,the basic telecommunication system consists of a transmitter end and receiver end the main aim is to transmit the information from transmitter region that is message signal which is desired to reach destination with out any disturbance ,this is done by adding noise to the carrier signal which is transmitted from source region or from transmitter end is passed through a channel and then the resulting signal will be passed through detector to get the message signal at the receiver end or destination

2. AIMS AND OBJECTIVES:

To design a basic telecommunication system by using BPSK(Binary phase shift keying) in matrix lab and to simulate the above process by developing the code so as to determine the BER(bit error rate) this is the main objective of the system and finally to plot the graph between BER and SNR(signal to noise ratio).

3. THEORY:

3.1) BASIC COMMUNICATION SYSTEM:

http://cnx.org/content/m21407/latest/pic002.png

Fig 1

In Basic telecommunication there are two major components such as transmitter and receiver, these two sections play an vital role in telecommunication system, in this transmitter section consists of two major parts

1. Source

2. Modulator

And similarly Receiver section consists of two main parts i.e.

1. Decoder

2. Demodulator

3.1.1. SOURCE:

Source is nothing but sender or transmitting origin. The main objective of source is to generate the signals or message or information, in this source section the information or message signals are propagated through a medium to modulator section.

3.1.2. MODULATOR:

Modulator receives the signal which is transmitted from source region, basically modulator is used to transform the signal from one form to another form for example modulator converts low frequency signal to high range frequency signals such as radio frequency signals .

Finally modulator generates modulated signal which is consists of message signal or information signal which is transmitted from source, this carrier signal is sent to channel. In general there are three types of modulation techniques are present they are

A) Amplitude modulation

B) Frequency modulation

C) Phase modulation

A) AMPLITUDE MODULATION:

In this modulation technique the carrier or message signal which is transmitted from source region and modulating signal at modulator will vary based on the amplitude of the signal.

B) FREQUENCY MODULATION:

In this modulation technique the carrier signal or information signal from the source region and modulating signal at the modulator region will vary based on frequency of the signal.

C) PHASE MODULATION:

In this modulation technique the carrier signal and modulating signal vary depending on the phase shift of the signal.

3.1.3) CHANNEL:

In any basic telecommunication system channel will works as mediator that means it will work at the transmitter region as well as at receiver end and it pass the information from one region to another region .The information which is transmitted from the source is passes to the receiver end or destination through the channel region .So channel plays very important role basic telecommunication system

3.1.4) DEMODULATOR:

Demodulator is also one of the main component in basic communication system , Demodulator receives the information or signal from the channel ,the main function of the demodulator is to give the original carrier signal or information signal which is transmitted from the source region .Demodulator job is to give exact signal which is desired to reach the destination.

4. METHOD:

4.1) BINARY PHASE SHIFT KEYING:

The main aim is to design the basic telecommunication system by using BPSK(binary phase shift keying) the below diagram to explain about BPSK.

source or carrier signal

's'

Modulator

' s mod'

Input

Noise' n'

Reciver output

Demodulator

Detector

Fig 2

In the above figure the signal transmitted from source is 's' ,then the signal from source is sent to modulator ,modulator will give the modulated signal then the modulated signal will be sent through a medium in that some amount of noise is added that noise is represented as 'n', after noise is mixed with modulated signal 's mod' then the resulted signal will be passed through a detector to detect the noise 'n' from the modulated signal ,after that the signal will be passed to demodulator this demodulator will demodulate the signal to get exact or original signal from modulated signal ,the resultant output will be received at receiver output.

Binary phase shift keying is used to reverse the phase shift so this type of phase shift keying is also known as phase reversal keying.

In BPSK according to binary data the phase shift of the carrier is varied

The phase shift of the carrier is '0 degrees' when binary data is '1'

The phase shift of the carrier is '180 degrees' when binary data is '0'

In binary phase shift keying the phase angle of the signal is varies between ' 0 degrees ' and '180 degrees'.

5. SOFTWARE SIMULATION:

x=randint(1,10000);

x_mod=(x*2)-1

snr=1;

sigma=10^(-snr/10)

n=randn(size(x))*sqrt(sigma/2)

n_noise=x_mod+n

x_mod=sign(x_mod)

y=sign(n_noise)

x_demod=(y+0.5)+0.5

error=sum(xor(x,x_demod))

ber=error./length(x)

snr=0:10

ber=[0.0790,0.0556,0.0366,0.0238,0.0122,0.0071,0.0020,8.0000e-04,3.0000e-04,1.0000e-04,0]

semilogy(snr,ber)

5.1) MATLAB CODE EXPLANATION:

RAND: rand key word is used when we require random numbers that is when we desired to select a number from set of numbers then 'rand' is used ,'rand int' is used to select a integer from set of integer values.

SNR: snr represents the signal to noise ratio.

SIGMA: sigma will generally take the singular values and they ploy under the LTI model. This LTI model can be continuous model or discrete model.

PLOT: To get graph in mat lab need to plot the values. In this code is used plot to get the graph between snr (signal to noise ratio) values to ber( bit error rate values).

LABEL: label is used to allocate x constraints and y constraints on the graph. In the above graph xlabel is used for snr and ylabel is used for the ber.

TITLE: Title is used to allocate some name or title to the graph. In the above code we allocated BPSK as the title of the graph.

GRID: Grid is used for the allocation of grid lines on the graph.

6. TABULAR FORM:

SIGNAL TO NOISE RATIO(SNR)

ERROR

BIT ERROR RATE(BER)=ERROR/LENGTH OF X

0

790

0.0790

1

556

0.0556

2

366

0.0366

3

238

0.0238

4

122

0.0122

5

71

0.0071

6

20

0.0020

7

8

8.0000e-04

8

3

3.0000e-04

9

1

1.0000e-04

10

0

0

7. GRAPHICAL REPRESENTATION:

The graph is obtained after simulation

8. RESULT:

Hence we have calculated the values of signal to noise ratio (snr) and bit error rate (ber) and tabulated those values , and then plotted the graph to show the comparison between snr and ber which is the main objective.

9. DISCUSSION:

After getting the values of snr (signal to noise ratio) and ber( bit error rate values) to get the graph for analysing the characteristics of snr and ber .In this the analysis of the characteristics is done by changing snr values from 0 to 10 calculated corresponding bit error rate values ,to get the graph i used semilogy(snr,ber) because to get the values of snr on x axis and ber vaues on y axis and if ber is logarithmic to get that value semilogy key word is used ,then graph is generated by running program ,this graph clearly shows that by increasing signal to noise ratio value the bit error rate is decreased at the end for snr=10 bit error rate=0.

10. CONCLUSION:

The basic telecommunication system is designed by using BPSK binary phase shift keying in mat lab after simulation i found the values of snr and ber values to check the performance of the telecommunication system and then I generated the graph by usind snr and ber values, from the above graph i will conclude that signal to noise ratio and bit error rate are inversely proportional to each other because by increasing snr values ber (bit error rate) will gets reduced. The performance of any telecommunication system is decided by using bit error rate if bit error rate is low then that telecommunication system is perfect telecommunication system.

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