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ECE Simulation Lab

SUBMITTED BY:-

Kuldeep Jaimini (10302166)

Monika Grewal (10302169)

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INDEX

S.No. EXPERIMENT NAME PAGE TEACHERSREMARKS

1 Study of a PCM system through

MATLAB simulation

2 Study and simulation of different

channel models; awgn channel,

frequency flat & frequency selective,

rayleigh fading channel

3 Simulation of BPSK & QPSK

communication systems and study of

their performance over AWGN channel

followed by verification with

theoretical results

4

5

6

7

8

9

10

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EXPERIMENT # 01

Problem Statement:- study of a PCM system through MATLAB simulation.

(a) Generate a sinusoidal signal of the form where the amplitude A is

uniformly distributed in the interval [1, 3] volts. Phase angle is uniformly distributed in

the interval [0, 2 ]. Sample the continuous time signal at a rate 20% higher than Nyquist

rate. Quantize the discrete time signal with a 16-level quantizer and encode the resulting

signal with a 4-bit encoder. Observe the signal at each stage.

(b) Simulate the PCM receiver and compare the recover waveform with the originalsinusoidal waveform. Assume noiseless channel with no losses.

Algorithm:-

(a) PCM encoder

Step 1:- Generation of sinusoidal signal

A sinusoidal signal to be generated is of the form- , where amplitude A

and phase angle are random variables having uniform probability distribution function.

Generate a random variable A in the interval [1, 3] and phi( ) in the interval [0, 2]

which are uniformly distributed in specified interval.

Step 2:- time interval

Time interval is taken from 0 to 2 so that cosine pulse is generated upto 5 complete

cycles. We have taken 800 samples of time t in the range 0 to 2.

The sinusoidal signal with amplitude A and phase phi( ) with time interval is thus

plotted.

Step 3:- quantization

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Since we have to make a 4-bit quantizer, total number of quantization levels are 24=16.

The interval [-3, 3] is divided into 16-levels and thus step size comes out to be-

So the 16 levels are:-

Level

no

Interval Assigned value Encoded value

1 -3 to -3+0.375 0

2 -3+0.375 to -3+2*0.375 0.1875+0.375 1

3 -3+2*0.375 to -3+3*0.375 0.1875+2*0.375 2

4 -3+3*0.375 to -3+4*0.375 0.1875+3*0.375 3

5 -3+4*0.375 to -3+5*0.375 0.1875+4*0.375 4

6 -3+5*0.375 to -3+6*0.375 0.1875+5*0.375 5

7 -3+6*0.375 to -3+7*0.375 0.1875+6*0.375 6

And so on upto 16.

For every sampled value, it is assigned the mid value of the interval (mid-tread

quantizer), if the sampled value lies into that interval.

If -3+j*0.375 < x < -3+(j+1)*0.375, assign it value 0.1875+j*0.375 where j=0 to 15.

The quantized levels are encoded with values from j=0 to 15.

Quantized signal is stem plotted in fig

(b) PCM receiver

Decode the received signal in exactly reverse manner as was followed at the encoder.

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Plot sinusoidal wave with recovered quantized levels.

Compute and plot the error by subtracting the recovered signal from the original signal.

MATLAB Code:-

clear all;

clc;

a=random('unif',1,3);

phi=random('unif',0,2*pi);

t1=0:0.0025:2-0.0025;

s1=a*cos(5*pi*t1+phi);

subplot(5,1,1),stem(t1,s1,'.')

title('pcm encoder'),ylabel('s1')

for i=1:800

for j=-8:7

x=0.375*j;

y=0.375*(j+1);

if s1(i)>=x & s1(i)

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s3(i)=j+8;

end

end

end

dec2bin(s3(i))

subplot(5,1,2),stem(s2,'.')

ylabel('s2')

subplot(5,1,3),stem(s3,'.')

ylabel('s3')

%pcm receiver

for i=1:800

for j=0:15

if s3(i)==j

s4(i)=0.1875+(j-8)*0.375;

end

end

end

subplot(5,1,4),plot(s4)

title('pcm receiver'),ylabel('s4')

e=s4-s1;

subplot(5,1,5),stairs(e)

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xlabel('time'),ylabel('s5')

Outputs:-

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EXPERIMENT:- 2

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Problem statement:- Study and simulation of different channel models; AWGN channel,

frequency flat & frequency selective, rayleigh fading channel.

1. AWGN channel-

AWGN stands for Additive White Gaussian Noise. This means the noise in the channel has

following characteristics:-

a) Additive: - The noise gets added to original signal i.e.

Received signal = input signal + noise

b) White: - The noise affects all frequency components equally i.e. the channel is not

frequency selective.

c) Gaussian: - The noise follows the Gaussian probability distribution function.

Algorithm:-

To simulate AWGN channel, well generate a random variable with Gaussian distribution and

add it to original signal.

Gaussian random variable is defined by two parameters- mean and variance. A Gaussian number

having can be generated from a normal distributed number by multiplying it with standard

deviation (square root of variance) and adding the mean into it.

Gaussian random variable with zero mean and unit variance:-

A normal distribution is Gaussian distribution with zero mean and unit variance.

Matlab code:-

N = 10000;x1 = -5:0.1:5;

n = randn(1,N)

hist(n,x1)

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-6 -4 -2 0 2 4 60

50

10 0

15 0

20 0

25 0

30 0

35 0

40 0

45 0

Gaussian random variable with specified mean and variance:-

Matlab code:-

N = 10000;

x1 = -5:0.1:5;

mu = input('mean =')

s = input('variance =')

n = randn(1,N)

hist(n,x1)

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Histogram:-

-0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.50

200

400

600

800

1000

1200

1400

Mean = 2

Variance = 0.1

2. FREQUENCY FLAT

Impulse response h(n) of frequency flat channel is constant for each frequency component.

i.e.

Matlab Code:-

clear all;

clc;

a=randn(1) + j*randn(1);

a1=abs(a);

l=0:10;

syms x;

stem(int(a1*dirac(x-l),0,10))

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1 2 3 4 5 6 7 8 9 100

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

3. FREQUENCY SELECTIVE

The impulse response of frequency selective channel is given by-

i.e. the weighting factor is not a constant but a random variable.

Matlab Code:-

clear all;

clc;

a=randn(1,11) + j*randn(1,11);

a1=abs(a);

l=0:10;

syms x;

stem(int(a1.*dirac(x-l),0,10))

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1 2 3 4 5 6 7 8 9 10 110

0.5

1

1.5

2

2.5

3

4. RAYLEIGH FADING CHANNEL

In Rayleigh fading channel the amplitude of the input signal is multiplying by a scaling factor

which follows Rayleigh distribution. Rayleigh fading channel is an example of frequency

selective channel.

Generation of Rayleigh random variable

A Rayleigh distributed random variable can be generated by adding two orthogonal Gaussian

random variables.

Matlab code:-

N=100;

x1 = 0:0.1:5;

n=randn(1,N) + j*randn(1,N);

n1=abs(n)

hist(n1,x)

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Histogram:-

-1 0 1 2 3 4 5 60

100

200

300

400

500

600

700

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EXPERIMENT NO-3

Problem statement:- Simulation of BPSK & QPSK communication systems and study of their

performance over AWGN channel followed by verification with theoretical results.

1. BPSK:-

Matlab Code:-

clear all;

clc;

N = 10^4;

% Transmitter

ip1 =1.*( rand(1,N)>0.5);

x= 2*ip1-1;

%awgn noise addition

SNR=[-3:10];

for i=1:length(SNR)

n=1/sqrt(2)*sqrt(10.^(-SNR(i)/10)).*randn(1,N);

y=x+n;

% receiver

%for j=1:N

%if y(j)>0

%y1(j)=1;

%else y1(j)=0;

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%end

%end

y1=real(y>0);

%error analysis

%e=ip1-y1;

%d=find(e);

%count(i)=size(d,2);

count(i)=sum(xor(ip1,y1));

end

tber= 0.5*erfc(sqrt(10.^(SNR/10)));

semilogy(SNR,count/N,'b*')

hold on

semilogy(SNR,tber,'m-')

xlabel('SNR');

ylabel('Bit error rate');

title('error performance analysis curve for BPSK modulation');

axis([-3 10 10^-4 0.5])

grid on

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2- QPSK

Matlab code:-

close all;

clear all;

clc;

N =10000;

% Transmitter

ip =( rand(1,N)>0.5);

x=[];

for k=1:N/2

Q(k)=(-1).^(ip(2*k-1)+1);

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I(k)=(-1).^(ip(2*k)+1);

x(k)=I(k)+(i*Q(k));

end


n = 1/sqrt(2)*[randn(1,N/2) + j*randn(1,N/2)];

SNR=[-3:10];

count=[];

for k=1:length(SNR)

noise=10.^(-SNR(k)/20).*n;

y=x+noise;

% receiver

I1=[];

Q1=[];

for t=1:N/2

I1=[I1 real(y(t))>0];

Q1=[Q1 imag(y(t))>0];

end

y1=cat(1,Q1,I1);

y2=reshape(y1,[1,N]);

count=[count sum(xor(ip,y2))];

end

err=count/N

semilogy(SNR,err,'b*')

tber=0.5*erfc(sqrt(10.^(SNR/10)));

hold on

semilogy(SNR,tber,'m-')

xlabel('SNR');


title('error performance analysis curve for QPSK modulation');

axis([-3 10 10^-6 1])

grid on

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RESULT:-

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EXPERIMENT # 04

Problem Statement:- study of performance of linear block code through simulator.

a) Implementation of a (3,1) repetition encoder.

b) BPSK modulation and transmission of coded data over noisy channel.

c) Decoding of received data using majority selector logic algorithm and evaluation of

performance in presence of AWGN.

THEORY:- Repetition code is an (r,1) block coding scheme that repeats the bits across a channel

to achieve error free communication (r is the number of bits in each codeword for each data bit to

be coded).

Matlab code:-

a) Implementation of (3,1) repetition encoder.

clear all;

clc;

N=100; %Number of input bits

data=rand(1,N)>0.5;

x=[];

for i=1:length(data)

x(3*(i-1)+1)=data(i);

x(3*(i-1)+2)=data(i);

x(3*(i-1)+3)=data(i);

end

x

Output for a 5-bit long data stream:-

data = 0 1 1 0 1

x = 0 0 0 1 1 1 1 1 1 0 0 0 1 1 1

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b) BPSK modulation and transmission of coded data over noisy channel.

Matlab code:-

%BPSK modulation

t=2*x-1;

%channel

n=1/sqrt(2)*randn(1,length(t)); %awgn noise

r=t+n;

c) Decoding of received data using majority selector logic algorithm and evaluation of

performance in presence of AWGN.

Matlab code:-

clear all;

close all;

clc

N=10^4; %Number of input bits

data=rand(1,N)>0.5

%repititive coding

x=[];

for i=1:length(data)

x(3*(i-1)+1)=data(i);

x(3*(i-1)+2)=data(i);

x(3*(i-1)+3)=data(i);

end

%BPSK modulation

t=2*x-1;

%channel

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n=1/sqrt(2)*randn(1,length(t));

snr=[1:5];

for j=1:length(snr)

noise=10.^(-snr(j)/20).*n; %awgn noise

r=t+noise;

%receiver decision making

y=real(r>0)

%decoder

e=[];

for k=1:length(data)

s(k)=y(3*(k-1)+1)+y(3*(k-1)+2)+y(3*(k-1)+3);

if s(k)=2

d(k)=1;

end

end

%counting errors

error(j)=sum(xor(data,d))/N;

end

error

semilogy(snr,error)

%axis([1 5 10e-4 10e-3])

RESULTS:-

N=10000

snr=1 2 3 4 5

error = 0.0082 0.0040 0.0017 0.0006 0.0002

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BER Plot:-

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EXPERIMENT # 05

Problem Statement: study of (2, 1, 3) linear convolution coder and its performance over

AWGN channel and BPSK through simulation.

THEORY: Convolutional code is a type oferror-correcting code in which

Each m-bitinformation symbol (each m-bit string) to be encoded is transformed into an

n-bit symbol, where m/n is the code rate (n m) and

The transformation is a function of the last k information symbols, where k is the

constraint length of the code.

To convolutionally encode data, start with kmemory registers, each holding 1 input bit. Unless

otherwise specified, all memory registers start with a value of 0. The encoder has n modulo-2

adders (a modulo-2 adder can be implemented with a single BooleanXOR gate, where the logic

is: 0+0 = 0, 0+1 = 1, 1+0 = 1, 1+1 = 0), and ngenerator polynomials one for each adder (see

figure below). An input bit m1 is fed into the leftmost register. Using the generator polynomials

and the existing values in the remaining registers, the encoder outputs n bits. Now bit shift all

register values to the right (m1 moves to m0, m0 moves to m-1) and wait for the next input bit. If

there are no remaining input bits, the encoder continues output until all registers have returned to

the zero state.

ALGORITHM: Block Diagram of given convolutional coder is:-

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Generate N-bit data stream and append three 0s after the data array in order to ensure

that the registers remain clear after coding.

Polynomial for code 1:- 1+x3

And that for code 2:- 1+x+x2

Where the power indicates the delayed form of input e.g. x2 indicates x(n-2) i.e. the data

has been delayed by 2 units.

The adder in block diagram is simply modulo-2 adder or Xor gate.

Code array is formed by alternatively sampling bits from code1 and code2 streams resp.

Decoder:

Decoding is done using MATLAB in-built function vitdec (.) which uses a trellis array

to decode the convolutionally encoded stream.

Trellis array is computed using inbuilt function poly2trellis(). Where first field is

constraint length(k) = m+1 = 4, and second field is generator polynomial.

Generator polynomial is a k*n matrix (k-input, n-output)

Where, each element gives connection of input to give output.

MATLAB CODE:

clear all;

clc;

N=1000;

data(1:N)=rand(1,N)>0.5;

ip=[data 0 0 0];

%convolutional encoder

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d1=0; d2=0; d3=0;

for i=1:N+3

code(2*i-1)=xor(ip(i),d3);

temp=xor(d1,d2);

code(2*i)=xor(ip(i),temp);

d3=d2;

d2=d1;

d1=ip(i);

end

%bpsk modulator

x=2*code-1;


SNR=[0 3 6];

for j=1:length(SNR)

noise=1/sqrt(2)*(10.^(-SNR(j)/20)).*randn(1,2*(N+3));

y=x+noise;

% receiver

r=real(y)>0;

%viterbi decoder

t=poly2trellis(4,[11 16]);

decoded=vitdec(r,t,3,'term','hard');

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error(j)=sum(xor(ip,decoded))/(N+3);

end

error

semilogy(SNR,error)

xlabel('SNR');


title('error performance analysis of BPSK with convolutional coding');

grid on

GRAPH:

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EXPERIMENT # 06

Problem Statement: Study the functionality of LAN trainer kit and connections of nodes in a

LAN configuration. Implement the MAC layer algorithms like ALOHA, CSMA and CSMA/CD

between the connected nodes.

THEORY:

1. ALOHA: ALOHA is a medium access protocol that was originally designed for ground based

radio broadcasting however it is applicable to any system in which uncoordinated users are

competing for the use of a shared channel. Pure ALOHA and slotted ALOHA are the two

versions of ALOHA.

With Pure Aloha, stations are allowed access to the channel whenever they have data to transmit.

Because the threat of data collision exists, each station must either monitor its transmission on

the rebroadcast or await an acknowledgment from the destination station. By comparing the

transmitted packet with the received packet or by the lack of an acknowledgement, the

transmitting station can determine the success of the transmitted packet. If the transmission was

unsuccessful it is resent after a random amount of time to reduce the probability of re-collision.

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Pure ALOHA protocol. Boxes indicate frames. Shaded boxes indicate frames which have

collided

2. CSMA: CSMA is a access method in which a transmitting data station that detects another

signal while transmitting a frame, stops transmitting that frame, transmits ajam signal, and then

waits for a random time interval before trying to send that frame again.

Carrier Sense describes the fact that a transmitter uses feedback from a receiver that detects a

carrier wave before trying to send. That is, it tries to detect the presence of an encoded signal

from another station before attempting to transmit. If a carrier is sensed, the station waits for the

transmission in progress to finish before initiating its own transmission.

Multiple-Access describes the fact that multiple stations send and receive on the medium.

Transmissions by one node are generally received by all other stations using the medium.

3. CSMA/CD: Carrier sense multiple access with collision detection (CSMA/CD) is a computer

networking access method in which:

A carriersensing scheme is used. A transmitting data station that detects another signal

while transmitting a frame, stops transmitting that frame, transmits a jam signal, and then

waits for a random time interval before trying to send that frame again.

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http://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Frame_(telecommunications)http://en.wikipedia.org/wiki/Jam_signalhttp://en.wikipedia.org/wiki/Timehttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Frame_(telecommunications)http://en.wikipedia.org/wiki/Jam_signalhttp://en.wikipedia.org/wiki/Timehttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Frame_(telecommunications)http://en.wikipedia.org/wiki/Jam_signalhttp://en.wikipedia.org/wiki/Timehttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Carrier_wavehttp://en.wikipedia.org/wiki/Datahttp://en.wikipedia.org/wiki/Transmission_(telecommunications)http://en.wikipedia.org/wiki/Frame_(telecommunications)http://en.wikipedia.org/wiki/Jam_signalhttp://en.wikipedia.org/wiki/Time

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CSMA/CD is a modification of pure carrier-sense multiple access (CSMA). CSMA/CD is used

to improve CSMA performance by terminating transmission as soon as a collision is detected,

thus reducing the probability of a second collision on retry.

CONFIGURATION SETTING:

1. Network Emulator Unit (NEU)

Data rates 8, 16, 32, 64,128, 256, 512Kbps, 1Mbps

Topology Bus, Ring, Star (optional)

Delay 0 to 15 bits between each pair of nodes

Error Generators (between one pair of

nodes)

Bit Error 0 to 10-6

Frame Error 0 to 10-5

Nodes 6 nodes per NEU (3 PCs can be connected

per NEU. Each PC acts as 2 nodes)

PC plug-in card 32 bit, 33MHz PCI Bus (PCI ver 2.0

compliant)

MAC Layer support ALOHA, CSMA, CSMA /CD

Nodes 2 nodes per NIU

2. Network Interface Unit (NIU)

PC1 PC2

Node ID 0 at config menu 1 and 1 at

config menu 2

0 at config menu 1 and 1 at

config menu 2

Baud rate 8 Kbps(at both configuration

menu and NEU)

8 kpbps( at both configuration

menu and NEU)

Protocol ALOHA/CSMA/CSMA-CD ALOHA/CSMA/CSMA-CD

Duration 100s 100s

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Packet length 1000 bits 1000 bits

Bit delay 0(at NEU) 0(at NEU)

Direction Sender Sender

FORMULAE USED FOR CALCULATION:

Offered load = ratedataxperimenteofDuration

)bitsin(lengthpacketnodesallbypacketedtransmiittofsum

ratedataxperimenteofDuration

bitin(lengthpacketnodesallbypacketedtransmiittlysuccessfulofsumThroughputacticalPr

=

Theoretical Throughput (ALOHA) = G*e-2G

Theoretical Throughput (CSMA) = G*e-aG

Theoretical Throughput (CSMA/CD) = 1/ (1+k*a)

Where, a=no. of Nodes (N)*Bit Delay/no. of Packets (P)

k is a factor determined by various parameters and generally varies from 3 to 6.

OBSERVATIONS & GRAPHS:

1. ALOHA:

IPD(Inter

Pkt Delay

in ms)

G-Practical

Offered

Load

X-Practical

throughpu

t

Theoretical

throughput

16000 0.2 0.15 0.1341

8000 0.38 0.23 0.1777

4000 0.444 0.22 0.1800

2000 0.60 0.27 0.1807

1000 1.03 0.23 0.1313

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100 1.293 0.074 0.04

40 1.53 0.26 0.0717

Packet Length=1000 Bytes

Duration of Experiment =100 Second

Data rate = 8Kbps, No. of nodes = 4(3 senders and 1 receiver)

Graph Obtained:

2. CSMA:

IPD(Inter

Pkt Delayin ms)

G-Practical

OfferedLoad

X-Practicalthroughput

Theoreticalthroughput

16000 0.28 0.22 0.2116

8000 0.43 0.33 0.2797

4000 0.83 0.39 0.3619

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2000 1.24 0.4 0.3588

1000 1.66 0.26 0.3156

500 1.92 0.08 0.2815

Packet Length=1000 Bytes

Duration of Experiment = 100 Second

Data rate = 8Kbps, No. of Nodes = 4 (all senders)

Bit Delay = 2s so that a = N (No. of)* =1 thus, theoretical Throughput:- X=G*e-G

Graph Obtained:

3. CSMA/CD:

IPD(Inter

Pkt Delay

in ms)

G-Practical

Offered

Load

X-Practical

throughput

16000 0.33 0.25

8000 0.45 0.27

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4000 0.86 0.6

2000 0.98 0.86

1000 1 0.97

Graph Obtained:

Packet Length = 1000 Bytes

Duration of Experiment = 100 Second

Data rate = 8Kbps, No. of Nodes = 4 (all senders)

Calculation for Theoretical Throughput:-

Theoretical Throughput = 1/(1+k*a)

Where a = N (No. of Nodes)*Bit Delay/Packet Length

Since bit delay is zero, Theoretical Throughput = 1.

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RESULT & CONCLUSION: The functionality of LAN trainer kit and connections of nodes in

a LAN configuration have been studied successfully. MAC layer algorithms like ALOHA,

CSMA and CSMA/CD have been studied and graphs have been obtained showing Throughput

v/s Offered Load.

EXPERIMENT # 07

Problem Statement: Implementation of flow control algorithms Stop and Wait, Sliding

Window, GO Back N-ARQ for data transmission between nodes connected via LAN,

Requirements:

PC 2 No. (with NIU card plugged into them)

LAN Trainer

DB-37 Connectors

Network Emulator Unit

LAN Trainer Shell (to provide a menu-driven interface)

C Library (to provide programming interface to the NIU)

THEORY: In data communications, flow control is the process of managing the pacing of data

transmission between two nodes to prevent a fast sender from outrunning a slow receiver. It

provides a mechanism for the receiver to control the transmission speed, so that the receiving

node is not overwhelmed with data from transmitting node. Flow control should be distinguished

from congestion control, which is used for controlling the flow of data when congestion has

actually occurred.

STOP AND WAIT

Stop-and-wait ARQ is a method used in telecommunications to send information between two

connected devices. It ensures that information is not lost due to dropped packets and that packets

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http://en.wikipedia.org/wiki/Data_communicationshttp://en.wikipedia.org/wiki/Congestion_controlhttp://en.wikipedia.org/wiki/Telecommunicationshttp://en.wikipedia.org/wiki/Data_communicationshttp://en.wikipedia.org/wiki/Congestion_controlhttp://en.wikipedia.org/wiki/Telecommunications

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are in the correct order. It is the simplest kind ofautomatic repeat-request (ARQ) method. A

stop-and-wait ARQ sender sends one frame at a time; it is a special case of the general sliding

window protocol with both transmit and receive window sizes equal to 1. After sending each

frame, the sender doesn't send any further frames until it receives an acknowledgement (ACK)

signal. After receiving a good frame, the receiver sends an ACK. If the ACK does not reach the

sender before a certain time, known as the timeout, the sender sends the same frame again.

Typically the transmitter adds a redundancy checknumber to the end of each frame. The receiver

uses the redundancy check number to check for possible damage. If the receiver sees that the

frame is good, it sends an ACK. If the receiver sees that the frame is damaged, the receiver

discards it and does not send an ACK, pretending that the frame was completely lost, not merely

damaged.

Stop-and-wait ARQ is inefficient compared to other ARQs, because the time between packets, if

the ACK and the data are received successfully, is twice the transit time (assuming the turn-

around time can be zero).

SLIDING WINDOW

A sliding window protocol is a feature of packet-based data transmissionprotocols. Sliding

window protocols are used where reliable in-order delivery of packets is required, such as in

the Data Link Layer(OSI model) as well as in the Transmission Control Protocol (TCP).

Conceptually, each portion of the transmission (packets in most data link layers, but bytes in

TCP) is assigned a unique consecutive sequence number, and the receiver uses the numbers to

place received packets in the correct order, discarding duplicate packets and identifying missing

ones.

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http://en.wikipedia.org/wiki/Automatic_repeat-requesthttp://en.wikipedia.org/wiki/Frame_(telecommunications)http://en.wikipedia.org/wiki/Sliding_window_protocolhttp://en.wikipedia.org/wiki/Sliding_window_protocolhttp://en.wikipedia.org/wiki/Acknowledgement_(data_networks)http://en.wikipedia.org/wiki/Redundancy_checkhttp://en.wikipedia.org/wiki/Data_transmissionhttp://en.wikipedia.org/wiki/Protocol_(computing)http://en.wikipedia.org/wiki/Data_Link_Layerhttp://en.wikipedia.org/wiki/OSI_modelhttp://en.wikipedia.org/wiki/Transmission_Control_Protocolhttp://en.wikipedia.org/wiki/Automatic_repeat-requesthttp://en.wikipedia.org/wiki/Frame_(telecommunications)http://en.wikipedia.org/wiki/Sliding_window_protocolhttp://en.wikipedia.org/wiki/Sliding_window_protocolhttp://en.wikipedia.org/wiki/Acknowledgement_(data_networks)http://en.wikipedia.org/wiki/Redundancy_checkhttp://en.wikipedia.org/wiki/Data_transmissionhttp://en.wikipedia.org/wiki/Protocol_(computing)http://en.wikipedia.org/wiki/Data_Link_Layerhttp://en.wikipedia.org/wiki/OSI_modelhttp://en.wikipedia.org/wiki/Transmission_Control_Protocol

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GO BACK N-ARQ

Go-Back-N ARQ is a specific instance of the automatic repeat request (ARQ) protocol, in which

the sending process continues to send a number offrames specified by a window size even

without receiving an acknowledgement (ACK) packet from the receiver. It is a special case of

the general sliding window protocol with the transmit window size of N and receive window size

of 1.

Go-Back-N ARQ is a more efficient use of a connection than Stop-and-wait ARQ, since unlike

waiting for an acknowledgement for each packet, the connection is still being utilized as packets

are being sent. In other words, during the time that would otherwise be spent waiting, more

packets are being sent. However, this method also results in sending frames multiple times if

any frame was lost or damaged, or the ACK acknowledging them was lost or damaged, then that

frame and all following frames in the window (even if they were received without error) will be

re-sent. To avoid this, Selective Repeat ARQ can be used.

CONFIGURATION SETTINGS

1. Network Emulator Unit:

Data rates 8, 16, 32, 64,128, 256, 512Kbps, 1Mbps

Topology Bus, Ring, Star (optional)

Delay 0 to 15 bits between each pair of nodes

Error Generators (between one pair of Bit Error 0 to 10-6

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http://en.wikipedia.org/wiki/Automatic_repeat_requesthttp://en.wikipedia.org/wiki/Data_framehttp://en.wikipedia.org/wiki/Acknowledgement_(data_networks)http://en.wikipedia.org/wiki/Sliding_window_protocolhttp://en.wikipedia.org/wiki/Stop-and-wait_ARQhttp://en.wikipedia.org/wiki/Selective_Repeat_ARQhttp://en.wikipedia.org/wiki/Automatic_repeat_requesthttp://en.wikipedia.org/wiki/Data_framehttp://en.wikipedia.org/wiki/Acknowledgement_(data_networks)http://en.wikipedia.org/wiki/Sliding_window_protocolhttp://en.wikipedia.org/wiki/Stop-and-wait_ARQhttp://en.wikipedia.org/wiki/Selective_Repeat_ARQ

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nodes) Frame Error 0 to 10-5

Nodes 6 nodes per NEU (3 PCs can be connected

per NEU. Each PC acts as 2 nodes)

PC plug-in card 32 bit, 33MHz PCI Bus (PCI ver 2.0

compliant)

MAC Layer support ALOHA, CSMA, CSMA /CD

Nodes 2 nodes per NIU

2. Network Interface Unit:

Configuration PC1 PC2

Node ID 0 0

Baud rate 8 Kbps(at both configuration

menu and NEU)

8 kbps( at both configuration

menu and NEU)

IPD(Inter Packet Delay) 2000ms 2000ms

Protocol ALOHA ALOHA

Duration 100s 100s

Packet length 1000 bits 1000 bits

Bit delay 0(at NEU) 0(at NEU)

Direction Sender Sender

My Address 1 2

Time Out Time = 3000ms

FORMULA USED:

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OBSERVATIONS & GRAPHS

1. STOP & WAIT PROTOCOL:

Bit Error Rate No. of Transmitted

Packets

No. of Received Packets

0 14 14

1.00E-05 12 12

1.00E-04 11 11

1.00E+05 10 10

1.00E-02 10 10

1.00E-01 9 9

Graph:

2. SLIDING WINDOW PROTOCOL

Observations:

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Bit Error Rate No of Transmitted

Packets

No. of Received

Packets

14 14

1.00E-04 12 12

1.00E-02 10 10

Graph:

3. GO BACK-N PROTOCOL

Observation Table:

Time Out ( in No. of Transmitted No. of Received

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ms) Packets Packets

0 14 14

1.00E-06 12 12

1.00E-04 11 11

1.00E-02 10 10

Graph:

RESULT & CONCLUSION:

Flow Control algorithms e.g. Stop and Wait, Sliding Window, GO Back N for data transmission

have been implemented between the connected nodes using the LAN Trainer Kit and graphs

have been obtained showing Transmitted packets v/s BER.

EXPERIMENT # 8

Problem statement: Study and implementation of DS-SS modulation and demodulation through

programming of CDMA kit.

REGISTER SETTING FOR MODULATION:

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1. Chip rate calculation:

Chip rate = fchiprate*2^24/40MHZ

Fclk = 40MHZ

We have chip rate of 1MHZ,

Chip rate = 1MHZ*2^24/40MHZ

= 2^24/40

= (419430) DEC

= (066666) HEX

= (06 66 66) HEX

Register 0 - 66

Register 1 - 66

Register 2 - 06

2. Spreading factor calculation:

We take 1+x+x^4 as a generator polynomial

i.e. N = 4 (maximum power of polynomial)

Code period = (2^N)-1 = (2^4)-1 = 15

We can write this = (00010010) DEC

= (00 00 0F) HEX

Register 3 - 0F

Register 4 - 00

Register 5 - 00

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3. Code Selection:

001 = Gold code = (01) H

010 = MLS code = (02) H

011 = Barker code = (03 )H

Register 6 - MLS (02)

4. Sequence generator polynomial: 1+x+x^4

Register 7 - 09

Register 8 - 00

Register9 - 00

Register 10, 11, 12 are changed when we use gold code or Barker code, for MLS these registers

are set to 00

5. Offset carrier frequency = fc*2^24/fsample_clk = REG13, REG14, REG15.

6. Signal gain: maximum 255 = (FF) HEX = REG16

7. Noise gain: AWGN

Maximum 255 = (FF) HEX = REG17

Minimum 0 = (00) HEX = REG17

We take minimum (00) HEX

8. For Spreading: (MODULATION)

REG18 = (bit7, bit6, bit5, bit4, bit3, bit2, bit1, bit0)

Bit0 for internal/external clock selection

0 = internal clock

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1 = external clock

We select internal clock so set Bit0 to 0

Bit1 for output sample format

0 = 2s complement

1 = unsigned

We select Output sample format to unsigned so Bit1 set to 1

Bit3-2 for Modulation scheme

00 - BPSK

01 = QPSK

10 = OQPSK

We select modulation to BPSK so Bit3-2 set to 00

Bit5-4 for Test mode

0- Disabled

1- Pseudo random bit sequence (PBRS-11)

10- un-modulated carrier

We select Test mode as PRBS-11 so Bit5-4 set to 01

Bit6 for Spectrum inversion

Invert Q bit

0-off

1-on

Bit7 for Interpolation

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Interpolation to maximum clock rate

0 = off

1 = on

REG18 = (1001 0010) = (92) HEX

9. REGISTER 19 Setting:

REG19 = (bit3, bit2, bit1, bit0)

Bit- 0 for output data flow

0 = output data is pushed to the next module

1 = output data is pulled by next module

We set this to 0

Bit1 for input format

0 = 1-bit serial

1=2-bit parallel

We set this to 0

Bit-2 for output spectrum shaping filter enables/disable

0 = disabled

1 = enabled

We set this to 1

Bit-3 for Enable/Disable spectrum spreading

0 = disabled

1 = enabled

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We set this to 1

REG19 = (1100) = (0C) HEX

Table: COM1012 DSSS MODULATOR REGISTERS (HEX)

REG 0 66 REG 10 00

REG 1 66 REG 11 00

REG 2 06 REG 12 00

REG 3 0F REG 13 00

REG 4 00 REG 14 00

REG 5 00 REG 15 00

REG 6 02 REG 16 00

REG 7 09 REG 17 00

REG 8 00 REG 18 92

REG 9 00 REG 19 0C

REGISTER SETTING FOR DEMODULATION:

Chip rate calculation:

1. Chip rate = fchiprate*2^24/40MHZ

Fclk = 40MHZ



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= 2^24/40

= (419430) DEC

= (066666) HEX

= (06 66 66) HEX

Register 0 - 66

Register1 - 66

Register2 - 06



i.e. N = 4(maximum power of polynomial)

Code period = (2^N)-1 = (2^4)-1 = 15

It can be written as = (00010010) DEC

= (00 00 0F) HEX

Register 3 - 0F

Register4 - 00

Register5 - 00

3. Code Selection:

001 = Gold code = (01) H

010 = MLS code = (02) H

011= Barker code = (03) H

Register 6 we set to MLS code - 02

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Register 7 - 09

Register8 - 00

Register9 - 00


are set to 00

5. Nominal carrier frequency (NCCF) = fc*2^24/fchiprate = REG13, REG14, REG15.

6. Register Setting For REG 16.

REG16 (bit7, bit6, bit5, bit4, bit3, bit2, bit1, bit0)

Bit0 = 0 (always)

Bit1 for input sample format

0 = 2s complement

1 = unsigned

Bit3-2 for Carrier frequency loop gain

00 = nominal

01 = 2*loop gain

10 = 4*loop gain

11 = 8*loop gain

Bit4 Reserved so always 0

Bit5 for spectrum inversion

Invert Q bit

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0 = off

1 = on

We select invert off i.e. 0

Bit 6 always 0

Bit7 0 (Freeze)

Now REG16 = (0 0 0 0 0 0 1 0) BIN = (02) HEX

7. Register Setting for REG 17


Bit1-0 is for output sample format

00 = I/Q parallel

01 = I/Q serial (never use with BPSK as there is no information data on the Q channel)

Bit3-2 for demodulation scheme

00 = BPSK

01 = QPSK

REG17 = (0 0 0 1) = (01) HEX

Table: COM1012 DSSS DEMODULATOR REGISTERS (HEX)

REG 0 66 REG 10 00

REG 1 66 REG 11 00

REG 2 06 REG 12 00

REG 3 0F REG 13 00

REG 4 00 REG 14 00

REG 5 00 REG 15 00

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REG 6 02 REG 16 02

REG 7 09 REG 17 01

REG 8 00

REG 9 00

RESULT & CONCLUSION: The implementation of DS-SS modulation and demodulation

through programming of CDMA kit have been studied and graphs have been traced.

EXPERIMENT # 09

Problem statement: Addition of AWGN to the signal and evaluation of BER performance

BPSK/QPSK DSSS signal.

# Register setting for BPSK with addition of AWGN:



Fclk = 40MHZ



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= 2^24/40

= (419430) DEC

= (066666) HEX

= (06 66 66) HEX

Register 0- 66

Register1- 66

Register2- 06




Code period = (2^N)-1 = (2^4)-1 = 15

Can be written as = (00010010) DEC

= (00 00 0F) HEX

Register 3- 0F

Register4-00

Register5-00

3. Code Selection:

001 = Gold code = (01) H

010 = MLS code = (02) H

011 = Barker code = (03) H

Register 6 we set to MLS code - 02

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4. Sequence generator polynomial :1+x+x^4

Register 7- 09

Register8-00

Register9-00


are set to 00

5. Offset carrier frequency = fc*2^24/fsample_clk=REG13, REG14, REG15.

6. Signal gain: maximum 255=(FF)HEX=REG16

7. Noise gain: AWGN



We take maximum (FF) HEX

8. For Spreading: (MODULATION)

REG18=(bit7,bit6,bit5,bit4,bit3,bit2,bit1,bit0)


0 = internal clock

1 = external clock



0 = 2s complement

1 = unsigned

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0- BPSK

01 = QPSK

10 = OQPSK


Bit5- 4 for Test mode

0- Disabled


10- unmodulated carrier



Invert Q bit

0- off

1- on



0 = Off

1 = on

REG18 = (1001 0010) = (92) HEX

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Bit0 for output data flow

0 = Output data is pushed to the next module


We set this to 0


0 = 1-bit serial

1 = 2-bit parallel

We set this to 0

Bit2 for output spectrum shaping filter enables/disable

0 = disabled

1 = e nabled

We set this to 1

Bit3 for Enable/Disable spectrum spreading

0 = disabled

1 = enabled

We set this to 1

REG19 = (1100) = (0C) HEX


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REG 0 66 REG 10 00

REG 1 66 REG 11 00

REG 2 06 REG 12 00

REG 3 0F REG 13 00

REG 4 00 REG 14 00

REG 5 00 REG 15 00

REG 6 02 REG 16 00

REG 7 09 REG 17 FF

REG 8 00 REG 18 92

REG 9 00 REG 19 0C

Register setting for QPSK with addition of AWGN



Fclk = 40MHZ



= 2^24/40

= (419430) DEC

= (066666) HEX

= (06 66 66) HEX

Register 0- 66

Register1- 66

Register2- 06

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Code period = (2^N)-1=(2^4)-1=15

we can write this = (00010010)DEC

= (00 00 0F)HEX

Register 3- 0F

Register4- 00

Register5- 00

3. Code Selection:

001 = Gold code = (01) H

010 = MLS code = (02) H

011 = Barker code = (03) H

Register 6- 01


5. Register 7- 00

6. Register8- 00

7. Register9- 09


are set to 00

8. Offset carrier frequency = fc*2^24/fsample_clk=REG13, REG14, REG15.

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9. Signal gain: maximum 255 = (FF) HEX = REG16

10. Noise gain: AWGN



We take maximum (FF) HEX

11. For Spreading (MODULATION)

REG18 = (bit, bit6, bit5, bit4, bit3, bit2, bit1, bit0)


0 = internal clock

1 = external clock



0 = 2s complement

1 = unsigned



0- BPSK

1- QPSK

10- QPSK


Bit5-4 for Test mode

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0- Disabled


10- unmodulated carrier



Invert Q bit

0- off

1- on



0 = Off

1 = on

REG18 = (1001 0110) = (96) HEX



Bit0 for output data flow

0 = Output data is pushed to the next module


We set this to 0


0 = 1-bit serial

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1 = 2-bit parallel

We set this to 0

Bit2 for output spectrum shaping filter enables/disable

0 = disabled

1 = enabled

We set this to 1

Bit3 for Enable/Disable spectrum spreading

0 = disabled

1 = enabled

We set this to 1

REG19 = (1100) = (0C) HEX


REG 0 66 REG 10 00

REG 1 66 REG 11 00

REG 2 06 REG 12 00

REG 3 0F REG 13 00

REG 4 00 REG 14 00

REG 5 00 REG 15 00

REG 6 02 REG 16 FF

REG 7 09 REG 17 00

REG 8 00 REG 18 96

REG 9 00 REG 19 0C

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RESULT & CONCLUSION: Addition of AWGN to BPSK and QPSK DSSS signal has been

performed and graphs have been obtained.

78919288 simulation lab

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