# How to determine bit rate and symbol rate

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#### Shruti01

##### Member
Hello all,

Can anybody tell me how to determine the bit rate and symbol rate of a signal.

Thanx

#### Shruti01

##### Member
My received signal contains just a set of sample points...... How to determine bit rate and symbol rate from such a received signal.......

Thanx....

#### SCPD

##### QRT
Use a program that can display an eye pattern.

Adjust the program's symbol rate until you have a consistent eye pattern.

An eye pattern with one opening (the "eye") is a two-level signal - each symbol is one bit.

An eye pattern with three openings (three vertical eyes) is a four level signal - each symbol is two bits.

For some waveforms (like FFSK), the "eyes" are aligned horizontally, not vertically.

#### Shruti01

##### Member
Could u post a matlab code for display eye pattern of BPSK, DBPSK (Differential BPSK), QPSK, DQPSK, OQPSK (Offset QPSK), BFSK, BASK............

Thanx.............

#### Shruti01

##### Member
Hello,

I have got the eye patterns for BPSk and QPSK.... I have attached the eye patterns in attachments.... The 1st image is the eye pattern of bpsk and the 2nd image is the eye pattern of qpsk.... Kindly let me know whether the eye patterns I got are right or wrong.

Thanx...

#### Attachments

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#### Shruti01

##### Member
Hello,

I have written matlab codes for plotting of eye patterns for BPSK and QPSK... How to determine bit rate and symbol rate from these patterns....Thanx...

The matlab code for BPSK is follows:

clc;
close all;
clear all;
no_of_bits=10;
no_of_samples=200;
threshold = 0.5;
Fs=30; % Sampling frequency
rand('state',123);
t1=linspace(0, 1, no_of_samples);
w=cos(2*pi*1000*t1);
A = rand(1,no_of_bits); % Generate a random sequence
for i=1:no_of_bits
if (A(i)>=threshold)
A(i)=1;
else
A(i)=0;
end
end
d = A(1:no_of_bits); % Binary sequence
b=2*d-1;
for j=1:length(b)
bpskmod=b(j).*w; % BPSK modulated signal
bpskmod;
received=bpskmod;
end
subplot(2,1,1)
axis([0 1.5 -1.5 1.5])
eyescat(received,0.5,Fs);

Eye pattern for bpsk is as follows:

The matlab code for qpsk is as follows:
clc;
close all;
clear all;
no_of_bits=10;
no_of_samples=200;
Fs=30;
threshold = 0.5;
rand('state',123);
t1=linspace(0, 1, no_of_samples);
inPhaseOsc = cos(2*pi*1000*t1);
quadPhaseOsc = sin(2*pi*1000*t1);
A = rand(1,no_of_bits); % Generate a random sequence
for i=1:no_of_bits
if (A(i)>=threshold)
A(i)=1;
else
A(i)=0;
end
end
d = A(1:no_of_bits); % Binary sequence
b=2*d-1;
o = b(1:2:end); % Separating odd bits
e = b(2:2:end); % Separating even bits
for j=1:5
qpskmod= e(j).*inPhaseOsc+o(j).*quadPhaseOsc;
qpskmod;
received=qpskmod;
end
% plot the eye pattern diagram of the received signal
subplot(2,1,1)
eyescat(received,0.5,Fs)
axis([0 1.5 -1.5 1.5])

Eye diagram for qpsk is as follows:

#### Attachments

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• 15.1 KB Views: 2,086
Last edited:

#### SCPD

##### QRT
The 1st image is the eye pattern of bpsk and the 2nd image is the eye pattern of qpsk.... Kindly let me know whether the eye patterns I got are right or wrong.
The first image looks good. The second looks as though the time interval of the image is slightly longer than the symbol time period. The left/right edges don't seem to coincide with the symbol boundaries.

#### Shruti01

##### Member
Hello,

M not getting proper eye pattern for BPSK.... I should be getting an eye pattern with one opening i.e. only one eye for BPSK but I am not getting that... I have attached my matlab code for BPSK as follows:

clc;
close all;
clear all;
no_of_bits=10;
no_of_samples=200;
threshold = 0.5;
Fs=30;
rand('state',123);
t1=linspace(0, 1, no_of_samples);
w=cos(2*pi*1000*t1);
A = rand(1,no_of_bits); % Generate a random sequence
for i=1:no_of_bits
if (A(i)>=threshold)
A(i)=1;
else
A(i)=0;
end
end
d = A(1:no_of_bits); % Binary sequence
b=2*d-1;
for j=1:length(b)
bpskmod=b(j).*w; % BPSK modulated signal
bpskmod;
received=bpskmod;
end
subplot(2,1,1);
eyescat(received,0.5,Fs);
axis([-0.5, 0.5, -1.5, 1.5]);
xlabel('Symbol timing');
ylabel('Amplitude');
title('Eye Diagram for BPSK');
grid on;

Eye pattern which I got after running the above program is as follows:

#### Attachments

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