How to determine bit rate and symbol rate

Hello all,


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


Thanking You.

If ts is the sample time of the input signal, in seconds, then bit_rate=bit_per_sample/ts;
bit_per_sample=1 for BPSK; 2 for QPSK etc...

what if ts is not given ten how to determine bit rate and symbol rate.....

As far as i know u need at least the highest frequency in your signal.
bit_rate= sampling rate x bit_per_sample (According to Nyquist theorem sampling rate must be at least 2 times the highest frequency in the signal.)
(Sample Rate = 2 X Highest Frequency Used)

Maybe there are other ways...

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

The terms bit rate and symbol rate can't be related to an empirical waveform (except for obvious cases, e.g. a binary data stream), because you can't see per se the implemented modulation scheme. You need to know it.

But if a choice of possible modulation schemes is known, you should be able to determine which is actually used by interrogating the waveform.

To give a simple visual example. If you see a multilevel signal, you can't know exactly how many different amplitude levels are actually coded in it. A similar problem will be faced in time domain.

Hi FvM,
So when u know the modulation scheme beforehand, how can you determine the bit rate and the symbol rate? Is the formula given above correct?

Hello,
I have got following eye diagrams for bpsk and qpsk... Kindly have a look at the eye patterns n lemme know whether the eye patterns are right or wrong...
eye diagram for bpsk
View attachment eye diagram for bpsk.bmp
eye diagram for qpsk
View attachment eye diagram for qpsk.bmp

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:
View attachment eye diagram of bpsk.bmp


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:
View attachment eye diagram of qpsk.bmp