# Wrong number of samples per symbol for BPSK in MATLAB?

Goal is to achieve 8 samples per symbol for BPSK signal. After analyzing the plot of below code, IMHO its not 8 sps, I am right? If yes what I do wrong?

% Generate BPSK signal
data = randi([0 1],20,1);
bpskModulator = comm.BPSKModulator;
modData = bpskModulator(data);
% Filter parameters
rolloff = 0.35;
span = 6;
sps = 8;
rrcFilter = rcosdesign(rolloff,span,sps);
txSig = upfirdn(modData,rrcFilter,sps);
figure
plot(real(txSig), '-*')
title("Upfirdn interpolated")


• Marcin- this does look like 8 samples per symbol to me. Can you add the eye diagram of this and show your symbol boundaries and what you count for samples per symbol? – Dan Boschen Jun 9 at 15:00
• Dan- after plotting an eye diagram, 8 samples per symbol gives good result so it has to be correct. My understanding was wrong. You made me realize that sampling points do not always occur at peak points in time domain waveform. Here is the eye diagram. I added some noise (30 dB SNR) postimg.cc/LgHyj42X – Marcin Puchlik Jun 10 at 8:25