Mar 05

The Last Chapter

Being back for almost a week now and I figured I should post a closing blog thing here.

A last look at the exams perhaps: I passed all my four exams (20, 22, 28 and 30 on 30), now I still need to get the “Transcript of Records” with those grades so I can officially present them to Group T. Mailing the incoming office of PoliTO asking for it is all you have to do… if all your professors have registered your grades already, which one of mine hasn’t done yet. Typically Italian-style, no rush ;)

There have been a lot of rumors about the exams at PoliTO, I can’t confirm them but ‘my sources’ tell me 90% of the people cheat on their exam and they easily get away with it! Such a thing is completely unthinkable in Belgium but scenarios such as “Please put away your slides, if I see them when I pass next time, you’ll get minus 4” aren’t uncommon. People texting, taking photos and collaborating, it’s pretty insane if you ask me.

I’m not generalizing of course but I’ve heard this from a lot of different people so it must be a thing. Italians are so focused on getting 28 or higher as companies expect nothing less than those grades. I’ve seen people retake their exam with a 25 out of 30 because they thought it was a “low” grade.

Retaking at PoliTO isn’t really hard, so failing the first time is not a big issue. You can send an email to your professor asking to delete the ‘bad’ grade and register for the second time which is usually about two weeks later. If you still haven’t passed then you’ll have to come back in another exam period (February, July or September).

That was it for me, Erasmus has been such a great experience you can only believe it if you have experienced it yourself. And so I close this Erasmus segment of my blog, feel free to ask me questions about Torino or PoliTO in case something is not clear for you, I’ll be happy to help you!

Mar 01

Copper Line Attenuation MAR1 Model

One of the homeworks I had to do during my Communication Systems course at the PoliTO was calculating some attenuation values of a copper line in function of distance and frequence, based on the MAR1 model. Oddly enough, Googling MAR1 I couldn’t find a single thing about the model so I decided to post my work here so people can take a look at how it works. I’ve made this in Matlab.

The following function computes the attenuation:

function [att] = mar1(d, f)
% mar1(d, f)    Calculates the attenuation in dB
%               depending on length d (in km) and
%               frequency f (in Hz)
 mu0 = 4*pi*10^-4;
 R0 = 277.623806;
 Lalpha = 421.576013 * 10^-6;
 Linf = Lalpha;
 a = 1.470148;
 b = 2;
 c = 2.765;
 delta = 0.001123;
 C1Mhz = 49.792437 * 10^-9;
 Zl = 100;
 Zs = Zl;
 Cf = C1Mhz * (f / 10^6)^-(2*delta/pi) * cos(delta);
 sf = (mu0 * 1i * f) / ((0.75^2) * R0);
 Zf = 1i * 2 * pi * f * Linf + R0 * ((1/4) + (3/4) * sqrt(1 + (a*sf*(sf+b))/(sf+c)));
 Yf = 2*pi*f*Cf*(1i+tan(delta));
 Z0 = sqrt(Zf/Yf);
 gamma = sqrt(Zf * Yf);
 A = cosh(gamma*d);
 B = Z0*sinh(gamma*d);
 C = (1/Z0) * sinh(gamma*d);
 D = cosh(gamma*d);
 ratio = Zl / (A*Zl + B + C * Zl * Zs + D * Zs);

If you put this in a nested loop that iterates over some distances and frequencies and plot it afterwards, you get a nice result such as this.

MAR1 Copper Line Attenuation

MAR1 Copper Line Attenuation

This shows you why ADSL is slower than for example internet access by cable. A reason why more recent versions of ADSL and VDSL are faster is because the line length is shortened and thus the frequency can be raised, and in turn so is the symbol rate.

Jan 29

Communication Systems Exam ’12-’13

Today I had my first exam at PoliTO. When I first came to Torino in September there were also exams going on and they seemed to be pretty organised. People were called by their name to be able to enter the room, they told us you needed to use the terminals in the hallways to print some kind of “entry ticket” which you had to show as your name was called.

Fast forward to today, we could just enter the room where we had exam, everyone was just talking until the professor arrived. People just had to sit at both ends of a row and one in the middle, didn’t matter if your coat and backpack were next to you. Nothing was said about having your wallet or a cellphone in your pocket but to be sure I turned it off and put it away.

The professor came around during the exam, writing down your name on a paper to ‘register’ your attendance. That’s about all the formalities there were today, no papers or name calling at all!

For those who want to know which questions we got on the first exam day of Communication Systems, feel free to download the list of all possible questions: List of questions 2012 2013

The ones asked on the exam were questions 2, 5, 7, 14, 18 and 21.