Category Archives: English

English posts

Jan 15

The Bingham formula

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During my time at the Politecnico di Torino I attended a Communication Systems course which focused on systems such as ADSL/VDSL, DVB-T, LTE and modulation techniques such as PSK, QAM, DMT/OFDM. That being said, the one formula we always used to compute the cardinality of the constellation used was the famous Bingham formula.

When I was looking at the different parameters of this formula I figured I would do a search on Google to see if there was more information to be found. However, a search for “Bingham formula” resulted in not a single useful link. If this is such a famous and used formula, why is there nothing on the searchable web about it? Not even an entry on Wikipedia? This is an honest question, if someone knows please tell me.

What does this formula look like you ask? Here it is:

Bingham Formula

with:
m: the number of bits
1/10: used when solving for a BER of P(e) = 10^-7, 1/14 if you’re using a BER of 10^-10 (e.g. for DVB-T)
Prx: received power
Pn : noise power
Yc/Ys: non-ideality in relation to Shannon + recovery by coding gain
Ym: margin parameters taking other losses into account

When computing the achievable bitrate for a given band, you’d use Rb = Rs * m, where Rs is the symbol rate. Not going in to much detail here as I could spend another three paragraphs on things such as delay spread, guard time and cyclic prefix, just know that once you have solved the equation and have m, you know which QAM you can use. For example, if m = 3, you can use a 2^m = 2^3 = 8-QAM constellation, so that would mean 3 bits per symbol.

The difference with the Shannon formula is that you take into account some non-ideal properties, if you want the ideal bitrate, just take Yc/Ys = 1 and neglect 1/Ym.

Dec 16

MySQL Can’t get hostname for your address

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Error No. 1042
Can’t get hostname for your address

That’s what I got greeted by today. Not sure why as I was connecting to a database that I use almost every day. You’d think it to be a DNS issue, but the url was already resolved to the IP. Anyway, if you get this error and you want to fix it, go to the following folder

C:\ProgramData\MySQL\MySQL Server 5.5\ (or whatever version of MySQL you have installed)

Just add skip-name-resolve option to the [mysqld] section of your my.cnf/my.ini and reboot your MySQL server. That fixed the issue for me.

Dec 10

Italian A1 exam

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Last week we finally had our Italian level A1 exam. This is the most basic version of the Italian language course you can take. If you don’t know a single word (besides mama mia! perhaps) you usually take this difficulty level.

For anyone coming to Politecnico di Torino and having this exam as a part of their Learning Agreement, rejoice, as it’s six credits you will never get as easy again as these. Basically, if you summarize the grammar rules you get from the coursebooks and learn the gender of a handful of words along with the irregular participio passato forms table you will do just fine on the exam.

This is a multiple choice test without error correction. There are fifty questions testing your knowledge of prepositions, verb conjugation and the like. However, of the five possible answers there are always four that are too obviously wrong. If you have some notion of Italian you can easily guess the correct answer by eliminating the, sometimes hilarious, possibilities.

So don’t be afraid or be stressed for this exam. It’s easy, especially if you went to the courses at the beginning of the semester. I’d say you would need about 2 to 4 hours of studying if you want to get 45+ out of 50. To my surprise I only made one mistake, sadly enough you cannot view what it was.

I really don’t know if the A1 exams of Italian are all this easy around the world, but an A1 certification tells someone you understand Italian on a really basic level. If you’re motivated I suggest you skip A1 and start with the A2 level, that might be more interesting and challenging for any student who has notion of Roman languages.