Thursday, December 18, 2008

Argh. the stupidity !

Picture this..
you leave home and you wonder, what if you might be hit by some 1/4" steel balls at 150 feet/second in the eye ? Fear no more, coz you could always buy this.

The lenses run almost perfectly clear to a nice, dark tint in the sun, with nearly 100 percent UVA/B protection. They have an ANSI Z87.1+ rating, which means they’re shatter-proof even when struck by a 1/4-inch steel ball at 150 feet/second. The lenses are polycarbonate, so a significant scrape against sand, ground, etc. would probably scratch them.


I read the ANSI Z87 part, and I thought wtf !

Just imagine wearing these and feeling safe coz you're protected from 1/4" inch steel balls hitting your eyes at 150feet/second and then a little while later absentmindedly dropping your shades on the road. You pick them up and find out that you cant really use them anymore coz now they're scratched. How ridiculously stupid will you feel then ? protection against 1/4" steel balls (dont forget the speed: 150 feet/ second) but no protection against a simple ground scratch. what about 151 feet /second ?

damn i dont know if im just too happy coz my exams are over that makes me giggle , or is this just pure stupidity.

Thursday, December 11, 2008

Some more WiFi

Recently, I tried a simple experiment. In WiFi you can choose to transmit each packet at different bit rates. eg. for 11b, your options are 1, 2, 5.5, 11Mbps. There's a lot of research in getting the best throughput by controlling the Tx rates. This is usually done to adapt to the flaky medium. I didnt find any research on the power consumptions of these rate control algorithms. So here's what I did and found out ..

Linux Kernel, hostAP driver, Prism3 chipset based PCMCIA adapter, and really old laptop (P3 something or other, doesnt matter). Implemented ARF, AARF and SampleRate and compared their PS.

Proved the theory that Bicket states in his paper; lower bit rates dont necessarily give better delivery probabilities. Lower bit rates infact consume more power. Intuitively, they take longer to transmit, hence keep the Tx circuit alive for longer. Given a flaky medium, these lower bit rates are major power hogs, coz of the packet retries involved. The following graphs show these results ..

This is w/o wifi ON, just for comparison. ~0.7V drop.

This is for AARF. ~1.5V drop. (ARF is similar)

This is SampleRate. ~1.0V drop.

Basically, SampleRate looks at a 10 sec history and chooses the best rate that gave an average Tx time thats lower than the current bit rate. In short it's got some intelligent way of switching.(Read the thesis if you're really interested), or ask me :p

This actually is quite important. Think embedded systems. Every device has WiFi out there. Power saving features directly affect the usability of these devices. My guess is, the differences in voltage drops will be more significant in those kind of devices.

More later ..

Monday, April 21, 2008


I've been wanting to have an Aha! -moment for quite sometime now and I think I got it today.

An Aha!-moment is one where something suddenly makes sense. Unfortunately, I cant remember the last time I had one of these, but I'm sure I've had em, but never really gave it enough thought to objectify it.

So, Dad sent me this link. It's about this Neuroanatomist who watched her own brain deteriorate and was able to narate this after she recovered. Very touching and inspiring !

What I gathered from it, is a startling realization of my own way of thinking. Just the realization of how the 2 halves of my brain can think in different ways and also realizing 'when' it happens, suddenly seems to explain 'why' it happens. Now, I've yet to see, if my theory is right, but I think I've got something interesting going on here. Hopefully, I will be able to convince myself through some experiments.

The way I understand it is, the Left brain = Logical thinking and Right brain = Day dreaming. Honestly, I dont find much use of my Right brain .. yet... (maybe I can sell it off for a couple of million bucks and get that Bugati Veyron) :p

Even now, as I'm writing this, there's something interesting happening. As I'm thinking of what to write, my left brain is controlling the flow of thought into words and the right brain is simultaneously thinking of how to phrase it, so that YOU find it interesting. This is easier if you can visualize someone you know well when he/she is reading this. If I were to write this in a personal journal which noone but me, is going to read, it would be very different. Probably more detailed with more examples/instances. Think of it like preparing for a presentation. You study the topic so you understand it well, now the next task is to prepare slides and a Talk so that your audience follows it. Especially, when your audience is predominantly Chinese. :) You have to re-phrase it, use simple english, multiple ways of getting the point across and so on. If it were your friends/colleagues (people you know well), you'd be thinking very differently. This probably is an example of both halves coming together in harmony.

While reading something highly technical, for the kind of 'effective' reading required, I think the Left brain is most dominant. It tries to relate concepts learned from the past to what you're reading now. And when the topic is really boring, and you loose your discipline, the right brain leads to digression/distraction. At other times, the out-of-the-box thinking comes from the Right half. Its when your left brain has done its job and you have understood a concept very well, your right half could perhaps try to apply it in a completely different angle. (Lateral thinking ?)

There's a lot more to this, but for further discussion, a couple of Beers/Wine, would get me talking...

Come to think of it, I should try some experiments the next time I'm High. I've always been intriguied by the fact that whenever I'm inebriated I loose all inhibitions and am able to make better conversations with the 'other' species. (read: females) ... or maybe not. :D