802.11n - The NeXt Generation Wireless Standard

From my first blog, you may know that I have joined another firm recently. Here, I will be working in the same domain as my earlier one - IEEE 802.11 a.k.a Wi-Fi or Wireless LAN [WLAN], my personal favorite. Now that I am having some free time at my new firm since my joining formalities are not finished, I thought I will spend some time researching the new trends in wireless domain. It is then that I came across a commercial claiming a data rate of around 300Mbps for a wireless product. But the products which I worked in, 802.11g compliant, will provide a maximum of 54Mbps (raw data speed) only. I had some idea about 802.11n, but I never thought they will provide this much speed. And thus, I thought I’ll spend some of my time researching about 802.11n.

A word of caution before I go in to the details: I am assuming the reader of this blog is familiar with IEEE 802.11 basics, not in the user perspective, but in a developer one since this contains technical stuff unlike my other blogs. Non-technical people, skip to the summary section.

Setting the new standard
As I said, the wireless product I previously worked had a maximum data rate of 54Mbps. It was an 802.11g certified product. In the 802.11 base spec (1999), three PHY layers were defined, an FHSS (Frequency-Hopping spread spectrum), a DSSS (Direct Sequence Spread Spectrum), both in the 2.4GHz band and an Infrared PHY which is obsolete now. Then released were the 802.11b (DSSS) (July 1999) which supports 11Mbps, 802.11a (OFDM – Orthogonal Frequency Division Multiplexing) (July 1999), which supports the 54Mbps raw data rate. But 11a didn’t get in to that wide acceptance because of the very fact that it operated in the 5GHz spectrum. Then the 11g came with 54Mbps data rate which operated in 2.4GHz spectrum and is used by almost all the Wi-Fi certified products now. In the case of 802.11n, the draft specifies many ‘options’, like many configurations and we can make it work in any possible configurations. With every possible options turned on, you will get a raw data rate up to 600Mbps. (Data taken from http://www.broadcom.com/docs/WLAN/802_11n-WP100-R.pdf) I will give a comparative table to show the details rather than explaining.

As you can see from the table, 11n has a very high data rate compared to others. But that is the raw data speed with the entire data rate options turned on. From the user level perspective, you will get around 100-200Mbps. Even that is a great boost from the conventional 802.11ga mode.

802.11n specific features
One of the great features of 11n is the use of multiple antennas which is known as MIMO - Multiple Input Multiple Output. Basically it uses more than one antenna to send the data packets in multiple streams. It exploits the phenomenon called multipath, which usually is treated as interference in radio communications. Two important benefits of MIMO are antenna diversity and time-space multiplexing. The draft specifies antenna configuration option of up to 4x4. This feature can be a power consuming one and so the draft n specifies a power save mode also. So the multiple antenna configurations are used only when maximum throughput and data rate is required.
Other options in the 11n specification are,

• Better OFDM - The OFDM in 11n is improved so that the maximum data rate which can be achieved is 65Mbps rather than 54Mbps in 11g.
• Wider channels – 11n provides options for 40MHz channels instead of the conventional 20MHz ones. But the downside is that the number of channels will be less and so it doesn’t give much space for other devices to transmit in the same airspace.
• Reduced Inter-frame Spacing [RIFS] - A smaller inter-frame spacing than that of 11a or g which uses the SIFS [Short IFS], PIFS [PCF IFS], DIFS [DCF IFS]& EIFS [Extended IFS]
• Aggregation - This feature is used in the case of inter-operability between the legacy modes 11b/g and 11n. It uses transmission burst in between the overhead communication there by improving the efficiency.
• Greenfield Mode - This is an optional mode which allows an all 11n network which doesn’t have to give any backward compatibility with the 11b/g devices.

These are some of the options which can be turned on and off. So by fine tuning them, you can attain really high data rates as compared to the present 11g devices.

Summary
Just going through the table above itself, we can see that the 802.11n will surely bring a revolution in the wireless domain in the case of both data rates and range. But only at the cost of MAC/PHY layer becoming more complex. The applications of 802.11n will become prominent in VoIP (Voice over IP), streaming video and music, gaming, NAS (Network Attached Storage) etc. Already there are around 70 products in the market which are 802.11n Draft 2.0 certified. The 11n standard is supposed to be ratified by fall 2007 or early 2008.

References

• IEEE 802.11 Specifications, 1999 Edition.
• IEEE 802.11a-1999 - Amendment 1: High-speed Physical Layer in the 5 GHz band
• IEEE 802.11b-1999 - Amendment 2: Higher-speed Physical Layer (PHY) extension in the 2.4 GHz band
• IEEE 802.11g-2003 - Amendment 4: Further Higher-Speed Physical Layer Extension in the 2.4 GHz Band
• http://www.broadcom.com/docs/WLAN/802_11n-WP100-R.pdf
• http://www.deviceforge.com/articles/AT5096801417.html
• http://en.wikipedia.org/wiki/802.11#802.11n

ps: If you come across any discrepancies, please do comment on it.

The Tomb Raider in Me...

Some of my friends know that I am a huge fan of the Action/Adventure computer game series, Tomb Raider - starring Lara Croft. If I just say that I like that game, it may be an understatement. I love the game so much that I will do almost anything to get my hands on one of them (I already have all of them) and play them. I even built a website about Lara [I never finished it though]. But there was a time when I browsed through the game reviews me heart really sank [before releasing Tomb Raider Legend]. Even if the first game was a huge success, as the sequels came on, the popularity began going down. And after the fourth in the series, Tomb Raider - The Last Revelation, I was outraged by their [creators] decision to kill such a finest creation of character among all the video games. But on the other side, I have read many gamer reviews screaming for her head after the third game in the series. May be that’s why they killed her. And there was the expansion [as always] Tomb Raider - Chronicles, with the level editor. When they released the level editor, I was sad and happy at the same time. Happy, because I can create and play almost infinite number of custom levels [fan creations also]. Sad, because, I thought that would be the end of it.
To my astonishment, they came again with Angel of Darkness, the 6th in the series. I can’t really say about that game, because, to this day I am not able to fully play it, even if I have the game with me. When it released, I was busy with my studies and career plans and all. Still, somehow I managed to get it, but couldn’t make it to play it. [Its only recently that the computer games are available in India, that too only in cities. In my home place, even now, you won’t be able to find computer games in any store. Back then, in order to get my hands on a Tomb raider game, I had to travel around 500 ~ 700 kilometers to Bangalore or Chennai (~12 hrs - Indian Roads)]

I had been closely watching the tomb raider websites out of my curiosity to know what will happen next. Its then that I saw the ads about Tomb Raider - Legend, the 7th in the series. When I read about the details and expectations and saw the game play trailers, I thought it might be a joke. At the same time I was really excited about it that I bought it at the first chance possible and what to say, it broke all my expectations. Wow! It really was amazing, I couldn’t really believe my eyes first. Eidos did a really wonderful job in bringing back Lara in to the scene. It had almost every element you could hope for in a Tomb Raider game, except that I felt it was a bit easier, even as compared to the first one, that it took only around 8-9hrs to finish the whole game. The graphics, the puzzles, the movements of Lara, the incorporation of mouse to the game play, the environments, the stunt scenes, the music and the list goes on unending.
Now that they have released the latest in the series - Tomb Raider: Anniversary. I started playing it and it is amazing, not just because of its graphics [Legend’s game engine] and game play, but because it is the remake of the first game. Also I was in the middle of playing the first tomb raider game in my N-gage QD (Nokia gaming mobile). So it is much more fun going through the same locations and remembering the first time you played it.
To me, all the Tomb Raider games are so fascinating. At times I asked myself why I love them so much, when my friends say they didn’t like it simply because, it is less in action and more in puzzle solving and at times you get stuck in some unrealistic situations. May be it’s because I like to explore/work alone, the worlds, humans has never set their foot on, like she do, or her boldness that she will do almost anything, just for sport, or the mystic beauty in the music and background sounds they have used, or the locations which coincides with my interests or all of it together. [Sometimes, I did agree to my friends, (only secretly, before Legend), that the game play and graphics are not that good. Also the movies too pictured the ‘relic huntress’ as a super human which I didn’t like much] But the last one is the answer for all their protests against Lara. To all my friends, just play it and you will love the game…
Just refer to this “She’s spent and awful lot of time getting kicked around by her creators. But last year’s Legend went a long way toward redeeming Lara and compensating for the many wrongs done to her and the franchise. Now, Tomb Raider: Anniversary proves that was no fluke.
Gone are the vast black, cubist spaces of the first game, replaced by enormous, gorgeous, detailed levels with plenty of opportunities for vertical movement and vertigo-inducing acrobatics” - Games for Windows Magazine, August 2007, Page 76.
And so my friends, Lara is back in business and she will always remain as a Legend, who hunts for relics and raids the hearts and minds of gamers with her boldness sexiness and her pistols…
http://www.tombraider.com/ [Use your headphones and explore all the pages]

My experiments with 'Call Centres'

Call center girl: [Confident and cheerful] Good morning sir, this is Sonya Mishra calling from airtel mobile to tell you about one of our new schemes.

Me: [Surprised] But I am not using an airtel connection.

Call center girl: It is ok sir, you just listen to our new scheme and then if you like it, you can switch to an airtel connection.

Me: [It was around 9am] No miss, I am not interested, besides, its time for me to go to office, I am a little busy.

Call center girl: But sir, you can at least spare some time to hear the offer and then decide, right? It is very attractive. I am sure you’ll like it.

Me: [Uh! Somehow I want to stop this] But I don’t have connectivity for airtel in my home place. If I take airtel, I won’t be able to get calls when I go home.

Call center girl: [I will make him take it] Do you go home everyday, sir?

Me: No, Here I stay with my friends. I go home mostly once or twice a month.

Call center girl: Then that is ok sir. Since you will be going home once in a month, you won’t miss any important calls right??

Me: [Ok! Lets have some fun] Ok miss, what’s your name again??

Call center girl: Sonya Mishra.

Me: Where are you from?

Call center girl: [Slightly annoyed] Maharashtra, can I tell about the offer, sir?

Me: Wait a sec miss, how old are you??

Call center girl: [Confused] 24, Why sir??

Me: [With a naughty smile ;)] Perfect, I hope you are fair too.

Call center girl: [More confused] Why sir?

Me: Will you marry me?

Call center girl: [Flabbergasted] Sorry sir?

Me: [It was very hard to suppress my laugh, still I managed it ;)] Will you marry me? Or at least we can get together sometime, well lets see my timings... what about today?

beep beep......... the connection got cut… and I was on the floor laughing loudly… ;)

Me and the Dragonfly

Hey you guys, most of you may be wondering whats with me and the dragonfly. Actually its 'thumbi', the Malayalam translation of Dragonfly. It used to me my nickname when I was doing my graduation. It was an accident actually. I was the one who really started it. I don’t know exactly why - may be its my weird imagination - I used to think one of my friends resembled a dragonfly, not the body language, its something about his face. And I started calling him that.. [in the public too]. Unfortunately, I was the only one who could find the resemblance [I told you, it was my weird imagination] and I was the only one calling him that. And it backfired... Soon people started calling me that. May be they thought it suited me well. Later I too 'realized' that it suited [again weird imagination] me. Moreover, I was in search of a nickname for my Internet profiles and I adopted it. Voila!! I became a Dragonfly.

When things got this far, I thought, doing some research on dragonflies may be a good idea... When I was a child, these creatures really amazed me a lot. And checkout what I have found out[Leave the really biological stuff to wiki - http://en.wikipedia.org/wiki/Dragonfly]. Its really an amazing creature you know...

• Dragonflies have been around 300 million years. One prehistoric fossil had a wingspan of 2 1/2 feet! [Oh! My god!!]
• Dragonfly eyes contain up to 30,000 individual lenses. Human eyes only have one.
• They have two sets of wings. Their front wings can be going up while their backs ones are going down. They only flap their wings at about 30 beats per second (bps) compared to a bee’s 300 bps. [I have heard about bytes per second]
• Excellent and strong fliers, they can loop-the-loop, hover, and fly backwards. [We can use them as a model design some fighter planes, may be the helicopters are designed after them (I guess the aliens do, in most of the alien movies ;))]
• While underwater the dragonfly nymphs (the first stage after hatching) eat mosquito nymphs, tiny fish, and pollywogs. When they have matured to airborne insects, they catch mosquitoes and gnats in mid-air before devouring them. [The Kerala government should really try them to tackle the ever growing mosquito problem]
• There is a British Dragonfly Society which “aims to promote and encourage the study and conservation of dragonflies and their natural habitats, especially in the United Kingdom.” [Wow! Hope they wont include me]

More Funny Facts

• There is an OS named DragonFly [http://www.dragonflybsd.org/index.shtml] which is originally based on FreeBSD.
• They have even released a movie named Dragonfly (2002) [http://www.dragonflymovie.com/]. The listed genre is horror/thriller. Have to watch it.
• There is even a night club which goes by the name Dragonfly [http://www.dragonflynightclub.com/].

And the list goes on.. Now I don’t regret giving myself the name Dragonfly… ;)

Footnote: We need a Dragonfly Day too... ;)

My First Blog [19 Aug 2007, Sunday]

I have been thinking about writing a blog (starting one) for sometime. When I say some time, it means, around 2-3 months. I wanted to write the [funny] ideas, [crazy] thoughts etc, but when i sit and try to write something, well, i go blank :( But today, I am having a lot of free time and usually when I get some free time, its because, I am lazy, that I don't want to do something I am supposed to do. But today its not like that. After a long time, I don't have practically anything to do. I have resigned my work and relocating to Bangalore. So I thought I could use a small vacation before that and here I am, having almost nothing to do, staring at the monitor of an old PIII machine...

[After 2 days]
I've written the above paragraph 2 days before. So, I guess this is my first blog.
Yeah! That's it.

ps: I have written this on Aug 19th and posted on Aug 27th ;)