wirelezz blog

waves're in the air everywhere I look around…

Archive for the ‘etc’ Category

Awesome video explaining Diffie-Hellman Key Exchange

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I found this video I wanted to share with everyone. Explains the Diffie-Hellman key exchange algorithm pretty awesomely



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October 14, 2012 at 4:00 pm

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Although I have left this blog a little unattended for a while, I am taking a chance to write something a little off-topic here yet very important in my life.

I believe that the hard work you put into what you want for your future will someday yield success if you do it right. After one year of hard work (which was in fact two years ago) I finally made it to open a path to continue my studies in the U.S.. It’s been another whole year of preparation, exams and lots of thoughts into this. Tomorrow I will travel to pursuit a Master of Science in Telecommunications in the University of Maryland, College Park, after being granted with a Fulbright scholarship. I could definitely not have done this without the aid of my parents, my friends and of course @johiiis, who has been my support throughout the whole process. Thank you a lot.

There are always costs and sacrifices that have got to be made. In my case (and I’m pretty sure that this is the same for everyone else), it’s about leaving my country, my family and friends to a whole new different day-to-day that might be hard in the beginning, but that will hop onto the bulk of experiences in life.

Let this be a beginning to something great. And let it also be an inspiration for anyone who said once “it’s too hard”. Believe me, it is possible.

Cheers and see you again soon!

Written by Wirelezz

August 11, 2012 at 12:31 pm

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A small lesson about wireless signal loss

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I’ve seen how WLAN professionals folks have stressed the fact that a WLAN has to be properly installed and designed. And it is true. In this post I want to share an small experience with you regarding the importance of NOT underestimating obstacles, interference and so on.

The government entity where I work has been lately providing a small public service outside its main building. For its purpose, a group of technicians installed a small wireless network with a simple wireless (home) router to share a connection with 4 wireless devices. At the time I was called to help, one of the clients could not connect to the internet-hosted web service. This was a little weird since it showed an “Internet connection”, but no real connectivity. They had replaced 2 laptops already, and wondered why would that laptop not connect.

Then I saw this:

That metal entrance door was actually not fully opened, and was “surprisingly” aligned with the router and the client without connection. After relocating the router, the problem was solved.

Then I stopped a moment to remember the many times I have read on twitter how so many WLAN experts always accentuate the importance of correct wireless network planning, which includes all sources of possible interference or signal loss due to obstacles, and extended to other issues that can jeoparize the network reliability.

In this case, the metal door was undoubtedly generating problems to one client. How can someone anticipate this without understanding the very basics of signal degradation and how electromagnetic waves and wireless signals behave.

I think this is a good moment for every person who may have a great technical background on Wireless Networks but not on the physical layer concepts to give it more importance, it could save you A LOT of time.


Written by Wirelezz

July 31, 2012 at 1:10 pm

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[Solved] That Atheros AR9285 WLAN Card Problem

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About six months ago, I bought this awesome Samsung laptop at a great price. It’s been working just great, the only problem has been the WLAN card. It’s an Atheros AR9285 802.11a/b/g/n. At the beginning it worked fine, but lately it’s been failing like mad: it randomly loses connectivity from the WiFi network, although Windows stated otherwise.

I quickly thought it should have been a driver issue, so I looked for one that would do the job, and I found it at HP’s support website. Since it’s just a driver, it wouldn’t be a problem, right?

Here is the driver’s link: It’s for an AR9285 WLAN card running under a 64-bit Windows 7 (be sure to read that)

In case you don’t know how to install it, here’s how to:

  1. Extract its contents and then, under network connections, get in the properties of your wlan card
  2. Click on configure
  3. Then click on driver’s tab and then click on update driver
  4. Now click on Browse my computer for driver software.
  5. Click on the “Let me pick from a list…”
  6. Click on “Have a disk” and then click on browse, and search for the netathr.inf file. Then next.
  7. Select AR9285 802.11a/b/g/n from the list, then next. That should install it.

It works great now. It was just a matter of updating the driver, but looking for the right one is a real pain in the neck. Let me know if it works for you too.

Written by Wirelezz

September 17, 2011 at 2:21 pm

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A Proximity-Aware Transparent Handoff Mobility Scheme for VoWMN (PATH)

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Last year, I dedicated an important part of my work and time at the research center of my University to develop a way to provide fast handoffs within a 802.11s network. This post briefly describes it, named PATH after several attempts to make it sound cool.

Related Work

Most of the inspiration came from a great and interesting project called SMesh, a fast handoff mobility system created by the DSN Labs staff at Johns Hopkins University. One of the people behind the system is @ralucam, who helped me to understand the protocols of this system.

Yet another work that was taken into consideration is LCMIM, which is a Light-weight Client Mobility approach for Infrastructure Mesh networks. It is basically a simpler solution than SMesh but it is somewhat inefficient as it continuosly contends for the medium by broadcasting gARP messages, flooding the channel even though no Client is really using the network and that is bound to be used with a reactive routing protocol, in the case presented in the paper, AODV. The good side is that its nodes maintain independence and that it’s a simpler solution as well.

The PATH scheme

After several months of hard work and going through a learning process, I developed PATH, a Proximity-Aware Transparent Handoff mobility scheme. I should state that it is by no means a solution as complex and complete as SMesh as it only addresses the reversed channel latency issues caused by handoffs, but it certainly is simpler to install, follows a simpler logic and is independent of the type of routing protocol used as well.

The paper that describes its procedures has been recently accepted in INTERCON 2011, in Peru, for publication. I’ve shared the presentation here:

It all went good. It basically sends gARP messages based on client proximity (which is measured by the perceived RSSI on each node), thus associating clients to new nodes and switching its connectivity. Take a read to the presentation!. It should be noted that all three: SMesh, LCMIM and PATH create an infrastructure Mesh Network by setting wireless nodes into adhoc mode. By using this mode, all three schemes do not let the client decide when to roam but leave the responsibility to the network nodes.

It was designed to provide fast handoffs for real-time voice applications. Although it is essentially a work in progress and there are lots of ways to improve the scheme, I had the opportunity to share the results and they were all great 🙂

I will be posting a link to the paper soon!. Hope you like the presentation.

Written by Wirelezz

August 14, 2011 at 11:00 am

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Just started a new Game Dev blog

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Hey! I just started a new blog. No, I won’t leave or quit this one! it’s just about a hobby that I’ve recently (and finally) started. After some years of programming experience and a childhood dream of writing a game, I finally started doing this as a hobby.

I hope you like it: http://nullbox.wordpress.com


Written by Wirelezz

July 18, 2011 at 12:19 am

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First Post

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Hello! Welcome to my blog. I don’t know how you got here, I just hope that you find it useful and interesting!.

Keep reading!

Written by Wirelezz

June 25, 2010 at 9:16 pm

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