InterSys - my solution for Wireshark

As some of you may have seen in other posts in this blog, I always mention the error packets or error in transmissions through networks. That happens because my Master degree work (which I will translate to English asap) was focused on studying the errors in transmission.

Wireshark is an awesome program, but lacks in this aspect.

To solve this, I wrote some lines in C# and created a program to count the packets associated with errors: InterSys.

It's not superb, but works for what I designed. I am offering it to you guys in this link:

http://www.4shared.com/file/160548455/6f1c0a5e/InterSys.html

It has the installer and the readme, and no malware, I swear ;)

I wish that all of you take a look and help me improve it, so that more users can used it to solve their problems.

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Near-Far Revealed - 2/2

WiFi networks are my focus, and we'll look into those. Of course that there will be some kind of interference when we put devices that are using the same frequency to to talk to each other, which are not in the same network. But if we put then into different 802.11 channels, would they still suffer interference from the others? The answer is no, and yes. If they are able to avoid the power of the in-between device(s), they will do fine. But that doesn't happen very often. My tests and observation have shown that it's more likely to have a failed communication than a correct one. And that depends mostly on two factors: power and distance. Referring to the in-between device, higher power makes communication more difficult, but greater distances (to the transmitter) will make communication easier.

That's because the power received by the elements is greatly influenced by the distance, as it is reduced by the square power of the distance.
The surprise is that should not affect different channel transmitters, which is something that hasn't been correctly measured by device developers teams. As ad-hoc networks and mobile devices with access to 802.11g become more popular, this problem will be seen many more times, and could be addressed as soon as possible to prevent major difficulties. Specialists say that's happening because frequency filters that are now being used are not so sharp, or good, as they should be, but improving them implies in greater costs, which is something none wants right now.

Well, more on that someday...

Part 1

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Near-Far Revealed - 1/2

I have spoken in The Near-Far Effect about the Near-Far Effect, and I myself didn't know much about it, so I had to go and find some info on it.
Well, the concept is quite easy, but the implications can be seen in many applications, and more often at these times in which wireless communication has become a casual matter. Imagine yourself in a corner of a room with a friend of yours, who is sitting on the other side of the same room. You can still talk to each other, a bit loud, of course, but there's no problem.
Now, someone carrying his loud mp3 sits close to you. It's much easier for you to listen to the mp3 than to your friend, and, if you still want to talk to her, you start to scream, or speak a lot louder. That brings us to the situation where things get rough: the unpolite guy sets his sound even louder, so that he can enjoy his music, and everyone starts getting louder and louder, until nothing else can be heard correctly (or people start punching each other...).

Some wireless communication systems work in the same manner: transmitters and receivers work in a certain power level, but when something with equal or higher power comes between them, they try to set higher powers, till their possible limits.
CDMA is a cell phone channel division standard that allows transmition towers to select which phones they will serve, and they pick them using their power as choice parameter. When a phone (P1) moves closer to another tower, and may eventually have greater power than another phone (P2) that's already registered in that tower, the tower may, and probably will, disconnect P2 in preference of P1, which is not fair (at least for the user). Regulating organizations are developing ways to mitigate this problem, through power control inside the CDMA cells.

Part 2

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HDI handbook - 1st steps

Well, I'm involved in a personal activity in researching the development of HDI circuitry. And what that means?
HDI stands for High Density Integration (Circuits), better translated as small PCB (Printed Circuit Board) with lots of IC's (Integrated Circuits) and possibly RF (Radio Frequency) use or connection.

As you may think, working with small things is difficult not only because it's hard to find spaces in it, but also because putting somethings close to each other may lead us to disaster (just being bold...). Some of you know that EMI (ElectroMagnetic Interference) is a commonplace these days, as the actual trend in electronics is removing the wires, and send any type of information, or raw data, over the air. But although we can't visualize it, there's a real crowd of "wireless-wires" passing over our heads all the time. And that make the work of circuit dseginers a little harder (as if it weren't enough).

Placing the "wires" in the PCB, or routing, for those familiar with it, has become a matter of life and death for the project design, if you really want it to work in the real-world environment. Not only it may suffer from outside influence, but also from itself, as placing routes to close to each other, or in the same position in different layers may lead to parasite capacity, as any kind of loops can create inductance and fake antennae. These can still be fixed, in some extreme ways, but when it comes choosing the IC's or connections we want to place in the PCB, sometimes we don't have enough room for choice.

I heard from a friend of mine, working in a HDI project that there were no buttons small enough to fit his PCB, and we are talking of 4 x 4 mm! Yeah, milimeters. We almost can't see them, what about actually pushing them?

That's why we are going, in the next steps, to try to show you some knowledge on HDI design with good results. Until them, start looking for EM books, if you enjoy it ;)

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The Near-Far Effect

As a MSc. candidate, I should be executing some kind of experiment, you should think. Yeah, you're right.
I'm working with Wireless Communications standards at the moment (maybe you just deduced it from the blog's title, didn't you?), more especifically on the IEEE 802.11g WiFi standard.

For those of you wich have some base on this field, WiFi can work at different channels, 11 are available for FCC compliants, 13 for ETSI. Most of them overlaps each other, which results in interference when devices use frequency-close channels.
You then may ask: are there any channels that don't overlap, so that no interference is present? The answer is yes... and no. As we pick channels that are 25MHz away from each other (5 channels of difference) we have a clear channel. As factory default is usually set in channel 6, if you feel that your neighborhood is crowded with WiFi nets, you should set your devices to channel 1 or 11.
Back to my experiment... I'm checking how strong is the interference in nets that are in the same indoor space, and started with 2 nets, both at channel 6. Results were that interference is present and reduces a lot the throughput and channel capacity. So I moved one net to channel 8... results were similar, but with less interference. Then came channel 11, for conclusion...
And no communication was possible!! The non-overlapped channels led to a total-wireless-massacre, no one survived. I tried to make it work for 15 days and nothing came out of it. As I lifted my white flag, and went to the Google altar, I found an article that presents exactly what I'm telling you and presented to me the experession Near-Far effect.
It happens with almost any kind of radio device, as they found themselves near to another device that works in close frequency and close distance... tendency is that the devices try to lock the signal and get confused, not knowing whom to answer to.
Trying not to step on my shoelashes, I'll stop here as I'm trying to get more information on that.
This post works as a warning: keep your wireless devices away from each other, they just don't get along ;)

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