28. New readers, RF intruders in wireless alarm systems

Radio Frequency (RF) intruders.

The whole RF spectrum is divided and regulated by international committees who define the allowances on each frequency. The Wireless Alarm Systems have free multi user "shared" frequencies assigned with no waranty that it is free for communication at any requested time. Keeping in mind that only one operator can transmit on the same frequency at the same time, a protocol is laid-out to circumvent the shared frequency restrictions. Each user has to respect some transmission rules like:

- Limit the transmit power;

- Each transmission has to have an identifier;

- transmit in a BURST transmission mode, to mention the most essentials.

Limited transmission power. By limiting the transmission power the signal reception range is reduced and by consequence the possible mutual interference on that frequency.

Personal identifier (ID). As multiple users uses the same frequency and in order to retrieve only the information belonging to hiss personal system, each user identifies themselves during hiss transmission with a unique ID. Some transmitters uses ID rolling codes, the code changes each time in order to make sure that at repetition he has a unique ID. Realize that sometimes this rolling code may not be unique, the individual receivers have to keep trace of the temporary intruder ID in order to retrieve only hiss data. This requires multiple transmission/reception attempts before true validation of the corresponding ID and by consequence causes a reception DELAY.

Burst transmission. Burst transmission is one way to circumvent mutual interference. Each transmitter sends hiss data information during a small period of time hoping that the frequency is unoccupied while he transmits. When two or more transmissions occur at the same time, interference is generated and the receivers are disturbed, they can't decode the data information. This is not a real problem, the transmission is repeated several time with the hope that at some time during the repetitions the frequency is free. This require multiple transmission/reception attempts before data is passing true, by consequence this causes a reception DELAY of the data involved.

The whole burst transmission protocol has restrictions, the burst length and repetition rate, the number of possible systems and different types using the same frequency and more..

Now, back to the header, intruders. As described above, the validity of data transmission of all transmissions using the shared frequency spectrum are depending on the respect of the burst transmission requirement/principle. If one, lets call them INTRUDER, uses a different protocol and transmits without the respect of the burst principles, the whole frequency utilization goes bingo in the distance range of hiss transmitter. That's the case during Radio Frequency Interference (RFI).

Hope this clarifies a little the wireless alarm system shared frequency operation fragility.

NOTE: I don't mind if "so called professionals" explain it in a better and more detailed way but it never happened... Criticism is easy, explaining instead... Paul

Reply to
-pull
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What total rubbish! You do not understand rolling code or its true purpose. And as for the rest of it...delays - what a joke. You make me laugh you really do. Anyone reading this diatribe should simply ignore it. Take it from me that the guy doesn't know what he's talking about.

Reply to
Roger

The only time most of us even see it is when someone like you posts a 4 line response and completely fails to trim any of the original rubbish.

Reply to
Andrew Gabriel

I didn't trim any of it because my 4 line response was for all of the original message posted ;-).. as is this one

Reply to
Roger

Rubbish oh yes you are to elementary to understand wireless, poor guy.

Rolling code is of any use ONLY when the transmitted data is valid. During Radio Frequency Interference (RFI) there is NO VALID INFORMATION included ID.

What is your technical knowledge and what measurement tools do you have beside your little wet finger in the wind? Your professionals wet finger idiocy is coming from head to bottom!

RFI brain probe \\ / ____\\/____ / ___ ___ \\ / / @ \\/ @ \\ \\ \\ \\___/\\___/ /\\ \\____\\/____/|| \\Bottle/ |neck | Pro's in / \\ Pissing / \\ Contest | \\ | | / | | ===. 10 mW \\ OO \\ output | | o power! | / o \\_________/ o || || \\___,,,__ / || || | WAS |O WAS = Wireless Alarm System _||_||_ \\_______/

The desire to not understand wireless alarm techniques is far less intelligent than the inability to understand them

Reply to
-bull

Not quite sure what you are trying to say here, you're English is good but sometimes a bit garbled. Anyway, my technical knowledge in this area is abosolute. I am an engineer working in both hardware & software. Over the years I have been a part of various design teams producing to manufacture various equipment utilizing wireless technologies and using rolling code for encryption. I am a design enginner and have been for over 20years.

What about you?

Reply to
Roger

Perhaps I should have extrapolated. I design alarm panels. Wireless included. Thought that was obvious what with this being a security alarms area.

All wireless alarm systems worth anything use encryption. The only way to stop grab & play-back attacks on wireless systems is to use rolling code to change the encrypted data on every transmission. Even the simple systems using Microchips keeloq technology use rolling code in this way. Do you know nothing?

As I mentioned earlier. You talk rubbish. As such it's useless responding to you. As you say... bye bye

Reply to
Roger

The problem is that you don't know wireless alarm systems. There is no data transmission rolling coding in those systems (its of no use either), the only varying code who can be called rolling is the ID number.

FULL ST>Not quite sure what you are trying to say here, you're English is good but

Reply to
-pull

It is useless responding to him although it is still fun, he knows nothing about wireless sensors but thinks he does, try throwing out some facts and he'll do the usual song and dance

Reply to
Mark Leuck

And your not the only one who thinks that, our "friend" from Belgium has done no research, never contacted the manufactures, has no idea how modern wireless works, never done any real world testing other than his old obsolete crappy system

He's still fun to play with tho, ask Crash

Reply to
Mark Leuck

I guess you're right. I have read some of his posts before and usually totally ignore them. I must have a had a bad day to even bother to respond. I guess he has his opinion and he's welcome to it, but it seems a shame that unknowing readers 'might' believe all that he is saying and get the wrong impression about the current state of wireless systems.

Reply to
Roger

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