28. New readers, RF intruders in wireless alarm systems

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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




Re: 28. New readers, RF intruders in wireless alarm systems
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.


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Re: 28. New readers, RF intruders in wireless alarm systems
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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.

--
Andrew Gabriel


Re: 28. New readers, RF intruders in wireless alarm systems
I didn't trim any of it because my 4 line response was for all of the
original message posted ;-).. as is this one

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Re: 28. Nw readers, RF intruders in wireless alarm systems

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


wrote:

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Re: 28. Nw readers, RF intruders in wireless alarm systems
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?


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Re: 28. Nw readers, RF intruders in wireless alarm systems
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 STOP, bye

wrote:

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Re: 28. Nw readers, RF intruders in wireless alarm systems


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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




Re: 28. Nw readers, RF intruders in wireless alarm systems

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to
know
to

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




Re: 28. Nw readers, RF intruders in wireless alarm systems

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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.




Re: 28. Nw readers, RF intruders in wireless alarm systems

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nothing
and
respond.
that

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




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