| Author |
Message |
|.........
Guest
|
 Posted:
Wed Jan 26, 2005 7:08 pm Post subject:
24/ 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
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observer
Guest
|
| Posted:
Wed Jan 26, 2005 7:41 pm Post subject:
Re: 24/ New readers, RF intruders in wireless alarm systems |
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"|......... " <nomail@aol..com> wrote in message
news:uh5fv09imqi9e7r0r8254vaiv7rsi3ghnd@4ax.com...
| Quote: |
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
sounds about right. |
thanks for explaining that for us so concisely |
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Guest
|
| Posted:
Thu Jan 27, 2005 9:35 am Post subject:
Re: 24/ New readers, RF intruders in wireless alarm systems |
|
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Radio Frequency
Signals whose frequency is less then 1000 MHZ.
Receiver
Electronic device which when combined with an antenna can receive
signals transmitted over the air and "demodulate" the carrier to
provide a faithful reproduction of the base-band signal fed to the
transmitter.
RFI
Radio Frequency Interference.
Wavelength
The peak to peak distance between two adjacent cycles of a wave (or any
other identical points on two adjacent cycles). In free space the
wavelength of an electrical signal is equal to the ratio of the speed
of light to the frequency of the signal.
Wireless Transmission
When an electrical signal is radiated from an antenna into air or
space.
Spread Spectrum Modulation (SS Modulation)
A type of modulation where a pseudo-random code is combined with the
information carrying base-band signal before modulation of the main
carrier. The effect is to "spread" the bandwidth of the modulated
carrier over a much greater spectrum then if just the base-band signal
was modulating the carrier. This type of modulation is typically used
with digital base-band signals. The SS technology was originally
developed by the military as a means of "hiding" wireless transmissions
from the enemy and making it more difficult to "jam" with intentional
RF Interference. The primary commercial advantages of SS are a greater
immunity to RF Interference from other signals in the same frequency
band and in mobile applications less susceptibility to multipath
problems. The two primary types of SS modulation are frequency hopping
and direct sequence. For equipment designed to operate under the FCC
"Part 15" or "no user license" rules, a significant advantage is that
the FCC allows spread spectrum systems to operate at much higher
powers, which results in improved performance.
Bandwidth
The number of cycles per second (Hertz) expressing the difference
between the lower and upper limiting frequencies of a frequency band;
also, the width of a band of frequencies.
Frequency Modulation (FM)
A technique for continuously changing, or modulating, the frequency of
a carrier signal, in synchrony with the instantaneous amplitude
variations of an information-bearing base-band signal. One effect of
frequency modulation is to translate and expand the frequency spectrum
of the base-band signal. Another effect is to increase the noise
immunity of the FM signal, but this immunity is obtained at the expense
of a greater bandwidth required by the FM signal compared to amplitude
modulation
Frequency Response
The range of band of frequencies to which a unit of electronic
equipment will offer essentially the same characteristics.
Frequency
A measurement of the number of full repetitions, or cycles, that occurs
in one second of a periodic wave form.
Spammer
Typically posts in alt.security.alarms under various aliases of which
the latest in jabuary 2005 has been |.......... with little or no
knowledge of facts pertaining to the statements made.
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|.........
Guest
|
| Posted:
Thu Jan 27, 2005 10:03 am Post subject:
Re: 24/ New readers, RF intruders in wireless alarm systems |
|
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On 26 Jan 2005 19:35:58 -0800, rory@aspbahamas.com wrote:
| Quote: | Spammer
Typically posts in alt.security.alarms under various aliases of which
the latest in jabuary 2005 has been |.......... with little or no
knowledge of facts pertaining to the statements made.
|
Those who answer with arguments out of subjet. |
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Guest
|
| Posted:
Thu Jan 27, 2005 5:36 pm Post subject:
Re: 24/ New readers, RF intruders in wireless alarm systems |
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| spinner wheres the bon bons . momsy say sum jelly 'n peanuts ... |
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jackcsg
Guest
|
| Posted:
Thu Jan 27, 2005 7:39 pm Post subject:
Re: 24/ New readers, RF intruders in wireless alarm systems |
|
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<rory@aspbahamas.com> wrote in message
news:1106796958.131436.303890@z14g2000cwz.googlegroups.com...
| Quote: | Spammer
Typically posts in alt.security.alarms under various aliases of which
the latest in jabuary 2005 has been |.......... with little or no
knowledge of facts pertaining to the statements made.
|
Good one Rory! LOL |
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|.........
Guest
|
| Posted:
Fri Jan 28, 2005 4:29 am Post subject:
Re: 24/ New readers, RF intruders in wireless alarm systems |
|
|
On Wed, 26 Jan 2005 14:08:22 +0100, "|......... " <nomail@aol..com>
wrote:
| Quote: |
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
|
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| Back to top |
|
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|.........
Guest
|
| Posted:
Sat Jan 29, 2005 12:25 pm Post subject:
Re: 24/ New readers, RF intruders in wireless alarm systems |
|
|
On Wed, 26 Jan 2005 14:08:22 +0100, "|......... " <nomail@aol..com>
wrote:
| Quote: |
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
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Guest
|
| Posted:
Sun Jan 30, 2005 8:00 am Post subject:
Re: 24/ New readers, RF intruders in wireless alarm systems |
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The whole Belgium RF spectrum is divided and regulated by NATO who
define the allowances on each frequency.
yours~ Paul ... |
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