Steve, I asked a few simple questions about the amateur
implementation of ALE; these questions were not focused on
politeness, but rather on understanding how many ALE users can be
simultaneously QRV if there's one pilot channel per amateur band.
Bonnie claimed 1000, but two multiplications and a division yields a
much lower number. If the model underlying this math is incorrect,
please set me straight.
I have reviewed enough of the military documentation to understand
that they employ dedicated ALE transceivers capable of much faster
scanning rates. As a result, sounding duration is signficantly
reduced, and channel capacity increases in proportion. But one ham
with an amateur transceiver limited to a 2 channel-per-second scan
rate would force all ALE participants to sound for 20 seconds, even
if their equipment could scan more rapidly. Do I have this right?
Since the 20 second sounding time is calculated to allow each station
to scan 40 frequencies without missing a sounding, one obvious step
to increase capacity would be to reduce the number of frequencies
being scanned. If there's only one pilot channel per amateur band,
scanning could be reduced to 10 frequencies, which would allow
sounding time to be reduced to 5 seconds. This would increase
capacity by a factor of 4 -- to ~120 simultaneous users, if I
understand correctly.
73,
Dave, AA6YQ
--- In digitalradio@yahoogroups.com, Steve Hajducek <[EMAIL PROTECTED]>
wrote:
>
>
> Hi Dave,
>
> >At 10:53 PM 8/27/2006, you wrote:
> >Does ALE provide some means of reducing contention?
>
> I recommend that to answer all of your technical questions on
subject
> ALE that you refer the actual Federal, Military and STANAG
Standards
> which you can find on the Internet quite easily. You can start with
a
> number of them at the following URL:
> http://www.n2ckh.com/MARS_ALE_FORUM/tecref.html
>
> Listed below are the "ALE Operational Rules" taken directly from
> "MIL-STD-188-141B APPENDIX A", take the time to read this and do
> additional research WRT the details of the referenced items herein
> and you should be satisfied that ALE is the most courteous digital
> mode with automatic operation you could ever want to see, compared
to
> any other system that has ever been used on the Amateur Radio bands.
>
> /s/ Steve, N2CKH/AAR2EY
>
> A.4.4 ALE operational rules.
> The ALE system shall incorporate the basic operational rules listed
> in table A-V. Some of these
> rules may not be applicable in certain applications. For example,
> "always listening" is not
> possible while transmitting with a transceiver or when using a
common
> antenna with a separate
> transmitter and receiver.
>
> TABLE A-V. ALE operational rules.
> 1) Independent ALE receive capability (in parallel with other
modems
> and simular audio receivers) (critical).
> 2) Always listening (for ALE signals) (critical).
> 3) Always will respond (unless deliberately inhibited).
> 4) Always scanning (if not otherwise in use).
> 5) Will not interfere with active channel carrying detectable
traffic
> in accordance with table A-I (unless this
> listen call function is overriden by the operator or other
controller).
> 6) Always will exchange LQA with other stations when requested
> (unless inhibited), and always measures the
> signal quality of others.
> 7) Will respond in the appropriate time slot to calls requiring
> slotted responses.
> 8) Always seek (unless inhibited) and maintain track of their
> connectivities with others.
> 9) Linking ALE stations employ highest mutual level of capability.
> 10) Minimize transmit and receive time on channel.
> 11) Automatically minimize power used (if capable).
> NOTE : Listed in order of precedence.
>
> TABLE A-I. Occupancy detection probability (2G and 3G).
>
> Waveform SNR (dB in 3 kHz) Dwell Time (s) Detection Prob
>
> ALE 0 2.0 0.80
> 6 2.0 0.99
>
> SSB Voice 6 2.0 0.80
> 9 2.0 0.99
>
> MIL-STD-188-110 0 2.0 0.80
> (Serial Tone PSK) 6 2.0 0.99
>
> STANAG 4529 0 2.0 0.80
> 6 2.0 0.99
>
> STANAG 4285 0 2.0 0.80
> 6 2.0 0.99
>
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