Subject: [NEXTEL-1] Poll: Is APCO-25 an appropriate technology forPublic Safety?

From: Marcel <[email-masked]>
Date: Wed, 15 Jan 2003 15:03:38 -0500

------- Original Message --------
From: Glen Reid <[email-masked]>
Subject: RE:  Poll: Is APCO-25 an appropriate technology forPublic Safety?

At 10:22 AM 1/15/2003, you wrote:
>Glen, sorry about the delayed response, but my schedule has been fairly 
>hectic this week.  My follow-up comments are listed below:
>
> >- voice delay in multi-radio environments
>
> >> I am not sure what you are referring to here. There is noticeable
> >> processing delay if two radios are within ear shot of on another, which
> >> can be annoying. The practical solution to is simply to conduct "simplex,
> >> radio to radio operations" in analogue.
>
>Yes, this is what I was referring to.  This noticeable processing delay is 
>a real pain for public safety officials who are all congregated on a 
>scene.   Speaking into the mike, and hearing yourself 1/2 sec later around 
>the scene is somewhat disturbing to the human mind.

Agreed. The echo is a problem. But it is an artifact of all digital.

>The practical solution to conduct simplex operations really doesn't fit 
>the intention or model of the Project-25 standard, since the original 
>intention of Project-25 is to reduce usage of bandwidth for public safety 
>communications models.  Exceptions for analog will negate the reason to 
>have a digital standard in the first place.

Not so sure I agree with this...P25 actually requires compatibility with 
analogue to enhance interoperability and unit to unit communications.
I think the P25 committee anticipated the echo.  In fact at 700 MHz, where 
the FCC rules require P25 Phase I, there is an exception for low power fire 
ground type channels which can utilize analogue.

> >- high intensity voice handling (structure fire responses, foot pursuits
> >etc.)
>
> >>Again, I am not sure to what you are referring here.
>
>What I refer to is:
>
>1.  On Scene Fireground communications.  Ambient noise levels are 
>extremely high, and signal strengths are low inside structures.  On a 
>fireground, a crew tends to "scream" into a radio, not hold it 2 inches 
>from the face and talk gently.  IMHO, the IMBE vocoder does not do a good 
>job of "reproduction" in these environments.

No mode, digital or analogue, can provide proper response under those 
conditions.  My solution will be to use analogue on simplex channels with 
deviation set for the low side. Personnel training is the other key for 
fire ground  operation.  I am not an expert on the IMBE vocoder and can't 
speak to its capability vis a vis others

>2.  Ever heard an officer chase a suspect 10 blocks, in touch with a 
>dispatcher, over a Project 25 network?    Ask a seasoned police dispatcher 
>who works with a Project-25 system and they'll tell you it is extremely 
>difficult to understand the pursuing officer.

I agree, in these circumstances, ( I am a former police dispatcher, police 
officer and retired firefighter) speech intelligibility suffers.

>  Furthermore, as an officer gets into a remote area (creek bed etc.) 
> where signals are notoriously low, many times signal strength is low 
> enough that the vocoder can't recover  any voice frames.

The low signal areas are exactly where digital is more likely to be 
heard.  I can give you an anecdotal personal example regarding a 4 level 
underground parking garage, but that only proves that one case.

>  In most cases, analog will make it through enough to allow the 
> dispatcher to get required info.

That is pure speculation, it  depends on the auditory acuity of the 
dispatcher in recovering the speech amongst the noise.

>Project-25 signals do an outstanding job in low signal strength 
>environments.  The vocoder is able to use error correction to recover 
>voice frames that otherwise would generate a minor static on an analog 
>signal.  BUT, when you get to *very* low signal strength environments, 
>Project-25 doesn't make it through at all, whereas an analog signal might 
>barely make it to the repeater, but it still makes it, and a dispatcher's 
>trained ear is able to do a MUCH better job of voice recovery than any 
>vocoder on the market today.

That is possible, but again, it is speculation about an hypothetical 
situation.  The real advantage of P25 is its capability to make that noisy, 
analogue, very low signal area into a place of acceptable the speech 
intelligibility .

>To expand upon this further.  The IMBE vocoder does a very poor job of 
>conveying voice emotion, which is an integral part of the public safety 
>communications process.  The subtle nuances that are involved between 
>officer/dispatcher communications are huge, with dispatchers trained to 
>pickup on these and react accordingly.

I have not found that to be true.   As I said, even accents are conveyed. 
In my humble opinion, it is not overstating the fact to say that the latest 
implementations of P25 sound like FM broadcast, compared to AM.  It really 
sound good!

>  In fact, ask any professional scanner listeners (yes, there are some!)

Perhaps in newsrooms!

>and they'll tell you they can listen to 10 different scanners at once and 
>"pick out" a high priority distress incident in progress.
>A dispatcher is no differnt.

Dispatcher skill and training.

>  The IMBE vocoder  masks these nuances.

This has not been my experience

>..and I'll go even further.  Co-channel interference.   Ever heard 2 units 
>at once transmit at the same time on a Project-25 network?  Physics 
>doesn't allow it.

Yes, I have.  Damned PHYSICS!

>  Remember the days of Motorola Smartnet analog systems, where admins had 
> the choice of deploying the system in "message" or "transmission" 
> trunking formats.

The systems still allow that choice, if fact, they are so smart now that 
they will change from transmission to message, or vice versa, depending on 
the situation.

>  Transmission trunking was always chosen over message trunking, because 
> officers complained they could not transmit if someone else was on the air.

That choice varied by user and system.  Systems with  many talk groups 
and  few channels often used transmission trunking.  System with sufficient 
resources were usually operate better with message trunking, of course that 
is my opinion.

>  2 analog transmissions at the same time might cause a "Warble" or 
> "masking",

Actually, the most likely occurrence, in analogue, is that one signal, the 
stronger, will "capture" the receiver, eliminating the weaker signal 
completely.

The same thing happens  with P25, the difference is that, because of 
"network addressing",a P25 feature, neither of the signals is heard at the 
receiver.

>but a  trained dispatcher can typically determine who transmitted, and 
>pick out some of the details.

I never underestimate the skill and ability of a capable dispatcher.

>
> >- all or nothing coverage
>
> >> It is a commonly held perception among the uninformed, that digital
> >> coverage ends without warning. In reality, there is plenty of warning for
> >> the end of your coverage... IF... you are trained to recognize it.
>
>Yes, understood here.  In fact, Motorola's product line of Project-25 
>subscriber equipment provides features  which can indicate this to the 
>user (audibly).

I have heard that "out of range was a feature that was being considered for 
P25, I am not aware it has been implemented, except is trunking!
It is easy to do with trunking because the control channels is always 
present.  In conventional systems (not trunked) the system would need to 
interrogate the mobiles and the mobiles would have to know when it had 
missed an interrogation.

> >Has
> >APCO-25 *really* accomplished what the end-user (dispatcher, PD officer,
> >FF etc) needs to do his job in a *more* effective manner?
>
> >>Absolutely.
>
>If your response of "absolutely" is in regards to the above, then, I 
>respectfully disagree.  I don't believe that APCO-25 has provided to the 
>end-user any additional functionality.

How about :

continuous emergency
continuous unit ID
network ID,
Selective Radio Inhibit
Call Alert
Selective Call
Integrated Voice and Data
Radio Check
Adaptive Power Control on portables
Short text message
????

All of these are P25 required functions.

>   The only difference your average firefighter or police officer sees is, 
> well, everything that I have described above.

Are you sure?  I would have given lots of money just to have an "Emergency" 
button on my police radio, lo those many years ago!

>  If you mean Project-25  provides greater interoperability, then I really 
> disagree.
>Many vendors and agencies have publicly snubbed the Project-25 standard.

Aside from TYCO, I don't know of any manufacturers that "snubbed" P25 and 
even they (TYCO) claim to have it now, at least in combination with their 
other proprietary products.

  Many smaller manufacturers are simply waiting for a larger P25 market to 
develop, because they don't have the money to re-tool their entire product 
line.  There will be a period of time during which some agencies will meet 
the FCC "re farming" mandate with narrow band analogue, but I believe it 
will prove to be less that satisfactory for public safety.  AT least P25 
requires compatibility with NB analogue, so they won't be completely out of 
the loop.

EFJ, Thales(formerly RACAL), BK (formerly King), Datron and some Canadian 
company make P25.
TYCO claims to have P25 base stations
Kenwood and several other claim to have P25 radios in  the pipeline.

It looks like most of the Europeans are sticking with TETRA.

>  Just look at how my home town, San Antonio TX, has chosen the path of an 
> EDACS ProVoice  system.

But many agencies have chosen to go P25,

FBI
Customs
Border Patrol
Michigan
Ohio
Kentucky
Alaska
Colorado
South Dakota
Illinois

>  Even the state of FL has decided to dismantle a Project-25 statewide 
> system in favor of a Proprietary solution, EDACS ProVoice.

That one I don't understand, Florida has so much inter activity with the 
FEDs who are all mandated to P25 by 2005, you got me.  I think that was 
more politics than rational thinking...who knows.

>  Although the MA/COM solution is based on the same IMBE vocoder, it 
> doesn't help for statwide interoperability.

I don't think EDACS, Pro Voice, Aegis nor OPEN SKY is currently P25 
compatible.  They will have to put a P25 mode into their mobiles and 
portables, which is what they appear to be planning.   I must confess,  I 
have no intention of doing business with TYCO or any other company that 
moves its headquarters off shore to avoid paying US taxes, it just won't 
happen!    I will buy from a foreign company if they have the best 
products, but TYCO is just a slimey, disreputable bunch... only my opinion.

>Side Note:  I am pretty sure that MA/Com is now providing Project-25 
>Conventional capability on their newer subscriber units, so I suppose that 
>helps.

I think that's correct.

> >> As far as I know, the 6.25 KHz. FDMA part of P25 is standardized. Only
> >> the TDMA implementation is still unsettled. That appears to mired in a
> >> battle between various supporters of 2 slot vs. 4 slot vs. 12.5 KHz vs. 25
> >> KHz. including, but not limited to, Tetra like and multi-channel JPM
> >> modes. Only the Power above knows when or if that will be resolved.
>
>Oh Boy, another standard.  ;-)

The good part of that is that the TDMA version will be practical in only 
the largest cities and the smallest states.  And, it will have to have P25 
Phase I for interoperability.

>This has been a great discussion, and I enjoy the discourse.

I agree, it is not often that you can have a reasoned discussion on the 
Internet, without emotion or fames as high as the sky.

>  I do want to make it clear that I *do* support the Project-25 standard, 
> and I feel that it *is* needed.

I thought you did.

As a matter of interest, are you a Ham?

gr

DISCLAIMER:  Like a lot of folks in Austin, I work for MOTOROLA a 
manufacturer of and supporter of Project 25 for public safety.

GLEN REID
West of Austin, in the Texas Hill Country
[email-masked]

The difference between genius and stupidity is...
genius has it's limits.

Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

---

From: Marcel <[email-masked]>
Date: Wed, 22 Jan 2003 15:14:35 -0500

-------- Original Message --------
From: John Powell <[email-masked]>
Subject: Re:Poll: Is APCO-25 An Appropriate Technology forPublic Safety?

Jack,

Yes, the tests were conducted over a decade ago using state-of-the art 
equipment then available.  It was described to me directly by the two very 
competent engineers (one a PE) who conducted the tests, and it was my 
understanding that, if manufacturer representatives were not there at the 
time, they were in any case given an opportunity to comment on and offer 
corrective procedures for a retest.

Yes, that was then and much has happened since.  However, from what I've 
seen from acceptance of the 220 MHz commercial band, it is not the panacea 
that everyone (including me) thought it would be.  And I'd think that if 
the overall characteristics were as good as higher bands, the improvement 
in coverage would have people running to 220.  Doesn't seem to be the case.

At 10:44 AM 1/22/2003 -0800, Jack Daniel wrote:
>John,
>
>I use 5 KHz 220 radios at over 75 MPH with no problem and so can you.
>
>I'm sorry, but your comment about Washington's tests is not applicable
>in any way and a rehash of ancient history, rumors and incomplete
>details. I'm surprised because you normally have very complete comments.

---

From: Marcel <[email-masked]>
Date: Wed, 22 Jan 2003 15:16:19 -0500

-------- Original Message --------
From: Jack Daniel <[email-masked]>
Subject: Re: Poll: Is APCO-25 An Appropriate Technology forPublic Safety?

John,

The tests you refer to were conducted over 10 years ago using very old
generation, low power, VHF ACSB designs from a temporary base site. The
current 220 5 KHz designs are not ACSB and are many generations beyond
those days. There is just no similarity beyond using a derivative of SSB
modulation. 

As I recall, the WA test was not conducted with the participation of the
radio manufacturer and there is no way to verify the installation and
alignment was proper. Many tests in those days were conducted using
cigarette lighter plugs for DC power which would not handle the
instantaneous current peaks of AM or SSB modulation (when an inadequate
power source 'sags' due to current changes, that degrades the modulation
because it is an undesired AM modulation in itself). I have also found
techs with FM experience don't worry much about 'a little' mobile
antenna VSWR, but in the old generation VHF ACSB designs, reflected
power was sensed as improper operation of the ultra linear RF power amps
and RF power was reduce to maintain amplifier amplitude linearity. 

This may sound like a lot of techno-babble, but the bottom line is test
installs may not be as good as REAL installs and the tests will be
colored by that fact.

A test of P-25 or so called 'digital' designs at that same date would
have been a TOTAL failure. (grin)

Let's please stay focused on today's technology, my friend, which is 5
KHz Very Narrow band technology DOES work and being delivered while 6.25
KHz "digital" technology is ????????????

I'm glad you posted this because it demonstrates the fact that no matter
what you do, old stories continue to be retold as though they were
today's news.

Jack Daniel
=========================================

John Powell wrote:
> 
> Have you ever tried to communicate on an ACSB radio at freeway
> speeds?  Washington State Patrol did some tests a while back using the
> popular commercial units in the 220 MHz band.  Not only could you not
> understand what was being said, you could not even tell the gender of
> the speaker!
> 
> John
> 
> At 03:28 PM 1/21/2003 -0500, Todd Ellis wrote:
> 
>      "urn:schemas-microsoft-com:vml" xmlns:o =
>      "urn:schemas-microsoft-com:office:office" xmlns:w =
>      "urn:schemas-microsoft-com:office:word">
>      David:
> 
>      Minor difference in opinion.  ACSB works well in a 6.25
>      channel and is completely analog.  Yes, FM does not work,
>      but other modes (like ACSB and digital) do work.
> 
>      Todd Ellis