Subject: [NEXTEL-1] Efficiency - Simulcast Synchronicity Style

From: [email-masked]
Date: Mon, 7 Apr 2003 19:04:47 -0400 (EDT)

Submitted for your consideration.

There are many ways to increase the effectiveness of a radio channel.
Using narrower bandwidths, increasing interference rejection, using
optimum verbal procedures, reducing dead spots, using trunking,
increasing receiver sensitivity, etc.

Another way to increase the efficiency of a dispatch radio channel is to
effectively use base stations that are equipped with synchronized
simulcasting capability.

Lets say that we are looking at 2 adjacent cities - East City and West
City. East City is east of West City - and West City is west of East
City. Each city has 2 transmit sites - East and West. So we have 4
transmit sites - East 1, East 2, West 1, and West 2. Lets say that East
1 is on the east side of East City and that West 1 is on the east side
of West City. East 2 is on the west side of East City, and West 2 is on
the west side of West City.

(Excuse for a second while I draw a map for myself).

Incidents in East City

For incidents on the east side of East City, the best site to use is
East 1. For calls in the center part of East City, using both the East 1
site and the East 2 sites (in a synchronized simulcast mode) is the best
choice. For incidents on the west side of East City, using East 2 and
West 1 (in synchro mode) is the best choice.

Incidents in West City

For incidents on the east side of West City, using the West 1 site and
the East 2 site (in synchro mode) is best. For incidents in the central
part of West City, using the West 1 and West 2 sites (in synchro mode)
is best. For incidents on the west side of West City, using just the
West 2 site is best.

----------------------

I am sure that none of this is groundbreaking. But perhaps it will help
radio engineers to visualize another axis of the wheel of radio
roulette.

Using this concept will keep the required radio signal in the smallest
possible footprint.

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From: "Mark" <[email-masked]>
Date: Tue, 08 Apr 2003 00:30:49 -0000

That's why the Motorola simulcast is so popular and works as 
advertised.  The cellular concept would work also in this situation 
transmitting the same information on 2 different frequencies but in 
my opinion isn't frequency efficient.

Also with the simulcast concept you get joint probability which 
allows for signals from different directions to get to the radio.  
Most public safety systems are already designed with a voting 
subsystem to increase the talk-back so why not do the same in reverse.

Of course licensing constraints may not allow for the simulcast 
configuration especially in 800 MHz where the commercial carriers 
have already boxed in most general category users in urban areas.

Mark

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From: "arclight_arclight" <[email-masked]>
Date: Wed, 09 Apr 2003 01:11:49 -0000

> my opinion isn't frequency efficient.

It depends on what the traffic model is.  For group call 
transmissions, undoubtedly the simulcast model is the most frequency-
efficient.  However, for private calls and data apps, simulcast does 
not appear to be anywhere near as efficient as the cellular model 
(that's why the cell folks do it the way they do).

I have been thinking for the last year or so that a "smart" simulcast 
system that could engage or disengage channels at a site on the fly 
would be the most efficient platform for a jurisdiction that had a 
traffic model that encompassed group call, private calls, and data.  
This would maximize efficiency of the spectrum usage, particularly 
for data (e.g. perhaps a data call could possibly seize multiple 
repeaters at a given location to increase data throughput, with 
prioritization given to group call if it occurred).  The system would 
definitely be more complex and would be optimized differently, but I 
think that the advantages might outweigh the disadvantages.  One 
thing the system would have to do better than current offerings is 
handoff from site to site.  This would probably drive toward some 
full-duplex transmission scheme, so that subscriber units could 
negotiate a handoff in the middle of a transmission.  

Lots of possibilities.  Wish there was an opportunity to come up with 
a new platform like this.  I think that would be lots of fun...

Just my thoughts, and all opposing comments welcome!

Dave Maples

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From: "Mark" <[email-masked]>
Date: Wed, 09 Apr 2003 01:47:35 -0000

Well of course, but it also depends on the user base and the 
licensing considerations also.  Most public safety voice systems 
cover too small an area for a cellular re-use concept and usually can 
put in a simulcast system with minimal issues.  I would rather have 
all the frequencies operational at all the sites giving better joint 
probabality than to have the system think that I'm in a particular 
location just because I voted in a particular especially if they 
can't be utilized by anyone else because of the proximity of the 
other users.

With a large system, like one that a state would put in, by all means 
this would kick butt and allow for frequency re-use cellular type 
system with steerable simulcast or single site transmitters.  
Motorola can do that with SmartZone and basis its decision on whether 
a user is affiliated with a particular zone and/or tower for groups 
and private calls.  I'm biased though being I manage a 10 site, 28 
channel simulcast system over an approximate 2500 square mile county.

I agree on the data...single site is the only way to go for best thru-
put on a multichannel system

--- In [email-masked], "arclight_arclight" <dsmaples@c...> 

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From: "Todd Ellis" <[email-masked]>
Date: Wed, 9 Apr 2003 07:03:52 -0400

Having remained silent for a while, what Dave is asking for is something I
asked for about 8 months ago - a simulcast MPT-1327 on steroids.
Unfortunately, no one is truly interested in offering a simulcast (not
quasi-simulcast) MPT system.  MPT would do everything he is asking for, and
more.  The only problem is the slow data handling capability due to lack of
efficient bandwidth and technology (ie. DataRadio's dual decoding scheme).
It would be relatively inexpensive (70% less than a SmartNet II OmniZone,
40% less than an EDACS simulcast system) and provide more features.  But,
alas, it would not be P25 or even P16 compatible.

Todd Ellis

-----Original Message-----
From: arclight_arclight [mailto:[email-masked]] 
Sent: Tuesday, April 08, 2003 8:12 PM
To: [email-masked]
Subject: [NEXTEL-1] Re: Efficiency - Simulcast Synchronicity Style

Dave Maples

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