Subject: [NEXTEL-1] in building coverage--moved over here

From: [email-masked]
Date: Sat, 13 Sep 2003 03:55:32 -0400

------- Original Message --------
From: Jack Daniel <[email-masked]>
Subject: Re:  in building coverage--moved over here

Peter,

General questions are short, specific answers are long.

I'm on the road so I must be brief now and will expand later if asked. 
(that's a joke)

Q & A 1. "Most" new complexes do not have ANY in-building wireless
distribution system to start with.

The old 'blast as far as we can and live with the dead spots' logic
still dominates the private user system mentality and very few
structures have private in-building coverage designed in at the start.

The reasons vary but mostly because (1) wireless comms is an
afterthought, (2) wireless hardware source (dealer, etc.) doesn't know
much about in-building distribution, (3) In-building coverage is
perceived as "expensive" by both the customer and dealer, (4) The choice
of equipment and bands of operation are not fixed at the time the
building is constructed.

If two separate systems are deployed, it's not usually because of the
frequency bands.
It is no longer a big technical task to have multiple band in-building
systems, but relatively few people are up on the technology simply
because the requirements (and an awareness of the value) is just
starting to become visible to non-specialists.

The reason two systems are deployed is because the two systems are used
for two different purposes, have two different 'owners', have two
different levels of reliability/survivability/peak capacity and two
different accessibility (maintenance, alteration, etc.) to the wireless
system end users.

There are three sub-sets of system justification and investment at play;
a. The cheapest non-critical private radio coverage: maintenance,
commercial building security, etc. Where some dead zones is acceptable
as a nuisance.

b. The purpose is maximum return on investment for a revenue generating
purpose. This is Nextel, cellular and PCS (plus WLAN in cases like
hotels, etc). Here the amount coverage and reliability is optimized for
average use loading to get the most bang for the buck. Definitely Not
suitable criteria for mission-critical or life protection.

c. The purpose is to protect property and life (i.e. public safety):
These systems have redundancy, back-up power, reliability and
survivability under the most extreme environmental (the building is on
fire, earthquakes, water spray on the equipment room, high temperatures,
etc) and extreme usage loading (max. traffic capacity possible). These
systems demand the highest, most robust grades of equipment and
hardware, emergency scenario coverage (i.e. stairwells instead of
elevators, high fire rated equipment/cable location, etc.) and rapid
restoration of service and repairs by using redundancy, modularity,
etc).

Obviously this grade of in-building coverage is not appropriate for
maximum return on investment.

Q & A 2. I see no particular trend other than some private users using
Nextel with is coincidently, not by plan, the same band that many newer
public safety systems operate on. 

Generally, in smaller structures (less than 4-5 floors with no
basements) local UHF and VHF radio systems may be adequate for category
1 (see above) without any in-building distribution.  That will tend to
skew a private user frequency band popularity contest.

Q & A 3. I know of no in-building specifications within P25 standards
but I am not an expert on P25.
I do know many P25 system coverage engineers are aware of the
in-building coverage requirement and build as much as possible into the
repeater coverage contour as is practical. Almost all new system
performance specifications now include in-building criteria and the
possibility of in-building equipment being required.

Q & A 4. 700 - 900 MHz operation within the passive portion of an
in-building system is not a problem. I regularly use designs that can
accommodate 100 MHz to 3 GHz. The tricky part is in the active devices
and the attendant IM's, noise floors and propagation phasing/delays.

Sorry for the long response but maybe it will preempt a lot of follow-up
questions.

DISCLAIMER: There is >> NO << single universal solution for any wireless
coverage challenge including in-building. Every requirement for large
structure coverage is unique and there may be more than one applicable
resolution.
Someone else's design may be equal to mine.

But I may be wrong.....
Jack Daniel

==============================================

hithel wrote:
> 
> Jack D - could you answer a couple of questions for me?
> 
> 1. Would it be accurate to say that most new complexes have 2 inhouse
> antenna systems? One for security and mtnce on UHF - and one on the
> higher freqs (800 Mhz and above) : "to make a profit" for the building
> owner.
> 
> 2. Do you see any movement away from UHF for security or mtnce units?
> Perhaps to 800 Mhz or 900 Mhz? So that building owners just have to
> build one interior antenna system.
> 
> 3. Is there any mention of interior antenna systems in the P25
> documents? Are any changes needed to P25 to ease the use of interior
> antenna systems?
> 
> Peter S
> 
> As I was typing this it occurred to me that a interior antenna system
> that covers 700 Mhz and above may be able to fulfill all wireless
> needs once public safety moves to 700 Mhz.
> 
> (Another thought - maybe fire departments should install some sort of
> antenna cables in their hoselines.)

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