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From: uswnvg!dfpedro@uunet.uu.net (Donn Pedro)
Newsgroups: comp.dcom.telecom
Subject: Re: Cellular Phone Signal Propagation Characteristics?
Message-ID: <15767@accuvax.nwu.edu>
Date: 2 Jan 91 17:08:37 GMT
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X-Telecom-Digest: Volume 11, Issue 5, Message 2 of 11


In article <15746@accuvax.nwu.edu>, chapman@alc.com (Brent Chapman) writes:

: On a drive from the San Francisco Bay Area to Northern Arizona and
: back over the holidays, I was amazed by the extent of cellular service
: coverage.  My phone was claiming there was at least intermittent
: service almost the whole time I was in California. 

With the advent, and installation of Cellular RSA (Rural Service
Areas), I would not be surprised.

: coverage and Needles coverage); even there, though, I would estimate
: that the phone showed coverage at least 75% of the time, and "No
: Service" only 25% of the time.  

Remember that the coverage could have been for carriers other than
your own if your mobile was set to scan both systems.

: I don't have a signal strength display
: on my phone, so I'm not certain how good most of the coverage was, but
: I successfully placed a few calls from these rather desolate areas,
: and the quality didn't seem much worse than what I usually get in the
: Bay Area.

You were most likely working off of one of the new RSAs.

: What are the propagation characteristics of cellular service?  

Depends on the site. A cell can be tuned to serve almost any area.
This can exceed ten miles, especially if it is a repeater site.
Transmit power can be as high as 500 watts in some instances.  The
pattern of service can also be shaped to meet the needs of terrain and
traffic considerations.

: I was under the impression that it was tuned to be strictly a
: short-range (i.e., less than ten miles) system, and that in fact this
: short-range characteristic is fundamental to making the system work
: (because shorter range allows smaller cells, and thus more total
: callers by reusing the same frequencies in more non-adjacent cells).

This is especially true in a densly packed metropolitan area.  In a
rural area, where it is not ecnomical to have a site every few miles,
power is stepped up to conpensate.

:How, then, was I receiving service when I'm sure I was at least 60
:miles from the nearest cell?

Sounds far away, but could have been if you were working off of a high
power repeater site.

: On a related topic, I've been told that cell size is not uniform, and
: that it is a common practice in densely populated areas (like downtown
: San Francisco, for instance) to reduce the power of each cell in order
: to reduce the cell size to the absolute minimum and thereby increase
: the total capacity of the system.  Is this true?

It is.  Cells can also be "tiered". That is: a single cell can
actually act like two cells.  An inner cell and an outer cell.  Cells
can also have "sides".  These can be tuned seperatly to deal with
traffic and terrain found in highly congested cities.

May I suggest a book.

	Mobile Cellular Telecommunications
	Author: William C. Y. Lee
	Publisher: McGraw Hill
	ISBN: 0-07-037030-3

It is pretty deep in places but should tell you almost anything you
would want to know about cellular, as of 1989.


Jenner    dfpedro@uswnvg.UUCP
*Disclaimer?  You bet!  I speak for myself only.*