From: Ira Brodsky (ibrodsky@ix14.ix.netcom.com)
Date: Thu Nov 14 1996 - 11:14:01 MST
Well, not exactly.
But now that I have your attention <g>, I'd like to bring up a topic close
to my heart: personal communications.
No, I am not talking about interpersonal relations. (I'm what you might
call an outgoing loner.)
In his book _How The World Was One_, Arthur C. Clarke quotes a
little-known, turn-of-the-century science fiction writer describing the
future of telecommunications. In essence, the sci-fi write concludes that
in the future, telecommunications will be so ubiquitous, so reliable, and
so personal that if you try to call someone and they don't answer, you will
know they must be dead. (Or frozen?)
My theory is that we are now beginning a second "PC revolution" -- only
this time the PC is the personal communicator. (Although it is also very
much a computer.) I believe that within the next decade, on a global
basis, wireless communicators will become as common as TVs, tape players,
and alarm clock radios. In developed countries, most people will own more
than one. In less developed countries, they will be quite common -- some
third-world governments will sustain their people's dependancy by giving
the phones away "free."
Sorry, but there is a "conspiracy theory" lurking even here. (!)
Yesterday, a major milestone was achieved with the rollout of a new type of
personal communications service in 11 cities across the U.S., based on a
technology called Code Division Multiple Access (CDMA). CDMA -- which has
its roots in jam-proof/secure military communications -- was invented by a
San Diego-based company, Qualcomm, Inc.
CDMA is a wonderfully unique technology. In fact, it seems to defy all of
the traditional rules of radio communications. Most engineers were taught,
and have scrupuously followed, the rule that the only way to accommodate
multiple conversations over the airwaves was to put different conversations
on different frequencies. In fact, it was obvious to any "good engineer"
that putting different conversations on the same frequency at the same time
was a sure-fire recipe for causing severe interference.
Cellular radio defied this rule just a little, by reusing frequencies at
safe distances (using relatively low power radios).
CDMA throws the rule completely out the window. It intentionally puts all
of the conversations right on top of each other. In fact, it requires that
all of the signals from portable handsets arrive at the base station at the
exact same power level -- a state of affairs that would normally guarantee
100% interference, rendering meaningful communications impossible.
However, each of the conversations is digitized (i.e., the voices are sent
as bit streams) and assigned a unique "code." The base station receiver
picks up all of the signals at once; a computer is able to distinguish and
separate the different conversations by "decoding" the composite bit
stream.
To the CDMA engineer, this means designing a radio network in which the
base stations must control the transmit power of every handset to within an
extremely fine tolerance -- no easy thing to do since signals received from
mobile handsets naturally vary more than ten thousand-fold due to fading
and multipath interference (i.e., signals taking different paths and
recombining at the receiver out-of-phase).
However, if one can make power control work it delivers significant
advantages to the end-user. Since the handset is continually compensating
for fading by adjusting its transmit power -- thousands of times each
second -- the hissing and fluttering sound normally associated with
cellular telephone completely vanishes. CDMA phones sound very much like
desktop phones; some people will refuse to believe you are calling them
from your car. And there is another beneficial side-effect of granular
power control: it greatly extends handset battery life.
Now to the "conspiracy." For the last few years, some of my colleagues in
the telecommunications industry have doubted that this technology could be
successfully commercialized anytime soon. Some have even claimed the
entire thing is a "fraud" merely designed to run up Qualcomm's stock price.
So as major manufacturers began licensing the technology, and network
operators began to embrace it, some "experts" came to the conclusion there
must be some sort of conspiracy at work. They began talking about how a
secret "CDMA mafia" was fooling some -- and coercing others -- into
believing this was a legitimate technology.
Well, I now have one of these CDMA personal communication phones in hand
and it does work. Sound quality is excellent. Due to its enhanced battery
life, you can leave the phone on all day. (Actually, it can be left in
standby for two days, or you can talk for four hours, or some combination
inbetween.) Initial prices are 10% - 15% less than cellular telephone.
However, CDMA claims ten times the capacity of conventional cellular, so
prices will probably go much lower as competition heats up. It is also
easy to provide features like caller ID over an end-to-end digital network,
so they are part of the standard package. Some of the conspiracy theorists
are now buying time for themselves by focusing on CDMA's capacity claims,
saying the technology will blow up in operators' faces *later* -- as they
bring more subscribers online.
In this case, the "conspiracy theory" is really just the predictable
reaction of the radio communication industry's equivalent of The Flat Earth
Society. It is peddled mainly by old-guard engineers (plus a couple of
well-known Stanford professors) who simply can't accept the shift from a
separate-frequency to a same-frequency paradigm.
There is also much progress being made toward accessing the Net via
wireless phones. AT&T is now selling a product called "PocketNet Phone"
that retrieves intelligently-filtered text from Web pages. Nokia has
introduced a phone with a somewhat larger screen and built-in Web browser.
If there is interest, perhaps I can post more on this later...
Ira Brodsky
Datacomm Research Company
Wilmette, Illinois
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