THE UNIVERSITY OF MARYLAND UNIVERSITY COLLEGE GRADUATE SCHOOL
OF MANAGEMENT AND TECHNOLOGY
A STUDENT RESEARCH REPORT
for
CSMN-636-1111: Telecommunications and Networks
Cellular/Wireless Communications:
Some Opportunities And Potential Pitfalls
David R. Mapes
10/23/96
Background and Introduction
Wireless telecommunication has been in use in one
form or another since before Marconi started
experimenting with spark generators just over a century
ago (Guglielmo Marconi, 1996, p. 4). Despite this long
history, it was not until the early nineteen eighties
that two-way wireless telecommunications became a mass
market business in the form of cellular phone service.
Now, with the advent of digital protocols such as time
division multiple access (TDMA) and code division
multiple access (CDMA) (All about, 1996, p. 3) , and
the connectionless/internet protocol cellular digital
packet data (CDPD)(Hughes cellular, 1996, p. 3),
cellular phone service is poised to offer a number of
new applications and additional (virtual) band width to
handle them. These applications include world-wide
personal voice and data communications, continuous
package/courier monitoring, mobile-distributed data
processing systems, global positioning and route
guidance, the automated tracking and dispatch of public
safety personnel, and the medical monitoring of
elderly/invalid individuals.
Cellular addresses one of the central problems of
duplex radio communication perhaps best stated by an
American Navy officer to Marconi in 1899:
When only one transmitter is
sending, everything is just fine.
When two transmitters are sending
at the same time, all the receiving
wires within range pick up both
messages simultaneously. We can't
read either one of them. How do
you propose to solve this, Mr.
Marconi? (Marconi, 1996, p. 7)
Marconi's answer to this problem of competing signals
was to control the frequency of the radio waves sent
and received by his transmitters and receivers. This
led, in 1900, to the awarding of British patent office,
patent #7777, for "Improvements in Apparatus for
Wireless Telegraphy"--"to control the action so as to
cause intelligible communication to be established with
one or more stations only out of a group of several
receiving stations" (Marconi, 1996, p. 7).
Marconi's patent #7777 was more than just an
answer to a navel officer's question; it was the first
attempt to address a problem that is still with us
today: How, within the limited space available (824
MHz to 849 MHz, and 869 MHz to 894 MHz, or about 40
channels per cell site allotted to cellular phones
(Morley and Gelber, 1996, p. 121)) can we meet the
demand for calling volume placed by the public.
Initially, cellular answered this question by taking a
divide and concur approach to contention for channels.
Even with the available 50 million Hertz of frequency
width to work with, only a few hundred subscribers
could be supported in a given calling area. Indeed the
first cellular phone systems used cell sites of 20
miles in diameter and, in the case of New York city,
supported only 550 customers with nearly 4000 on a
waiting list (Ramteke, 1994, p. 95). Since the 1970s
the size of cell sites and the output of their
transmitters have been progressively reduced. Each
round of down-sizing has allowed an increase in the
number of available channels for a given area, and the
number of customers who could be provided with service.
Ultimately, cells may shrink to only a block or two in
size in cities, while they remain relatively large in
more rural areas (Data on cellular, 1996,
mc43amp.html).
From the outset cellular phone service has been
primarily a service for highly paid professionals, but
as the costs of equipment and service continue to fall,
the demographics of the cell phone customer are
shifting down the economic scale. Increasingly, as the
available capacity of cell-phone systems grow, and the
service and hardware cost performance/price change
curves continue to mirror those of the personal
computer industry, it is the "normal" wireline phone
customer who is becoming a cellular subscriber (Jossi,
1996, pp. 1-2). Indeed, in cases where businesses
recognize the value of having their employees always in
touch, they are working with cellular carriers to offer
their workers basic service for as little as $39.95 for
a pocket phone and $8.00 a month for service.
Applications
Where is wireless telephone service headed? What
new services will it support and what new features will
it offer as it matures? Certainly, in the more
cosmopolitan service areas, carriers already offer many
"advanced" features like voice mail, paging, and
electronic messaging, but with the additional band
width provided by digital protocols like TDMA and CDMA,
many other services will become practical and
affordable. Indeed most of the conventional telephone
features have become relatively "old-hat", the big
gains in service are to be had in less conventional
areas like traffic routing, emergency dispatch, and
medical monitoring.
While other services can be piggy-backed onto the
expanded capacity of a TDMA or CDMA cell phone system
(i.e. package and/or courier tracking, auto security
systems, or mobil data acquisition systems), the three
areas mentioned in the preceding paragraph (traffic,
emergency, and medical) have the most potential for
positive impact on both individuals' lives and cellular
providers' bottom line. It may be nice to be able to
follow the movements of a package or courier in route
to its destination, locate a stolen car before it
becomes spare parts, or enter meter readings directly
into the electric company's database, but being able to
avoid traffic tie-ups, get police, fire, and rescue to
their destinations sooner, and remotely monitor and
respond to a person's health condition are services
that have the potential to both enrich and lengthen
customer's lives, and make the service provider a lot
of money.
It is interesting to note that these three areas
of digital cellular system exploitation have a degree
of vertical integration inherent in their
implementation. Systems that track and report traffic
information in real time are key to effective dispatch
of patrolling and stationed emergency personnel, and
this rapid, effective, automated dispatch is key to the
successful rescue of people undergoing a detected
medical emergency. While these systems may seem to be
tailor made for government sponsorship, there is no
real reason why either the traffic monitoring and
reporting system or the medical monitoring system could
not be implemented privately, for profit. With regard
to the emergency dispatch system, the police, fire, and
rescue organizations with whom it interfaces are
(usually) a part of the affected area's government, and
as such, control of the development and operation of
this system, properly lies in government hands.
However, the implementation of this system should
include the "hooks" to allow interfacing it with
traffic information and automated emergency calling
systems.
Traffic Information Systems
Traffic information systems range in complexity
and capability from the traffic report broadcasts
commonly heard at intervals on metropolitan radio
stations to fully integrated traffic information,
routing, tracking, and guidance systems. At the low
end of the scale, traffic broadcasts offer a lot of
content with minimal investment in additional
infrastructure. The almost universal distribution of
commercial/public radio transmitters and automobile
receivers means that, in terms of providing general,
regional traffic information, a radio station is
uniquely positioned to provide useful and timely
traffic information. In fact most radio stations do at
least make an attempt to provide reports on backups and
accidents on major routes, and information on expected
delays and alternate routes within their listening area
(Walker ed., 1990, p. 141).
While the radio broadcast method of providing
traffic information requires a minimal infrastructure
investment, depending primarily on how the radio
station wants to gather traffic data, it does have some
shortcomings. First, radio broadcasts are, by their
nature, periodic: if some one begins a trip between
traffic reports, they may well commit to a congested
route before hearing the next report (Walker ed., 1990,
p.141). Second, traffic reports at a useful frequency,
perhaps every ten minutes, can interfere with many
types of programming content: people listening to an
opera at home in Potomac Maryland do not want to have a
soprano's aria interrupted to learn about an overturned
truck on the Washington beltway. Third, this type of
generalized broadcast may aid a lot of people, but,
because it is general in nature, it can not provide
specific routing information tailored to the actual
destination of each vehicle on the affected route.
Fourth, simple broadcast systems provide no feedback to
the people and infrastructure responsible for traffic
control.
Various approaches have been taken to these
shortcomings in what is the defacto traffic information
system in most urban areas. Baseband signaling to
allow optional, automated tuning to traffic bulletins
has been tried with some success (Walker ed., 1990,
chapter 5). The more sophisticated versions of this
actually transmit the digitally encoded traffic report
over the baseband without the need to retune the
receiver to an alternate voice channel. These
approaches allow properly equipped motorists to receive
a continuous stream of traffic information at their
option, while those not so equipped may still receive
traffic reports as in the past. Digitally encoding
this data has the effect of compressing it and allowing
each receiver to handle it in a customized manner.
Indeed, using standardized phrasing and representation
can allow an individual to receive the information in
their own language, all that is required is a CD-ROM or
EPROM based lookup/translation table (Walker ed., 1990,
p.170). However, while baseband digital encoding of
traffic data can address the first two problems
described above it is not two-way, and therefore,
cannot provide either custom routing guidance, or
feedback to traffic control.
Various two-way schemes have been proposed and
tried. These schemes include roadside transceiver and
cellular radio based systems (Walker Ed., 1990, p.
192). The trick for two-way implementation is to
balance infrastructure/user hardware costs with those
of actually providing service to the customer. User
hardware costs are (if reasonable) fully recoverable.
Infrastructure costs, however, must be amortized
against the ongoing usage of the system. Over time, if
the system provides real value to its users, the cost
of implementing a dedicated traffic network (based
either upon roadside transceivers or cellular
technology) could be recovered, but the barriers to
entry are much lower for a company with an in place
network, given that it has the additional capacity to
handle the required information transfer and
processing. It is for this reason that an existing
digital cellular phone system using code division
multiple access (CDMA) will probably wind up as the
basic infrastructure for traffic information systems.
CDMA cellular systems offer a gain of about 10
times the carrying capacity of the next best systems
(TDMA) (All about, 1996, p. 3). This added band width
allows the cellular carrier to offer full feature
traffic information and route guidance without any need
for network enhancements; all that is required are the
implementation of the software and procedures to
support the system. Even the standard digital cellular
hand set need not change, the LCD display that supports
its text messaging feature can as easily display a
traffic bulletin, or routing instruction as any other
message.
The basic operation of the cellular network is one
of the points that makes it so good for two-way traffic
information systems. When a cell phone is turned on
it continuously monitors the available channels for
incoming calls, at the same time the cellular network
monitors the phone's relative signal strength at
various cell sites so it can decide which site should
handle a call to or from that phone (Morley, and
Gelber, 1996, p. 121). It is not much of a step from
this signal strength monitoring to automatically
tracking the phone's location. If adoption of the
signal strength monitoring method proves technically
un-feasible, then upgraded handsets using global
positioning system capabilities may be required
(Rockwell announces, 1995, p. 1). By tracking the
location of a phone the traffic monitoring part of the
cell phone system can provide both individualized route
guidance and automatic traffic backup detection. Given
a significant number of cell phone subscribers in the
service area (whether or not they subscribe to the
traffic information/route guidance service), and a GIS
style mapping of the road network for the area, sudden
changes in movement along various routes can be
detected and reported without any need for human
intervention.
Once a slowing or stoppage of traffic flow is
detected the system can query any user detected as
within sight of the incident for more information. Two
criteria could be used to select which users are
contacted for on-site information requests: first, did
the user volunteer for this duty (perhaps a reduced fee
structure could be used as a carrot to encourage this);
second, are they headed toward the incident. Given
there are no "volunteers" nearby, the cellular
subscriber that is closest could be queried. Any
information gained by this on-site observer query could
be formatted and passed on to both other subscribers
and the appropriate authorities.
Emergency Personnel Dispatch
Law Enforcement, Fire, and Rescue has had the
ability to indirectly monitor the location of patrol
vehicles since the installation of two-way radios
became commonplace. What neither Law Enforcement, nor
other emergency services has had the ability to do is
to continuously monitor the flow of traffic over a
whole metropolitan area and instantly respond to any
problems as they occur. Implementation of a cellular
based traffic information system would allow emergency
dispatch personnel to evaluate an incident based upon
on-site reports (granted, reports made by non-
professionals) and traffic flow impact, and respond in
an appropriate manor. Available personnel and
equipment could be dispatched where and when they are
most needed and spared any unnecessary calls. The
advantages of this approach are four fold:
1) Significant blockages can be rapidly assessed
both as to their physical severity and their
impact on traffic flow.
2) Response time is reduced because there is no
need to wait for a participant to report the
traffic problem.
3) Directly contacting an on-site observer
allows the cellular carrier to by-pass the
congested 911 system and provide direct, on-
site traffic flow and incident observation
data to authorities without blocking an
additional line into the standard 911
exchange.
4) This automatic detection, analysis, and
reporting of traffic problems will eventually
reduce the overload of 911 calls that has
become commonplace in areas of high cellular
usage, as people become accustomed to the
service and increasingly leave reporting of
traffic incidents to the automated system.
Medical Monitoring
I visited with her a few times a
year. She was living alone with
her dog in a mobile home out on the
Mojave, a desert rat to the end.
She said to me, "Well, goddamn it,
we had more fun in a week than most
weenies in the world have in a
lifetime." The saddest part about
her passing a few years back was
that it was nearly a week before
her body was discovered inside her
mobile home. (Yeager, 1985, p. 181)
This was how General Chuck Yeager USAF, Ret.
described the death of his friend Florence Lowe (a.k.a.
Pancho Barnes). While Pancho probably would never have
stood for it, there are many elderly people, living
alone or not, who could benefit from continuous
monitoring. Current monitoring systems rely on a
button warn as a pendant. When the button is pressed
this pendant signals a special dialer in the person's
home to call 911 and deliver a prerecorded message.
Once signalled the 911 operator can listen to an audio
monitor in the home for verbal messages or other noises
(Oliver, 1995, p. 1-2). This system has three
shortcomings:
1) It depends on the user being conscious for
activation; there is no provision for
automatic activation when a predetermined
level of distress is detected.
2) It must be in range of its automatic dialer
to function; if the person being monitored
moves out of range the pendant is useless.
3) It cannot detect emergencies on its own; in
the case of some health problems the user may
be unaware or unwilling to admit that they
have an emergency.
4) It cannot help pinpoint the victim's
location: beyond providing the victim's
address it cannot help emergency personnel
find where, within the range of the monitor
the person is.
Replacing this "panic button" with a smart,
cellular capable, monitor would solve these problems.
There is no reason why a unit the size of a wrist watch
could not monitor heart rate and rhythm, respiration,
and temperature, and, based on clearly defined
parameters, transfer that information to an emergency
response center in the event of a problem. Because
this smart monitor can track a person's vital signs it
can react both in cases where the user is incapable of
pressing a button, and when the user is unaware of a
problem. The monitor could also include a panic button
for those "help, I've fallen and I can't get up"
(Oliver, 1995, p. 1) situations. And, since it would
be integrated with a cell phone, it would allow for a
check call when the wrist unit reports a problem. Using
the cellular network for this medical monitoring
service would allow the wearer complete freedom of
movement within an ever expanding coverage area, while
maintaining medical vigilance. A continuous connection
is not required, the monitor can be smart enough to
track the person's condition while checking in only
periodically,or as required, either to down-load an
ongoing record of vital statistics, or to report
exception/emergency conditions. Indeed one of the
major factors favoring the development of this device
is that many health emergencies can go unnoticed by the
victim until too late. In cases such as this having a
little intelligence in the monitor can stop a problem
before it becomes terminal. Finally, if the phone
tracking and location capabilities required for the
traffic management system are implemented, then the
victim can be located any ware in the service area to
within some small distance.
Privacy Issues
One of the major stumbling blocks to the
implementation of these services is not the technical
challenges but the social ones. Implementing system
wide cell phone location tracking in support of a
traffic information system may be a little too
intrusive for some people. Many potential subscribers
to the health monitoring system may find it, despite
its obvious safety benefits, uncomfortable to have a
machine tracking every heart beat and breath, just
waiting to take exception. It should be remembered,
however, that both these services are strictly
voluntary. If someone really doesn't want their
movements tracked (even as part of an aggregate traffic
flow), they can:
A) Not subscribe to cellular service.
B) Leave the phone at home.
C) Turn the phone off.
The same rationales also apply to the health monitoring
system. If a user is offended by the vital signs
monitoring and reporting portion of the monitoring
service, they can always opt out of that feature and
just treat the monitor as a more traditional "panic
button."
Conclusion
The use and availability of cellular telephone
service is growing rapidly. The deregulation brought
about by the Telecommunications Bill of 1996 has opened
the mobile calling market to national carriers (AT&T is
about to bring a national, CDMA based, digital cellular
service on-line (WMAL/ABC, AM 630, Business News, 9:30
AM, 1996, October 2)). The capacity of cellular
networks is poised to grow as more and more couriers
implement digital protocols. The cost of both
equipment and service will continue to fall under these
duel pressures of network capacity and carrier
competition. While mobile communications may never
entirely replace wireline service, there are features
inherent to cellular systems that provide it with the
ability to profoundly impact the quality of life.
Traffic information, emergency vehicle dispatch
and health monitoring systems have the ability singly
and as a group to both enhance the quality and increase
the length of life for their subscribers. The improved
navigation and reduced congestion provided by a traffic
information system will help to both reduce the stress
associated with urban travel and cut the amount of smog
we all breathe. Getting emergency vehicles to the
scene of an accident quickly will both reduce the
degree of congestion suffered by travelers and increase
the chances of survival for any injured victims.
Health monitoring systems will provide both peace-of-
mind and real response time benefits to their users.
The traffic information and health monitoring
systems are somewhat independent in their
implementation needs. Except for the autolocation
feature, the health monitoring system could be
implemented tomorrow. Once the technical and social
challenges to tracking cell phones are worked out, the
traffic and emergency dispatch systems can and should
be brought on-line.
References
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