CSMN-636-1111: Telecommunications and Networks

Cellular/Wireless Communications:
Some Opportunities And Potential Pitfalls

David R. Mapes


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.


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

   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."


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.


All about cellular. (1996, April 3).  Available:

Data on cellular Vol IV No 3.  (1996, April 3).
     mcv4no3.html, mc43amp.html, mc43namp.html,

Guglielmo Marconi: A dilog from year 101 of the
     electronic era.  (1996, April 3).  Available:

Hughes cellular digital packet data.  (1996, April 3).

Jossi, F.  (1996, April 3).  Solely cellular.

Morley, J. C. and Gelber, S. S.  (1996).  The emerging
     digital Future: An overview of broadband and
     multimedia networks.     Danvers, MA:  Boyd &
     Fraser publishing company.

Oliver, A.  (1995, Nov 24).  Brodhead citizens can get
     help with push of button.  Beloit Daily News. 
     (1996, October 23). 

Ramteke, T.  (1994).  Networks.  Englewood Cliffs, NJ: 
     Prentice-Hall Inc.

Rockwell announces successful tests of cellular digital
     packet data with GPS-based vehicle location
     system.  (1995, July 5).  (1996, October, 22). 

Walker, J. ed. (1990).  Mobile information systems.
     Norwood, MA: Artech House, Inc.

Yeager, C., and Janos, L.  (1985).  Yeager.  New York:
     Bantam Books.