Tuesday 10 April 2012 at 8:49 pm. Used tags:

January 9, 2008

Re:  Cell Phone Research Inquiry for Middle School Student

Ava,  Your Grandpa, Chuck Lynk, managed one of those labs, the Communications Research Lab was listed as a co-inventor of the first cell phone

You have put together an excellent set of questions on the history of the cell phone!  You could almost write a book in answering the first six of them they are so comprehensive.  Rather than answering them in the order you asked them let me try to sketch out some of the ideas behind cellular telephone and its history that, I hope, will serve your needs.  (I will try to keep in mind that the audience is very talented and gifted middle school students – not engineers.)

First of all there is a cellular radiotelephone SYSTEM in which the cellular PHONE or HANDSET operates.  The PHONE is what everyone sees and touches and uses so it is most often identified with cellular telephony.  But it is the SYSTEM, the organization of the base sites (radio transmitters, receivers, antennas), the controllers and switches, and the operating logic behind the scenes that gives the system its CELLULAR identification and makes it possible for the PHONE to work.  The SYSTEM also defines what the PHONE must do and what it must be like.  There are or have been many cellular systems around the world (there are currently two major systems in the U.S., different from each other and requiring different phone designs in each one.)

The inspiration for the invention of the cellular SYSTEM was necessity.  (Remember the old saying “Necessity is the mother of invention”.)  The U.S. and other countries in the world were finding that they did not have enough RADIO SPECTRUM or CHANNELS available to meet the projected future need for mobile telephone service and other services called Land Mobile Radio Services, LMRS.  (LMRS generally serves police, fire departments, utilities and private business usage.) In about 1969 or 1970 the Federal Communications Commission (FCC) which regulates the use of spectrum in the U.S. started an inquiry called Docket 18262 that would make available 115 MHZ of spectrum they would reassign from television service for the use of LMRS and public radio telephone service.  That’s about 20 television channels taken from the high end of the television band.  While that was more spectrum than these two services already had, it was seen that it would eventually prove to be inadequate if used in the same way as in the past.  So the FCC asked industry to study and propose new techniques to improve the efficiency of the use of that spectrum and propose new systems.  Two major participants in that planning and in putting forward proposals were AT&T (at that time the only telephone system in the U.S. – a private monopoly) and Motorola Inc. (a private company very much involved in LMRS).  The FCC did not say how they would divide that 115 MHz of spectrum between LMRS and telephone and that created some differences of opinion and some competition between AT&T and Motorola because their primary interests were in different areas.  That competition made the years from 1969 through 1985 very interesting!
The invention of the cellular telephone SYSTEM can best be described as an evolution.  Think of that 115 MHz of spectrum as a loaf of bread that has to be shared between all
the people who want some of it.  You can slice the bread thinner and thinner as more users come forward (that is called using narrower channels per user); you can share the slices of bread in some way (something called trunking); and you might be clever and think of ways to “reuse” the loaf – sort of like creating duplicate copies of it.  That last point is the really unique feature of cellular systems – you figure a way to use some of those channels in one location (a cell) and then reuse those same channels in another location (another cell) some distance away.  The trick is that the distance between those same channels must be large enough to keep usage in the first cell from interfering with usage in the other.  (If you and another classmate each try to have a conversation with a friend while sitting next to each other you will both hear both conversations.  However, if the two of you and your friends go to opposite ends of a room and carry on the conversation you will not “interfere” with each other – you will each be reusing the audio “spectrum” in different “cells” – and your conversations will be private.)

That’s the basic idea behind a cellular radiotelephone SYSTEM.  I say it evolved because television channels and all radio systems had used that principle for years.  There are TV channels 2, 5, 7, etc. in Chicago, which I will assume, are also used in Dallas – Fort Worth.  The difference is that those “cells” are very large in area, covering an entire metropolitan area – over 50 miles in radius – and they are used in widely separated cities.  To make cellular radio telephone systems work and to meet all the projected demand in the future those cells could be no more than 5 miles in radius and be capable of being reduced in size through division of the cells to smaller and smaller radii, as small as one-half mile or less.  This meant that the height of the antenna towers would have to be 100 feet or less (television antennas are often on towers or buildings over 1000 feet high).  A city would thus be covered by a honeycomb of small cells, much like a pattern of small tiles covers a large floor.  In fact, the picture of six-sided tiles, hexagons, which was often found in flooring or in the honeycomb hive of bees, was used as the planning model for cellular coverage.  A channel, which was used in one cell of one-mile radius, might be reused in another cell less than 5 miles away.  As the size of the cell was reduced, to one-half mile say, the distance to the first reuse of that channel was also reduced, to less than 2.5 miles.  That’s a lot closer together than is the case with TV channels and allows for reuse of the same channel many times in a city.

This ability to reuse channels very often over a metropolitan area satisfying all the demand for usage is what made the proposals meet the FCC’s objectives.  It also meant that there would have to be techniques developed in the SYSTEM and the HANDSET or PHONE to LOCATE the phone in a particular cell, to SIGNAL that PHONE information telling it where it was and what channel to use, to HANDOFF that phone to another cell and another channel as it moved out of range of the cell in which it began its call, and to CONTROL the operation of the entire process.  Engineers at AT&T and at Motorola worked on these problems along with the definition of the basic radio parameters and over a period of many years came up with solutions.  While I said all of this started in 1969 the motto at Motorola at that time was “stay alive ‘til ‘85”.  This was because over that long period of time a great deal of investment had to be made to develop all of the system and find a large number of paying customers.  It wasn’t until 1983 that the FCC made all of its decisions and operating systems, and paying customers could come on line.

AT&T was a very large monopoly and the Bell Telephone Laboratories was its engineering research and development organization.  Motorola was a much smaller business – AT&T’s annual profits were bigger than Motorola’s annual sales.  They were at least 20 times as large.  At Motorola the work was started in what was then the Applied Research Labs of the Communications Division.  Your Grandpa, Chuck Lynk, managed one of those labs, the Communications Research Lab, and I reported to him.  Another engineer reporting to him was Don Linder.  While I had responsibility for the SYSTEMS aspects of the development, Don had responsibility for the development of the first PORTABLE PHONE.  That was the biggest difference between AT&T’s approach and that of Motorola.  AT&T kept talking about a MOBILE PHONE, one that would be as big as a suitcase, fit in the trunk of a car, and is used only in the car.  Motorola’s experience in LMRS showed that users wanted to use a phone anywhere, at any time; the SYSTEM would have to accommodate low-power, hand-held, lightweight cellular PORTABLE PHONES.  At a time when your Grandpa and I were involved in demonstrating all of our system development to the FCC and Congressional staff in Washington, DC (at a place called the Watergate – just after it had made news for a political trick that eventually brought an end to Richard Nixon’s presidency) two of Motorola’s top managers reached the decision that Motorola would have to demonstrate a portable system to the FCC to convince them of our point of view.

That event led to a very concentrated activity focused on the development of a PORTABLE RADIO TELEPHONE SYSTEM proposal and of the PORTABLE PHONE.
Motorola concentrated that activity into roughly a five-month period – a very demanding schedule.  It ended with a filing with the FCC for a portable cellular telephone system, which we called Dyna.T.A.C., using New York City as the model for its implementation, and a demonstration of a portable phone in New York in the spring of 1972.  While that phone would eventually not work in any of the actual cellular systems developed over the next dozen years, it captured the attention and the imagination of everyone, especially the FCC.  The system planning and the filing were an area where I had the major role.  The development of that phone and the team of Motorola engineers led by Don Linder who worked so hard on its creation were honored this past year as one of the “unheralded” engineering events that has affected our lives.  Motorola also filed a patent application that became U.S. Patent #3,906,166 for a “Radio Telephone System” issued on September 16, 1975, that was one of the basic methods of accommodating portable cellular phones.  Inventors’ names on patents are always listed alphabetically so the patent is referred to as “Cooper, et al”.  One of the top executives that urged us to develop this system was Marty Cooper and his name went to the top of the list – the other executive was John Mitchell and his name is in the middle of the list.  Your Grandpa’s name, Charles Lynk, and mine, James Mikulski, are on that list of inventors.  We sure did a lot of important work.  Motorola engineers continued to work on the development of portable cellular phones and systems for use throughout the world over the next 25 to 30 years and continue to do that even today.

James J. Mikulski, co-inventor of the first cell phone April 3, 1973

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