Mobile and Cellular Telephone History:

Introduction

Digital wireless and cellular roots go back to the 1940s when commercial mobile telephony began. Compared with the furious pace of development today, it may seem odd that mobile wireless hasn't progressed further in the last 60 years. Where's my real time video watch phone? There were many reasons for this delay but the most important ones were technology, cautiousness, and federal regulation.

As the loading coil and vacuum tube made possible the early telephone network, the wireless revolution began only after low cost microprocessors and digital switching became available. The Bell System, producers of the finest landline telephone system in the world, moved hesitatingly and at times with disinterest toward wireless. Anything AT&T produced had to work reliably with the rest of their network and it had to make economic sense, something not possible for them with the few customers permitted by the limited frequencies available at the time. Frequency availability was in turn controlled by the Federal Communications Commission, whose regulations and unresponsiveness constituted the most significant factors hindering radio-telephone development, especially with cellular radio, delaying that technology in America by perhaps 10 years.

In Europe and Japan, though, where governments could regulate their state run telephone companies less, mobile wireless came no sooner, and in most cases later than the United States. Japanese manufacturers, although not first with a working cellular radio, did equip some of the first car mounted mobile telephone services, their technology equal to whatever America was producing. Their products enabled several first commercial cellular telephone systems, starting in Bahrain, Tokyo, Osaka, and Mexico City.

Wireless and Radio Defined

Communicating wirelessly does not require radio. Everyone's noticed how appliances like power saws cause havoc to A.M. radio reception. By turning a saw on and off you can communicate wirelessly over short distances using Morse code, with the radio as a receiver. But causing electrical interference does not constitute a radio transmission. Inductive and conductive schemes, which we will look at shortly, also communicate wirelessly but are limited in range, often difficult to implement, and do not fulfill the need to reliably and predictably communicate over long distances. So let's see what radio is and then go over what it is not.

"1. A method of communicating over a distance by modulating electromagnetic waves by means of an intelligence bearing-signal and radiating these modulated waves by means of transmitter and a receiver. 2. A device or pertaining to a device, that transmits or receives electromagnetic waves in the frequency bands that are between 10kHz and 3000 GHz."

Interestingly, the United States Federal Communications Commission does not define radio but the U.S. General Services Administration defined the term simply:

1. Telecommunication by modulation and radiation of electromagnetic waves. 2. A transmitter, receiver, or transceiver used for communication via electromagnetic waves. 3. A general term applied to the use of radio waves.

Radio thus requires a modulated signal within the radio spectrum, using a transmitter and a receiver. Modulation is a two part process, a current called the carrier, and a signal which bears information. We generate a continuous, high frequency carrier wave, and then we modulate or vary that current with the signal we wish to send. Notice how a voice signal varies the carrier wave below: