Judy Berck, Intel Corporation
April, 1998

This document includes:

• Introduction
• Analog cellular, or AMPS (Advanced Mobile Phone Service)
• Digital cellular or PCS
• The FCC (Federal Communications Commission)

The cellular concept originated at Bell Labs in 1947. The first automatic analog cellular system started operation in Japan in 1979, and in the Nordic countries in 1981. The first commercial AMPS wireless cellular system in the United States started in October 1983 in Chicago. Analog cellular service operates on the 800 MHz frequency band, and are based on FDMA (Frequency Division Multiple Access).

While North and South American analog cellular systems conform to the AMPS standard, in the rest of the world there are several types of analog cellular. In Europe and Asia, these include Total Access Communications System (TACS), Nordic Mobile Telephone (NMT), CNet and MATS-E.

The FCC (Federal Communications Commission) regulates and licenses the use of radio spectrum in the US, while the Department of Communications (DOC) regulates it in Canada.

Within a few years after analog cellular systems were introduced in 1983, it became apparent that higher capacity, more reliable, and lower cost wireless systems were needed to meet booming demand. Predictions were made that system capacity would be saturated by the 1990’s, first in the largest cities, then in other locations.

When consumer demand saturates the capacity of a cellular system, there are three ways to expand: move into new spectrum bands, split existing cells into smaller cells, or introduce new technology to make more efficient use of existing bandwidth. Since no new radio spectrum would be available, and splitting cells requires very expensive additional network infrastructure especially in congested areas, new technology seemed to be the best route. To stimulate technology creation, the FCC declared in 1987 that cellular licensees may employ alternative cellular technologies in the 800 MHz band, provided that interference to other cellular systems was not created. This encouraged the cellular industry to search for new transmission techniques that would increase the efficiency of radio spectrum use compared to existing AMPS systems.

In 1988, a Cellular Technology Industry Association (CTIA) subcommittee was established in the United States to identify technology requirements. Cellular service operators and the manufacturing industry worked with CTIA to define a series of specific milestones to be achieved, with the goal of introducing new technology products and services by 1991.

The requirements and milestones included:

• A tenfold increase in system capacity compared to AMPS (analog)
• Dual-mode AMPS/digital capability during transmission
• New data feature capabilities, such as fax and Short Messaging Service
• Ensuring that equipment would be available by 1991
• Standards for high quality service

The Telecommunications Industry Association (TIA) was asked to create a specification based on these requirements. Many proposals and much debate ensued, with major factions backing Time Division Multiple Access technology (TDMA), and others backing Frequency Division Multiple Access (FDMA).  Both technologies evolved from the original AMPS. To make a long story short, a hybrid of the technologies, TDMA Interim Standard 54 (IS-54) was released in early 1991. TDMA equipment was demonstrated and tested in 1991 in Dallas and Sweden. Newer, more comprehensive standards have been released since, including TDMA IS-136 (also called Digital AMPS or D-AMPS), and CDMA IS-95, and the European GSM standard. Each of these has inherent advantages over AMPS technology.

In 1994, the FCC announced it was allocating spectrum specifically for PCS technologies at the 1900 MHz band, and began a series of auctions. In the years following, network operators deployed cellular service in each of the PCS technologies at the 1900 MHz frequency band.

 TDMA IS-136, also called D-AMPS or Digital AMPS, is based on the IS-136 specification. TDMA, or Time Division Multiple Access, is so named because frequency bands available to the network are divided into time slots, with each user having access to one time slot at regular intervals. TDMA thereby makes more efficient use of available bandwidth than the previous generation of analog technology. The current version, TDMA IS-136, is a revision of the original version of TDMA, IS-54, which was based in part on 1970’s technology and had limited system performance. The revised IS-136 standard was published in 1994, and took into account such later developments as digital control channels. 

CDMA, based on IS-95 technology, is a particular form of spread spectrum technology. Rather than dividing radio spectrum into separate user channels by frequency slices or time slots, spread spectrum technology separates users by assigning them digital codes within the same broad spectrum. Spread spectrum technology dates from the 1940’s, and was used in military communications systems, because spread spectrum signals were virtually immune to interference from enemy signals. The 1970’s and 1980’s saw growing interest in commercial applications, with the earliest proposals to apply spread spectrum to cellular systems appearing in the late 1970’s. In the late 1980’s and early 1990’s, the QUALCOMM corporation proposed and developed a CDMA system; in 1993, the Qualcomm system was modified and adopted by the Telecommunications Industry Association as the Interim Standard 95. Several network operators adopted this standard with plans to adopt CDMA for dual-mode operation with analog at both the 800 and 1900 MHz frequency bands. In 1996, commercial systems began operation.

The most important CDMA design goals were high spectrum efficiency, with a many-fold improvement in capacity over analog, privacy and network security. IS-95 incorporates a cryptographic authentication system.

GSM (Global System for Mobile Communications) was developed in Europe. Like TDMA IS-136, GSM's air interface is based on TDMA technology. Although GSM technology has a lot of similarities to TDMA IS-136, it developed along a very different path. Unlike the United States, where the FCC moved the industry from a single analog standard to a new generation of multiple competing digital standards, in Europe the direction was reversed.

Europe began with five incompatible analog air interfaces scattered around the continent. In the 1980’s, momentum increased to build Europe’s global influence as an economic block by integrating economically. As part of that movement, in response to a European Commission directive, international agreements were devised to develop a single international open, non-proprietary digital cellular standard, with the most important goal of seamless roaming in all countries. New spectrum at the 900 MHz band was set aside for cellular service. In 1982, the Conference of European Posts and Telecommunications, (CEPT) held a meeting to begin the standardization process. This meeting established the Groupe Special Mobile standards body, or GSM. During 1985, the Consultative Committee of International Telegraph and Telephones created a list of technical recommendations, and from these, through a remarkable cooperative effort, the GSM specifications were created. In 1987, all parties agreed to a framework of a compatibility specification, with an air interface based on hybrid FDMA (analog) and TDMA technologies. The GSM standard became the responsibility of ETSI, the European Telecommunications Standards Institute.

The FCC has played a large role in the development process and deployment of PCS technologies in the US. In contrast to the European development, competition among industry players, not cooperation, was the objective. There was no mandate for a national unified approach.

In 1994, the FCC began a series of auctions to sell licenses to what is considered a national resource, the airwaves. The goals and intended effects of these auctions were to foster competition in the communications industries, to raise money for the U.S. treasury, and to increase the number of providers in each cellular market from two to as many as eight, driving down prices. In 1995, the FCC's broadband PCS auction offered 99 licenses to provide wireless personal communications services across the United States and its territories. The PCS auction was the largest auction that the FCC has held to date, resulting in $7 billion going to the Treasury.

Cellular and PCS, the Big Picture; Harte, Prokup and Levine, McGraw-Hill Series on Telecommunications, APDG Publishing, 1997.

Wireless Personal Communication Systems; David J. Goodman, Addison-Wesley Wireless Communication Series, 1997.

Various FCC press releases.