| Early cellular handsets, such as this unit from 1983, were large compared to modern multifunction wireless handsets, and more like UHF tactical radios in appearance. |
WIRELESS TECHNOLOGY has become a way of life, with wireless devices available for telephone communications, for data/computer communications, and even for downloading entertainment in the forms of movies and video games. Nevertheless, as the history of this magazine reveals, wireless communications has not always had widespread popularity, nor has it always seemed like a sure bet to reach the massive markets of modern times. But fueled by the ingenuity of RF/microwave engineers, not only has cellular communications evolved through a total of four generations, but a host of additional wireless technologies have sprouted to provide a wide range of functions and services.
The costs for early cellular communications systems were high, with service in Bell Telephone's first cellular network in Chicago, IL averaging about $150 per month (in 1978 dollars). The cost of the "handset," which was large and designed more like a tactical military radio, ranged between $1000 and $3000 per unit. The economic model for these mobile radiotelephones was based on business people making calls from the roadparticularly salespeople, for whom immediate access to a telephone could be an advantage.
Conservative market projections at that time predicted more than 2 million mobile telephones by 1990, with some predictions reaching as high as 7 million by 1990. This early network was plagued by technical difficulties, with few base stations, many dropouts on calls, and instances of "blocking," where a caller couldn't gain access to the network because of lack of available capacity when too many users were on the network at the same time.
The United States Federal Communications Commission (FCC) was tasked with accepting applications for cellular radio licenses, starting in major markets. Two licenses were to be granted in each market, with one to the local telephone company and one to a radio common carrier (RCC). The beneficiaries of the rush to establish wireless cellular networks were the equipment suppliers, with companies such as Ericsson and Motorola receiving large orders at the system levels, and suppliers of power transistors and amplifier modules reaping the benefits of these large system-level orders.
The cellular communications concept was first proposed by Western Electric and Bell Laboratories in 1971. It is based on dividing a service area into cells so that channels can be reused when a mobile communications device moves from one cell to another. By handing a user from one cell station to another, the distance from the handset to the station is kept to a minimum, reducing requirements for transmit power from the handset to reach the base station. Mobile units were designed to sample over a thousand channels to find the one that provides the strongest signal, and then lock onto it. The communications between the handset and the network's base stations include determining which cell a call should be handed off to when a mobile unit is approaching the geographic limit of its coverage. Early cellular radiotelephone mobile units leveraged power transistors and amplifiers that had been developed by suppliers such as Motorola for the 800-MHz land-mobile market, so semiconductor devices and amplifiers were already available for early cellular transmitter-section development.
Of course, while the infrastructure for cellular communications technology was slowly being erected in major markets and cities, wired telephone companies maintained a strong business that also relied on wireless or microwave technologies to transport calls from one location to another. In 1984, for example, major US long-distance service provider MCI announced its intentions to buy large amounts of microwave hardware in order to expand its customer base. A Special Report in the March issue of Microwaves & RF detailed how the company was seeking to extend its long-distance coverage by upgrading its existing network of 6-GHz analog FM radios with single-sideband (SSB) radios from Rockwell-Collins, 4-GHz digital radios from Northern Telecom, and hybrid antennas from Thomson-CSF and Andrew Corp. The company planned on spending about $1 billion on microwave equipment in support of its long-distance telephone network.
The 4-GHz digital radios operated at 90 Mb/s, or about twice the capacity of AT&T's digital radios at that time. MCI was hoping to triple its capacity with the investments. One of the problems in building the system was finding suitable locations for the microwave towers, particularly in metropolitan areas where interference can be a problem.
Around that same time, the British government licensed two operators for its cellular-radio network: Racal-Vodaphone Ltd., a joint venture between Racal and Millicon, and Telecom Securicor Cellular Radio Ltd., a joint venture between British Telecom and Securicor. The British Total Access Communications System (TACS) cellular communications system scheduled for service in March 1985 would be based on AT&T's Advanced Mobile Phone Service (AMPS) first-generation (1G) cellular technology.
The British cellular network was slated to start service by the end of March 1985 and to reach 90% of the British population within five years. Estimates varied on how many British subscribers would be able to take advantage of the wireless service, with the British Department of Trade and Industry (DTI) estimating about 500,000 users by 1990 but with research firm Arthur D. Little projecting that the British portion of the world market for cellular communications would be less than 4%, compared to 42% for the United States, 11% for Japan, and 27% for the rest of Europe.
By 1994, the second year of the Wireless Symposium & Exhibition (sponsored by Microwaves & RF), the impact of the cellular communications expansion was evident on the RF/microwave industry, as hundreds of exhibitors rolled out components and test equipment in support of wireless equipment suppliers such as Motorola and Qualcomm. Many of the companies announced that their business plans were changing, away from a strong reliance on military orders to more of a split between military and commercial (wireless) business. At that second show, Qualcomm pointed to the coming commercialization of its code-division-multiple-access (CDMA) technology in expanding cellular networks, while companies such as Analog Devices were announcing communications chip sets for the ever-expanding GSM cellular networks in Europe. Even companies long associated with military work, such as Raytheon, were announcing their roles in supplying MMIC amplifiers for wireless communications applications.
But there were many questions by the end of that year regarding how wireless Personal Communications Services (PCS, as they came to be known) would be delivered, with so many cellular standards competing as part of the wireless technology's second generation (2G). Technologies included CDMA, TDMA, GSM, DCS- 1900 (a US version of GSM), and Japan's Personal Handyphone System. There was even some thought that subscribers might need satellite-based wireless telephones for truly effective cellular service, as companies such as Iridium and Globalstar touted the benefits of their low-earth-orbit (LEO) and medium-earth-orbit (MEO) satellite-based systems and their advantages over terrestrial-based cellular communications systems.
In 1999, more than 500 exhibitors gathered at the seventh annual Wireless Symposium & Exhibition to compare products aimed at the transition from 2G cellular technology to a more digital third-generation (3G) cellular network. CDMA by this time was well established, and variants such as wideband CDMA (WCDMA) had sprouted to support the needs of cellular networks to handle higher data rates and increased services for cellular customers. The number of handsets to be manufactured that year was projected at about 180 million, making those projections for year 1990 appear embarrassingly modest. Although CDMA had captured most attendees' attention, this show marketed the beginning of companies seeking to support multiple cellular air standards with a single device, including IS-95 CDMA with time-division-multiple-access (TDMA) technology. The number of base station buildups was growing, and the importance of digital components, such as analog-to-digital converters (ADCs), was also growing as a part of both wireless cellular handsets and base stations.
In support of the growing generations of cellular communications systems, RF/microwave companies have responded with higher levels of integration, guided by cellular equipment customers' needs for smaller size, lower power, higher efficiency, and lighter weight. The receiver and transceiver modules of the 1990s have become the integrated circuits (ICs) of the 2000s and 2010s in support of fourth-generation (4G) cellular systems. Also, a greater diversity of components, including analog and digital components, are being integrated on a single chip, so that transceivers may now include dedicated ADCs in addition to their usual cast of RF/microwave components.