The Wireless Revolution Rapid Multinational Progress Will Soon Make Global Wireless Communication a Ubiquitous Reality
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The Wireless Revolution Rapid multinational progress will soon make global wireless communication a ubiquitous reality. Theodore 5. Rappaport ver the past three years, the inter- formance, more flexibility, user options, etc.) est in wireless communications has than a present-day cellular telephone. been nothing less than spectacular. Cellular radio systems around the world have been enjoying 33 percent Current Demand to 50percentgrowth rates. Manypag- The premise that wireless personal communi- ing services have been gaining customers at a rate cations is emerging as a key, wide-sweeping tech- of 30 percent to 70 percent or more per year, and nology that will dramatically impact our society is within the last two years there has been intense supported in numerous sources, including world- corporate research and development aimed at com- wide trade journals and government agency mercializing new wireless communication services reports. As an example, in the United States called PCS (personal communications services). there were more than 6.3 million cellular tele- Meanwhile, new digital cellular technologies have phone users as of September 1991 [18]. This com- been installed in Europe, and developing nations are pares with 25,000 users in 1984, and 2.5 million beginning to install cellular infrastructure. U.S. users in late 1989 [l]. It is clear to most The first wide-scale adoption of a wireless per- industry experts that the Cellular Telephone sonal communications system was in citizens Industry Association's (CTIA) 1989 projections band (CB) radio during thelate 1960s and early 1970s. of 10 million United States cellular users by 1995 will Although it was a victim of its own success due to be exceeded in late 1992, and cellular radio carri- a rapid and uncontrolled saturation of the radio spec- ers are enjoying exponential increases in service sub- trum, and suffered severely from lack of traffic man- scriptions. This demand for mobileiportable agement and services, the staggering acceptance telecommunications is a worldwide trend and is par- of CB radio was a clear indication that consumers ticularly acute in Europe. For example, cellular tele- wanted an inexpensive, portable means of com- phone in Sweden already enjoys a 6.6 percent municating. A more modern wireless device that has adult market penetration [18], and this figure has enjoyed widespread popularity is the cordless been increasing by more than 0.1 percent per month. telephone. By the time you read this article, it is like- Finland, Norway, and France have been experiencing ly that more than 65 million cordless telephones similar growth rates. In Hong Kong, more than will have been sold in the United States alone 50percent of the adult population own or have oper- (although it is estimated that almost halfof the cord- ated cellular telephones. Although no spectrum less phones sold have been discarded or are not used). has yet been allocated to emerging PCS in the The convenience of portable telecommunications United States, industry analysts already are pro- offered by a device as simple as the cordless jecting annual U.S. revenues to be between $33 phone is clearly in demand. Although the design solu- billion and $55 billion by the year 2000 [17]. tions for a ubiquitous wireless communications In the United Kingdom, viewed by many as network will be tremendously complex, all mar- the leading country for PCS initiatives, three ket indications show that consumers wish to have major companies are investing hundreds of millions a small device, similar in size to a cordless phone, of dollars to install an infrastructure that may that would allow them to make and receive phone eventually allow citizens to use small 10 mW portable calls wherever they are. The idea behind wireless terminals to place and receive calls in populated areas personal communications networks (PCNs) is to throughout the country. At worst, PCS will pro- make communications truly personal, so that any- vide relief for users who operate in congested 900 one can place a call to anyone else. Much like the MHz United Kingdom cellular markets. At best PCS stereo Walkman'" or thelaptopcomputer, PCNwill will offer customers the ability to use a single Theodore Rappaport is U permit truly ubiquitous access regardless of the loca- wireless communications unit for home, office, or faculty member of the tion of the user at the time of access. Today, the terms automobile, thereby obviating the need for a tra- Virginia Polytechnic Institute, PCN and PCS often are used interchangeably. ditional wired phone to the home. Two of the the State Uniwrsit) in PCN refers to a concept by which a person can three companies involved, Microtel and Unitel, Blacksbq, virgmia. and at use a single communicator anywhere in a large are actually consortia consisting of many leading tlie Mobile and Portable geographic area. PCS refers to a service that may telecommunications companies. The third United Radio Research Group not embody all of the PCN concepts,but is more per- Kingdom PCN service provider, Mercury, is the lead- (.MPRG). sonalized (i.e., lightweight terminal, better per- ing non-wireline service provider of England's 52 0163-68O4/91/$Ol .OO 1991' IEEE IEEE Communications Magazine November 1991 present analog cellular system. These PCN com- Technology (VT)which features digital cellular tech- - panies are expected to become some of the biggest nologies. As indicated in the VT special issue, it is advertisers in the United Kingdom throughout conceivable that 50 million to 75 million sub- In lase this decade, as they strive to pioneer and market scribers could be using wireless systems for vari- the revolutionary PCN service [19]. ous types of personal communications by the United States The pervasiveness of PCN will be made available mid-1990s. This is corroborated by a recent Mor- by an immense infrastructureof low-power, suitcase- gan Stanley report that predicts cellular and PCN sized base stations which will provide portable systems will achieve at least 12 percent market markets, subscribers with wireless access to the local telephone penetration in many developed countries by the end loop in populated areas. PCN hopes to be able to of this century. the 832 offer wireline communications quality using radio as a transmission medium. Base stationswill be placed Recent Events in Wireless cellular on lamp posts, roofs, and ceilings of buildings and InlargeUnitedStatesmarketssuch asLosAnge- concourses, and in other locationswhere people con- les and New York, where hundreds of thousands gregate. Backbone links that connect PCN base of users can access the cellular radio spectrum, ana log-FA4 stations to other PCN base stations and to the the 832 cellular analog-FMvoice channels are unable public switched telephone network (PSTN) will to accommodate the number of users, and meth- channels are be supplied by one of two methods: either via the ods to improve capacity and cellular system existing telephone wire or fiber plant, or via line- design are desperately needed. For those not of-sight microwave links. Of course, the wide- familiarwith cellular radio, in each market (i.e., city) unable to scale deployment of such an extensive high-grade there are two cellular service providers: the radio wireless telephone system will require engineer- common carrier (non-wireline provider), called accommo- ing tools and techniques and antenna designs that the A channel provider, and the wireline, or B allow rapid and accurate propagation prediction and channel, provider. Each of the two service system design. The radio coverage of each base providers are allocated 416 duplexvoice channels in date the station will intentionally be limited by low transmitter a 25 MHz spectrum allocation. Each voice chan- power, so that the same frequencies can be re- nel is comprised of a 30 kHz base-to-mobile link and number of used many times within a few city blocks. Depend- a 30 kHz mobile-to-base link. ingon regulatory decisions by the British Post Office, Over the past four years, numerous standards users. PCN could compete directly with wired residen- have been proposed for digital cellular radio tial telephone service in the United Kingdom. Thus, communication interfaces throughout the world. it is conceivable that the customers could bypass Digital modulation offers improved spectral effi- the telephone company and use a single PCN ter- ciency and simultaneouslyoffers better speech intel- minal for communications at home or in the office. ligibility for a given carrier-to-interference ratio (CII). In the United States, more than 65 experimen- More importantly, digital modulation accommo- tal licenses have been issued within the last year dates powerful digital speech coding techniques that to regional bell operating companies (RBOCs), non- further reduce the spectrum occupancy of voice users. wireline cellular service providers, manufacturers, Using digital transmission formats, service cable companies, and new start-up companies providers will be able to offer customers addi- hoping to pioneer PCN service. Experimental tional features, such as dynamically allocated FCC licenses that allow limited use of radio data services, encryption, etc. transmissions for portable FAX service, wireless In early 1990, the CTIA and the Telecommu- spread spectrum PABX systems, and microcellu- nications Industry Association (TIA) approved Inter- lar and personal communication services have im Standard 54, which specifies a dual-mode cellular been granted and trials are in various phases. radio transceiver that uses both the analog FM To increase the competition and development (the present-day United States Advanced Mobile time of new wireless technologies and services, Phone System, or AMPS, standard) and a linearized the FCC created a special incentive, called the n/4 Differential Quadrature Phase Shift Keying mod- pioneer’spreference, that offers the exclusive use of ulation format with a Code Excited Linear Pre- reallocated radio spectrum to companies that dictive (CELP) speech coder (called the US.