AMPS(第一代移动通信系统)

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. VT-29, NO.2,MAY 1980
Advanced Mobile Phone Service
FRANKLIN H. BLECHER,FELLOW, IEEE
transmission facilities. Each voice radio at the cell site is connected tothe MTSO via a voice frequency trunk. In addition, 2400-bit/s data linksbetween the MTSO and each of the cell sites are used for the transmission of digital control signals. In a mature AMPS system’ such as shown in Fig. 1, directional antennas are employed with an RF beamwidth of 120”. Consequently, each cell site has three directional antennas for transmission and three pairs of receiving directional INTRODUCTION antennas in order to provide 360” of coverage. A maximum channels can be assigned to each directional HE advanced mobile phone service (AMPS) system was of 3 2 radio antenna. The use of directional rather than omnidirectional to satisfy the following objectives: antennas provides a 4-5 dBsignal-to-interferenceadvantage 1) nationwide service, and makesa sevencell clusterfrequency reuse pattern pos2) efficient use of allocated frequency spectrum, sible [2] . 3) service quality approaching the wireline network, As amobilein the calling state moves about the service 4) technical and economic capability of operating in area, a “location” measurement is made every fewseconds service areas as small as thousands of users and as large by the serving cell site. This measurement determines if the as hundreds of thousands of users. currently serving directional antenna should continue in this It is evident from thefourth objective that,notonly must role or if the mobile should be “handed-off” toanother a highcapacity mobile system be capable of serving large directional antenna associated withthe same cell siteor to numbers of subscribers, butthe capitalinvestment andanother cell site. By thismeans, the mobile is insuredasatisoperating expense per user mustbe reasonable. In the case factory signal-to-interference ratio over essentially theentire of FM systems, more than half of the investment is in the service area. Obviously, good system control is of major a s importancetothe successful operation of an FM cellular mobile telephone set. Consequently, considerable effort w expended to minimize the cost ofthe mobile setbyapprosystem. priately allocating requirements between mobile and landbased equipment. The AMPS system exploits three techAMPS SYSTEM CONTROL nologies: 1) a stored program controlcentralcomputerand Call Setup switching system, 2) large-scale integrated custom circuits, Every cell site has at least onesetupradiochannel which and3) microprocessors.Without the availability of these is used for paging and access. neterm paging describesthe if mobile a is available to receive technologies, AMPS would not have been economically process of determining a given incoming call. The term access complementary is the viable [ 1] .
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functionofstarting amobile-originated call or responding to a paging signal. Fig. 2showsa simplified diagram of the Fig* shows a simplified diagram Of the system plan* radio communication paths betweena mobile, cell site, and The allocated 4 0 - m b frequency spectrum is divided into MTSO. A mobile in the on-hook state (idle condition) auto666 duplex radio channels, providing about 96 per matically tunes to the strongest setup channel.The forward cell for the ‘luster frequency pattern* Cell setup channel contains a continuoussynchronousstream of sites (base stations) are locatedatalternate corners of the digital signals. Included in these signals are paging messages hexagonal cells. The cell sites contain radio, control, voice which contain the binary equivalent of the mobile frequency processing and maintenance equipment, as telephonenumber. When paging is not needed, the cell site as a complement Of transmitting and receiving antennas. adds “filler text” to preserve the synchronous format. Another The cell sitesare interconnectedwiththe Mobile Telecom- message called the 660verhead is transmitted periodically munications Switching Office (MTSo) by Of as part of the paging data and includes 1) the identification of SYSTEM OVERVIEW
Manuscript received July 14, 1979; revised November 1, 1979. This paper was presented at MIDCON‘78,Dallas, TX, December 12-14. The author is with Bell Laboratories, Room 3F326, Whippany, NJ 07981. Telephone (201) 3864056. center the cated at 1 An AMPS system is said to be mature when all cell sites are catedatalternatecorners of thehexagonalcellsandemploydirectionalantennas.Inaso-calledstart-upsystem,thecellsites are of the employ and cells omnidirectional antennas.
Absrrac-The advanced mobile phone service (AMPS) system, an FM cellular radio system i n the final stages of development, is described. A brief description of the system is foUowed by a disclrpsion of the control algorithms which are basic to its operation. Finally, a s a t h report is presented on the Chicago developmental system ( a n operational celFra Baidu bibliotekular system)and thecellular test bed in Newark, NJ (a field laboratory used to evaluate the radii performance of FM ceUular systems with cells as smaU as 1.4-mi radius).