Showing papers on "Cellular network published in 1977"

Spread Spectrum and Time Division Multiple Access Satellite Communications

Abstract: Although time division multiple access (TDMA) satellite communication provides the highest traffic capacity per satellite and offers efficient transmission of a wide variety of services, it suffers from network timing and ranging requirements and message security. On the other hand, spread spectrum multiple access (SSMA) satellite communication is suited for reliable random access and tactical transmission systems. Orthogonal functions such as Rademacher, Haar, and Walsh, or pseudonoise sequence coding of amplitude and phase of the analog message or code division of baseband signals, frequency and time hopping are among the several methods employed for spread spectrum communications. A combination of TDMA and SSMA can be used for asynchronous and reliable transmission of digital or analog signals.

Data signaling functions for a cellular mobile telephone system

Abstract: The Bell System is proposing to provide high capacity mobile telephone service in the 850-MHz band via a cellular system that employs frequency reuse within a geographic area. In this system, mobile units respond to orders received from base station sites, which are in turn controlled by data links from a telephone central office. Since all phases of the mobile telephone call, including call setup, handoff between base stations, and disconnect require extensive data signaling, a reliable data transmission facility must exist between the central office and the mobile units. The transmission facility consists of a land link and a radio link. The reliability of the radio transmission path is relatively low, and therefore error control techniques are necessarily more elaborate for the radio link than for the land link. Descriptions are given of the signaling requirements and of the signaling schemes devised for both the switching office-to-base station land path and base station-to-mobile unit radio path. The anticipated performance of the error control procedures for these paths is also presented.

A description of the Bell system HCMTS cell-site radio and control hardware

Abstract: Final planning and development is underway for a High Capacity Mobile Telecommunications System (HCMTS), a nationwide, compatible, cellular system that will permit a dramatic increase in the quantity of available mobile telephone service in the United States. In this cellular system the total coverage area is divided into a grid of small hexagonal cells. The radius of each cell is planned to be eight miles for startup systems, but might eventually shrink to one mile (by cell splitting) as traffic density increases. Mobiles located within the cells are serviced by low-power 850 MHz FM transceivers contained within cell-sites which are situated at alternate corners of each hexagonal cell. Two types of antennas may be used at a cell site. A startup system would employ omnidirectional antennas, since for this case traffic density is low and it is important to minimize first cost. Mature, high density systems, would employ three sets of directional antennas at alternate corners of each cell site, arranged such that the 120deg; beam from each antenna set would illuminate the interior of the corresponding cell. All cell sites are interfaced with one central control and switching center, the Mobile Telephone Switching Office (MTSO), by means of four-wire voice and data trunks. A call from the DDD telephone network is first routed to the MTSO, then over a voice trunk to the cell site which is to serve the mobile, and finally over an available radio channel to the called mobile. At call setup the mobile is located by measuring its received signal strength and range. During the call the mobile may be relocated several times a minute. If the mobile enters a new cell it is "handed-off" to a new cell site and radio channel by digital commands from the MTSO.