Showing papers on "Mobile telephony published in 1979"

A study of modulation for digital mobile telephony

Abstract: This paper describes a digital modulation technique for VHF and UHF land mobile telephony. After describing the requirements of voice coding and digital modulation for the narrowband digital voice transmission in the VHF and UHF land mobile radio channels, the feasibility of digital mobile telephony is clarified by showing the realizability of a digital modulation satisfying the requirements and supported by a few of the experimental test results. The remained technical problems, which should be solved in the near future, are enumerated.

Advanced mobile phone service: Mobile telephone switching office

Abstract: The Mobile Telephone Switching Office provides centralised control of the Advanced Mobile Phone Service. Using a No. 1/1A Electronic Switching System, the Mobile Telephone Switching Office coordinates and controls the activities of the cell sites, interconnects the mobile telephones with the land telephone network, and maintains system integrity through automated maintenance. This paper gives an overview of the Mobile Telephone Switching Office and addresses the unique call processing and maintenance aspects of mobile telephony.

Advanced mobile phone service: The developmental system

Abstract: A developmental amps system has been implemented in the urban and suburban areas of Chicago. A Mobile Telecommunications Switching Office at Oak Park, Illinois, controls the ten cell sites used in the system. An Equipment Test, serving approximately 100 mobile users, was initiated in mid-1978. A Service Test, involving approximately 2000 tariffed mobile units, will follow the Equipment Test. This paper describes the developmental system, the activities which were prerequisite to the major system test phases, and the status of the system as of July 1978.

Advanced mobile phone service: A service test mobile telephone control unit

Abstract: Guidelines for the design of a mobile telephone control unit have been determined, based on considerations of driving behavior, customer preference, automobile environment, and calling procedure. This paper explains these guidelines and illustrates their application in the design of a service test control unit.

Land mobile communications and position fixing using satellites

Abstract: In a recent series of experiments, the General Electric Corporate Research and Development Center demonstrated effective satellite-aided land mobile communications, analog and digital data relay, and automatic real-time vehicle position fixing. In one sequence of tests a station wagon was equipped with a specially designed antenna, a slightly modified commercial VHF transceiver, and a digital tone-code ranging responder that operated within the communications bandwidth. The General Electric Radio-Optical Observatory near Schenectady, NY, was the major earth terminal. A commercial VHF base station with a satellite antenna deployed first in an office building in Washington, DC, and later in Tucson, AZ, represented a headquarters or a sector office ground station. Communications were relayed by NASA's ATS-3 geosynchronous satellite. Both ATS-1 and ATS-3 were used for position fixing the vehicle. Voice, slow scan television, audio test tones, prerecorded intrusion sensor data, and telephone patches were relayed by the satellite to and from the vehicle under a variety of conditions in greater Washington, DC, and in the southwestern United States. The experiment demonstrated continent-wide communication of a quality comparable to fringe area reception of present local VHF mobile communications but with a notable lack of multipath flutter. Due to the high angle of signalling path from the vehicle to the satellite, solid structures such as buildings, mountains, bridges, or tunnels degraded communications only occasionally. An absolutely clear line-of-sight signalling path was not required. Trees directly in the signal path seldom interrupted communications. Noisy radio environments such as power lines and vehicle ignitions degraded signals received in the vehicle but did not affect vehicle transmissions. Vehicle positions to within one quarter mile were achieved in real time and within several hundred feet after post experiment recalibration and analysis. In another sequence of tests, similar equipments plus biomedical sensors and a medical telemetry unit were installed in an ambulance. NASA's ATS-3 satellite relayed two-way voice communications between a hospital and the ambulance and electrocardiograms from the ambulance to the hospital. Signals were received with excellent quality from various points within the United States, all well beyond the range of conventional line-of-sight communications. The future of operational systems depends not only on technology but on the need to define user requirements, international frequency allocations, and a commitment to support the initial hardware investment. One key technology that would have to be developed is a multibeam spaceborne antenna with low sidelobes. It has yet to be shown that a large space structure will be low enough in cost to attract the large number of subscribers needed to make it an attractive business venture. It appears likely, but not certain, that the cost of a satellite system to serve large, thinly populated areas may be less than a network of terrestrial repeaters that serve the same area. The likelihood is sufficient to justify further studies.

2GHz-band cordless telephone system

Abstract: Generaly, the cordless telephone has the function to eliminate the telephone line by using the radio so the operator can use the telephone anywhere in the service area of the radio without a limit of the telephone line. This paper describes about the cordless telephone using 2GHz-band and having the same functions as that of the ordinary telephone.

A taxi communication system

Abstract: This paper covers an integrated computer controlled booking and dispatching system for taxi cabs in which the cabs receive printed orders by means of mobile radio data communication, The system is being developed for the three major cities in Sweden and will be introduced in 1981.

Control signal relay system for mobile communication

Abstract: PURPOSE:To make dependent the subradio base station, without increasing control lines, by selecting the signal with maximum reception level among the subradio base stations and the radio base station and transmitting the signal to the radio channel control station. CONSTITUTION:The control signal received at receivers 23, 24 is added with the reception level information and transmitted to the radio base station. The radio base station compares the reception level at a receiver 28 of the station with each reception level transmitted from subradio base stations 11, 12, to select the radio base station or the subradio base stations having the maximum reception level, and the level information selected is added at the end of the digital control signal and the resultant is delivered to a radio channel control station 11.

Simultaneous multioffice diversity reception system

Abstract: PURPOSE:To simplify the constitution of a base station, and to improve an error ratio by exercising composition in a central station by controlling the level of the detection output in proportion to the center value of the envelope of a carrier in each base station on mobile communication

Nationwide mobile telephone operation

Abstract: Growing demand for more efficient communications combined with increasing mobility of system users has resulted in plans for very large mobile telephone systems. Systems cover large cities, states or even entire countries. A service need has developed for nationwide roaming operation. Since mobile telephone is connected to the wireline telephone system, call placement, routing and control must be coordinated between them. The mobile system must deal with the changing location of the subscriber and still meet land network interface requirements. Ideally, the mobile system should make maximum use of land network facilities as they are. The most difficult problem is selection of a numbering and routing plan for mobile users which is compatible with existing land network conventions. The optimum solution is a mobile network which is "overlaid" on the land network and is accessed by a nationwide "area" or access code. The mobile network then deals with the RF management and user mobility independently of land network hiearchy while maintaining a fully coordinated interface between the two systems.

Control system for mobile communication line

Abstract: PURPOSE:To simplify the base station euqipment, by using the communication channel in vacant condition to the transmission and reception of the line control signal at mobile set outgoing without providing the oscillation control channel of the base station, in the mobile communication line control system at the area less in mobile subscribers. CONSTITUTION:In the mobile communication line controller 12s in which the incoming control channel and a plurality of communication channels are assigned to each base station and the transceivers PTX, RTX for each channel and those VTX1 to VTXk and VRX1 to VRXk for the communication channel are provided, the vacant channel detection and number information generating circuit 23, selector circuits 231 to 23k, vacant line control circuits 241 to 24k, vacant memory 18 and the communication channel set control circuits 171 to 17k are provided. Further, the line control for the incoming of the mobile subscriber is made by using the control channel exclusive use for incoming, and the line control at outgoing from the mobile subscriber is made by transmitting and receiving the control signal via the communication channel in vacant condition.

Small K-band Mobile Earth station for Domestic Satellite Communication

Abstract: A simple and small K-band (30/20GHz) mobile earth station for domestic satellite communication was developed. This mobile earth station ( MES ), with 2.7m? non-divided Cassegrain antenna, has 132CH telephone transmission capacity and can be transported to any desired location by a truck or helicopter, if necessary. A satellite communication system using MES( mobile earth station ) intended for emergency relief or temporary communication purpose in domestic communication, will be a future effective system for either domestic, regional or international use. This paper describes (1) system outline, (2) K-band satellite link design philosophy, (3) equipment outline and (4) total system experimental results using Japanese Communications Satellite[l]. Results ably illustrate its system effectiveness.