Showing papers on "Mobile telephony published in 1977"

A spread spectrum technique for high capacity mobile communications

Abstract: A spread spectrum technique for cellular mobile communication systems is proposed and the results of an analytical study of this technique are summarized. It is found that degradation due to rapid fading is substantially reduced and that, with adequate power control, the user density in a high-quality small cell system may be significantly greater than with conventional FH systems. Furthermore, unique addresses may be permanently assigned to each user and no channel switching is required as the user moves from cell to cell.

Retrieval system for busy line mobile communication

Abstract: PURPOSE:To decrease the retrieval time and to simplify the maintenance oepration, by limiting the retrieval range to the exchanging station in the service area in which mobile unti is present.

Antenna selecting diversity system for mobile communication

Abstract: PURPOSE:To improve the signal transmitting performance, by making the selecting frequency of a plural number of antennas more than the transmitting speed of the base band digital signal.

Control system for mobile communication

Abstract: PURPOSE:To enable stable control through the waiting of normal control channel by mobile unit, by discriminating the reception wave of mutual modulatin by control channel in mobile unit. CONSTITUTION:The mobile unit can receive the specific signal of the control channel within a given time at the reception of the control channel for the respective radio zone and can not receive the specific signal at the reception of the communication channel by mutual modulation. Accordingly, the mobile unit can wait at the channel having the specific signal.

New automated maritime telephone system

Abstract: As one of the most valuable services in telecommunication service, NTT has developed a new automated maritime telephone system for public use. Calls between ship and land subscribers, or between one ship and another can be connected automatically by subscribers' dialing in the nationwide system. The new system adopts a lot of technical features such as automatic location registration, new signaling methods, etc. An outline of system performance and function is described herein.

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.

Word synchronization and digital signal processing for a high capacity mobile telecommunications system

Abstract: In the BTL developed High Capacity Mobile Telecommunications System a 10K bit/sec digital signaling system is used to provide information needed in the various stages of call set-up and control. This paper focuses particular attention on the word-sync reliability problem for data-burst signaling as used to provide channel designations for cell-to-cell handoffs. It is shown that a simple quasi-static model of the Rayleigh fading carrier can be used to predict miss and false response rates of a Barker framing sequence. Also, it is shown that by appropriately processing word-sync information, three orders improvement in the false response rates can be routinely achieved.