Communication system

Abstract: A system according to the present invention comprises a telephone switchboard 20 (central station 37) and first coupling distributors 17 - 19, which are arranged in a central telephone exchange 13, second coupling distributors 10 - 12 arranged in areas provided with public telephones 1 - 3, and connected to the first coupling distributors through transmission path 14 - 16, movable radio terminals 21 - 26, and base stations 4 - 6, connected to the second coupling distributors, for relaying radio signals between the radio terminals and the central station. The transmission path 14 - 16 are used for transmitting signals between the base stations and the central station, as well as between the public telephones and the telephone switchboard.

Description: This invention relates to a communication system having improved transmission path connecting a communication center to base stations for relaying voice and or data between the center and a movable radio terminal such as a radio telephone installed in a vehicle. The Japanese patent publication JP-A-1-200836 discloses a radio telephone system in conjunction with a private branch exchange. The wired telephone sets of the private exchange are provided with interfaces capable of multiplex transition of two voice signals and control signals. To each wired set is assigned a mobile telephone which is in radio communication with the interface. The private branch exchange comprises a control section which controls reception and transmission to the stationary telephone sets and their associated radio telephones. There are various kinds of movable radio terminals such as a mobile telephone, a portable telephone, and a convenience radiophone, which are used for communication in a small area. These terminals require assistance of a base station for relaying signals. To use the terminals, base stations must be set at desired locations, and dedicated transmission lines must be provided, connecting the base stations to a communication center. Without transmission lines and land spaces for installing the base stations, the movable radio terminals cannot be used. It is the object of the present invention to provide a communication system having portable radio terminals (including those installed in vehicles, ships, airplanes and the like), and using telephone transmission lines. The system of the present invention comprises movable radio terminals, a central station, and base stations as defined in claim 1. Embodiments of the invention are provided as defined in the claims 2 to 6. The transmission line is used for transmitting signals between the base stations and central station, as well as between the central telephone exchange and a public telephone. Preferably the base station is located in a telephone box, and a transmission path for the base station is used also for a telephone arranged in the telephone box, whereby more than one person can communicate simultaneously by using the telephone or portable radio terminal. This invention can be more fully understood from the following detailed description of embodiments when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a diagram showing a communication system; and Fig. 2 is a diagram showing a movable communication system according to an embodiment of the invention. Fig. 1 shows a movable communication system making use of a central station, instead of a common-use center. In the figure, the public telephones 1 - 3 and base stations 4 - 6 are housed in the telephone boxes 7 - 9, respectively. The base stations (BS) 4 - 6 relay signals between a central station, hereinafter referred to, and respective movable radio terminals such as a mobile telephone, a convenience radiophone, a portable telephone, a telepoint, a cordless telephone, a pocket bell, a teleterminal, and an AVM (Automatic Vehicle Monitoring) system. The telephone boxes 7 - 9 located on streets or so. The telephone boxes 7 - 9 further house coupling distributors (H) 10 - 12 for distributing respective cables to the base stations 4 - 6 or to the public telephones 1 - 3. The coupling distributors (H) 10 - 12 are connected to coupling distributors (H) 17 - 19 provided in a central telephone exchange 16 through cables 13 - 15, and can be connected to a telephone switchboard 20 and a central station 37 by the coupling distributors (H) 17 - 19. Radio communication is performed between the base stations 4 - 6, on one hand, and portable radio terminals (PT) 21 - 23 (such as a portable telephone, a cordless telephone, a pocket bell, and a teleterminal) or mobile terminals (MT) 24 - 26 (such as a mobile telephone, a convenience radiophone, and an AVM system), on the other hand. The telephone switchboard 20 provided in the central telephone exchange 16 is connected to home telephones (T) 32 - 36 through transmission lines (L) 27 - 31, respectively. The operation of the above-described communication system having movable terminals will now be explained. When communication such as conversation or facsimile data transmission is performed between the portable radio terminal 23 and home telephone 32, the following transmission route is used: portable radio terminal 23 -- base station 5 -- coupling distributor 11 -- cable 14 -- coupling distributor 18 -- telephone switchboard 20 (central station 37) -- transmission line 27 -- home telephone 32. Similarly, when communication is performed between the mobile terminal 24 and home telephone 34, the transmission route is: mobile terminal 24 -- base station 5 -- coupling distributor 11 -- cable 14 -- coupling distributor 18 -- telephone switchboard 20 (central station 37) -- cable 29 -- home telephone 34. Further, when communication is performed between the public telephones 2 and 36, the transmission route is: public telephone 2 -- coupling distributor 11 -- cable 14 -- coupling distributor 18 -- telephone switchboard 20 (central station 37) -- cable 31 -- home telephone 36. As is described above, some telephones and terminals use the same route of coupling distributor 11 -- cable 14 -- coupling distributor 18 -- telephone switchboard 20 (central station 37). To transmit signals (indicative of data) of three kinds through the same route, without causing interference between the signals, a multiplexing system such as time compression multiplexing transmission system or frequency division multiplexing transmission system is employed. Fig. 2 shows an embodiment. This embodiment is different from Fig. 1 in that it additionally employs a communication network comprising a common-use center 38 connected to coupling distributors (H) 17 - 19 through dedicated lines 37a, and user centers (A and B) 40 and 41 connected to the common-use center 38 through dedicated lines 39. This network enables communication between, for example, movable terminals (such as trucks and taxies for business use), on one hand, and their firms (user centers 40 and 41), on the other hand. As is described in detail above, the communication system of the embodiment places the base stations (BS) in telephone boxes (7 - 9) located in many places. Thus, the base stations do not require places dedicated to themselves. Further, since the cable 13 - 15 between the telephone switchboard 20 and base stations are telephone lines, but not lines dedicated to the base stations, the number of the base stations can be increased easily. Accordingly, a system including various movable terminals and telephones can be easily constructed. In addition to the above, since telephone boxes are located everywhere, even a small-output portable radio terminal can perform communication. The radio terminal can easily be made to have, for example, a wrist-watch size, and to be multifunctional. If the watch-size radio terminal is carried by a person, the following advantages are available: First, communication such as conversation or data transmission can be performed at any time between the radio terminal and telephone, irrespective of the location (indoor, outdoor, land, sea, or sky) of the person having the terminal. Further, persons who communicate between the radio terminal and telephone can confirm their safety to each other. Second, telephone calls normally are concentrated in a certain small zone. In case of an emergency such as a natural disaster, transient concentration of calls can easily be reduced by restricting the number of radio terminals used or determining a priority order of calls by the common-use center 38. Third, the small output radio terminal can be used as a sign post for an AVM system which detects the position of the terminal, or used in public traffic means such as a bus or taxi. A system linking the embodiment with the above-described AVM system can also be constructed. According to this system, the position of a moving terminal (mobile terminal or portable radio terminal) can be detected and recorded by the AVM system, and the terminal can easily be called by way of the user center. As is described above, the base stations for various movable terminals are located in existing telephone boxes, and the transmission lines provided between telephones housed in the boxes and the central telephone exchange are used also for transmitting signals between the base stations and central telephone exchange, thereby enabling access to places required for the base stations and accordingly enabling the number of devices contained in the base stations to increase.

Claims: A communication system for use in a telephone network including public telephones (1 - 3), private telephones (32 - 36), and a central telephone exchange (16), which are connected to each other via telephone lines (13 - 15), said system comprising: mobile radio terminals (21 - 26); base stations (4 - 6), each established in a place (7 - 9) where said public telephone (1 - 3) is installed and being connected to said telephone lines (13 - 15), said base stations (4 - 6) adapted for receiving and transmitting radio signals from and to said mobile radio terminals (21 - 26) and for performing radio signal to electric signal conversion and electric signal to radio signal conversion; and a central station (37) connected to said central telephone exchange (16) for relaying signals from said radio terminals (21 - 26) which are transmitted through said base station (4 - 6) and said telephone lines (13 - 15); wherein said central telephone exchange (16) comprises a telephone switchboard (20) and first coupling distributors (17 - 19) connected to said telephone switchboard (20), each for distributing a transmission path of each telephone line (13 - 15) to either the respective base station (4 - 6) or public telephone (1 - 3); and wherein said central station (37) comprises at least one common-use center (38) connected to said first coupling distributors (17 - 19) through first dedicated lines (37a) ; and at least one user center (40, 41) connected to said at least one common-use center (38) through a second dedicated line (39); and wherein said mobile radio terminals (21-26) are registered in said common-use center (38), and wherein voice and/or data signals are simultaneously transmitted between said registered mobile radio terminals (21 - 26) and said at least one user center (40, 41); and wherein each said base station (4 - 6) and said radio terminals (21 - 26) are adapted to perform transmission therebetween using a multiplexing system, whereby said voice and/or data signals are transmitted simultaneously from a plurality of said radio terminals (21 - 26) to each base station (4 - 6). The communication system of Claim 1, wherein second coupling distributors (10 - 12) are located in said places (7 - 9) of said base stations (4 - 6), each second coupling distributor having one end connected to said public telephone (1 - 3) and another end connected to said base station (4 - 6); said transmission paths of said telephone lines (13 - 15) being used for transmitting voice and data signals between respective base stations (4 - 6) and said switchboard (20) as well as between respective public telephones (1 - 3) and said switchboard (20). The communication system of Claim 1 or 2, wherein said voice and data signals are transmitted between desired mobile radio terminals (21 - 26) via the base stations (4 - 6) and the central telephone exchange (16). The communication system according to Claim 1 or 2, wherein when calls are concentrated in a small zone, said at least one common-use center (38) is adapted to restrict the number of said movable radio terminals (21-26) to be able to communicate with said at least one user center (40, 41), or determines the priority order of the calls. The communication system of any one of the Claims 1 to 4, wherein said radio transmission between the base station (4 - 6) and the mobile radio terminals (21 - 26) is performed by frequency division multiplexing. The communication system according to any one of the Claims 1 to 4, wherein said radio transmission between the base station (4 - 6) and the mobile radio terminals (21 - 26) is performed by time division multiplexing.

Inventors: NAGASAWA ZENICHIRO, SATO RISABURO, NAGASAWA, ZENICHIRO, SATO, RISABURO
Applicants: SMALL POWER COMMUNICATION SYST, SMALL POWER COMMUNICATION SYSTEMS RESEARCH LABORATORIES CO., LTD.
Application year: 1991
Main classification: H04Q7
IPC codes: H04W84