Radio paging system having a plurality of transmitter stations

• US 5,561,701 A
• Filed: 01/11/1993
• Issued: 10/01/1996
• Est. Priority Date: 01/10/1992
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Ichikawa, Yoshio
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): OEHLING, GEORGE J
• Application Number:
  US08/002,896
• Time in Patent Office: 1,359 Days
• Field of Search: 379/57, 379/58, 379/59, 455/33.1, 455/56.1, 455/12.1, 455/13.1, 455/13.2, 455/51.1, 455/51.2
• US Class Current: 340/7.26
• CPC Class Codes: H04B 7/18567 Arrangements for providing additional services to the basic mobile satellite telephony service
• CPC Class Codes: H04B 7/2625 using common wave
• CPC Class Codes: H04H 20/67 Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency
• CPC Class Codes: H04W 84/022 One-way selective calling networks, e.g. wide area paging

Abstract

A global radio paging system in which a plurality of radio frequency carriers having the same frequency are synchronously modulated in a plurality of base stations corresponding in number to the radio frequency carriers with the same digital paging signal and transmitted, respectively. A paging controller which receives paging calls through a public switched telephone network stores preliminarily the maximum value of a sum of a paging request signal transmission time in a transmission line and a time required to process the paging request signal in each of the base stations and a high precision time signal is produced on the basis of a reference signal from a GPS (Global Positioning System) satellite. A transmission time assigning code is attached to the paging request signal, which assigns a time instance which is delayed from a current time determined by the high precision time signal by the maximum value of the sum of the transmission time and the processing tame as a transmission start time. In each of the base stations, a high precision time signal is produced on the basis of the reference time signal from the GPS satellite and the paging request signal supplied through the transmission line is processed on the basis of the high precision time signal to convert a format into the digital paging signal to thereby realize a synchronous modulation of the carriers.

Claims

1. In a global paging system for providing paging services for a plurality of paging receivers distributed in service areas of a plurality of base stations, a paging controller responsive to a paging call received from a subscriber of a Public Switched Telephone Network (PSTN) therethrough for producing a paging request signal containing a subscriber number of an owner of said paging receiver called,

wherein each of said base stations are connected to said paging controller through one of a plurality of transmission lines having different transmission times, each of said base stations producing a plurality of radio frequency carriers having different frequencies and modulated synchronously with a digital paging signal corresponding to said paging request signal, respectively,

said paging controller comprising:

a delay time storage for preliminarily storing a first time value equal to a maximum value of the different transmission times of said transmission lines and a second time value required for converting said paging request signals to said digital paging signals at each of said base stations;

a first GPS receiver responsive to signals received from a plurality of NAVSTAR GPS (global positioning system) satellites for producing a time reference signal;

a first time reference circuit responsive to said time reference signal font producing high precision time signals having predetermined relation in time to a universal standard time;

code producing means for producing codes indicative of a time after a time instance, which is obtained by adding a sum of the first time value and the second time value to a current time, to said paging request signal as transmission start time assigning codes, and codes to specify one of said plurality of radio frequency carriers as channel number codes; and

a plurality of first transmitting means for transmitting said paging request signals, said transmission start time assigning codes, and said channel number codes to said base stations through a respective one of said plurality of transmission lines, each of said first transmitting means being connected to each of said base stations through a respective one of said transmission lines, a bit rate of said each transmission line being N times that of said plurality of radio frequency carriers; and

said base stations each comprising;

a reception buffer memory means for receiving said paging request signals and storing them temporarily;

a second GPS receiver responsive to the signals from said GPS satellites for producing said time reference signal having a predetermined relation in time to the universal standard time;

a second time reference circuit responsive to said time reference signal for producing a high precision time signal having a predetermined relation in time to the universal standard time;

a coincidence circuit for detecting a coincidence between the transmission start time assigning code accumulated in said receiving buffer memory means and said high precision time signal from said second time reference circuit;

a format conversion circuit for converting a format of said paging request signal into said digital paging signal from a time at which a coincidence output of said coincidence circuit is produced; and

a plurality of second transmitting means for producing said plurality of radio frequency carriers by said channel number codes, respectively.

2. The paging system claimed in claim 1, wherein said second time reference circuit includes a highly stable quartz oscillator, produces a clock impulse defining a time position of each bit of said digital paging signal in response to said time reference signal from said second GPS receiver and maintains the production of said clock pulse even after said time reference signal is stopped.