Simulcast satellite paging system with provision for signal interruption

• US 5,239,671 A
• Filed: 11/13/1990
• Issued: 08/24/1993
• Est. Priority Date: 11/13/1990
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Pagemart Inc. (Spok Holdings, Inc.)
• Inventors: Lorang, Malcolm M., Linquist, Roger D.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Pham, Chi H.
• Application Number:
  US07/612,064
• Time in Patent Office: 1,015 Days
• Field of Search: 455/12, 455/13, 455/33, 455/51, 455/54, 455/56, 455/12.1, 455/13.1, 455/13.2, 455/51.1, 455/51.2, 455/54.1, 455/54.2, 455/56, 455/1, 455/33.1, 455/33.4, 340/825.44, 379/57, 379/59, 379/60
• 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: 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 paging system includes a satellite uplink (40) for assembling paging information and transmitting it to a satellite (26). The satellite (26) is then operable to transmit in a simulcast manner all the information to various regional paging systems (42). Each of the paging systems (42) includes a plurality of towers (10) each containing a satellite receiver (50), a satellite dish (48) associated therewith and a paging transmitter (52). Each of the satellite receivers (50) are operable to receive the information transmitted from the satellite (26) at substantially the same time such that there is no phase difference between any of the towers, regardless of location. Therefore, the transmitters (50) can transmit through antennas (12) information at the paging frequency with substantially no relative delays relative to each of the antennas (12). A backup link receiver (28) is provided for interfacing with a backup link transmitter (70). In the event of a failure of the receivers (50) or the satellite (26), the link transmitter (70) will transmit the paging information directly to select ones of the towers (10) over a separate frequency.

Claims

1. A paging system, comprising:

a satellite having a predetermined footprint for received paging information from a paging information source and transmitting said paging information on a down link channel;

a plurality of paging sites disposed in the footprint of said satellite;

a satellite receiver disposed at each of said paging sites for receiving the paging information from said satellite, said paging information received at the one of said satellite receivers associated with each of said paging sites at substantially the same time;

a paging transmitter disposed at each of said paging sites for receiving the paging information on the output of said satellite receiver and transmitting said received paging information on a paging frequency within a predetermined locale proximate to each of said paging sites for reception by a paging receiver within said paging locale;

a detection circuit for detecting the integrity of the signal received by said satellite receiver; and

a transmission inhibiting circuit for inhibiting transmission by said paging transmitter when said integrity detection circuit detects that the integrity of the signal received by said satellite receiver is below a predetermined integrity threshold.

2. A paging system, comprising:

a satellite having a predetermined footprint for received paging information from a paging information source and transmitting said paging information on a down link channel;

a plurality of paging sites disposed in the footprint of said satellite;

a satellite receiver disposed at each of said paging sites for receiving the paging information from said satellite, said paging information received at the one of said satellite receivers associated with each of said paging sites at substantially the same time;

a paging transmitter disposed at each of said paging sites for receiving the paging information on the output of said satellite receiver and transmitting said received paging information on a paging frequency within a predetermined locale proximate to each of said paging sites for reception by a paging receiver within said paging locale; and

said predetermined locales for substantially all adjacent ones of said paging sites having substantial overlap such that if one of said paging transmitters fails in its associated predetermined locale, said paging transmitters at the adjacent ones of said paging sites will provide sufficient field strength to be received by a paging receiver in substantially all locations within the predetermined locale associated with the failed one of said paging transmitters.

3. A paging system, comprising:

a satellite having a predetermined footprint for received paging information from a paging information source and transmitting said paging information on a down link channel;

a plurality of paging sites disposed in the footprint of said satellite;

a satellite receiver disposed at each of said paging sites for receiving the paging information from said satellite, said paging information received at the one of said satellite receivers associated with each of said paging sites at substantially the same time;

a paging transmitter disposed at each of said paging sites for receiving the paging information on the output of said satellite receiver and transmitting said received paging information on a paging frequency within a predetermined locale proximate to each of said paging sites for reception by a paging receiver within said paging locale;

a backup system for being disposed at a fixed location for receiving the paging information from the paging information source;

a link transmitter for receiving paging information from the output of said backup system and transmitting it over a communication link to select ones of said paging sites;

a link receiver disposed at each of said select paging sites for receiving the paging information from said link transmitter over said communication link;

delay circuitry for adjusting the time delay of said received paging information received by said link receiver; and

an arbiter circuit for selecting the output of said link receiver for input to said paging transmitter when the output of said satellite receiver falls below a predetermined threshold.

4. The paging system of claim 3 wherein said arbiter circuit is operable to inhibit transmission by said paging transmitter if the output of both said satellite receiver and said link receiver fall below a predetermined threshold.

5. The paging system of claim 3 and further comprising:

a comparator for comparing the output of said delay circuitry with the output of said associated satellite receiver to determine the difference in time therebetween;

a synchronizer for controlling said delay circuitry to adjust the delay of the received paging information output by said link receiver to minimize the time difference between the output of said delay circuitry and the output of said associated satellite receiver to substantially zero; and

said arbiter circuit operable to hold the delay of said delay circuitry at the value that existed previous to selecting the output of said link receiver in response to the output of said satellite receiver falling below said predetermined threshold.

6. A method for transmitting paging information from a paging information source to mobile paging receivers, comprising the steps of:

providing a satellite having a predetermined footprint;

transmitting paging information from the paging information source to the satellite;

transmitting the paging information from the satellite on a downlink channel within the footprint of the satellite;

providing a plurality of paging sites within the footprint of the satellite;

receiving the transmitted paging information from the downlink at each of the paging sites, the paging information received at each of the paging sites at substantially the same time;

transmitting the paging information on a paging frequency from each of the paging sites within a predetermined locale proximate to each of the paging sites for reception by the mobile paging receiver when the paging receiver is within one of the predetermined locales associated with the paging sites;

detecting the integrity level of the signal received by the step of receiving at each of the paging sites;

inhibiting transmission of the paging information on the paging frequency at a given one of the sites when the integrity level detected by the step of detecting at the given site falls below a predetermined integrity threshold.

7. A method for transmitting paging information from a paging information source to mobile paging receivers, comprising the steps of:

providing a satellite having a predetermined footprint;

transmitting paging information from the paging information source to the satellite;

transmitting the paging information from the satellite on a downlink channel within the footprint of the satellite;

providing a plurality of paging sites within the footprint of the satellite;

receiving the transmitted paging information from the downlink at each of the paging sites, the paging information received at each of the paging sites at substantially the same time;

transmitting the paging information on a paging frequency from each of the paging sites within a predetermined locale proximate to each of the paging sites for reception by the mobile paging receiver when the paging receiver is within one of the predetermined locales associated with the paging sites; and

each of the predetermined locales for adjacent ones of substantially all of the paging sites having substantial overlap such that if transmission of the paging information on the paging frequency from any of the paging sites fails, transmission on the paging frequency at the adjacent ones of the paging sites will provide sufficient field strength to be received by the mobile paging receiver in substantially all locations within the predetermined locale associated with the failed one of the paging sites.

8. A method for transmitting paging information from a paging information source to mobile paging receivers, comprising the steps of:

providing a satellite having a predetermined footprint;

transmitting paging information from the paging information source to the satellite;

transmitting the paging information from the satellite on a downlink channel within the footprint of the satellite;

providing a plurality of paging sites within the footprint of the satellite;

receiving the transmitted paging information from the downlink at each of the paging sites, the paging information received at each of the paging sites at substantially the same time;

transmitting the paging information on a paging frequency from each of the paging sites within a predetermined locale proximate to each of the paging sites for reception by the mobile paging receiver when the paging receiver is within one of the predetermined locales associated with the paging sites;

receiving the paging information from the paging information source at a fixed location;

transmitting the received paging information from the fixed location as backup paging information on a communication link to select ones of the paging sites;

receiving at the select ones of the paging sites the transmitted backup paging information from the communication link;

adjusting the time delay of the received backup paging information to provide delayed backup paging information; and

selecting the delayed backup paging information for transmission on the paging frequency from the select ones of the paging sites when substantially error free paging information transmitted by the satellite is not received at the select ones of the paging sites.

9. The method of claim 8 wherein the step of selecting the backup paging information is operable to inhibit transmission of paging information on the paging frequency if it is determined that the paging information from the satellite is not received and the paging information from the communication link is not received.

10. The method of claim 8 and further comprising the steps of:

comparing the paging information received from the satellite on the downlink and the delayed paging information received from the communication link and determining the difference in time therebetween;

adjusting the delay between the paging information received from the satellite and the delayed backup paging information received from the link frequency to minimize the difference therebetween to substantially zero; and

the step of selecting the backup information operable to prevent further adjustments in time delay thereof.

11. A paging system, comprising:

a paging source for generating paging information for transmission to a paging receiver disposed at one of a plurality of paging sites;

a satellite having a predetermined footprint that includes said paging sites, said satellite operable to receive said paging information from said paging source and transmit said received paging information on a downlink channel within said footprint;

a satellite receiver disposed on each of said paging sites for receiving said paging information from said satellite on said downlink channel, said paging information received at each of said satellite receivers at substantially the same time;

a backup paging system having;

a backup transmitter for receiving paging information from said paging source,

a communication link connecting said backup transmitter to select ones of said paging sites, and

a backup receiver disposed at the select ones of said paging sites for receiving said paging information from said backup transmitter over said communication link;

synchronizing circuitry for synchronizing said paging information received over said communication link by said backup receiver to said paging information received by said satellite receiver;

an arbiter for detecting the integrity level of the signal received from said satellite and selecting the paging information received by said backup receiver when said the detected integrity level is less than a predetermined integrity threshold level; and

a paging transmitter disposed at each of said paging sites for transmitting said received paging information on a paging frequency within a predetermined locale proximate to each of said paging sites for reception by a paging receiver within said paging locale.

12. A method for transmitting paging information from a paging information source to local paging receivers, comprising the steps of:

transmitting the paging information from the paging information source to a satellite;

transmitting the received paging information from the satellite to a plurality of paging sites in a simulcast manner;

transmitting the paging information from the paging information source to a backup transmitter;

transmitting the received paging information from the backup transmitter over a communication link to select ones of the paging sites;

receiving at each of the select ones of the sites the transmitted paging information from the communication link;

synchronizing the paging information received from the communication link with the paging information received from the satellite at each of the select sites;

detecting the integrity level of the signal received from the satellite at each of the select sites;

selecting the paging information received from the satellite when the detected integrity level is above a predetermined integrity threshold and selecting the signal received from the communication link when the detected integrity level is below the predetermined threshold level; and

transmitting the selected paging information on a paging frequency from each of the paging sites within a predetermined locale proximate to each of the paging sites for reception by the paging receiver when the paging receiver is within one of the predetermined locales associated with the paging sites.