Position locating transceiver

• US 5,414,432 A
• Filed: 04/22/1993
• Issued: 05/09/1995
• Est. Priority Date: 03/04/1992
• Status: Expired due to Term

• Current Assignee: CDC Propriete Intellectuelle
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Penny, Jr., Robert E., Mihm, Jr., Thomas J.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/051,584
• Time in Patent Office: 747 Days
• Field of Search: 342/42, 342/43, 342/44, 342/50, 342/51, 342/52, 342/59, 342/133, 342/146, 342/357, 342/454, 342/457, 342/463
• US Class Current: 342/357.59
• CPC Class Codes: G01S 19/17 Emergency applications
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: H04B 7/18552 using a telephonic control signal and a second ranging satellite determining absolute distances from a plurality of spaced points of known location G01S5/14

Abstract

A hand-portable position locating radio has a geolocation (e.g. GPS) receiver providing local position and timing information from geolocation means (e.g. GPS or IRIDIUM satellites) and a local transceiver for sending local position and other information to a communication system (e.g., an IRIDIUM or MILSAT satellite). A data processor coupled to the local transceiver and receiver controls operation of the device, including storing local position information and separating signals broadcast by the communication system into those intended or not intended for the device. The radio prepares an emergency access message which it sends to the satellite communication system in a manner to insure rapid detection of the emergency signal and allocation of a clear channel and time slot for further communication.

Claims

1. A transceiver, said transceiver being a portable radio transceiver, said transceiver comprising:

a first radio receiver for receiving first signals from a satellite providing geolocation and timing information;

processor means coupled to said first radio receiver, said processor means for determining, based in part on said first signals, an estimated time window when a listening satellite communication system receives access messages, said processor means providing an access message having a predetermined format including an index;

transmitter means coupled to said processor means, said transmitter means for sending a predetermined sequence of repetitions of said access message to said satellite communication system at least partially during said estimated access time window, each access message of said predetermined sequence having a different index; and

an input device for indicating an alert condition, said input device coupled to said processor means and to said transmitter means, said input device for detecting said alert condition and, when said alert condition is detected, reporting said alert condition and geolocation information describing location of said radio to said satellite communication system.

2. The transceiver of claim 1, further comprising a second receiver for receiving second signals from said satellite communication system.

3. A transceiver, said transceiver being a portable radio transceiver, said transceiver comprising:

a first radio receiver for receiving first signals from a satellite providing geolocation information;

processor means coupled to said first radio receiver, said processor means for determining an estimated time window when a listening satellite communication system receives access messages, said processor means providing an access message having a predetermined format including an index;

transmitter means coupled to said processor means, said transmitter means for sending a predetermined sequence of repetitions of said access message to said satellite communication system at least partially during said estimated access time window, each access message of said predetermined sequence having a different index; and

an input device for indicating an alert condition, said input device coupled to said processor means and to said transmitter means, said input device for detecting said alert condition and, when said alert condition is detected, reporting said alert condition and geolocation information describing location of said radio to said satellite communication system;

a second receiver for receiving a second signal from said satellite communication system; and

means for identifying an address in said second signal, said identifying means coupled to said second receiver and to a message indicator, said address identifying said transceiver as a desired recipient of said second signal and enabling said message indicator to indicate that said second signal was received.

4. A transceiver, said transceiver being a portable radio transceiver, said transceiver comprising:

a first radio receiver for receiving first signals from a satellite providing geolocation information;

processor means coupled to said first radio receiver, said processor means for determining an estimated time window when a listening satellite communication system receives access messages, said processor means providing an access message having a predetermined format including an index;

transmitter means coupled to said processor means, said transmitter means for sending a predetermined sequence of repetitions of said access message to said satellite communication system at least partially during said estimated access time window, each access message of said predetermined sequence having a different index; and

an input device for indicating an alert condition, said input device coupled to said processor means and to said transmitter means, said input device for detecting said alert condition and., when said alert condition is detected, reporting said alert condition and geolocation information describing location of said radio to said satellite communication system;

a second receiver for receiving a second signal from said satellite communication system; and

means for detecting a portion of said second signal, said detecting means coupled to said second receiver and to said processor means, said portion indicating that a base station coupled to said satellite communication system has received position information transmitted by said transceiver.

5. The transceiver of claim 4, further comprising means for indicating receipt of said portion indicating that said base station has received said position information transmitted by said transceiver, said indicating means coupled to said detecting means.

6. A radio, said radio being a hand-portable radio, said radio comprising:

a global positioning system (GPS) receiver responsive to GPS satellites for receiving therefrom information permitting said radio to determine its local position;

a device for indicating an alert condition;

a transceiver for exchanging messages with a listening satellite communication system; and

a processor coupled to said device, said transceiver and said GPS receiver for (i) determining in part based on information from said GPS receiver an estimated time window when said listening satellite communication system is able to receive messages, (ii) providing to said transceiver a sequence of repeated access request messages for transmission to said listening satellite communication system during at least a portion of said estimated time window, wherein each of said repeated access request messages in said sequence contains a index, (iii) after said transceiver receives an acknowledgment message from said satellite communication system containing an indication of which index was received by said satellite communication system, correcting said estimated time window and (iv) transmitting a message containing said alert condition and local position information during said corrected time window.

7. The radio of claim 6, wherein said acknowledgement message contains an address identifying said radio.

8. The radio of claim 7, wherein said processor further comprises means for detecting said address identifying said radio, said address being included in the access acknowledgement message so that the transmission of said local position information is initiated thereby.

9. A radio, said radio being a hand-portable radio, said radio comprising:

a global positioning system (GPS) receiver responsive to GPS satellites for receiving therefrom information permitting said radio to determine its local position;

transceiver means coupled to said GPS receiver, said transceiver means for communicating with one or more remote stations via a transceiver satellite, by sending digital information containing said local position to said one or more remote stations via said transceiver satellite and receiving therefrom an acknowledgement that said local position has been received;

annunciator means coupled to said transceiver means, said annunciator means for providing an indication of received messages;

processor means coupled to said transceiver means and said annunciator means, said processor means for receiving said acknowledgement from said transceiver means and generating an output signal to actuate said annunciator means to indicate that said acknowledgement was received; and

an input device for indicating an alert condition, said input device coupled to said processor means and to said transceiver means, said input device for detecting said alert condition and, when said alert condition is detected, reporting geolocation information describing location of said radio and said alert condition to said one or more remote stations;

clock means coupled to said processor means, said clock means for maintaining local radio time;

memory means coupled to said processor means, said memory means for storing information describing relative timing of transceiver satellite transmit and receive times; and

wherein said processor means further comprises;

computation means coupled to and responsive to the clock means, said computation means for determining actual local radio time when said transceiver satellite broadcasts and for combining relative timing information from said memory means with observed actual local radio time when said transceiver satellite broadcasts, in order to estimate therefrom local radio time intervals when said transceiver satellite is able to receive messages transmitted from said radio.

10. In a radio frequency communications system comprising a radio and a satellite communication system, the satellite communications system comprising a constellation of communications satellites, a method for communicating an alert condition existing at the radio, said method comprising steps of:

retrieving an emergency access message (EAM) format from a local store within the radio in response to an alert condition;

estimating or recalling from memory an anticipated satellite communication system receive time window;

transmitting an EAM signal having the EAM format to the satellite communication system during at least part of the anticipated satellite communication system receive time window;

waiting for a response during a satellite communication system transmit time window;

detecting a response from the satellite communication system;

aligning an internal clock in the radio to provide a radio transmit time window substantially coinciding with a subsequent satellite communication system receive time window;

providing an emergency data message (EDM) including the local position of the radio; and

transmitting the EDM containing the local position of the radio to the satellite communication system during the subsequent satellite communication system receive time window.

11. In a radio frequency communications system comprising a radio and a satellite communication system,

wherein the radio comprises a portable radio including a memory, a processor, a transmitter, a receiver and a clock for keeping internal time, and

wherein the satellite communications system comprises a constellation of communications satellites,

a method for communicating an alert condition existing at the radio, said method comprising steps of:

recalling a satellite communication system access message format from the memory;

estimating by the processor an access message receive time window and a response transmit time window for the satellite communication system;

transmitting by the transmitter an access message having the satellite communication system access message format to the satellite communication system during at least part of the estimated satellite communication system receive time window;

waiting for a response during the satellite communication system transmit time window;

correcting by the processor internal time in the clock to provide a subsequent radio transmit time window substantially coinciding with a subsequent satellite communication system receive time window when a response is received by the receiver from the satellite communication system; and

transmitting by the transmitter a data message containing information on local position of the radio to the satellite communication system during the satellite communication system receive time window.

12. The method of claim 11 further comprising, prior to said second transmitting step, a step of determining a local position of the radio using information from a GPS receiver within the radio.

13. The method of claim 12, wherein said step of estimating an access message receive time window for the satellite communication system comprises steps of:

(i) correcting local time in the radio using time information derived from the GPS receiver;

(ii) retrieving from the memory information describing transmit and receive times for the communications satellites expected to be visible to the radio depending upon its local position; and

(iii) calculating therefrom the local time in the radio when the access message receive time window occurs for visible communications satellites of the satellite communication system.

14. The method of claim 11, wherein said step of estimating an anticipated access message receive time window for the satellite communication system comprises steps of:

(i) detecting broadcasts from the satellite communication system to locally determine broadcast times when such broadcasts occur;

(ii) comparing observed broadcast times with information stored in the radio describing intervals between transmit and receive time windows of the satellite communication system; and

(iii) calculating therefrom a local time in the radio when the anticipated access message receive time window for the satellite communication system occurs.

15. The method of claim 11, wherein said steps of recalling an access message format and transmitting an access message comprise steps of:

providing an access message format including a time related variable from the memory; and

transmitting by the transmitter multiple repetitions of the access message wherein each of the multiple repetitions has a different value of the time related variable, thereby allowing a satellite receiving one or more of the multiple repetitions to detect time displacement between a radio transmit time window and a satellite communication system receive time window, so that a response message sent to the radio can contain time difference information for subsequent use in said step of correcting internal time in the radio.

16. A radio, said radio being a hand-portable radio, said radio comprising:

a global positioning system (GPS) receiver responsive to GPS satellites for receiving therefrom information permitting said radio to determine its local position;

transceiver means coupled to said GPS receiver, said transceiver means for communicating with one or more remote stations via a transceiver satellite, by sending digital information containing said local position to said one or more remote stations via said transceiver satellite and receiving therefrom an acknowledgement that said local position has been received;

annunciator means coupled to said transceiver means, said annunciator means for providing an indication of received messages;

processor means coupled to said transceiver means and said annunciator means, said processor means for receiving said acknowledgement from said transceiver means and generating an output signal to actuate said annunciator means to indicate that said acknowledgement was received; and

an input device for indicating an alert condition, said input device coupled to said processor means and to said transceiver means, said input device for detecting said alert condition and, when said alert condition is detected, reporting geolocation information describing location of said radio and said alert condition to said one or more remote stations, wherein said processor means further includes;

means for providing a priority access message having a predetermined format; and

means for actuating said transceiver means to cause said transceiver means to transmit at least N repetitions of said priority access message, each of said at least N repetitions containing variable data identifying when within said at least N repetitions it was transmitted.

17. The radio of claim 16, wherein said processor means further includes means for adjusting, based on a timing correction signal received by said transceiver from said transceiver satellite, a time of transmission of a subsequent data message to said transceiver satellite to more closely match a reception time window of said transceiver satellite, said timing correction signal being based in part on said variable data included in said priority access message, said adjusting means coupled to said transceiver means and to said processor means.

18. A communication system comprising:

one or more satellites;

a radio, said radio comprising a portable radio for communicating with said one or more satellites, said radio comprising;

a geolocation receiver for providing geolocation information;

a transceiver for sending and receiving messages;

a memory for storing message format information;

a local clock for providing local time information;

a processor for controlling said transceiver, memory and clock such that said processor retrieves from said memory an access message format comprising a time index and said processor actuates said transceiver to broadcast multiple repetitions of an access message, each of said multiple repetitions having a different value of said time index, and subsequent to a response received from said one or more satellites via the transceiver, corrects time obtained from said local clock to provide substantial coincidence of a radio transmit time and a satellite receive time for a subsequent data message; and

an input device for indicating an alert condition, said input device coupled to said processor and to said transceiver, said input device for detecting said alert condition and, when said alert condition is detected, reporting said alert condition and geolocation information describing location of said radio to said satellite communication system via said transceiver.

19. The system of claim 18, wherein said processor further receives current local position information of said radio from said geolocation receiver and incorporates current local position information in a message sent to said one or more satellites by said transceiver.

20. A radio, said radio comprising a portable communication system radio for communicating with one or more satellites, said radio comprising:

a geolocation receiver for providing geolocation information;

a transceiver for sending and receiving messages to the one or more satellites;

a memory for storing message format information;

a local time base for providing local time information; and

a processor for controlling said transceiver, memory and time base such that said processor retrieves from said memory an access message format comprising a time index and actuates said transceiver to broadcast multiple repetitions of an access message, each repetition having a different value of said time index, and subsequent to receipt of a response from said one or more satellites received via said transceiver, said processor corrects time obtained from said local time base to provide substantial coincidence of a radio transmit time and a satellite receive time for a subsequent data message; and

an input device for indicating an alert condition, said input device coupled to said processor and to said transceiver, said input device for detecting said alert condition and, when said alert condition is detected, reporting said alert condition and geolocation information describing location of said radio to said satellite communication system said transceiver.

21. The radio of claim 20, wherein said processor further receives current local position information of said radio from said geolocation receiver and incorporates current local position information in a message sent to said one or more satellites by said transceiver.