Method of locating a subscriber unit within the coverage area of a communication system

• US 6,486,794 B1
• Filed: 04/05/1996
• Issued: 11/26/2002
• Est. Priority Date: 02/26/1996
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Flippo, Robert S., Bailey, Troy A., Calistro, Enrique E.
• Primary Examiner(s): Horabik, Michael
• Application Number:
  US08/628,361
• Time in Patent Office: 2,426 Days
• Field of Search: 340/825.49, 340/825.44, 340/825.36, 379/56.1, 455/39, 455/503, 455/440, 455/441, 455/11.1, 455/13.1, 455/500, 455/456, 455/457, 370/310, 370/312, 370/313, 370/314, 370/328
• US Class Current: 340/8.1
• CPC Class Codes: H04W 52/04 TPC
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 distributing total power among users or channels
• CPC Class Codes: H04W 84/022 One-way selective calling networks, e.g. wide area paging

Abstract

In a communication system (800) having transmitters (108) for transmitting location information to subscriber units (102) located with the transmitters'"'"' coverage areas, a method of determining the location of a subscriber unit. At least some of the transmitters use different assigned time intervals to transmit their information, and a subscriber unit receiving such information can determine its location based, at least in part, on the time interval during which it received information. Received location information is stored in a dedicated portion (808) of a subscriber unit'"'"'s memory for later retrieval by the user. In a two-way system, a subscriber unit can transmit its stored location information to a system receiver (802) for storage in a system memory (804). The system memory (804) is accessed by a system operator or other authorized person to determine the location of a subscriber unit and/or its pattern of movement throughout the coverage areas.

Claims

1. A method of determining the location of a subscriber unit operating in a communication system having transmitters that transmit information to the subscriber unit, each transmitter transmitting substantially within its own coverage area, the method comprising:

causing at least some of the transmitters to use different assigned time intervals of a transmission cycle for transmitting information;

receiving, at the subscriber unit, information transmitted during at least one of the assigned time intervals;

identifying, at the subscriber unit, the coverage area of a transmitter from which received information was transmitted, based, at least in part, on which time interval was used to transmit the received information; and

storing an indication of an identified coverage area for later retrieval.

2. A method as set forth in claim 1 wherein the communication system includes a receiver and a memory, wherein the subscriber unit stores location information sent by the transmitters, and further including:

causing the subscriber unit to transmit stored location information to the receiver; and

storing, in the memory, location information transmitted by the subscriber unit, thereby to record movement of the subscriber unit.

3. A method as set forth in claim 1 wherein the transmitters are low power transmitters, and wherein the communication system includes a high power transmitter for transmitting throughout a large coverage area that substantially includes coverage areas of the low power transmitters, and where all the transmitters transmit on a common frequency.

4. A method as set forth in claim 1 wherein the information transmitted includes an indicator for location information, wherein the subscriber unit includes a memory for holding information relating to location, and wherein the subscriber unit responds to the indicator by storing location information in the memory.

5. A method as set forth in claim 4 wherein the transmitters transmit the indicator periodically.

6. A method as set forth in claim 5 wherein the transmitters transmit a time stamp with the indicator, and wherein the subscriber unit stores the time stamp with location information.

7. A method of determining the location of a subscriber unit operating in a communication system having a high power transmitter for transmitting information throughout a wide coverage area, and having low power transmitters for transmitting information within their own smaller coverage areas located substantially within the wide coverage area, the method comprising:

causing the high power transmitter and the low power transmitters to repeatedly transmit information throughout their respective coverage areas, the transmitters using a common frequency and different assigned frames of a transmission cycle for transmitting information, and the information transmitted by the low power transmitters including an indicator for location information and a time stamp; and

at the subscriber unit;

receiving information transmitted during at least one of the assigned frames;

identifying a coverage area from which received information was transmitted, based, at least in part on which frame was used to transmit the received information;

and storing location information, including the identity of an identified coverage area with a time stamp for later retrieval.

8. A method as set forth in claim 7 wherein the communication system includes a receiver and a memory, and further including:

causing the subscriber unit to transmit stored location information to the receiver; and

storing, in the memory, location information transmitted by the subscriber unit.

9. A method of tracking the movement of a subscriber unit operating in a communication system having transmitters that are located in different coverage areas and that use different frames of a transmission cycle to transmit information on a common frequency, the method comprising, in the subscriber unit:

receiving transmitted information;

identifying a coverage area from which received information was transmitted, based, at least in part, on which frame was used to transmit the received information; and

storing an indication of an identified coverage area for later retrieval.

10. A method as set forth in claim 9, including:

storing successive indications of identified areas as the subscriber unit moves from coverage area to coverage area; and

displaying, at user demand, at least a most recently stored indication to show the subscriber unit'"'"'s current location.

11. A method as set forth in claim 9 wherein the communication system includes a receiver, and further including causing the subscriber unit to periodically transmit, to the receiver, stored indications of identified areas.

12. A method as set forth in claim 11 including transmitting a time stamp with a transmitted indication.

13. A method as set forth in claim 9 wherein the communication system includes a receiver and a memory, wherein a transmitter sends location queries to subscriber units, and further including causing the subscriber unit to respond to a location query by transmitting at least one stored indication to the receiver for storage in the memory.

14. A method of tracking the movement of a subscriber unit operating in a communication system having a receiver and having transmitters that are located in different areas and that use different frames of a transmission cycle to transmit information on a common frequency, the method comprising, in the subscriber unit:

receiving transmitted information;

identifying a coverage area from which the received information was transmitted based, at least in part, on which frame was used to transmit the received information;

storing indications of identified coverage areas, and storing a time stamp with each such indication; and

transmitting to the receiver at least a most recently stored indication of an identified coverage area.