Method and apparatus for enhanced 911 location using power control in a wireless system

{
  "publication_number": "US6590533B2",
  "country": "US",
  "kind": "B2",
  "title": "Method and apparatus for enhanced 911 location using power control in a wireless system",
  "abstract": "A method of locating a mobile telephone includes steps of receiving, transmitting, increasing and determining. In the receiving step, a first base station receives a call from a mobile telephone, the call including a dialed number and a TDMA signal. In the transmitting step, the base station transmits a control message to the mobile telephone when the dialed number meets a predetermined criterion, such as being 911. The control message instructs the mobile telephone to transmit the TDMA signal at a maximum power. In the increasing step, the mobile telephone increases the TDMA signal to maximum power in response to the control message. Then in the determining step, location information for the mobile telephone is determined based on at least one characteristic of the TDMA signal received at at least one of the first base station and other base stations. In an alternate embodiment, the method is practiced in a mobile telephone and the power level is automatically increased in response to the dialed number meeting a predetermined criterion.",
  "claims": [
    "1. A method of locating a mobile telephone, the method comprising: receiving at a base station a call from a mobile telephone, the call including a dialed number and a signal; transmitting from the base station to the mobile telephone a control message instructing the mobile telephone to transmit the signal at a maximum power; increasing the signal to maximum power in response to the control message; and determining location information for the mobile telephone based on at least one characteristic of the signal received at the base station.",
    "2. The method according to claim 1, wherein the at least one characteristic of the signal is the time of arrival of a portion of the signal.",
    "3. The method according to claim 1, wherein the at least one characteristic of the signal is the angle of arrival of the signal.",
    "4. The method according to claim 1, further comprising: receiving a MN from the mobile telephone; querying a user profile database with the MN to determine whether the location function should be invoked; and invoking location function based on the query.",
    "5. The method according to claim 1, further comprising: receiving a dialed number from the mobile telephone; and invoking the location function when the dialed number meets a predetermined criterion.",
    "6. The method according to claim 1, further comprising: determining location information for the mobile telephone based on pre-specified data comprised by the signal received at the base station, the pre-specified data selected to assist in location determination.",
    "7. The method according to claim 6, further comprising: providing the location information to a recipient of the call.",
    "8. The method according to claim 7, further comprising: providing the location information to a geographic information system for displaying the location information on a map.",
    "9. A method of locating a mobile telephone, the method comprising: receiving at a base station a signal from a mobile telephone; invoking a location function in response to the signal; determining whether the mobile telephone should increase power for location determination; transmitting from the base station to the mobile telephone a control message instructing the mobile telephone to transmit a signal at an increased power level based on the determining; receiving at least one of a plurality of base stations the signal transmitted at the increased power level; and calculating a location of the mobile telephone based on the signal received at least one of the plurality of base stations.",
    "10. The method of claim 9, further comprising: calculating a location of the mobile telephone based at least in part on pre-specified data comprised by the signal received at least one of the plurality of base stations, the pre-specified data selected to assist in location determination.",
    "11. The method according to claim 9, wherein determining is performed based on the time of arrival of the signal at least one of the plurality of base stations.",
    "12. The method according to claim 9, wherein determining is performed based on the angle of arrival of the signal at least one of the plurality of base stations.",
    "13. The method according to claim 9, further comprising: receiving a MN from the mobile telephone; querying a user profile database with the MN to determine whether the location function should be invoked; and invoking location function based on the query.",
    "14. The method according to claim 9, further comprising: receiving a dialed number from the mobile telephone; and invoking the location function when the dialed number meets a predetermined criterion.",
    "15. An apparatus for locating a mobile telephone, the apparatus comprising: a plurality of base stations communicating signals with a mobile telephone; a mobile switching center, coupled with the plurality of base stations, the mobile switching center a) receiving from one of the plurality of base stations a call that includes a dialed number of the mobile telephone, b) determining whether the dialed number invokes a location function, and c) sending an instruction to the mobile telephone via one of the plurality of base stations to increase transmission power when the location function is invoked; and a location processor, coupled with the plurality of base stations and the mobile switching center, the location processor determining the location of the mobile telephone based on the signals received from the mobile telephone via at least one of the plurality of base stations at the increased power level.",
    "16. The apparatus according to claim 15, further comprising: a geographic information system, coupled with the location processor, the geographic information system receiving the location from the location processor and plotting the location on a map.",
    "17. The apparatus according to claim 15, further comprising: a public switched telephone network, coupled to the mobile switching center, for transmitting a call to a destination telephone corresponding to the dialed number.",
    "18. The apparatus according to claim 15, wherein the mobile switching center further determines whether the call invokes the location function based on a mobile identification number received from the mobile telephone.",
    "19. The apparatus of claim 15, the location processor determining the location of the mobile telephone based at least in part on pre-specified data comprised by the signals received from the mobile telephone, the pre-specified data selected to assist in location determination.",
    "20. A method of locating a mobile telephone, the method comprising: receiving at a base station a call from a mobile telephone, the call including a dialed number and a signal; invoking a location function in one of a mobile switching center and a location system; transmitting from the base station to the mobile telephone a control message instructing the mobile telephone to transmit the signal at a maximum power; increasing the signal to maximum power in response to the control message; and determining location information for the mobile telephone based on at least one characteristic of the signal received at the base station.",
    "21. The method of claim 20 further comprising: invoking the location function according to a result of an A/B number analysis.",
    "22. A method comprising: a mobile telephone determining to transmit at a higher-than-normal operating power level according to a number to dial; the mobile telephone placing a call to the number to dial and transmitting at the higher power level; the mobile telephone receiving a signal in response to successful location determination of the mobile phone; the mobile telephone decreasing transmission power in response to receiving the signal.",
    "23. The method of claim 22 further comprising: the mobile telephone receiving and displaying information describing the location of the mobile telephone."
  ],
  "description_excerpt": "This patent application is a continuation of U.S. patent application Ser. No. 09/489,477, entitled METHOD AND APPARATUS FOR ENHANCED 911 LOCATION USING POWER CONTROL IN A WIRELESS SYSTEM, and filed on Jan. 21, 2000, now U.S. Pat. No. 6,404,388 and hereby claims priority to the earliest filing date thereof.\n\nThe present invention relates generally to location and communication systems and, more particularly, to determining the location of a mobile telephone within a service area of the mobile telephone.\n\nMobile telephone system operators provide telephone service to subscribers by providing a mobile communications infrastructure in a geographic region or by negotiating access for subscribers to other mobile telephone system operators. Each mobile telephone system generally includes a plurality of cell sites distributed over a geographic region. Each cell site includes a base station having a transmitter and receiver for communicating with mobile telephones within a coverage area or “cell” around the cell site. Cell sites are placed such that there is a continuous or nearly continuous coverage area over a geographic region. This allows mobile telephone users the freedom to use a telephone over a wide geographic area.\n\nThe freedom of movement afforded by mobile telephones is advantageous. However, during an emergency such as a 911 telephone call originated from a mobile telephone, locating the mobile telephone is difficult as compared with locating a land-line originated 911 telephone call.",
  "cpc": [
    "H04W 52/283",
    "G01S 2205/06",
    "G01S 5/019",
    "G01S 5/02",
    "H04W 4/02",
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  ],
  "ipc": [
    "G01S 19/06",
    "G01S 5/02",
    "H04W 4/029",
    "H04W 4/90",
    "H04W 52/28",
    "H04W 52/36"
  ],
  "assignees": [
    "AT&T Wireless Services Inc"
  ],
  "inventors": [
    "Nelson Ray Sollenberger",
    "Jack Harriman Winters"
  ],
  "filing_date": "2002-05-24",
  "publication_date": "2003-07-08",
  "grant_date": "2003-07-08",
  "priority_date": "2000-01-21",
  "application_number": "US-15538002-A",
  "family_id": "23944031",
  "cited_by_count": 81,
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}