Automated testing for cellular telephone system including emergency positioning

• US 6,424,837 B1
• Filed: 04/19/1999
• Issued: 07/23/2002
• Est. Priority Date: 04/19/1999
• Status: Active Grant

• Current Assignee: Christopher J. Hall, Ray, Jimmy C., Turner, Clay S.
• Original Assignee: Christopher J. Hall, Ray, Jimmy C., Turner, Clay S.
• Inventors: Hall, Christopher J., Ray, Jimmy C., Turner, Clay S.
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): Milord, Marceau
• Application Number:
  US09/294,278
• Time in Patent Office: 1,191 Days
• Field of Search: 455/456, 455/509, 455/67.1, 455/67.2, 455/67.4, 455/560, 455/457, 455/423, 455/424, 455/436, 455/439, 455/437, 455/404
• US Class Current: 455/456.5
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic

Abstract

A method for automatically testing cellular telephone equipment includes a method for determining a geographic location of a mobile unit. The system includes monitoring sites located, e.g., at high elevations, so that each monitoring site electronically covers a geographical area including several cellular telephone base stations. Locations of mobile cellular stations, especially of such stations placing emergency 911 calls, are determined by comparing signal time-of-reception and other observable signal parameters at a combination of three cell sites and/or monitoring sites. Testing functions include transmitting gradually increasing power levels on a frequency assigned to a particular base station to determine the power level required to acquire service from that base station. Periodic repetitions are monitored over time to indicate any changes or degradation in performance. A scanner scans a designated group of control-channel frequencies, selecting active channels for measurement of transmission parameters and detection of anomalous transmission characteristics on any particular channel.

Claims

1. A method for determining a geographic position of a mobile telephone station in combination with automatic testing of cellular telephone equipment, comprising the following steps:

locating a plurality of monitoring sites so that each said monitoring site receives cellular-frequency transmissions within a geographical area including one or more cellular telephone base stations,

electronically connecting said monitoring sites to a computer controller,

monitoring cellular-frequency control channels accessible by a cellular telephone mobile station within a radio horizon of said monitoring site,

measuring, at said monitoring site, signal parameters of monitored transmissions from said mobile stations and from said base stations, and

determining a position of a mobile telephone station by determining and analyzing the phase difference for a plurality of component frequencies of the signals received at two or more monitoring sites from said mobile telephone station.

2. The method as described in claim 1, wherein one or more said monitoring sites are colocated with cellular telephone base stations.

3. The method as described in claim 1, wherein the step of determining a position of a mobile telephone station further comprises:

decomposing a signal received from a mobile telephone station into said signal'"'"'s component frequencies,

determining a magnitude and a phase for a plurality of said component frequencies,

determining, versus frequency, differences in phases for a plurality of individual frequencies received at two or more monitoring sites,

measuring a slope of a phase-vs-frequency relationship for a plurality of frequencies, said slope being directly proportional to a relative time of arrival of said signal at differing monitoring sites, and

computing from said time of arrival at different monitoring sites a geographic location estimate for said mobile telephone station.

4. The method as described in claim 1, wherein the step of locating a plurality of monitoring sites further comprises:

locating at least one said monitoring site at a sufficiently high elevation so that said monitoring site receives cellular-frequency transmissions within a geographical area including two or more cellular telephone base stations.

5. The method as described in claim 1, wherein the step of monitoring cellular-frequency control channels further comprises:

scanning a pre-determined group of control channel frequencies using an automated scanner.

6. The method as described in claim 1, further comprising the following steps:

measuring a power level required to access service from a particular base station by transmitting from one said monitoring site, at a gradually increasing power level, on a control channel assigned to said base station,

recording a transmitted power level at which said base station responds to a transmission from said monitoring site,

repeating the measuring step and the recording step from time to time, and

comparing recorded transmitted power levels from repeated measuring steps to detect any change in a power level required to access service from said base station.

7. The method as described in claim 1, further comprising the following steps:

measuring dynamic power-control performance of a particular cell site by establishing a test call between a monitoring site and said cell site,

transmitting from said monitoring site at different power levels during said test call,

recording a power level transmitted from said monitoring site at which said cell site initiates a power-adjustment command, and

repeating said transmitting step and said recording step for different levels of power transmitted from said monitoring site.

8. The method as described in claim 1, further comprising the following steps:

measuring a power level required to access service from a particular base station by transmitting from one said monitoring site, at a gradually increasing power level, on a control channel assigned to said base station,

recording a transmitted power level at which said base station responds to a transmission from said monitoring site,

repeating the measuring step and the recording step from time to time, and

comparing recorded transmitted power levels to detect any change in said power level required to access service from said base station.

9. A method for determining a geographic position of a mobile telephone station in combination with automatic testing of cellular telephone equipment, comprising the following steps:

placing a plurality of monitoring sites at sufficiently high elevations so that each said monitoring site receives cellular-frequency transmissions within a geographical area including one or more cellular telephone base stations,

electronically connecting each said monitoring site to a computer controller,

monitoring cellular-frequency control channels accessible by a cellular telephone mobile station within a radio horizon of said monitoring site,

detecting a call access attempt from said mobile station,

determining a time of arrival for said access attempt by analyzing the phases of a plurality of component frequencies obtained from the mobile station transmission,

recording a time at which said call access attempt was received at said monitoring site,

recording an electronic identity of said mobile station making said call access attempt,

determining a base station through which said call access attempt is routed, comparing said time at which said call access attempt was received at said monitoring site to a time at which said call was received at said base station, and

comparing the recorded times to determine a position estimate of said mobile station.

10. The method as described in claim 9, wherein said call access attempt includes dialled digits “

911”

.

11. The method as described in claim 9, wherein the step of recording said electronic identity of said mobile station includes recording other observable signal parameters from said mobile station.

12. The method as described in claim 9, wherein the step of recording said electronic identity of said mobile station includes recording a serial number (ESN) of said mobile station.

13. The method as described in claim 9, wherein the step of recording said electronic identity of said mobile station includes recording a mobile identification number (MIN) of said mobile station.

14. The method as described in claim 9, further comprising the following steps:

comparing said recorded times with a recorded time at which said call access attempt was received at a third cellular facility, and

calculating from the recorded times at which said call access attempt was received at said monitoring site and at said base station and at said third cellular facility station to determine an exact location of said mobile station.

15. The method as described in claim 9, further comprising the following steps:

comparing said possible position of said mobile cellular telephone station with information on a geographic map to determine a most likely position of said mobile station.

16. A method for determining a geographic position of a mobile telephone station comprising the following steps:

locating a plurality of cellular facilities for transmitting signals to and/or receiving signals from a mobile telephone station, wherein a portion of the radio coverage area of at least one of said plurality of cellular facilities overlaps a portion of the radio coverage area of at least one other of said plurality of cellular facilities;

electronically connecting said plurality of cellular facilities to a computer controller;

receiving signals from a mobile telephone station within a radio horizon of one or more of said plurality of cellular facilities; and

determining a position of a mobile telephone station by determining and analyzing the phase difference for a plurality of component frequencies of the signals received at two or more of said plurality of cellular facilities from said mobile telephone stations.

17. The method of claim 16 wherein the plurality of cellular facilities are selected from among a cellular base station and a monitoring site having a radio coverage area overlapping a plurality of cellular base station coverage areas.

18. The method of claim 17 further comprising measuring, at a cellular facility, signal parameters of monitored transmissions from said mobile telephone stations and from said cellular base station.

19. A method for determining a geographic position of a mobile telephone station, comprising:

locating a plurality of cellular facilities, for transmitting signals to and/or receiving signals from a mobile telephone station, wherein a portion of the radio coverage area of at least one of said plurality of cellular facilities overlaps a portion of the radio coverage area of at least one other of said plurality of cellular facilities, and wherein said plurality of cellular facilities comprise one or more cellular telephone base stations and one or more monitoring sites, and wherein said one or more monitoring sites receive cellular frequency transmissions within a geographic area including one or more cellular telephone base stations;

electronically connecting each said plurality of cellular facilities to a computer controller;

monitoring cellular-frequency control channels accessible by a cellular telephone mobile station within a radio horizon of at least two of said plurality of cellular facilities;

detecting a call access attempt from said mobile telephone station;

determining a time of arrival for said access attempt by analyzing the phases of a plurality of component frequencies obtained from the mobile station transmission;

recording a time at which said call access attempt was received at said at least two of said plurality of cellular facilities;

recording an electronic identity of said mobile station making said call access attempt;

comparing said time at which said call access attempt was received at said at least two of said plurality of cellular facilities to determine a position estimate of said mobile telephone station.

20. The method as described in claim 19, further comprising the following steps:

comparing said recorded times with a recorded time at which said cell access attempt was received at a third and/or additional cellular facilities; and

calculating from the recorded times at which said call access attempt was received at said at least two of said plurality of cellular facilities and said third and/or additional cellular facilities to determine an exact location of said mobile telephone station.