WO2004079928A2

WO2004079928A2 - Pde autonomous accuracy certification testing method and system

Info

Publication number: WO2004079928A2
Application number: PCT/US2004/006180
Authority: WO
Inventors: Joseph P. Kennedy
Original assignee: Andrew Corporation
Priority date: 2003-03-03
Filing date: 2004-03-03
Publication date: 2004-09-16
Also published as: WO2004079928A3

Abstract

A system and method determines a statistical location accuracy of a geolocation system by collecting statistical data, without unduly burdening the host communication system. The system utilizes a test device (365) that interfaces with a test mobile phone (320), a global positioning system (GPS) (362) co-located with the test mobile and connects with the geolocation controller system (GCS) (340) over a communication link that is has a wireless portion (363). The test device gathers ground truth information from the GPS, traffic information from the test mobile phone and uses the traffic information to directly request the GCS to locate the test mobile. The GCS reports the ground truth and the estimated location of the test mobile phone to a database, where the data is associated as a function of the time of the call or other identifying parameters. The system and method may operate without requiring the host communication system to provide operations other than those necessary for communicating with the test mobile phone.

Description

PDE AUTONOMOUS ACCURACY CERTIFICATION TESTING METHOD AND

SYSTEM

CROSS REFERENCES

[0001] The present application is co-pending with and claims priority benefit of provisional application entitled "PDE autonomous accuracy certification testing," Application Serial Number 60/450,706 and filed on March 3, 2003, the entirety of which is incorporated herein by reference.

BACKGROUND

[0002] In the United States, mobile wireless appliance locating equipment is being deployed for the purpose of locating wireless callers who dial 911. Other services in addition to emergency call servicing are contemplated and are referred to as location based services (LBS). Wireless location equipment is typically employed as an overlay to wireless communication networks, thus forming a network overlay geolocation system.

[0003] In operation, these network overlay location systems take measurements on radio frequency (RF) transmissions from mobile appliances at base station locations surrounding the mobile appliance, and estimate the location of the mobile appliance with respect to the base stations. Because the geographic location of the base stations is known, the determination of the location of the mobile appliance with respect to the base station permits the geographic location of the mobile appliance to be determined. The RF measurements of the transmitted signal at the base stations may include the time of arrival, the angle of arrival, the signal power, or the unique/repeatable radio propagation path (radio fingerprinting) derivable features. In addition, the geolocation systems may also use collateral information, e.g., information other than that derived for the RF measurement to assist in the geolocation of the mobile appliance, i.e., location of roads, dead-reckoning, topography, map matching, etc.

[0004] In a network-based geolocation system, the mobile appliance to be located is typically identified and radio channel assignments determined by (a) monitoring the control information transmitted on radio channel for telephone calls being placed by the mobile appliance or on a wire line interface to detect calls of interest, i.e., 911, and (b) a location request provided by a non-mobile appliance source, i.e., an enhanced services provider. Once a mobile appliance to be located has been identified and radio channel assignments determined, the location determining system is first tasked to determine the geolocation of the mobile appliance and then directed to report a determined position to the requesting entity or enhanced services provider.

[0005] The monitoring of the RF transmissions from the mobile appliance or wire line interfaces to identify calls of interest is known as "tipping", and generally involves recognizing a call of interest being made from a mobile appliance and collecting the call setup information. Once the mobile appliance is identified and the call setup information is collected, the location determining system may be tasked to geo-locate the mobile appliance.

[0006] Figure 1 shows a conventional mobile-appliance communication system having base stations 10 a-c for communicating with a mobile appliance 20. Each base station 10 contains signal processing equipment and an antenna for transmitting to and receiving signals from the mobile appliance 20 as well as other base stations. A Base Station Controller ("BSC") and/or Mobile Switching Center ("MSC") 45 is connected to each base station 10 through wireline connection 41. A mobile appliance location determining sensor 30, i.e., wireless location sensor ("WLS"), maybe positioned at some or all of the base stations 10 to determine the location of mobile appliance 20 within the signal coverage area of the communication system. A network overlay system is generally composed of two main components, one that resides at the base station that makes measurements on the RF signal emanating from the wireless device, the WLS 30, and one that resides at the mobile switch that tasks the WLS groups to collect data and then uses the data to compute a location estimate. This latter component is generally referred to as the Geolocation Control System ("GCS") 50.

[0007] In the normal course of operation, the GCS is tasked by an outside entity, e.g., the Mobile Positioning Center ("MPC") 40, to generate a location estimate on a particular mobile appliance. The tasking is accompanied by information on the mobile of interest including the serving base station and sector for the call and the RF channel (frequency, time slot, CDMA code, etc.) being used by the wireless communications network to complete the wireless connection. Once the GCS receives this tasking, based on the serving sector, it tasks a set of WLS units to make measurements on the RF emissions of the mobile. The WLS units make the measurements, and report them to the GCS. The GCS then computes a location estimate using a mathematical or data matching algorithm. Alternatively, control signaling on RF or wireline interfaces used to set up calls in the wireless network may be scanned to detect the placement of a call of interest. The signaling that occurs on the RF control channel may be used to determine location, or call setup/channel assignment parameters may be extracted from the control messaging to determine which traffic channel to use for location related measurements.

[0008] Network overlay location systems typically locate a mobile appliance on the traffic channels of a wireless network. The system typically uses sensors employing techniques of Time Difference of Arrival ("TDOA") supplemented with Angle of Arrival ("AOA") in some cases to perform a multi-site location computation. The traffic channel assignment information is provided through a separate process, with one option being a wireline interface providing MOBINFO (IS-41 Mobile Information) parameters passed by the Mobile Positioning Center 40 as part of the GPOSREQ (J-STD-036 Geolocation Position Request) message from the MPC 40 to the GCS 50.

[0009] The wireless location network entities and location function oriented entities are numerous and a description of the entities and processes involved in the call routing, location determination and location reporting may be found in recognized standardized bodies such as ANSI and ETSI. Applicable standards covering these topics include ANSI J-STO036 and ETSI 3GPP TS 3.71.

[0010] In the current state of the art, to test the accuracy of the entity (i.e. Position Determining Equipment "PDE" for ANSI) that determines position, other network entities must be involved and processes associated with live call routing, position determination and reporting must be invoked. This is undesirable because it slows the process of placing test calls and collecting accuracy test data, invokes entities that may be needed to process live calls, and involves entities that include human interaction/intervention which must be diverted from other purposes to support testing.

[0011] The subject matter of the present disclosure isolates the portion of the system that determines position (PDE) from the other location-oriented network entities such that test data may be collected and reduced in a PDE-autonomous configuration to accomplish accuracy certification.

[0012] Thus in order to obviate the deficiencies in the prior art, it is an object of the present disclosure to present in a network overlay geolocation system, a novel method for determining a statistical location accuracy of said geolocation system. The method includes placing a call from a test device; determining an independent location of the test device independently of the geolocation system; and storing the independent location to a database. The method also includes transmitting from the test device traffic channel assignment information to a geolocation controller system of the network overlay geolocation system; determining a location estimate of the test device by the geolocation system; and storing the location estimate of the in the database. The method repeats these steps at a plurality of instances to determine the statistical location accuracy of the network overlay geolocation system.

[0013] It is further an object of the present disclosure to present a novel improvement in a method for determining the statistical location accuracy of a network overlay geolocation system. In the method a call is placed from a test mobile appliance having a known location, and a location estimate of the test mobile appliance is determined by measuring an attribute of the test mobile appliance's signal received at a plurality of wireless location sensors tasked by a geolocation controller system which is provided with traffic assignment information of the mobile appliance and a request to determine the location of the test mobile from a mobile positioning center (MPC), the MPC obtaining the traffic assignment information from the mobile switching center which controls a base station in wireless communication with the test mobile appliance and wherein the location estimate is associated with the known actual location of the mobile appliance over a plurality of instances and stored as data in a database for statistical analysis. The novel improvement includes the steps of obtaining the traffic channel assignment information from the test mobile appliance and tasking the GCS to locate the test mobile over a data link between the GCS and the test mobile appliance.

[0014] It is also an object of the present disclosure to present a system for collecting data for determining a statistical location accuracy of a network overlay geolocation system. The system includes a mobile test device with an independent location determining device; and, a receiver and transmitter capable of wireless communication with a wireless communication system that the network overlay geolocation system is associated with. The system also includes a data link operably connected to the mobile test device and capable of communication with a GCS of the network overlay geolocation system; a database capable of receiving location estimates from the GCS and operably connected to said data link.

[0015] These objects and other advantages of the disclosed subject matter will be readily apparent to one skilled in the art to which the disclosure pertains from a perusal or the claims, the appended drawings, and the following detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

16] Figure 1 is a prior art wireless communication system with a network overlay geolocation system.

[0017] Figure 2 is a schematic of a prior art wireless communication system tasking and accuracy testing method.

[001 §] Figure 3 is an illustration of a Drive Test Platform system according to an embodiment of the current subject matter.

[0019] Figure 4 is a representative flow chart according to an embodiment of the current subject matter.

DETAILED DESCRIPTION

[0020] The present subject matter will be described in the context of the ANSI network reference model as defined in J-STD-036 for illustrative purposes only. Equivalent embodiments may be described for other reference models such as those described in ETSI, and thus the subject matter is not limited to the ANSI model.

[0021] The ANSI reference model is shown in Figure 2. Under normal operation the mobile terminal makes a call that is to be located. The wireless infrastructure equipment (base station 210 and switch 245) processes the call, and informs the MPC 240 that the call has been placed and a location is requested. The MPC 240 tasks the PDE (GCS 250 and WLS 230) to locate the call, thereby providing to the PDE information about the mobile terminal and the traffic channel assignments in the wireless network

[0022] The GCS 250 collects location related measurements on the mobile terminal via the WLS 230, and based on these measurements, estimates the location of the caller. The MPC 240 may use these measurements for call routing by reporting them to the MSC 245 to route the call. The MPC 240 reports these measurements, usually in conjunction with a data base access (CRDB), to the end user (a public safety answering point 260 (PSAP) for emergency services support, for example).

[0023] As illustrated in Figure 2, the host communication network and its entities are burdened by the overlay location system to service a number of tasks unrelated to its primary communication functionality.

[0024] As the location accuracy of the location system is an important metric for obvious reasons, sample data is often collected to monitor the accuracy of the system. To certify the location accuracy performance of the location equipment (PDE)_S multiple location estimates need to be made, and compared to some "ground truth" in order lo gauge the statistical accuracy performance. The "ground truth" is a location determined independent of the geolocation system from a reliable source such as GPS, maps, loran, etc. The prior art approach for determining the system accuracy involves performing the above tasking and location determining steps many times over using calls made from known locations to generate location accuracy statistics; however, as noted previously, this repetition places an unnecessary burden on several system resources that may tax or reduce the capacity of the primary function, i.e., wireless communications.

[0025] An embodiment of the improved method for determining the statistical location accuracy as envisioned in the present disclosure adds test network elements as shown in Figure 3. [0026] A mobile terminal 320 is connected to a new network element called a Drive Test Platform 360 (DTP). The DTP 360 is composed of a controlling computer 361, a GPS 362 or a differential GPS (DGPS) receiver and a wireless data link 313. The GPS or DGPS are used to establish a "ground truth" as will be described later.

[0027] The controlling computer 361 may be a computer or processor preferably driven by software, but may also be a dedicated hardwired processor.

[0028] The GPS 362 may be a differential GPS as stated above and may be a standalone GPS receiver in communication with the computer or integrated in the computer or processor. The wireless data link connects the DTP 360 with the GCS 350 and may be over POTS lines as shown in Figure 3. The wireless link is beneficial to the mobility of the DTP and as such portions of the link that do not restrict this mobility may be wire lines. The wireless link 363 is enabled by a modem 364 in the DTP 360 as shown in Figure 3.

[0029] In order to collect the necessary statistical data, calls are placed to a known phone number, preferably a known number dedicated for accuracy certification purposes. The calls may be initiated either under operator control or automatically through the controlling computer 361.

[0030] When the call is placed by the mobile terminal 320, a test connector 365 (wireless mobile interface "WMI") on the base of the phone is monitored to collect mobile terminal and traffic channel assignment information. This information is substantially the same as the information provided by the MPC in the normal system operation as described previously.

[0031] The terminal information and the traffic channel assignment information are transferred from the mobile terminal through the controlling computer through the wireless data link to the GCS 340. (The GCS is also sent the location of the mobile terminal being used to place calls using the DGPS data and the start time of the call).

[0032] The GCS 340 uses this data to tasks the WLS 330 to make location related measurements at base station locations, and to estimate the position of the test mobile. The tasking of the WLS 330 by the GCS 350 is achieved in much the same manner as is known in the prior art. In the embodiment shown, a router 341 connects to a PSTN 342 which in turn connects to the WLS 330 over a respective number of data channels; of course, this disclosure is not intended to be limited to this specific embodiment with routers and data channels as shown.

[0033] Instead of the GCS 340 sending the location data to the MPC as in the prior art, the GCS 340 stores the location estimates (as well as the time or instances the estimates are made) in a database.

[0034] This process is performed many times to collect location estimates and location "ground truth." Each data point with a different time of call is referred to as an instance.

[0035] At the conclusion of this data collection, statistics may be generated from the collected files by matching location estimates to ground truth estimates through common time stamps and calculating the statistics of their differences (location errors). Figure 4 is an illustrative flow chart of the prior art approach in comparison with an embodiment of the current subject matter.

[0036] As discussed in the background, an initiating call is made from a mobile appliance 420a as indicated in block 401a. Simultaneously with the initiation of the call, a ground truth or known location of the mobile is determined exclusively of the geolocation system indicated by block 402a. Generally,, the known location is accomplished through a GPS system 415 connected to the test mobile 420a as described previously. This known location is then stored in a database as shown in block 403a.

[0037] The MPC 440a recognizes a call of interest and prompts the MSC to provide traffic assignment information and call set up information as shown in block 404a. The MPC 440a transmits this information as a location request to the GCS 450a as shown in block 405 a. The GCS 450a tasks the WLS to take AOA, TOA or other such measurements of the mobile's signal as shown in 406a. The GCS 450a uses the measurements provided by the WLS to estimate the mobile's location as shown in block 407a and reports the location estimate to the MPC 440a which stores the estimate in a database 453a as shown in block 409a.

[0038] The ground truth stored in the database of 415a is then associated with the estimated locations as shown in 410a such that statistical measurements of the system may be compiled. Normally the database of 415 is co-located with the test mobile and its data is transferred to the database 453 in a data dump.

[0039] An embodiment of the current subject matter is shown as 400b for comparison against the prior art. In the embodiment shown, a call from the mobile 420b is initiated as shown in block 401b. The mobile may initiate the call with a dedicated number or use an arbitrary number. The mobile test phone 420b is operably connected to a DTP 460. The DTP 460 obtains traffic assignment and call set up information from the mobile test phone 420b as shown in block 404b and determines the ground truth through GPS or differential GPS as shown in block 402b.

[0040] The DTP 460 then tasks the GCS 450b to locate the mobile test phone (or appliance) 420b, as represented by block 405b. This tasking is conducted over a wireless link between the DTP 460 and the GCS 450b. The wireless link may, as discussed previously, include along with a wireless portion, portions of transmission such as dedicated lines or POTS.

[0041] Along with the request for location, the DTP 460 transmits the known locations as determined from the GPS or DGPS in block 402b along with an identifier, such as time of call, to the GCS 450b for storage in database 453b as shown in block 41 lb.

42] The GCS 450b, in the embodiment shown as 400b, tasks the WLS lo locate the mobile test phone in block 406b and determines a location estimate in block 407b in much the same manner as the GCS 450a in prior art system 400a. However, the GCS 450b does not receive the request from the MPC or report the estimates back to the MPC. Rather, the GCS 450b passes the estimated location of the mobile test phone 420b and the information regarding the ground truth received from the DTP 460 to the database 453b as shown in block 412b. The estimated location and the known locations are then associated in database 453b as shown in block 410b.

[0043] This alternative method does not involve the participation of any of the network entities in Figure 2 that are location-only oriented (MPC, CRDB, etc.). Other network entities besides the PDE that participate in the process only provide functionality related to non-location oriented operations (i.e., the wireless network connects a wireless may as it would for any wireless call servicing independent of location services). [0044] While preferred embodiments of the present inventive system and method have been described, it is to be understood that the embodiments described are illustrative only and that the scope of the embodiments of the present inventive system and method is to be defined solely by the appended claims when accorded a full range of equivalence, many variations and modifications naturally occurring to those of skill in the art from a perusal hereof.

Claims

I Claim:

1. In a wireless network including an overlay geolocation system serving a geographic area, a method for determining a location accuracy metric of said geolocation system for locating mobile appliances within the geographic area, comprising:

(a) transmitting a signal from a test device at a location within the geographic area;

(b) detern±iing the location of the test device independent of the geolocation system;

(c) receiving traffic channel assignment information from the test device in response to said transmitted signal;

(d) determining a location estimate of the test device from the geolocation system using the traffic channel assignment information; and

(e) comparing the independent location of the test device with the location estimate of the test device to thereby determine a location accuracy metric of the geolocation system.

2. The method of Claim 1 further including the steps of:

(f) storing the independent location information and the location estimate information in a database; and

(g) repeating steps (a)-(f) at a plurality of locations within the geographic area to thereby create a statistical location accuracy database for determining location accuracy metrics of the geolocation system.

3. The method of Claim 2 wherein the step of storing the independent location information includes the step of transmitting the independent location information from the test device to the geolocation system over a wireless link.

4. The method of Claim 1 wherein the transmitted signal comprises a phone call serviced by the wireless network.

5. The method of Claim 3 wherein the phone call is directed to a dedicated phone number.

6. The method of Claim 1 further including the step of measuring an attribute of the transmitted signal so that the step of determining a location estimate of the test device is based in part on the measurement of the attribute.

7. The method of Claim 6 wherein the attribute is TO A, AOA or a combination thereof.

8. The method of Claim 7 wherein the location estimate is determined at least in part by TOA, TDOA or AOA.

9. The method of Claim 1 wherein the location estimate is determined at least in part by collateral information.

10. The method of Claim 1 wherein the step of determining an independent location comprises the step of co-locating a GPS or a DGPS receiver with the test device and determining the independent location from the GPS or DGPS receiver.

11. The method of Claim 2 wherein the location estimate information and independent location information are associated in the database.

12. The method of Claim 2 wherein the step of storing the independent location information further comprises storing the time of the transmission of the signal from the test device.

13. The method of Claim 12 wherein the independent location information and location estimate information are associated by the time of transmission.

14. The method of Claim 1 wherein the test device comprises a processor, a GPS or DGPS receiver, and a wireless data link to the geolocation system.

15. The method of Claim 2 wherein the geolocation system stores the time of the transmission of the signal from the test device and associates the time of transmission with the location estimate information.

16. The method of Claim 1 wherein the test device comprises a mobile appliance.

17. The method of Claim 1 wherein the traffic channel assignment information is received from the down link to the test device.

18. In a wireless communication system having a network overlay geolocation system, a method for locating a mobile test device wherein a mobile positioning center tasks the geolocation system to estimate the position of the mobile test device, the improvement wherein the mobile test device tasks the geolocation system to estimate the position of the mobile test device over a non traffic channel.

19. The method of Claim 18 wherein the geolocation system locates the mobile appliance based on an attribute of a signal transmitted by the mobile test device.

20. The method of Claim 19 wherein tasking the geolocation system includes transmitting the traffic assignment information to the geolocation system.

21. The method of Claim 19, further comprising the step of determining a known position of the mobile appliance independently of the geolocation system.

22 The method of Claim 21 , wherein tasking the geolocation system includes transmitting the traffic assignment information and the known position to the geolocation system.

23. The method of Claim 18, further comprising the step of the geolocation system reporting the estimate of the position to a database.

24. The method of Claim 21 , wherein the step of determining a known position further comprising associating a time of the signal with the known position in the database.

25. The method of Claim 23, further comprising reporting a time associated with the estimated position to the database.

26. The method of Claim 21 , wherein the estimate of the position and known position are associated in the database by time.

27. The method of Claim 18, wherein the mobile test device comprises a processor, a GPS or DGPS receiver and a non traffic wireless data link to the geolocation system.

28. The method of Claim 19, wherein the estimate of the position is determined in part by TOA, TDOA or AOA of the signal.

29. The method of Claim 28, wherein the estimate of the position is determined in part by collateral information.

30. The method of Claim 23, wherein the known position is determined using a DGPS or GPS receiver co-located with the mobile test device.

31. A system for collecting data for determining a location accuracy metric of a network overlay geolocation system for a wireless network where the geolocation system is capable of providing location estimate information for a mobile appliance within a geographic area, comprising:

a mobile test device capable of communicating with the wireless network, said test device including:

a location determining device for providing independent location information wherein said location determining device is independent of the geolocation system; and

a wireless mobile interface for obtaining traffic channel assignment information;

a data link capable of communicating the independent location information and the traffic channel assignment information to a database; and

said database capable of storing:

the location estimate information received from the geolocation system; and the independent location information and the traffic channel assigmnent information received from the test device;

wherein the information stored in the database can be used to determine the location accuracy metric for the geolocation system.

32. The system of Claim 31 wherein the independent location determining device is a GPS receiver.

33. The system of Claim 32 wherein the GPS receiver is a Differential GPS receiver.

34. The system of Claim 31 wherein the data link is a wireless data link.

35. The system of Claim 34 wherein the data link further comprises a POTS line.

36. The system of Claim 31 wherein the database comprises a computer.

37. The system of Claim 31 wherein the mobile test device further comprises a processor.

38. The system of Claim 31 wherein the database is connected lo the geolocation system over an internet connection.