Patent Grant
8019353
When a user in a wireless communications network initiates a communication session, the nature of the communication may necessitate locating the user. Commonly, a user must be located when the user places a “9-1-1” emergency telephone call. Other scenarios exist as well. For example, a user may contact a service provider requesting directions to nearby restaurants or to a gas station. To provide accurate information, the service provider must be able to determine the user's location.
The advent of cellular telephones required new locating technology. Previously, 911 calls originated mainly from landline telephones. Therefore, the process of determining the location of a caller was usually a simple matter of looking up the street address of the calling telephone number. Unlike landline telephones that were fixedly associated with particular street addresses, cellular telephones could place calls from anywhere within a cellular coverage area. Thus, a more complex system of position determination was required in order to determine the location of a calling cellular telephone.
To facilitate 911 services for cellular telephone callers, the United States Federal Communication Commission (FCC) mandated the implementation of “Enhanced 911” (“E911”) services. The E911 mandate was divided into two phases. According to Phase 1, the location had to be identified with an accuracy of at least cell and sector. As this information is typically maintained by a cellular wireless carrier in a subscriber's home location register (“HLR”), Phase 1 presented little technical challenge. According to Phase 2, the location must be provided with far more granularity than the cell and sector information maintained in the HLR. In response, the Telecommunications Industry Association (TIA) has proposed a standard entitled “Enhanced Wireless 9-1-1 Phase 2” or “J-STD-036-A” (including a recent addendum, J-STD-036-A-2002), the entirety of which is hereby incorporated by reference.
In order to achieve the accuracy specified by Phase 2, a service provider may employ a wireless position determining system that communicates with a wireless communication device (WCD), such as a cellular telephone, in order to determine its current location. The positioning system could be “handset-based,” in which case the cellular telephone would read its geographic coordinates from a satellite based positioning system (e.g., GPS) and report the coordinates over an air interface to the carrier. Alternatively or additionally, the positioning system could be “network-based,” in which case the carrier might employ a technique such as triangulation, (e.g., Advanced Forward Link Trilateration (AFLT) or Enhanced Forward Link Triangulation (EFLT)), to measure the telephone's location. Such network-based techniques may also be combined with handset-based techniques.
When a positioning system performs triangulation, the system determines the location of a WCD based on two or more fixed locations, such as the locations of base transceiver stations (BTSs). Triangulation can be carried out using various methods. In its most basic form, the angle of arrival of an incoming signal is measured at two or more stationary locations. Then, a system performing triangulation creates paths, extending radially at the angle of arrival, from each stationary location. The intersection of these paths is the estimated location of the device.
Recently, more sophisticated triangulation techniques have been developed, using the delay between a WCD and two or more BTSs (preferably three BTSs) to locate a device. Specifically, the time a signal spends traveling over an air interface between the WCD and each BTS is measured and reported to a positioning system. Using that delay, along with the known speed of the signal, the distance between the WCD and each BTS can be calculated. Then, an arc with a radius extending the distance to the WCD is centered on each BTS. The intersection of these arcs provides the estimated location of the WCD.
When a repeater is present in a wireless communication network, locating a user can be difficult. Repeaters are commonly used in wireless communication networks to extend coverage and/or amplify signals in areas that are not adequately served by a BTS (e.g., rural areas or enclosed areas such as buildings or subways). Typically, repeaters are placed between a WCD and a BTS. Therefore, a WCD may communicate over an air interface with a repeater that receives, amplifies, and transmits the communication to a BTS (and vice versa). The presence of the repeater introduces additional time delay between the WCD and the BTS. In the case of a fiber-fed repeater, which is connected to a RAN with a fiber optic cable, a signal may experience delay when traveling from the repeater to the BTS via the fiber optic cable. Since positioning systems using triangulation often rely on the delay between the WCD and the BTS, the delay introduced by a repeater can significantly impact locating accuracy.
Disclosed herein is a method for locating a wireless communication device communicating via a communication path, wherein the communication path includes a fiber optic cable. The method comprises: (i) receiving at least one measure of temperature associated with the fiber optic cable, (ii) using the measure of temperature to determine a delay associated with the fiber optic cable; and (iii) using the determined delay to determine a location of the wireless communication device.
Also disclosed herein is another method for locating a wireless communication device communicating via a communication path, wherein the communication path includes a fiber optic cable. The method comprises (i) measuring temperature associated with the fiber optic cable (ii) using the measured temperature as a basis to determine a delay associated with the fiber optic cable, and (iii) sending an indicator of the determined delay to a position-determining system. The positioning system can then use the determined delay as a basis to determine a location of the wireless communication device.
Additionally, described herein is a system facilitating location of a wireless communication device engaged in a communication via a communication path, wherein the communication path comprises a fiber optic cable. The system comprises (i) a processor for executing program logic, (ii) a reporting modem communicatively linked with the processor, and (iii) data storage communicatively linked with the processor and containing program logic executable to (a) compute a delay associated with the fiber optic cable and (b) cause the reporting modem to send an indicator of the computed delay to a positioning system. The position-determining system may function to use the indicator of the delay as a basis for locating the wireless communication device.
An exemplary system uses the delay associated with a fiber optic cable to locate a WCD when the communication path includes a fiber-fed repeater, which is connected to a radio access network via a fiber optic cable. Initially, the determined delay can be used to determine the delay between the repeater and the WCD, which in turn can be used as a basis for calculating the distance between the WCD and the repeater. The position-determining system may then use the distance between the WCD and the repeater to improve triangulation calculations.
An exemplary embodiment of the present invention is described herein with reference to the drawings, in which:
Referring to the drawings,
In a common arrangement, a wireless carrier will operate a mobile positioning center (MPC) 24 that is arranged to determine and report WCD locations to requesting entities. The MPC may include or have access to a position determining entity (PDE) 26 (also referred to herein as a “positioning system”), which may operate to determine the location of a given WCD based on (i) network information and/or (ii) satellite-based positioning information.
In a typical arrangement, the communications from the positioning system 28 to the WCD 22 will go to and from the MPC/PDE over a signaling network 34 (e.g., a Signaling System #7 (SS7) network or an IP signaling network) to the MSC 14 of the RAN. In order to send any such requests, the MPC 24 may query a home location register (HLR) 36, also via the signaling network, to determine the point code subsystem number (PC_SSN) of the MSC currently serving the WCD. For instance, the MPC may send an IS-41 Location Request (LOCREQ) to the HLR, or an IS-637 SMS Request (SMSREQ) message to the HLR, providing the HLR with an identifier of the WCD, and the HLR would respond (in a Location Request return result (locreq_rr) or SMS Request return result (smsreq_rr)) with the PC_SSN of the currently serving MSC (or a last known serving MSC). The query to the HLR could carry an identifier of the WCD (such as a mobile directory number (MDN)) as indicated in the initial location request to the MPC. The PDE can then establish communications with the WCD via the MSC currently serving the WCD.
The PDE 26 may employ various techniques to locate a WCD 22. For example, the PDE may use triangulation, GPS tracking, or a combination of these techniques (e.g., Advanced GPS software such as SNAPTRACK, manufactured by Qualcomm Incorporated of San Diego, Calif., which uses triangulation to enhance GPS coordinates). To perform triangulation, exclusively or in combination with other locating techniques, a positioning system uses at least two stationary sources capable of communicating with a WCD, such as two or more BTSs accessible to the WCD via an air interface. In particular, the PDE can use the round-trip delay between the WCD and each BTS, along with the location of each BTS, as a basis for triangulation. In practice, triangulation usually requires three or more BTSs. Theoretically, only two BTSs are required, but the accuracy using two BTSs is usually inadequate. The explanation of
Triangulation may be “angle-based” or “delay-based” (or may take other forms now known or later developed). Older triangulation algorithms were generally angle-based, using an angle of arrival at a plurality of stationary sources to estimate the location of a device. Currently, most triangulation algorithms are delay-based, using the delay between each of a plurality of BTSs and a WCD as a basis for locating a WCD. Examples of such techniques include time of arrival, time difference of arrival, enhanced observed time difference of arrival, advanced forward link trilateration, and enhanced forward link triangulation, among others. For simplicity, delay-based triangulation will be described generally. However, those skilled in the art will recognize that the present invention can be used to enhance networks using most any delay-based triangulation technology, and perhaps other location-determination techniques as well.
When performing delay-based triangulation, a positioning system must first identify a sufficient number of BTSs capable of serving the WCD 22 (usually three or more). In addition, the positioning system must know the distance between each identified BTS 44-48 and WCD 12, and the location of each BTS. The PDE may use the delay between the BTS and the WCD to calculate distance between the BTS and the WCD. For example, the PDE may calculate the distance by multiplying the delay by the signal speed over the air interface between the BTS and WCD. The delay may be retrieved from WCD 22 and may include identifiers of each BTS 44-48 and the round-trip delay between each BTS 44-48 and the WCD 22.
To retrieve the location of each BTS the positioning system may include or have access to a BTS-location database (not shown). This database could be coupled directly to the positioning system, or could be accessible to the positioning system via a radio access network, packet-switched network, or other means. Therefore, to retrieve the locations of the BTSs 44-48, the positioning system can conveniently query the BTS-location database with the identifier of each BTS 44-48. The positioning system can then use the location and associated round-trip delay of each BTS 44-48 to perform triangulation.
To perform triangulation, the positioning system may create an arc centered around each BTS 44-48, each arc having a respective radius 50-54. Radii 50-54 represent the distances between each BTS 44-48 and WCD 22, respectively. As discussed above, radii 50-54 can be calculated using the delay between each BTS 44-48, respectively, and WCD 22. Utilizing the arcs created by radii 50-54, the positioning system may conclude WCD 22 is located at the intersection of these arcs.
More specifically, locating accuracy may be improved by using attributes of repeater 40 in lieu of BTS 48 when locating WCD 22. For instance, when performing triangulation based on repeater 40, the PDE may use the delay between the repeater 40 and WCD 22 to calculate the distance between repeater 40 and WCD 22. The PDE may then use the location of repeater 40 and the distance between repeater 40 and WCD 22 (radius 64), rather than the location of BTS 48 and the distance between BTS 48 and WCD 22, as a basis for triangulation.
While
Processor 64 may execute program logic causing the modem 66 to send an indicator of delay associated with the fiber optic cable 20. Alternatively, the processor may execute program logic causing the modem to send an indicator of the temperature associated with the fiber optic cable. In either case, the respective indicator may be sent to a positioning system 28, or sent elsewhere. The positioning system 28 can use the indicator for locating WCD 22. Alternatively, the positioning system 28 can use an indicator of temperature to calculate a delay associated with the fiber optic cable 20, and then use the calculated delay for locating WCD 22.
Monitoring unit 60 may include additional functionality for sending an indicator of delay according to varying schedules, when prompted by various stimuli, and/or in response to various situations. As an example, monitoring unit 60 may periodically instruct modem 66 to send an indicator of delay to positioning system 28 (e.g. on an hourly basis). As such, positioning system 28 can maintain a record of the recent delay associated with fiber optic cable 20. It should be noted, that periodically reporting delay may not provide the positioning system the fiber optic cable delay at the exact time the system performs triangulation. However, temperature generally changes slowly enough that a recently reported delay, such as a delay reported within the last hour, is sufficient. In some embodiments, however, the system may sync reporting delay to the locating process. In such embodiments, delay indicators may be sent when the system detects or is informed that a WCD 22 is being located.
Modem 66 may take various forms, arranged to communicate via a landline or wireless connection. By way of example, modem 66 may be an MSM series chipset manufactured by Qualcomm (e.g., an MSM6700 or MSM6800 chipset), or some other chipset capable of cellular wireless connectivity. Such a chipset is of the type that would be conventionally included within a cellular telephone or other end-user WCD (e.g., wireless PDA, or wirelessly equipped computer) and advantageously enables the device to attain wireless packet-data connectivity so as to be able to engage in wireless IP-based communication. In a preferred embodiment, the MSM chipset would include logic compliant with CDMA2000, and preferably the well known 1XRTT and EVDO air interface standards. But the chipset could equally take other forms as well. For example, modem 66 may be a wired connection providing packet-data connectivity.
In order to send an indicator of delay, processor 64 may execute program logic for calculating a delay associated with fiber optic cable 20. Monitoring unit 60 may use temperature measurements taken by digital thermometer 62 for delay calculations. In an exemplary embodiment, processor 64 may receive a continual temperature reading from thermometer 62. In other embodiments, processor 64 may request a temperature reading from the thermometer 62. As another alternative, processor 64 may periodically receive a temperature reading from the thermometer, or may receive temperature measurements by other means.
Digital thermometer 62, or any other temperature measuring device, can measure the temperature associated with the fiber optic cable. Measurements can be taken in units determined by engineering design choice. For example, the thermometer may measure the temperature in degrees Celsius, degrees Fahrenheit, or any other measure of temperature. The thermometer 62 is preferably located so that the measured temperature accurately reflects the temperature of the fiber-optic cable. For example, the thermometer 62 may measure the temperature on the surface of the cable. As another example, if the fiber-optic cable 20 is located below-ground, the thermometer may measure the temperature of the earth surrounding the cable. As a further example, if the fiber-optic cable 20 is above-ground, the air temperature near the cable may be measured. Other possibilities exist as well. In addition, the location of the thermometer 62 along the fiber-optic cable 20 may vary. For instance, the thermometer may be placed near repeater 40, or at a central location along fiber-optic cable 20, or elsewhere.
When calculating fiber optic cable delay, processor 64 may account for temperature deviation by employing a delay adjustment coefficient associated with fiber optic cable 20. The delay adjustment coefficient is generally a known constant determined by the type of fiber optic cable used (the type of fiber optic cable is a matter of engineering design choice). Manufacturers of fiber optic cable generally specify a delay for their cables at a specific temperature. However, the actual delay will deviate from the manufacturer specified delay as temperature changes. By using a delay adjustment coefficient, the system can account for variations in delay due to temperature changes. For instance, by multiplying the delay adjustment coefficient by the length of the cable and the temperature, the system can determine by how much the manufacturer specified delay should be adjusted. In embodiments where the manufacturer has not specified a delay, the delay at a specific temperature can be measured before deploying the system.
As a specific example of system calculations, the monitoring unit 60 may determine the delay associated with a 10 kilometer cable made of single mode fiber, for which the manufacturer's delay specification at a specified temperature is 30 μsec. Single mode fiber may have a delay adjustment coefficient of 30 picoseconds per kilometer per degree Celsius. Therefore, if the measured temperature differs from the temperature of the manufacturer specified delay, processor 64 may adjust the manufacturer's delay by 30 picoseconds per kilometer per degree Celsius. For example, if the temperature differs by 30 degrees Celsius, processor 64 may adjust delay by performing the calculation, (30 picoseconds/(degree Celsius*kilometer))*10 kilometers*30 degrees Celsuis=9 μsec adjustment. Therefore, the calculated delay for the 10 kilometer, single mode fiber optic cable, would be 21 μsec.
In addition to single temperature measurements, monitoring unit 60 may consider other factors when calculating delay. As an example, the monitoring unit may periodically store temperature readings in data storage, creating a history of temperatures. The monitoring unit 60 may then use the temperature history to adjust delay calculations. For example, temperature history may be used to account for any difference in the rate of temperature change for the fiber optic cable, as compared to the rate of temperature change for the material surrounding the cable. As another example, temperature readings from multiple locations associated with the fiber optic cable may be included in delay calculations. Other factors may be incorporated as well.
Various configurations of the system depicted in
Monitoring unit 72 may work with reporting module 78 to provide an indicator of fiber optic cable delay to a positioning system when a WCD is being located. To do so, the system may send an indicator of fiber optic cable delay whenever a repeater location message is sent to a positioning system. Reporting module 78 may function to send a repeater location message to positioning system 28 when repeater 70 detects a communication possessing a predetermined characteristic (e.g. an emergency 9-1-1 phone call). For example, repeater 70 may send a repeater location message when a phone call has the dialed digits “9-1-1,” a characteristic that often indicates that location of the calling party is necessary. Therefore, when reporting module 78 detects a characteristic invoking a repeater location message, monitoring unit 72 may simultaneously report delay associated with fiber optic cable 20.
As an alternative to simultaneously sending a delay indicator and a repeater location message, reporting module 78 may include the delay associated fiber optic cable 20 in the repeater location message. In such an embodiment, processor 74 may execute program logic incorporating the functionality of both the monitoring unit and the reporting module. Specifically, processor 74 may execute program logic to detect a predefined characteristic in a communication, calculate fiber optic cable delay, and responsively instruct modem 76 to send a repeater location message. The repeater location message may include the fiber optic cable delay, and/or other data. The inclusion of the fiber optic cable delay in the repeater location message may remove the need for separate reporting of fiber optic cable delay by the monitoring unit.
Digital thermometers 94-98 may function to measure temperature associated with fiber optic cable 92 at a plurality of geographic locations. In
More specifically, processor 100 may execute program logic for calculating delay based, at least in part, on a plurality of temperature readings taken at a plurality of geographic locations. Each thermometer 94-98 may be operable to communicate a temperature measurement associated with the geographic location of the thermometer, to processor 100. Processor 100 can then consider the plurality of temperature measurements from thermometers 94-98, rather than basing delay calculations on a single temperature measurement. For example, processor 100 may average of the temperature measurements taken by thermometers 94-98, and use the average temperature to calculate delay.
Further, processor 100 may use of the geographic locations associated with the temperature measurements to further improve calculation of delay. As an example, the monitoring unit 90 may use the geographic locations of thermometers 94-98 to calculate a separate delay for multiple segments of fiber optic cable, totaling the delay for all segments to determine the delay associated with the entire cable. To do so, the cable may be divided into multiple segments, each segment associated with a temperature from a different digital thermometer. For instance, a first segment may measure from the beginning of fiber optic cable 92 to halfway between digital thermometer 94 and digital thermometer 96 and be associated with digital thermometer 94. A second segment may extend from halfway between thermometer 94 and 96, to halfway between thermometer 96 and 98, and so on. Other segmenting procedures are possible as well. The processor can then determine the delay for each segment using the length of the segment, the temperature measurement from the thermometer associated with the segment, and the delay coefficient for the cable. Additionally, delays from each segment can be weighted, based on the length of the associated segment as compared to the length of the cable, when totaling segment delays to ascertain the delay for the cable.
Segmenting the cable may further improve delay calculations in many situations, such as when cables pass through multiple temperature environments. As an example, a segment of a cable may be located below-ground, and associated with a below-ground temperature, while another segment of the same cable may be located above-ground, and associated with an above-ground temperature. When a fiber optic cable is located partially above and below-ground, segmenting the cable may further improve delay calculations accounting for variance in temperature along the cable.
An exemplary embodiment of the invention has been described above. Those skilled in the art will understand, however, that changes and modifications may be made to the embodiment described without departing from the true scope and spirit of the invention, which is defined by the claims.
This is a continuation-in-part of U.S. patent application Ser. No. 11/365,379, filed on Mar. 1, 2006.
| Number | Name | Date | Kind |
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| 20040166873 | Simic et al. | Aug 2004 | A1 |
| 20050113117 | Bolin et al. | May 2005 | A1 |
| 20070127919 | Kallstenius | Jun 2007 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11365379 | Mar 2006 | US |
| Child | 11455955 | US |
