WO2006065839A2

WO2006065839A2 - Method and system for tracking mobile devices using radio frequency identification (rfid) tags

Info

Publication number: WO2006065839A2
Application number: PCT/US2005/045123
Authority: WO
Inventors: Billy G. Echols
Original assignee: Mci, Inc.
Priority date: 2004-12-16
Filing date: 2005-12-12
Publication date: 2006-06-22
Also published as: WO2006065839A3; CA2591695A1

Abstract

An approach is provided for tracking a mobile device (105) over a wireless network. Multiple Radio Frequency Identification (RFID) tags (101, 103) are affixed correspondingly to stationary (or fixed) points to form a grid for conveying location information. The module device includes an RFID reader (105a) configured to obtain an identifier of one of the RFID tags (101, 103) , wherein the one RFID tag represents a particular location of the mobile device within the grid.

Description

METHOD AND SYSTEM FOR

TRACKING MOBILE DEVICES USING

RADIO FREQUENCY IDENTIFICATION (RFID) TAGS

100011 The present invention relates to data communications, and more particularly, to tracking mobile devices.

[0002J Modern wireless networks can readily be configured to offer a variety of device tracking and telemetry services. One such service is fleet and asset management, whereby the management of vehicles within a fleet as well as assets involves obtaining information, generally in real-time, about the location and movement of these objects. The fleet manager utilizes this information, for instance, to maximize use of fleet resources. With the advent of the Global Positioning System (GPS) supported by a constellation of satellites, a vehicle may determine its location with great accuracy and convenience if no obstruction exists between the GPS receiver within the vehicle and the satellites. Because the GPS receiver must obtain all of the ephemeris data from the satellite signals, weak signals can be problematic. A building location or a location in any area that does not have clear view of the satellite constellation can prevent the GPS receiver from determining its geolocation. Thus, when the GPS receiver encounter situations where no signals can be received, i.e., assets are indoors, tracking of objects is not possible. j 00031 Therefore, there is a need for a tracking system that effectively integrates GPS technology to ensure timely acquisition of location information in a multitude of environments (outdoors and indoors). There is also a need to deploy, cost-effectively and rapidly, an indoor tracking system.

[0004| These and other needs are addressed by the present invention. According to one aspect of the present invention, a method for tracking a mobile device is disclosed. The method includes retrieving an identifier from a Radio Frequency Identification (RFID) tag associated with a fixed point. The method also includes transmitting the identifier to a processor, wherein the processor determines location of the mobile device based on the identifier.

[0005] According to another aspect of the present invention, an apparatus for supporting a tracking system is disclosed. The apparatus includes a Radio Frequency Identification (RFID) reader configured to retrieve an identifier from a RFID tag associated with a fixed point. Additionally, the apparatus includes a communication module configured to transmit the identifier to a processor, wherein the processor determines location of the apparatus based on the identifier.

10006) According to yet another aspect of the present invention, a tracking system includes a plurality of Radio Frequency Identification (RFID) tags affixed to stationary points forming a grid for conveying location information. The system also includes a mobile unit including an RFID reader configured to obtain an identifier of one of the RFID tags, wherein the one RFID tag represents a particular location of the mobile unit within the grid.

[0007] Still other aspects, features, and advantages of the present invention are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the present invention. The present invention is also capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

(0008] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

]0009| FIG. 1 is a diagram of a Radio Frequency Identification (RFID) system capable of tracking mobile devices, according to an embodiment of the present invention;

(00l0| FIG. 2 is a flowchart of a process for switching between a Global Positioning System (GPS) and the indoor tracking system of FIG. 1, according to an embodiment of the present invention;

[00111 FIG. 3 is a flowchart of a process for tracking a mobile device utilizing the system of FIG. 1 , according to an embodiment of the present invention;

[0012] FIG. 4 is a diagram of an integrated GPS and RFDD system for fleet and asset tracking, according to an embodiment of the present invention;

J 0013 J FIG. 5 is a diagram of a telemetry device used in the system of FIG. 4, according to an embodiment of the present invention; and [0014] FIG. 6 is a diagram of a computer system that can be used to implement an embodiment of the present invention.

[0015J A system, method, and software for tracking of mobile devices are described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It is apparent, however, to one skilled in the art that the present invention may be practiced without these specific details or with an equivalent arrangement. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention.

[0016] According to an exemplary embodiment, an approach is provided for tracking mobile devices via Radio Frequency Identification (RFID) tags. The RFID tags are affixed to stationary structures in a configuration to provide location information about the mobile devices. This configuration, thus, constitutes a geo-coded interior grid. An RFID reader associated with the mobile device reduces transmission power in response to the detection of multiple tags, and sends the RFID number corresponding to the strongest signal strength RFID tag. In one embodiment of the present invention, the indoor tracking system is integrated with a Global Positioning System (GPS) for locating the mobile device outdoors to support fleet or asset management. The location of the mobile device is stored and made accessible by a graphical user interface (GUI), such as a web browser. The above arrangement advantageously provides cost-effective acquisition of location of the mobile device, irrespective of whether the device is outdoors or indoors.

[0017] FIG. 1 is a diagram of a Radio Frequency Identification (RFID) system capable of tracking mobile devices, according to an embodiment of the present invention. An indoor tracking system 100 deploys RFID tags (or transponders) 101, 103 within, for example, stationary points in a ceiling to track a mobile device 105 within a facility, building, or enclosed structure.

]0018] Unlike conventional application of RFID tags, the system 100 utilizes RFID tags 101, 103, not on the item to be tracked, but permanently affixed to stationary structures in a configuration to provide location information about the mobile device 105. As such the tags 101, 103 are considered fixed, or stationary relative to a RFED reader 105a. This configuration, thus, constitutes a geo-coded interior grid. The specific configuration depends on the physical and environmental conditions of the system 100. It is contemplated that the geo-coded interior grid can be deployed in moving structures, such as a ship, an airplane, etc.; in such scenarios, the tags 101, 103 are still considered to be situated at fixed, or stationary points.

[00l9| As the mobile device 105 moves indoors, the RFID reader 105a detects different RFID tags 101, 103 and captures the associated RFID signals. Each RFID tag 101, 103 includes a microchip and a coiled antenna for storing and transmitting location data. The RFID tags 101, 103 can be active or passive, and need not be within line-of-sight with the RFID reader 105a. Active tags include electronics that require power to transmit data to the RFID reader 105a, and thus, are generally more costly than passive tags. Passive tags utilize the magnetic field generated between the tags and the RFID reader 105a as power to modulate and reflect RF signals emitted by the reader 105a. Additionally, the RFID tags 101, 103 can be read-only, volatile read/write, or write one/read many. The particular type of RFID tags 101, 103 depend on the particular application and other factors, such as cost.

[0020] To convey its location, the mobile device 105 includes an RFID reader 105a for obtaining tag identification. The RFID reader 105a tunes to the same frequency as the tags 101, 103. The system 100 can be configured to operate in a variety of frequencies from low to ultra-high frequency (UHF) or even microwave, depending on the separation between the RFID tags 101, 103 and the RFID reader 105a. For example, UHF frequencies can support applications distances of up to about 20 feet. The system 100 can operate in the frequency ranges of about 50 kHz to about 2.5 Ghz.

[0021] The output of the RFID reader 105a is then transmitted via a wireless communication module 105b of the mobile device 105, using various wireless protocols and frequency ranges, to a wireless system controller 109. In an exemplary embodiment, the RFID reader 105a is mounted to operate upwards towards the ceiling, where the RFID tags 101, 103 are permanently mounted in a numbered grid near the ceiling. The wireless system controller 109 matches the RFID tag number to a specific interior location and displays identifying information (e.g., a mobile number uniquely identifying the device 105) to a graphical user interface (GUI) using, for instance, conventional Geographic Information System (GIS) software, e.g., MAPINFO®. [00221 In an exemplary embodiment, a lookup table is used by the wireless system controller 109 to match the RFID tag number with a known location inside the facility. This known location is referenced to an exterior surveyed benchmark. Alternatively, the mobile device 105 can itself locally determine the location via a processor 105c; thus, the lookup table is stored locally at the mobile device 105. The determined location information (e.g., geographic coordinates, Global Positioning System (GPS) data, etc.) can then be forwarded to the wireless system controller 107.

[0023] According to one embodiment of the present invention, each RFID tag 101, 103 is assigned a twenty-four-digit number for specifying location information as well as account information. For example, the first four digits from the left can designate a customer number. The second four digits represent the specific facility number for the customer. The next three numbers can denote the facility floor number beginning with zero for the ground floor. The next five digits specify a west-to-east grid location number. The next five digits denote a north-to-south grid location number. The remaining three rightmost digits can be reserved for other fields, which can be specified by the customer or the service provider to accommodate scaling or future developments.

10024] As shown, the mobile device 105 has an optional capability to be tracked, when outdoors, using a Global Positioning System (GPS) through a GPS module 105d. It is contemplated that any type of global positioning system (with or without enhanced and/or differential assistance) or navigational system can be used — e.g., GLONASS (Global Orbiting Navigation Satellite System), GPS, etc. This embodiment can be implemented as part of a fleet and asset management system, as more fully described in FIGs. 4 and 5.

[0025] In the example of FIG. 1, the wireless system controller 109 can interface a local area network (LAN) 109. The LAN 109 provides connectivity for a web server 111 to store and present the location of the mobile device 105, along with information about the mobile device 105 itself. The LAN 109 has connectivity to a public data network 113, such as the global Internet, whereby a web browser 115 can access the information stored within the web server 111.

[0026] FIG. 2 is a flowchart of a process for switching between a Global Positioning System (GPS) and the indoor tracking system of FIG. 1, according to an embodiment of the present invention. In step 201, the mobile device 105 is monitored and tracked by a GPS system. Next, it is determined whether the GPS system is available, as in step 203. This determination can involve detecting whether a GPS "LOCK condition" exists by the GPS module 105. If the GPS signals can still be received and the location of the device 105 can be determined, then the mobile device 105 continues to use the GPS system. However, if the GPS system is not available, then the mobile device 105 switches, per step 205, to the indoor tracking system 100.

[0ϋ27| At this point, the location of the mobile device 105 is monitored using the array of RFID tags 101, 103 (step 207). In the event that the indoor tracking system 100 becomes unavailable, for example, through equipment malfunction or failure, as determined in step 209, then an operator or administrator of the indoor tracking system 100 is notified (step 211).

[0028J FIG. 3 is a flowchart of a process for tracking a mobile device utilizing the system of FIG. 1, according to an embodiment of the present invention. The mobile device 105 moves into an area where the GPS system is not available, such as indoors (as in step 301). The RFID reader 105a, in one embodiment of the present invention, can intelligently provide power control such that if the GPS system that is used outside the facility fails to "LOCK" because, for example, the mobile device 105 has moved indoors, an RFID transmitter (not shown) associated with the RFID reader 105a will increase its output power until it starts to decode the RFID tags 101, 103, per step 303. However, if the RFID reader 105a begins to decode too many tags 101, 103 (as determined in step 305), such as alternate rather than adjacent RFID tags, or ones on different floors, the RFID transmitter power is reduced until only one or two RFID tags are decoded (per step 307). Such determination can be based on a pre-determined, configurable threshold of the number of tags detected. The RFID reader 105a includes a signal strength indicator, e.g., Received Signal Strength Indicator (RSSI), to determine the signal strength from each of the respective RFID tags 101, 103. This approach advantageously ensures accurate mobile positioning when the RFBD reader 105a sends the RFID number of the strongest signal strength RFID tag on for processing.

[0029] In this example, the RFID reader 105a first communicates with the RFID tag 101 to obtain the tag number and subsequently transfer the tag number to the wireless communication module 105b for transmission to the wireless system controller 109, per steps 309 and 311. During step 313, the mobile device 105 also transmits its identification information, e.g., mobile number. This mobile number is needed to uniquely identify the device, as multiple mobile devices are used in practical systems.

[0030] In step 313, the wireless system controller 109 then determines the location information conveyed by the RFID tag number that was transmitted by the mobile device 105. The controller 109 can determine the location by simply mapping the tag number to a location point within the grid defined by the RFID tags 101, 103.

(00311 The location of the mobile device 105 as well as information about the device 105, such as its mobile number, is supplied to a web browser or interface 117 (step 315).

[0032] Among the many advantages of the tracking system 100 are its versatility and cost- effectiveness. The system 100, for instance, can be used in manufacturing and warehousing facilities. Additionally, the system 100 can be implemented in military pre-positioning pools, as well as hospitals and office parks. Further, the system 100 can be used in apartment houses and business high-rises. Underground parking garages can also benefit from the tracking capability of the system 100.

(0033) Further, the tracking system 100 can be deployed in a variety of applications. One such application is fleet and asset management, as explained below.

[0034] FIG. 4 is a diagram of an integrated GPS and RFID system for fleet and asset tracking, according to an embodiment of the present invention. The system 400, in contrast to the system of FIG. 11, utilizes a combination of autonomous GPS and Assisted GPS (A-GPS); in particular, mobile-centric A-GPS. The system 400 includes a Network Operation Center . (NOC) 401 for tracking telemetry devices 403, which, under this scenario, are resident within vehicles 405. It is contemplated that the telemetry device 403 can be affixed to an asset (or any other object). A wireless network 407 supports two-way communication among the telemetry devices 403 and the NOC 401; the wireless network 407, in an exemplary embodiment, is a two-way paging system employing the ReFLEX™ protocol by Motorola for two-way advanced messaging. The telemetry devices 403 have two modes of operation: autonomous GPS mode, and A-GPS mode. When operating in A-GPS mode, the system 400 can provide for better in building or obstructed view geolocation with in a paging system zone. When out of network coverage, the autonomous GPS may be used to obtain geolocation data that may be stored on the device for later transmission. [0035! According to one embodiment of the present invention, the wireless network 407 provides over the air encrypted messages.

[0036] The NOC 401 provides the necessary fleet and asset management functions, such as user account creation and management, access control, and deployment of business rules. The NOC 401 also supports remote management capabilities by hosts 409 over a data network 411, such as the global Internet.

|0037| To better understand the hybrid A-GPS environment of the system 400, it is instructive to describe the operation of the general operation of a mobile-centric A-GPS system. The telemetry device 403 has GPS hardware and intelligence, whereby the network 407 in conjunction with the NOC 401 employs mechanisms for providing GPS aiding data (or assistance data). The network 407 includes base transmitters and some base receivers containing GPS hardware from which the ephemeris and approximate location can be obtained, constituting a GPS reference network 413.

100381 The assistance data that is transmitted to the devices 403, in an exemplary embodiment, can include ephemeris data differential GPS correct data, timing data and/or other aiding data. Using the aiding (or assistance) data, the telemetry devices 403 performs geolocation calculations, yielding a number of advantages. For example, the telemetry devices 403 can generate real-time speed and route adherence alerts. Additionally, transmission of geolocation data need not be frequent. Transmission of geolocation data is more compact because it is true location rather than pseudo range data. Also, the telemetry devices 403 can more intelligently request assistance data because the devices 403 themselves can determine when the ephemeris data is no longer valid.

[0039] The hybrid A-GPS system 400 thus permits fast and precise geolocation when in network coverage of the network 401, while providing immunity from obstructed view of the sky. Also, when the switch is made to autonomous GPS mode (when outside of the coverage area of the network 401), the devices 403 can still obtain geolocation data. This data can be stored within the device 403 and transmitted to the NOC 401 when the associated vehicle 405 returns to the network coverage area.

[0040J As noted earlier, the telemetry devices 403 may be attached to a host entity such as a vehicle or other valuable asset. The device may be used to track, monitor, and control aspects of the host entity. These devices 403 are configurable with respect to the existence and number of digital inputs/outputs (I/O), analog inputs/outputs (I/O), and device port interfaces for connection with peripheral devices. By way of examples, the digital inputs can be used to monitor various components of the vehicles 405: ignition status, door lock status; generic switch status, headlight status, and seat occupancy status. The digital outputs can be used to control, for example, the starter, and door locks, and to monitor such parameters as engine temperature, cargo temperature, oil pressure, fuel level, ambient temperature, and battery voltage. The exact configuration of the telemetry devices 403 can be based on cost consideration and/or applications.

10041] The telemetry devices 403, in an exemplary embodiment, employ a wireless protocol to receive commands and transmit data and alerts (e.g., high speed alert) over the radio network 407. The telemetry devices 403 can queue alerts, message responses, and scheduled data, whereby if the devices 403 are unable to send the messages, the messages are queued and sent when the device 403 returns to wireless network coverage. Prioritized queues are used and include, for example, queues for high, normal, and low priority messages. In the exemplary implementation, critical device status changes are given highest priority, while other alerts and responses are given normal priority. Scheduled data messages are given the lowest priority. The queues are configured, as first in yields first out, wherein new messages are dropped when its corresponding queue is full. This arrangement advantageously allows for the status of the device 403 at the time of transmission failure to be known even when the data stored in the data log at time of the transmission has been overwritten.

[0042] The telemetry devices 403 can also respond to status (e.g., of position, speed, digital I/O port status, analog input channel status, peripheral status or other device status) queries transmitted by the NOC 401. The status query may request either current status or status within a time and date range. The device 403 responds to the query with either the current status or all status within the date and time range that is currently stored in the device's data log.

[0043] As regards data logging, the devices 403 support use of one or more schedules for the data acquisition. The data logging involves storing of the data locally on the device 403. This data, which can include position, speed, digital I/O port status, analog input channel status, peripheral status or other device status is not automatically transmitted over the air. Instead, the data is stored for a finite period of time and made available for use by scheduled data acquisitions, data acquisitions on demand, and data acquisitions associated with alerts. The data log is circular in that when the last available memory for the data logger has been written, the data logger begins recording new data at the first location of memory available for the data logger.

100441 With scheduled acquisitions of the data collected by the data logger, the data within the data log is transmitted by the device 403 according to a configurable schedule at the configured transmission rate. Multiple schedules may be configured on the device 403. Schedules are configured to obtain data at a regular interval based upon calendar time and date. Schedules may be configured such that they are enabled and disabled based upon status of a digital input. For example, an ignition status input may be used to turn a schedule on when the engine is on and turn the schedule off when the engine is off.

100451 As mentioned previously, the telemetry devices 403 can be configured to monitor a variety of information relating to the vehicle or asset through the digital I/O and analog I/O. For instance, alerts can be used to indicate status change of the digital inputs. Each Digital Input Status Change Alert can be enabled and disabled through configuration. The alert may be configured to transmit other device status recorded at the time of the alert such as position, speed, status of other digital I/O ports, analog input status, peripheral status, or other device status. As regards the digital output, the status of each available digital output can be changed or read.

[θ()46| Similarly, the statuses of analog inputs of the devices 403 are monitored for change. In an exemplary embodiment, multiple threshold levels (e.g., high and low) can be set, whereby alerts are generated (e.g., Low Range Entry alert, Low Range Exit, High Range Entry, and High Range Exit). That is, if the value of the Analog Input falls below the Low Threshold, a Low Range Entry Alert is generated. If the value of the Analog Input rises above the Low Threshold plus a Hysteresis is value, a Low Range Exit Alert is generated. In similar fashion, if the value of the Analog Input rises above the High Threshold, a High Range Entry Alert is output from the device 403. Also, if the value of the Analog Input falls below the High Threshold minus a Hysteresis value, a High Range Exit Alert is generated. The alert may be configured to transmit other device status recorded at the time of the alert such as position, speed, status of other digital I/O ports, analog input status, peripheral status, or other device status. |0047) By way of example, the devices 403 can be used to monitor excessive speed via a High Speed Alert Control, whereby a High Speed Threshold can be set by a fleet manager. In addition, a duration parameter (i.e., High Speed Duration) can be utilized to specify the time at which the High Speed Threshold must be exceeded before an alert is generated. Further, a configurable High Speed Hysteresis parameter is set as the delta change below the High Speed Threshold used to determine when the High Speed Threshold has no longer been exceeded. The alert may be configured to transmit other device status recorded at the time of the alert such as position, speed, status of other digital I/O ports, analog input status, peripheral status, or other device status.

[0048] The system 400 also permits users via the hosts 409 to specify and configure areas of interest within the coverage area of the network 401 such that alerts can be generated when a device 403 enters or exits the configured areas. The alert may be configured to transmit other device status recorded at the time of the alert such as position, speed, status of other digital I/O ports, analog input status, peripheral status, or other device status.

|0049) The data collected and transmitted by the telemetry devices 403 are processed by the NOC 401.

[0050J FIG. 5 shows a diagram of a telemetry device used in the system of FIG. 4, according to an embodiment of the present invention. The telemetry device 403, which can be deployed within a vehicle (as shown in FIG. 4 or coupled to any asset), operates within the wireless network 407. By way of example, the components of the telemetry device 403 are described in the context of a narrowband network, such as a paging system; however, it is contemplated that the components for communications can be tailored to the specific wireless network.

[005 IJ In this exemplary embodiment, the telemetry device 403 includes a two-way wireless modem 501 for receiving and transmitting signals over the wireless network 407 according to the communication protocols supported by the wireless network 407, such as the Motorola ReFLEX™ protocol for two-way paging. By way of example, a Karli ReFLEX™ module by Advantra International can be used for the modem 501. The two-way wireless modem 501 couples to a two-way wireless antenna (not shown) that can be placed local to the device 403 or remote from the device 403 (e.g., 12 or more feet) to enhance flexibility in installation.

[0052] The telemetry device 403 also contains a GPS module 503 that is capable of operating in the multiple GPS modes: autonomous GPS mode, and mobile-based A-GPS mode. The GPS module 503 can employ, for example, a GPS receiver manufactured by FastraX - iTraxO2/4. In autonomous mode, GPS data may be acquired with no assistance data provided by the wireless network 407. The GPS module 503 operates in the A-GPS mode when the device 403 is in wireless network coverage, in which assistance data is supplied and can include ephemeris data and data to obtain location in obstructed view locations (in building, wooded areas, etc.). Further, the assistance can include differential GPS (DGPS) to enhance location accuracy under some conditions. The GPS module 503 couples to a GPS antenna (not shown) that can be placed local to the device 403 or remote from the device 403 (e.g., 12 or more feet) to enhance flexibility in installation.

[0053 j Attachment of peripheral modules to the telemetry device 403 are supported by one or more peripheral ports 505. The ports 505, for example, can be used to connect to intelligent peripherals that operate according to business rules and logic. These business rules and logic can be housed in a vehicle harness (not shown), which include an On-Board Diagnostic (OBDn) interface and intelligence. Under this arrangement, a user (e.g., fleet manager) can query any parameter available through the OBDII interface. For example, data obtained for each tracking record can include any combination of the following items: RPM (Revolutions Per Minute), oil pressure, coolant temperature, etc. Such data recorded by the telemetry device 403 is stored in memory 513. The acquisition period for the data is configurable, as well as the transmission interval to the NOC 401. Furthermore, the monitoring and subsequent data exchange can be governed by a configurable schedule, which can specify such parameters as start date, start time, end time, recurrence (e.g., daily, weekly, monthly, etc.), and duration.

10054 j Data is logged by a data logger 507, made available for use by scheduled data acquisitions, data acquisitions on demand, and data acquisitions associated with alerts. As mentioned, the telemetry device 403 also can be configured to include digital I/O 509 and analog I/O 511 for monitoring and control of the vehicle or asset. The data logger 507 also collects data associated with these I/O ports 509, 511.

[0055] The telemetry device 403 also includes a processor 525 that may handle arithmetic computations, and may support operating system and application processing. The processor 525, while shown as a single block, may be configured as multiple processors, any of which may support multipurpose processing, or which may support a single function. |0056| The memory 513 of the telemetry device 403 can be organized to include multiple queues for prioritizing the messages to be processed by the device 403. In an exemplary embodiment, the memory 513 includes a High Priority queue 515, a Medium Priority queue 517, and Low Priority queue 519. The memory 513, while shown as a single block, may be configured as multiple memory devices, any of which may support static or dynamic storage, and may include code for operating system functionality, microcode, or application code.

[0057| Data recorded by the telemetry device 403 may additionally be stored in a storage medium other than the prioritized queues 515, 517, and 519, such as in a flash memory 523. A log (not shown) of information may be kept so that the information may be transmitted according to a schedule, as discussed above, or, e.g., upon receipt of a request to send all data that has been collected. Storage devices have only a finite amount of space for storage of information, and thus the information for only a finite number of messages may be stored in either the prioritized queues 515, 517, 519 or the flash memory 523.

[0058] To improve availability of the telemetry device 403, an internal battery 521 is optionally included. With the internal battery, the telemetry device 403 can continue to monitor and transmit alerts and status information to the NOC 401 even if the electrical system of a vehicle is inoperable. Additionally, the internal battery 521 can be used by the device 403 to gracefully report power status wirelessly and shut down gracefully when the energy level of the internal battery is becoming to low to sustain operation of the device.

[0059| The telemetry device 403 includes an RFID reader 527 for indoor operation, as described previously with respect to FIGs. 1-3. This approach advantageously provides an integrated GPS system that supports continual monitoring and tracking of the device 403 with minimal cost.

[0060] FIG. 6 illustrates a computer system 600 upon which an embodiment according to the present invention can be implemented. The computer system 600 includes a bus 601 or other communication mechanism for communicating information and a processor 603 coupled to the bus 601 for processing information. The computer system 600 also includes main memory 605, such as a random access memory (RAM) or other dynamic storage device, coupled to the bus 601 for storing information and instructions to be executed by the processor 603. Main memory 605 can also be used for storing temporary variables or other intermediate information during execution of instructions by the processor 603. The computer system 600 may further include a read only memory (ROM) 607 or other static storage device coupled to the bus 601 for storing static information and instructions for the processor 603. A storage device 609, such as a magnetic disk or optical disk, is coupled to the bus 601 for persistently storing information and instructions.

[00611 The computer system 600 may be coupled via the bus 601 to a display 611, such as a cathode ray tube (CRT), liquid crystal display, active matrix display, or plasma display, for displaying information to a computer user. An input device 613, such as a keyboard including alphanumeric and other keys, is coupled to the bus 601 for communicating information and command selections to the processor 603. Another type of user input device is a cursor control 615, such as a mouse, a trackball, or cursor direction keys, for communicating direction information and command selections to the processor 603 and for controlling cursor movement on the display 611.

[0062| According to one embodiment of the invention, the processes of the servers and clients in the systems of FIGs. 1 and 4 are performed by the computer system 600, in response to the processor 603 executing an arrangement of instructions contained in main memory 605. Such instructions can be read into main memory 605 from another computer-readable medium, such as the storage device 609. Execution of the arrangement of instructions contained in main memory 605 causes the processor 603 to perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the instructions contained in main memory 605. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement the embodiment of the present invention. Thus, embodiments of the present invention are not limited to any specific combination of hardware circuitry and software.

100631 The computer system 600 also includes a communication interface 617 coupled to bus 601. The communication interface 617 provides a two-way data communication coupling to a network link 619 connected to a local network 621. For example, the communication interface 617 may be a digital subscriber line (DSL) card or modem, an integrated services digital network (ISDN) card, a cable modem, a telephone modem, or any other communication interface to provide a data communication connection to a corresponding type of communication line. As another example, communication interface 617 may be a local area network (LAN) card (e.g. for Ethernet™ or an Asynchronous Transfer Model (ATM) network) to provide a data communication connection to a compatible LAN. Wireless links can also be implemented. In any such implementation, communication interface 617 sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information. Further, the communication interface 617 can include peripheral interface devices, such as a Universal Serial Bus (USB) interface, a PCMCIA (Personal Computer Memory Card International Association) interface, etc. Although a single communication interface 617 is depicted in FIG. 6, multiple communication interfaces can also be employed.

[0064 J The network link 619 typically provides data communication through one or more networks to other data devices. For example, the network link 619 may provide a connection through local network 621 to a host computer 623, which has connectivity to a network 625 (e.g. a wide area network (WAN) or the global packet data communication network now commonly referred to as the "Internet") or to data equipment operated by a service provider. The local network 621 and the network 625 both use electrical, electromagnetic, or optical signals to convey information and instructions. The signals through the various networks and the signals on the network link 619 and through the communication interface 617, which communicate digital data with the computer system 600, are exemplary forms of carrier waves bearing the information and instructions.

[0065J The computer system 600 can send messages and receive data, including program code, through the network(s), the network link 619, and the communication interface 617. In the Internet example, a server (not shown) might transmit requested code belonging to an application program for implementing an embodiment of the present invention through the network 625, the local network 621 and the communication interface 617. The processor 603 may execute the transmitted code while being received and/or store the code in the storage device 609, or other non-volatile storage for later execution. In this manner, the computer system 600 may obtain application code in the form of a carrier wave.

[0066] The term "computer-readable medium" as used herein refers to any medium that participates in providing instructions to the processor 605 for execution. Such a medium may take many forms, including but not limited to non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as the storage device 609. Volatile media include dynamic memory, such as main memory 605. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise the bus 601. Transmission media can also take the form of acoustic, optical, or electromagnetic waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, CDRW, DVD, any other optical medium, punch cards, paper tape, optical mark sheets, any other physical medium with patterns of holes or other optically recognizable indicia, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave, or any other medium from which a computer can read.

100671 Various forms of computer-readable media may be involved in providing instructions to a processor for execution. For example, the instructions for carrying out at least part of the present invention may initially be borne on a magnetic disk of a remote computer. In such a scenario, the remote computer loads the instructions into main memory and sends the instructions over a telephone line using a modem. A modem of a local computer system receives the data on the telephone line and uses an infrared transmitter to convert the data to an infrared signal and transmit the infrared signal to a portable computing device, such as a personal digital assistant (PDA) or a laptop. An infrared detector on the portable computing device receives the information and instructions borne by the infrared signal and places the data on a bus. The bus conveys the data to main memory, from which a processor retrieves and executes the instructions. The instructions received by main memory can optionally be stored on storage device either before or after execution by processor.

100681 While the present invention has been described in connection with a number of embodiments and implementations, the present invention is not so limited but covers various obvious modifications and equivalent arrangements, which fall within the purview of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method for tracking a mobile device, the method comprising: retrieving an identifier from a Radio Frequency Identification (RFID) tag associated with a fixed point; and transmitting the identifier to a processor, wherein the processor determines location of the mobile device based on the identifier.

2. A method according to claim 1, further comprising: determining whether a Global Positioning System (GPS) is available to determine location of the mobile device.

3. A method according to claim 2, the method further comprising: detecting a lock condition to determine whether the Global Positioning System (GPS) is available.

4. A method according to claim 1 , wherein the mobile device supports telemetry functions.

5. A method according to claim 1, the method further comprising: communicating with a server to supply the location of the mobile device in support of fleet or asset management.

6. A method according to claim 1, wherein the location and information about the mobile device are accessible by an on-line graphical user interface (GUI).

7. A method according to claim 1, wherein the identifier is transmitted over a wireless network to the processor.

8. A method according to claim 1, wherein the processor resides in the mobile device.

9. A method according to claim 1, wherein the fixed point is physically situated above the mobile device.

10. A method according to claim 1, wherein the RFID tag is electrically passive.

11. A method according to claim 1, wherein the RFID tag is among a plurality of RFID tags arranged in a grid, the method further comprising: detecting signals corresponding to some of the RFID tags; and determining the RFID tag associated with the identifier exhibits the strongest signal.

12. A method according to claim 1, wherein the RFID tag is among a plurality of RFID tags, the method further comprising: detecting a plurality of signals corresponding to the RFID tags; and reducing power of an RFID reader in response to the detection of the plurality of signals.

13. An apparatus for supporting a tracking system, the apparatus comprising: a Radio Frequency Identification (RFID) reader configured to retrieve an identifier from a

RFID tag associated with a fixed point; and a communication module configured to transmit the identifier to a processor, wherein the processor determines location of the apparatus based on the identifier.

14. An apparatus according to claim 13, further comprising: means for determining whether a Global Positioning System (GPS) is available to determine location of the apparatus.

15. An apparatus according to claim 14, further comprising: means for detecting a lock condition to determine whether the Global Positioning System (GPS) is available.

16. An apparatus according to claim 13, further comprising: logic configured to provide telemetry functions.

17. An apparatus according to claim 13, wherein the communication module is configured to communicate with a server to supply the location of the apparatus in support of fleet or asset management.

18. An apparatus according to claim 13, wherein the location and information about the apparatus are accessible by an on-line graphical user interface (GUI).

19. An apparatus according to claim 13, wherein the identifier is transmitted over a wireless network to the processor.

20. An apparatus according to claim 13, wherein the processor resides in the mobile device.

21. An apparatus according to claim 13, wherein the fixed point is physically situated above the apparatus.

22. An apparatus according to claim 13, wherein the RFID tag is electrically passive.

23. An apparatus according to claim 13, wherein the RFID tag is among a plurality of RFID tags arranged in a grid, wherein the RFID reader is further configured to detect signals corresponding to some of the RFID tags, and to determine the RFED tag associated with the identifier exhibits the strongest signal.

24. An apparatus according to claim 13, wherein the RFID tag is among a plurality of RFID tags, and the RFID reader is further configured to detect a plurality of signals corresponding to the RFID tags, and to reduce power in response to the detection of the plurality of signals.

25. A tracking system comprising: a plurality of Radio Frequency Identification (RFID) tags affixed to stationary points forming a grid for conveying location information; and a mobile unit including an RFK) reader configured to obtain an identifier of one of the

RFID tags, wherein the one RFID tag represents a particular location of the mobile unit within the grid.

26. A system according to claim 25, wherein the mobile unit is configured to determine whether a Global Positioning System (GPS) is available to locate the mobile unit.

27. A system according to claim 26, wherein the mobile unit is configured to detect a lock condition to determine whether the Global Positioning System (GPS) is available.

28. A system according to claim 25, wherein the mobile unit is configured to provide telemetry functions.

29. A system according to claim 25, wherein the mobile unit is configured to communicate with a server to supply the location of the system in support of fleet or asset management.

30. A system according to claim 25, wherein the location and information about the system are accessible by an on-line graphical user interface (GUI).

31. A system according to claim 25, wherein the identifier is transmitted over a wireless network to a remote processor for determining geographic coordinates of the mobile unit.

32. A system according to claim 25, wherein the mobile unit determines geographic coordinates of the mobile unit based on the one RFID tag.

33. A system according to claim 25, wherein the stationary points are physically situated above the mobile unit.

34. A system according to claim 25, wherein the RFID tags are electrically passive.

35. A system according to claim 25, wherein the mobile unit is configured to detect concurrently signals corresponding to some of the RFID tags, and to determine the one RFID tag associated with the identifier exhibits the strongest signal.

36. A system according to claim 25, wherein the mobile unit is configured to detect concurrently a plurality of signals corresponding to the RFID tags, and to reduce power in response to the concurrent detection.