System for locating and communicating with mobile vehicles

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FIELD OF THE INVENTION

This invention relates to the field of mobile vehicle location determination and corresponding messaging systems and, more particularly, to a system that allows relatively low-cost fleet management of vehicles over a wide geographical area.

BACKGROUND OF THE INVENTION

Demand for mobile vehicle positioning and messaging is growing very rapidly. A typical application for such a mobile vehicle positioning and messaging system is in the field of truck fleet management whereby a central dispatch office of a trucking company may obtain the location of each truck in a widely dispersed geographical area upon demand. Using such a system, the dispatch office can track the location and progress of each vehicle, thus updating the vehicle's arrival time for customers. Some systems currently available also allow the transmission of messages between the truck and dispatch office while enroute; this facilitates diversion of the truck to additional pick-up sites, for example.

One class of available system that allows the sending and receiving of messages is provided by Qualcomm. The system, named Omnitracs.TM., uses satellites to determine vehicle position via triangulation. A dish antenna which tracks the satellites is mounted within each vehicle in a pod placed, generally, upon the vehicle roof. The dish must continuously track the location of the satellite as the vehicle moves. Messages to and from the vehicle are limited to pager style alpha-numeric readouts. Voice and facsimile messages are also unavailable due to the limited bandwidth of satellite transmission. However, the most significant disadvantage to the Qualcomm system is cost. The vehicle-borne base unit and the satellites are rather expensive to maintain. Additionally, the dish mechanism may be prone to breakage since it is an electromechanical link that must maintain fairly precise alignment while subjected to extreme vibration and jarring in the normal highway environment.

Another class of available vehicle location systems are systems such as Motorola's CoveragePLUS.TM. system based upon the Specialized Mobile Radio (SMR) system. In these systems vehicles carry conventional 2-way SMR units for mobile radio communication. These units communicate with one of a number of dedicated and proprietary fixed earth stations that have been installed or converted expressly for vehicle location use. The system determines which earth station is within range of the mobile unit, thereby obtaining the approximate vehicle location. The location determination is based largely upon signal strength. A major disadvantage of the CoveragePLUS.TM. system is the large investment necessary to deploy the required dedicated earth stations. Since accuracy of the CoveragePLUS.TM. system is inversely related to the range of each earth station, a large number of stations is required to provide adequate coverage. In order to cover the continental United States, therefore, CoveragePLUS.TM. requires over 1,200 dedicated earth stations. Even using existing radio towers, the cost of equipment would be quite substantial and on the order of tens of millions of dollars. Higher accuracy may be obtained by equipping the vehicle with an outside positioning system such as LORAN C, and transmitting the LORAN C longitude and latitude data over the radio link. This higher accuracy comes at the cost of equipping each vehicle with a LORAN C receiver, which at the time of this application involves about $700 per vehicle.

Another class of vehicle location system utilizing a somewhat unconventional antenna medium is the meteor-burst system. Vehicles are equipped with a LORAN C device or equivalent triangulation system that establishes each vehicle's position using government-operated transmitters. The position data from these LORAN C units is then transmitted from the vehicle to the base station via reflections off of the ionized "tails" of micro-meteorites entering the earth's atmosphere. Signals in the range of 37 Mhz to 70 Mhz are reflected by these tails. Thus, short packets of radio signals may be transmitted from the vehicle to the base station during meteor bursts. These bursts may also carry rather short data/text messages to and from the vehicle. A great disadvantage to this system is that a number of base stations (100 or more) must be dedicated to receiving transmissions from meteor bursts. Since meteor bursts are intermittent and unpredictable in time and location, in order to insure the receipt of a signal from one of the bursts, a very large number of costly base stations would be required. Continuous signals carrying the same data would be repeated until the correctly positioned "burst" appeared, allowing transmission to one of the base stations. Clearly, this system also requires somewhat costly vehicle-borne transceivers for utilizing the meteor bursts.

Yet another class of system that has been proposed would utilize a cellular telephone network to determine the approximate position of a vehicle. Such a system is proposed in U.S. Pat. No. 4,891,650 to Sheffer for locating stolen vehicles. The system fixes upon the position of a stolen vehicle by triangulating the signal strength of the vehicle's cellular transmissions between three or more base station transmitters, or "cells" in a given cellular system. To do so, the vehicle must first register a signal to its transmitter that is activated via a signal indicating that the vehicle carrying it is being stolen. The transmitter then places a dialed call over the cellular network to a base unit which then searches through the system to determine which cells the vehicle is currently near. This information may be utilized to locate the vehicle. Clearly, one disadvantage to the Sheffer system is that it requires placing a call over the cellular network, which actively engages the voice channels on the cellular network. While this form of direct transmission is perfectly acceptable in the somewhat infrequent occurrence of a vehicle theft, it would prove rather costly, and wasteful of cellular voice channels, when utilized to track an entire fleet of vehicles. Basically, it would require a continuous placement of expensive long distance cellular phone calls to continuously update vehicle location.

Additionally, the coverage of the Sheffer system is limited to only one cellular system having been modified to implement it. This would necessarily limit such a system's operation to an area such as a single city. To provide wider coverage, all switches (groupings of cells) of a particular system must be modified. This would prove very costly and require approval of all the cellular operators serving the area of interest. All the cells in each of the switches to be tapped must be similarly modified, and the interconnections between these switches must also be modified in order to provide the requisite wide coverage. Even if one were to provide a LORAN C or similar positioning unit and merely make a phone call to report the data, the cost of cellular telephone-based vehicle location would remain high since the calls themselves are expensive and continuously occupy a large number of scarce voice channels.

A vehicle location system that, unlike the above-described systems, is based entirely upon existing and established system hardware is highly desirable since implementation costs would be minimized. As such, the growing cellular telephone network currently being implemented throughout the nation, and the world, provides a likely candidate for a vehicle location system. As noted above with reference to the Sheffer system, however, a system that requires placement of costly telephone calls is wasteful and expensive to operate.

A basic cellular telephone system 32 is depicted in FIG. 1. The concept of a cellular system involves utilization of a number of base stations 36a-f each having a transceiver that covers a particular transmission area known as a "cell" 38a-f. There are usually a number of cells, and an equal number of corresponding "base stations" within a particular cellular system. Often, such a system covers a given metropolitan area or highway stretch between metropolitan areas. In this example each cell 38a-f has coverage boundaries 35 that are schematically depicted as defining a hexagon. In reality, boundaries will tend to be circular and overlap each other, and may vary in dimensions based upon such factors as terrain and obstructions. Base stations are generally positioned so that a given system area is fully served in transmission and reception. The outer boundaries 41 of the system 32 are generally defined by the outermost cells therein. The base stations 32a-f are all interlinked to a particular "switch" or mobile switching center (MSC) 37. There may be more than one MSC within any given cellular system. The system 32 of FIG. 3 depicts one MSC 37 for simplicity. The MSCs are connected to the public switched telephone network (PSTN) 39 which is more commonly known as the local telephone company. The telephone company interlinks the various subscribers each having a hard wired conventional telephone set, shown schematically as the single handset 43.

Each vehicle 34a-d in communication with a particular base station includes its own on-board transceiver more commonly termed a cellular telephone or cellular subscriber station (CSS). The transceiver allows communication with a particular base station. Base stations throughout a cellular system, and throughout the country, utilize a standard communication protocol, thus, CSSs moving from one "cell" to another are equipped to continue to communicate with other cells in the system.

Communication of CSSs traveling between cells in a system is coordinated by means of a communication protocol carried out between the CSSs and the switching center (MSC) via the base station covering the area in which the CSS is currently located. Thus, as a vehicle 34a moves from cell 38a to cell 38c (as shown in FIG. 1A), while engaged in a call, CSS communication from base station 36a is transferred, in an uninterrupted manner to base station 36c. The link between the vehicle CSS and a given cell is maintained because the MSC 37 is constantly updated as to the particular position of the vehicle. The MSC 37 tracks the CSS even if it is not engaged in a call because each CSS transmits, at a predetermined time, a so-called "self-registration" signal over a control radio channel. This signal comprises data representing a unique identification number (Mobile Serial Number (MSN)) identifying the particular CSS. It is transmitted on both a time-dependent periodic basis and each time the CSS sends or receives a call. The Mobile Serial Number matches a number registered in the MSC for that CSS. Note that the MSC is programmed with the CSS's Mobile Serial Number, because the CSS user is a subscriber to that particular cellular system and, thus, the user's CSS is registered with the system. Thus, when a particular cell receives the self-registration signal from a CSS, the MSC is alerted that the recognized CSS is now within that particular cell.

Until recently, the automatic updating of vehicle location occurred only on a system-wide basis (e.g., only between cells in a single system). It was generally not possible to move to an adjacent cellular system and maintain uninterrupted cellular service (particularly reception) since the new system did not recognize the presence of the "foreign" CSS's transmitted MSN number automatically. However, large groups of systems in various geographical areas are now implementing a so-called "roaming" network whereby suitably equipped cellular systems are alerted to the presence of foreign (unregistered) CSSs within their system. Each switch in the roaming network is connected to the others, usually by land lines carrying telephone calls and/or data. Data is passed between the systems relative to CSSs currently present in their coverage areas on certain of these lines. The network is a system for controlling the direction of the data. As such, uninterrupted communication (roaming) is possible for CSSs traveling between systems.

It is important to note that each cellular system is identified by a unique 15 bit System Identification Number (SID) that is assigned by the FCC. Each CSS is registered only with a single cellular system, termed the "home" system as described above to which its user subscribes. In general, a CSS's home system is a cellular system that covers the area in which the CSS's user lives or travels most of the time. The SID number of the home system is stored in the CSS's internal memory (usually set by the system operator when the user's subscription begins) and is transmitted as part of the self-registration process.

This basic vehicle and host/home system identification information is carried on the roaming network in order to keep track of the various CSSs traveling within the network.

It is, therefore, an object of the present invention to provide a system for locating vehicles utilizing existing cellular telephone hardware and software for implementing a roaming standard in an unintended manner that allows location of vehicles over a widely dispersed geographical area without the need of complex, specialized and costly vehicle-borne hardware and without the need to modify the cellular network equipment.

SUMMARY OF THE INVENTION

The objects of this invention are achieved by tapping roaming network information through which one can derive the location of particular vehicles without actually placing costly telephone calls. Thus, an inexpensive system for tracking vehicles over a wide geographical area is possible. Additionally, there is no need to alter existing base station or switch hardware or software to tap the data, thus lowering location system implementation costs. In fact, access to only one switch that is part of a given roaming network allows access of all CSS data relative to all switches in the network since all the roaming data is shared by all the switches in the network. Using the tapped data it is possible to develop a data base of vehicle locations. To locate any vehicle it need only carry a basic cellular telephone transceiver.

In addition, using a cellular system, one is not limited to obtaining location data only. Rather, since the cellular system is designed to carry large volume voice information, one may also transmit various data and facsimile information to vehicles having cellular transceivers. Thus, location and messaging services are possible via the cellular roaming network.

A vehicle location system according to a preferred embodiment of the present invention provides an interface computer that is connected to a roaming network that joins a number of individual cellular systems. Each of the cellular systems stores data relative to and identifies cellular subscriber stations that are based within that particular system and also identifies visiting cellular subscriber stations from other cellular systems that are currently within the given system. The roaming network transfers identification data between each of these cellular systems so that each cellular subscriber station's home system may keep track of the cellular subscriber station and transfer calls to and from the station while the station is situated in another cellular system.

The interface computer accesses roaming network data via a given cellular system and scans that data for predetermined cellular subscriber station identification numbers that correspond to particular stations of interest to a user. These stations, which may comprise a fleet of vehicles, generally carry the tapped cellular system as their registered "home" system. That user may be a fleet operator or other mobile vehicle management entity.

In order to interpret the tapped interface data relative to predetermined subscriber stations, a location computer taps, on demand of a user or at predetermined intervals of time, into the interface computer data. The location computer then interprets, cellular system identification data corresponding to each predetermined vehicle. Location data is particularly derived by comparing system identifications to known geographical locations for those particular systems. This data is then correlated to each vehicle and formatted so that a user may easily review the location of various subscriber stations. Such review may include electronic display maps, charts, graphs and textual formats.

This system may be adapted to tap multiple roaming networks, where more than one network is in place, by determining the probable location of moving vehicles from one roaming network to another. This may entail predicting vehicle location using previous vehicle position, speed and approximate direction. Such data would be stored within the memory of the location computer for each vehicle and would be transferred to an appropriate interface computer interconnected with each roaming network through a given cellular system attached thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and advantages of the invention will become clearer by referring to the following detailed description and the drawing, in which:

FIGS. 1 and 1A are schematic diagrams of a simplified cellular system as utilized by the vehicle location system according to this invention with vehicles moving between different system cells at first and second times;

FIG. 2 is a schematic diagram of an overview of the vehicle location system according to this invention;

FIG. 3 is more detailed schematic diagram of the peripheral transmission and data display elements of the vehicle location system of FIG. 1;

FIG. 4 is a schematic diagram of a roaming network for joining a plurality of cellular systems utilized in the vehicle location system according to this invention;

FIG. 5 is a schematic diagram of a basic location system implementation according to this invention;

FIG. 6 is a flow diagram of an interface procedure for use by the interface computer of FIG. 5;

FIG. 6A is a schematic diagram of memory locations for a typical interface computer according to this invention;

FIG. 7 is a flow diagram of a procedure for use by the location computer of FIG. 5;

FIG. 8 is a flow diagram of the location update procedure for use by the location computer based upon reported changes from the interface computer of FIG. 5;

FIG. 9 is a schematic diagram of a typical mobile vehicle cellular telephone configurator including data and facsimile peripherals according to this invention;

FIG. 10 is a schematic diagram of the mobile vehicle cellular configuration of FIG. 9 including LORAN C for more accurate location determination according to this invention;

FIG. 11 is a schematic diagram of a vehicle location system according to an alternative embodiment of this invention in which multiple roaming networks are accessed;

FIG. 12 is a flow diagram of the main procedure for a location computer interfaced with multiple roaming network systems according to the FIG. 11 embodiment of this invention;

FIG. 13 is a flow diagram of a procedure for use in computing and updating location information by the location computer of FIG. 12; and

FIG. 14 is a flow diagram of a procedure for expanding and restricting the search for a vehicle based upon its last known location, for use in the multiple roaming embodiment of FIG. 12.

DETAILED DESCRIPTION

An overview of the cellular vehicular location system according to this invention is depicted in FIG. 2. A vehicle 34 (similar to the multiple vehicles 34a-d of FIG. 1) having an on-board cellular subscriber station (CSS) 47 is served by base station 36c.sub.HOST of cell 38c.sub.HOST of one of a plurality of cellular systems. The systems depicted include the vehicle's "home" system 33 and a remote "host" system 31. Each system includes one corresponding switch, 40.sub.HOME and 40.sub.HOST respectively, interconnecting various base stations 36a-b.sub.HOME and 36a-c.sub.HOST in cells 38a-b.sub.HOME and 38a-c.sub.HOST. It is assumed that the cellular systems described herein implement a protocol defined in ELECTRONIC INDUSTRIES ASSOCIATION/TELECOMMUNICATIONS INDUSTRIES ASSOCIATION (EIA/TIA) Standard for Mobile Station-Land Station Compatibility, Specification EIA/TIA-553 (September 1989 publication) which is incorporated by reference herein. As previously discussed, according to this standard, each vehicle which carries a CSS is assigned a unique 32 bit Mobile Serial Number (MSN) that is permanently stored in its security memory (not shown). The vehicle 34 in this figure is traveling in a system 31 other than its own registered " home" cellular system 33. The remote "host" system 31 within which the vehicle 24 is traveling may recognize the vehicle by means of its 32 bit MSN which is transmitted at regular time intervals by the vehicle Cellular Subscriber Station (CSS) 47. By "registering" or, in the case of automatic signalling "self-registering" with the host system 31, the vehicle 34 CSS makes its presence known to the host.

It is assumed, for the purposes of this description, that the vehicle's host system 31 and home system 33 are joined together by a network 42 adhering to the standards set forth in EIA/TIA-553 and also to the so called "roaming" standard currently being instituted under ELECTRONIC INDUSTRIES ASSOCIATION/TELECOMMUNICATIONS INDUSTRIES ASSOCIATION (EIA/TIA) IS.41 Interim Standard for Cellular Radio Telecommunications Intersystem Operations, Specification (January, 1991). This standard should be deemed to be incorporated herein by reference. As previously discussed, this roaming standard allows a vehicle to be located and to communicate with another cellular system via a link referred to as the "roaming network". Thus, as a vehicle 34 moves from the area serviced by one cellular system to the area serviced by another, the roaming network 42 informs the vehicle's home system 33 of this new location, allowing the home system to route calls to the CSS vehicle 34, wherever it may be in the network 42, as a result of which callers can reach the CSS 35 of the vehicle 34, and vice versa.

As discussed above, minimum communication linkage via a roaming network is maintained, particularly by means of the self-registration process carried out by the CSS. According to this process an identification signal (MSN) is sent by the vehicle, and received by the host MSC, at a predetermined time interval or when the CSS user makes and receives calls. The self-registration process, thus, acts as a tracking "beacon" that is received by the closest base station in the system in which the CSS is currently present. The roaming network allows the base station and, hence, the system to identify the CSS. Therefore, means for tracking a vehicle as it travels has been developed by us, using this network. Data received by the home system 33 from the host system 31 through the roaming network 42 is utilized by depicted interface and location computers 44 and 46, respectively, according to this invention, to determine the current location of each vehicle carrying a CSS. The vehicle location is thus known to within the geographic area of a single cell and/or the geographic area served by the MSC serving that cell. The particular mechanics involved in interfacing with the roaming network will be described further below.

Vehicle and user peripherals for use with the vehicle location system are illustrated in FIG. 3. The system implementation includes the mobile equipment 48 of a vehicle CSS's 34' which includes a standard cellular telephone 50 and may include peripherals such as a modem 52 to interconnect a text terminal and/or on-board computer and a facsimile machine 56. The mobile equipment is joined by a standard cellular radio link, which transmits both voice line and self-registration signals, to the cellular network which includes the various cellular systems joined by the roaming network which allows conventional calls or facsimile messages to be transferred to and from the vehicle from the vehicle's home base 60. According to this invention, information from the cellular network 58 (systems joined by a roaming capability) is utilized by the interface computer 44 and location computer 46, to determine and transmit the vehicle's location data to a home base terminal or computer system 62 adapted to receive external communications via an electronic mail system 61 to which the interface and location computers 44, 46 are linked. This customer may have its own voice unit (e.g., telephone) 63 and facsimile unit 65 as well. Note that, according to this invention, it is equally possible to transmit and display location information to the customer premises through a variety of other links, such as direct transmission without an electronic mail link.

FIGS. 2 and 3, thus, generally depict the vehicle location system according to this invention and should be referred to generally throughout the following detailed description.

As noted, a CSS operating outside the area served by its home system may be referred to as "roaming". While roaming, a CSS is thus being served by a non-home "host" system. Absent agreed protocols, the host has no way of recognizing the identity of the CSS and no data exchange necessary for communication as be carried out by the host. Thus, an agreed, standardized (and preprogrammed) protocol, via the roaming network, is necessary in order to allow each cellular system to recognize other systems' roaming registered CSSs.

To provide "seamless" roaming capability to users (i.e., without interruption in service when traveling from one cellular system to another) while traveling over geographical areas served by several cellular systems, roaming under EIA/TIA IS.41 standard is being implemented. This standard specifies how individual cellular systems are interconnected to form a "roaming network". All relevant portions of EIA/TIA IS.41 are hereby incorporated herein by reference.

Detailed Operation of The Roaming Network and System Implementation

The "mechanics" of the roaming network are further detailed in FIG. 4. Each of cellular systems I, II and III, 64, 66 and 68 respectively, maintains a group of data bases (registers) that include the Home Location Register (HLR) 70.sub.I, 70.sub.II and 70.sub.III and the Visitor Location Register (VLR) 72.sub.I, 72.sub.II, and 72.sub.III that are part of each switch (MSC) in the system. The HLR 70.sub.I-III store specified information relating to each CSS registered with that specific cellular system. In other words, each HLR 70.sub.I-III stores information relating to those CSSs whose home is specified as being that HLR's particular cellular system. Records of all registered CSSs are maintained even when CSSs roam outside the region served by their home cellular system. Conversely, the VLRs 72.sub.I-III store specified information relating only to CSSs currently roaming within the area served by the particular cellular system in which the VLR is located. HLRs and VLRs are usually located within Mobile Switching Centers (MSCs) 40.sub.I-III but may be implemented in separate units.

According to the EIA/TIA IS.41 standard, when an MSC determines, from information received over the roaming network 42, that a roaming Cellular Subscriber Station (CSS) has entered its service area, it initiates a Registration Notification Procedure. Part of the procedure calls for transmitting a Registration Notification message to the HLR of the CSS's home system over the roaming network 42. The transfer is performed by network landlines that interconnect all systems therein. The data passed to the home HLR 70.sub.HOME by the host MSC, as detailed by the HLR registers 74, 76 and 78 in FIG. 5, includes:

1) the unique Mobile Serial Number (register 74) (MSN) of the CSS;

2) the Mobile Switching Center Identification 76 (MSC ID or SID) number (register 76) of the host system now serving the CSS;

3) the Switch ID (register 78)(SWID), which is defined as the Identification (ID) number of the switch (SW) and MSC within the host system serving the CSS.

The SID (System Identification Number) and SWID (Switch ID) of the host switch serving the roaming CSS are stored in the home HLR so that telephone calls bound for the CSS from the Public Switched Telephone Network (PSTN) 39 or the cellular network 58 may be forwarded to the called CSS's current host system. These procedures insure that the home system HLR is always updated with the SID and SWID of the switch (MSC) serving the CSS while it is roaming. If the CSS is not roaming, but rather, is still within its home system, the HLR simply contains the Identification Number (SWID) of the home system switch serving the CSS. In order to initiate a registration notification, first an autonomous registration signal (self-registration) by the CSS must be transmitted to the base station. As noted previously, this can also be triggered by a call origination, a call termination (i.e., a page response) or a service order. While call origination, call termination or service orders may require action by the user (using scarce voice channel capacity), a calling party or a system operator, autonomous self-registration occurs automatically at regular time intervals as described above and does not use voice channels. The frequency of this autonomous registration is a function of a number of parameters set forth by the system operator and defined in EIA/TIAV553. In general, the parameters are set so that CSSs self-register each 30 minutes or less.

The implementation of a basic system for locating vehicles through the roaming network 42 is depicted in FIG. 5. This system is interfaced with a particular MSC 40.sub.HOME interconnected with the roaming network 42. At least one interface computer is interconnected with the switch 40.sub.HOME and receives information on CSS registration from the switch. In this example, three interface computers IC I (44.sub.I), IC II (44.sub.II) and IC III (44.sub.III), are assigned to the MSC 40.sub.HOME in order to lighten the processing load. The switch selected for connection to the interface computer(s) according to this invention may be considered the home switch in the home system for the purposes of CSS registration. In other words, each CSS to be located will carry a registration number (MSN) that identifies that CSS as belonging to the depicted home MSC 40.sub.HOME. Each switch is connected with CSSs that are registered to it. These CSSs are in their respective "home" switch/system. Each switch may also at any time be connected with a number of CSSs that are registered to a different switch or system. These CSSs, therefore have a different "home" switch than that in which they are currently present. The non-home switch is, therefore considered to be a "host" switch and system. The roaming network 42 allows the MSC 40.sub.HOME to record periodically the location (i.e., the particular host cellular system) of each home-registered CSS even if it is visiting in another host system. The home registered CSS registration data (stored in HLR registers MSN 74, SID 76 and SWID 78), termed HLR data, is read from the home MSC 40.sub.HOME by one of the interface computers 44.sub.I, 44.sub.II and 44.sub.III. These computers store the information in an internal data base for subsequent transmission to a central location computer 46 of this embodiment. This computer concentrates and coordinates all data received from the various interface computers 44.sub.I-II connected to the switch (MSC) 40.sub.HOME. The location computer 46, according to this invention, then processes the HLR data from the interface computers 40.sub.I-II and determines the cellular system location of each CSS registered to this home MSC 40.sub.I-III. This information is then forwarded to the electronic mailbox system 61 that, in turn, transfers the location information to the customer site 60. The customer, which is generally connected by modem to the electronic mail system, maintains a terminal or computer 62 for receiving the data in a readable format (e.g., terminal 62 of FIGS. 2 and 3). As will be described further below, the interface and location computers 44 and 46 are adapted to provide to a particular customer only data relative to that customer's vehicle fleets. As such, the customer only receive