Patent Publication Number: US-2003235172-A1

Title: Asset tracking methods and apparatus

Description:
BACKGROUND  
       [0001] Asset tracking systems exist to track the location of assets. For example, in a hospital, the location of medical equipment may be tracked using an asset tracking system. Also for example, in a retail shop, the location of goods for sale may be tracked using an asset tracking system.  
       [0002] Some asset tracking systems are “perimeter systems” that track assets by detecting whether any assets have crossed a boundary or perimeter. Perimeter systems are common in retail environments. Other asset tracking systems are “location-based systems” that track the location of assets more closely than perimeter systems. For example, location-based asset tracking systems are common in hospitals and in other environments where it is convenient to know the location of an asset with a greater degree of precision than is offered by perimeter systems.  
       [0003] For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for improved location-based asset tracking systems. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0004]FIG. 1 shows a diagram of a wireless network;  
     [0005]FIG. 2 shows a diagram of a network access point device;  
     [0006]FIG. 3 shows a diagram of a network server;  
     [0007]FIG. 4 shows a diagram of a mobile network node;  
     [0008]FIG. 5 shows a diagram of another mobile network node;  
     [0009]FIG. 6 shows a perspective view of a tactile display;  
     [0010]FIG. 7 shows a top view of a visual display;  
     [0011]FIG. 8 shows a diagram of an asset tag; and  
     [0012]FIGS. 9 and 10 show flowcharts in accordance with various embodiments of the present invention. 
    
    
     DESCRIPTION OF EMBODIMENTS  
     [0013] In the following detailed description of the embodiments, reference is made to the accompanying drawings which show, by way of illustration, specific embodiments in which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments maybe utilized and structural, logical, and electrical changes may be made without departing from the scope of the present invention. Moreover, it is to be understood that the various embodiments of the invention, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described in one embodiment may be included within other embodiments. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.  
     [0014] In various embodiments of the present invention as described in more detail below, assets that are “tracked” have an asset tag affixed thereto, and a network that includes many components may track the location of the asset. The network may also track the location and orientation of wireless network nodes and provide the network nodes with information to display a direction to a tracked asset. A user in possession of the mobile network node may then be able to find the tracked asset.  
     [0015]FIG. 1 shows a diagram of a wireless network. Network  100  includes server  122 , network access points (NAPs)  102 ,  104 , and  106 , mobile network node  120 , asset  140 , and asset tag  142 . Access points  102 ,  104 , and  106  are coupled to server  122  by media  116 , and one or more of access points  102 ,  104 , and  106  are coupled to node  120  by wireless links  132 ,  134 , and  136 . The combination of access points  102 ,  104 , and  106 , and server  122  provide network services to mobile network node  120  and asset tag  142 . In addition, node  120  may, in some embodiments, provide network services to other nodes (not shown), or to any of access points  102 ,  104 , and  106 .  
     [0016] Wireless network  100  may be any type of network that allows a node to access network services using a wireless link. For example, in some embodiments of the present invention, wireless network  100  represents a cellular telephone network, and in other embodiments, wireless network  100  represents a wireless local area network (WLAN) or wireless wide area network (WWAN). In still further embodiments, network  100  is a hybrid system that provides a combination of different services to network nodes and access points. For example, in some embodiments, wireless network  100  provides asset tracking services to mobile network nodes. Media  116  may be any type of signal transmission media capable of providing a data communication path between server  122  and access points  102 ,  104 , and  106 . Examples include, but are not limited to: wires, fiber optic cables, and wireless links.  
     [0017] Asset tag  142  is an item that can be physically affixed to an asset that is tracked. For example, in the embodiments represented by FIG. 1, asset tag  142  is affixed to asset  140 . As described below, the location of asset tag  142  may be tracked by network  100 , and the location of tracked assets may be communicated to network nodes such as mobile network node  120 .  
     [0018] Mobile network node  120  may be any type of network node capable of accessing network services using a wireless link. For example, node  120  may be a cellular telephone, a computer, a personal digital assistant (PDA), or any other type of device that can access a network using a wireless link. In some embodiments, node  120  may be a combination cellular phone and computer that provides both wireless data and voice services. In other embodiments, node  120  may be a device that displays asset tracking information to a user having access to node  120 .  
     [0019] In general, nodes and access points are network elements that may provide network services, receive network services, or both. For example, in cellular network embodiments, access points  102 ,  104 , and  106  may be cellular base stations that provide network services and node  120  may be a cellular telephone that primarily receives network services. Also for example, in wireless LAN embodiments, access points  102 ,  104 , and  106 , and node  120  may be computers that provide and receive network services. The remainder of this description describes many different embodiments of the present invention, with an emphasis on wireless LAN embodiments useful for asset tracking. The emphasis on wireless LAN embodiments is provided for clarity, and one of ordinary skill in the art will understand that the present invention is not to limited wireless LANs.  
     [0020] In operation, network  100  provides the ability to determine the location of mobile network nodes and asset tags. Throughout this description, this ability is referred to as “location determination.” Network  100  provides location determination of node  120  through the use of wireless links  132 ,  134 , and  136 . Network  100  also provides location determination of asset tag  142  through the use of wireless links  152 ,  154 , and  156 . Networks that provide location determination are referred to herein as “location-aware networks.” Network  100  is a location-aware network that provides location determination of node  120  and asset tag  142  through the use of the various wireless links.  
     [0021] Wireless links  132 ,  134 , and  136  provide communication paths between node  120  and access points  102 ,  104 , and  106 . Wireless links  152 ,  154 , and  156  provide communication paths between asset tag  142  and access points  102 ,  104 , and  106 . The various access points send and receive wireless signals to and from node  120  and asset tag  142  on the wireless links, and also send and receive signals to and from server  122  using media  116 . In some embodiments, network node  120  communicates with the network using only one of the wireless links shown, but multiple network access points receive the signals transmitted by network node  120 .  
     [0022] In some embodiments, the wireless links utilize a pulse-based radio frequency (RF) protocol to provide communications between node  120  and access points  102 ,  104 , and  106 . In these embodiments, short RF pulses are transmitted by node  120  and asset tag  142 , and these short RF pulses are received by access points  102 ,  104 , and  106 . In other embodiments, the wireless links utilize baseband modulated protocols in which the desired data to be transmitted is superimposed by various means on a sinusoidal carrier signal. One example of a suitable pulse-based protocol is the emerging ultra-wideband (UWB) protocol in which low power, short duration, pulses are transmitted over the wireless link. Another example of a suitable pulse-based protocol is described in U.S. Pat. No. 6,031,862, issued to Fullerton et al., on Feb. 29, 2000. In other embodiments, wireless links  132 ,  134 ,  136 ,  152 ,  254 , and  156  utilize a data modulated sinusoidal carrier. Any type of wireless protocol can be utilized for the wireless links.  
     [0023] Information received from wireless network node  120  may include any information contained within the signals received from node  120 . For example, the signals may contain voice information or data information, in any analog or digital format suitable for requesting or providing network services. Information received from asset tag  142  may also include any type of information. For example, an asset tag may send information representing a serial number, an asset description, or any other information of use to network  100 .  
     [0024] When receiving wireless signals from node  120  and asset tag  142 , the various access points may also gather information describing attributes of the wireless signals. For example, in pulse-based embodiments, the access points may gather pulse time-of-arrival, information as well as angle-of-arrival, pulse amplitude, pulse duration, and rise/fall time information. In sinusoidal carrier embodiments, the access points may gather center frequency, amplitude, angle-of-arrival, phase offset, or other information. In general, information gathered describing attributes of the received signals may include any information suitable to support location determination or asset tracking. For example, pulse time-of-arrival information or angle-of-arrival information, or both, may be used to determine the location of network node  120  relative to the locations of the access points. Also for example, phase offset of a received sinusoidal carrier signal may also be used in support of location determination.  
     [0025] Attributes of received wireless signals may be transmitted from the various access points to server  122 . These attributes may then be used by server  122  to determine the locations of node  120  and asset tag  142 . For example, in pulse-based embodiments, pulse time-of-arrival and optionally pulse angle-of-arrival information gathered by the access points may be used to resolve the locations of node  120  and asset tag  142  relative to the locations of the access points that measure the time-of-arrival and/or angle-of-arrival. Also for example, in sinusoidal carrier embodiments, phase offsets may be used to resolve the locations of node  120  and asset tag  142 .  
     [0026] In addition to location determination, network  100  may provide the ability to determine the orientation of a mobile network node. For example, network  100  may determine the orientation of mobile network node  120  in two or three dimensions. Mobile network node  120  may then display information describing the direction to a tracked asset that is associated with an asset tag. As shown in FIG. 1, the direction from mobile network node  120  to asset  140  is shown by arrow  160 .  
     [0027]FIG. 1 shows three access points. In embodiments with three access points capable of receiving signals from node  120  and asset tag  142 , the location and orientation of node  120  and asset tag  142  can be determined in two dimensions. Some embodiments have more than three access points. In embodiments with four or more access points capable of receiving signals from node  120  and asset tag  142 , the location and orientation may be determined in three dimensions. In some embodiments, information about the environment may be combined with information from access points to determine the location of node  120 . For example, information describing the placement of walls, ceilings, or obstructions may be combined with information from two network access points to determine the location of node  120  in two dimensions.  
     [0028]FIG. 2 shows a diagram of a network access point device suitable for use at the network access points shown in FIG. 1. Network access point device  200  includes transmitter  202 , receiver  204 , time-of-arrival detector  206 , angle-of-arrival detector  214 , processor  208 , and transceiver  210 . Transceiver  210  communicates with a server (not shown) using media  116 . Transceiver  210  also communicates with processor  208 . Transmitter  202  and receiver  204  both communicate with processor  208  and antenna  220 .  
     [0029] Antenna  220  receives wireless signals from network nodes and asset tags on wireless link  230 . In some embodiments, wireless signals on wireless link  230  include electromagnetic pulses as described above with reference to FIG. 1. In these embodiments, receiver  204  receives the pulses, and time-of-arrival detector  206  detects the arrival time of the pulse. Time-of-arrival information is one of many possible attributes of a wireless signal that may be measured by receiver  204 . For example, in some embodiments, angle-of-arrival detector  214  detects the angle from which the pulse arrived as an attribute of the wireless signal. Some embodiments measure both time-of-arrival and angle-of-arrival. Processor  208  receives information describing the wireless signal from receiver  204  and provides it to a network server using transceiver  210 .  
     [0030] Time-of-arrival detector  206  can be implemented in a number of different ways. In one embodiment, the function of the time-of-arrival detector is a separate module within the network access point device  200 . In other embodiments, time-of-arrival detector  206  is integrated into receiver  204 . In yet other embodiments, time-of-arrival detector  206  utilizes processing capabilities of processor  208  to perform its function.  
     [0031] Angle-of-arrival detector 2 l 4  can also be implemented in a number of different ways. In some embodiments, angle-of-arrival detector  214  is a circuit that receives signals from a phased-array antennal to measure the angle from which the signals are received. In these embodiments, antenna  220  represents a phased-array antenna. Many other mechanisms can be used to measure the angle-of-arrival of the wireless signal.  
     [0032] Processor  208  may be any type of processor suitable to perform actions to support the operation of network access point device  200 . For example, processor  208  may be a microprocessor, a microcontroller, or the like. Also for example, processor  208  may be a hardware controller or a collection of hardware controllers that perform specific task. Memory  212  represents an article that includes a machine-accessible medium. For example, memory  212  may represent any one or more of the following: a hard disk, a floppy disk, random access memory (RAM), read only memory (ROM), flash memory, CDROM, or any other type of article that includes a medium readable by a machine. Memory  212  may store instructions for performing the execution of the various method embodiments of the present invention. Memory  212  may also include data describing the current state of network access point device  200  and the entire network.  
     [0033] When multiple network access point devices  200  measure attributes of a single electromagnetic pulse, a network server may utilize this information to resolve the location of the network node from which the pulse originated. In some embodiments, multiple electromagnetic pulses are received by receiver  204 . The multiple electromagnetic pulses may represent any type of communication from a network node. For example, a group of pulses may represent a request from a network node to locate a particular asset. Also for example, a group of pulses may represent a different data communication from a network node. Receiver  204  derives information from groups of pulses, as well as from attributes describing the pulses. Processor  208  receives from receiver  204  information describing both groups of pulses as well as attributes of individual pulses. For example, processor  208  may receive data from a network node, as well as receiving time-of-arrival and angle-of-arrival information of pulses received by receiver  204 .  
     [0034]FIG. 3 shows a diagram of a network server suitable for use in a wireless network such as network  100  (FIG. 1). Server  300  includes processor  302 , memory  304 , and transceiver  306 . Transceiver  306  is coupled to media  116  at port  310 . As described above with reference to FIG. 1, media  116  couples the network server with any number of network access point devices such as network access point device  200  (FIG. 2). Transceiver  306  receives information from network access point devices on media  116 . In some embodiments, wireless signal attributes are received from multiple network access point devices, and processor  302  determines the location of a transmitter from which the wireless signals originated. Server  300  may be a personal computer (PC), server, mainframe, handheld device, portable computer, or any other system that may perform the operations described herein.  
     [0035] Memory  304  represents an article that includes a machine-accessible medium. For example, memory  304  may represent any one or more of the following: a hard disk, a floppy disk, random access memory (RAM), read only memory (ROM), flash memory, CDROM, or any other type of article that includes a medium readable by a machine. Memory  304  may store instructions for performing the execution of the various method embodiments of the present invention. Memory  304  may also include data describing the current state of server  300  and the entire network. For example, memory  304  may include data describing assets, asset serial numbers, locations of assets, as well as the locations of network nodes.  
     [0036]FIG. 4 shows a diagram of a mobile network node. Mobile network node  400  is a mobile network node suitable for use as mobile network node  120  (FIG. 1). Node  400  includes transceiver  402 , processor  404 , memory  406 , orientation unit  410 , and display  420 . Transceiver  402  includes a transmitter and receiver to communicate with a network on wireless link  430  using antenna  434 . As described above, transceiver  402  may communicate with a network using pulse-based wireless signals, modulated sinusoidal wireless signals, or any other suitable wireless signal protocol.  
     [0037] Processor  404  may be any type of processor capable of communicating with other portions of node  400 . As described above with reference to FIG. 1, node  400  may be one of many different types of devices, and this also true of processor  404 . For example, processor  404  may be a microprocessor, a microcontroller, or the like. Also for example, processor  404  may be a hardware controller or a collection of hardware controllers that perform a specific task.  
     [0038] Memory  406  represents an article that includes a machine-accessible medium. For example, memory  406  may represent any one or more of the following: a hard disk, a floppy disk, random access memory (RAM), read only memory (ROM), flash memory, CDROM, or any other type of article that includes a medium readable by a machine. Memory  406  may store instructions for performing the execution of the various method embodiments of the present invention.  
     [0039] Orientation unit  410  may be a device that allows node  400  to determine its physical orientation. In some embodiments, orientation unit  410  may be a compass, and in other embodiments, orientation unit  410  may be an accelerometer that is periodically reset. In these embodiments, processor  404  may determine the orientation of node  404  by reading a status of orientation unit  410 , and then utilize the orientation information when displaying information using display  420 .  
     [0040] Display  420  may be a display unit that displays information to a user. For example, in some embodiments, display  420  may be a visual display, and in other embodiments, display  420  may be a tactile display. Example visual and tactile displays are shown in FIGS. 6 and 7, and are described below with reference thereto. In some embodiments, display  420  may be used to display a direction to a tracked asset. For example, display  420  may display an arrow that points toward the tracked asset. When the orientation of node  400  is utilized for this purpose, the arrow that is displayed may be made to point toward the tracked asset regardless of the orientation of node  400 .  
     [0041]FIG. 5 shows a diagram of another mobile network node. Mobile network node  500  represents an embodiment of mobile network node  400  (FIG. 4) in which orientation unit  410  is implemented as transmitter  520  and antenna  534 . In some embodiments represented by FIG. 5, the mobile network node includes multiple transmitters ( 402 ,  520 ) and multiple antennas ( 434 ,  534 ). In other embodiments, transmitter  520  is omitted, and antenna  534  is coupled to transmitter  402 .  
     [0042] Antennas  434  and  534  are physically spaced apart, or “spatially diverse,” on mobile network node  500  such that a wireless network may separately determine the locations of the two antennas. For example, signals on wireless links  430  and  530  may be received by multiple network access points, such as those shown in FIG. 1, and the locations of antennas  434  and  534  may be determined separately. In these embodiments, the network determines the orientation of mobile network node  500  by determining the location of multiple, spatially diverse, antennas. The network may transmit information describing the orientation to the mobile network node. For example, signals on wireless link  430  may include orientation information transmitted to mobile network node  500  by the network.  
     [0043]FIG. 6 shows a perspective view of a tactile display. Tactile display  600  may be a display device that can be held by a user to provide tactile information regarding the direction to a tracked asset. Shown on tactile display  600  are a number of indicating elements including indicating elements  602  and  604 . Indicating element  604  is raised to indicate the direction to a tracked asset. The user holding display  600  may receive tactile feedback from indicating element  604  to direct the user toward the tracked asset.  
     [0044] Display  600  is a tactile display that is part of a mobile network node such as mobile network node  400  (FIG. 4) or mobile network node  500  (FIG. 5). As such, tactile display  600  may be used to display the direction to a tracked asset. As display  600  is rotated, a different indicating element may be raised to indicate the direction to the tracked asset. Because the orientation of the mobile network node is known, display  600  may properly indicate the direction to a tracked asset regardless of its orientation.  
     [0045]FIG. 7 shows a top view of a visual display. Display  700  is an example of a visual display that can display the direction to a tracked asset in either two or three dimensions. Included on display  700  is arrow  702 . As display  700  is rotated, arrow  702  rotates such that it continues to point in the direction of the tracked asset. In some embodiments, display  700  includes a grid or shape representing the environment in which display  700  operates. For example, in a warehouse environment, a series of aisles may appear on the display to help visually orient the user.  
     [0046] Display  700  may be a display device dedicated to the use of tracking assets, or may be a display device that is part of network node that is not dedicated to tracking assets. For example, in some embodiments, the mobile network node is a personal digital assistant (PDA), and display  700  is a display device used for many purposes such as reading e-mail, and navigating the Internet.  
     [0047]FIG. 8 shows a diagram of an asset tag. Asset tag  142  is an asset tag suitable for use in a mobile network such as network  100  (FIG. 1). Asset tag  142  includes transmitter  802 , controller  804 , and memory  806 . Transmitter  802  is a transmitter capable of transmitting wireless signals using antenna  810 . Referring now back to FIG. 1, asset tag  142  sends wireless signals to network access points, and the network determines the location of the asset tag. As shown in FIG. 1, asset tag  142  sends and receives wireless signals  152 ,  154 , and  156 .  
     [0048] Referring now back to FIG. 8, controller  804  may be any type of controller, and memory  806  may be any kind of memory. For example, controller  804  may be a microprocessor, a microcontroller, or the like. Also for example, controller  804  may be a hardware controller or a collection of hardware controllers that perform a specific task. Memory  806  represents an article that includes a machine-accessible medium. For example, memory  806  may represent any one or more of the following: a hard disk, a floppy disk, random access memory (RAM), read only memory (ROM), flash memory, CDROM, or any other type of article that includes a medium readable by a machine. Memory  806  may store instructions for performing the execution of the various method embodiments of the present invention. Memory  806  may also include information related to an asset such as a serial number or an asset description. In some embodiments, memory  806  may be a dedicated write-only memory that is inexpensively produced.  
     [0049]FIGS. 9 and 10 show flowcharts in accordance with various embodiments of the present invention. The flowcharts shown in FIGS. 9 and 10 illustrate various method embodiments that may be performed in an asset tracking network. In some embodiments, the methods may be performed by a server such as server  300  (FIG. 3) or by a mobile network node such as mobile network node  120  (FIG. 1). In other embodiments, the methods may be distributed across a server and network access point devices. The various actions shown in the figures may be performed in the order presented, or may be performed in a different order. Further, in some embodiments, some actions listed in the figures are omitted.  
     [0050] Referring now to FIG. 9, method  900  begins at  910  when information describing pulse-based wireless signals is received from a plurality of network access points devices. In some embodiments, this information includes time-of-arrival and/or angle-of-arrival information that describes the arrival time or arrival angle of pulses in the wireless signals. In some embodiments, block  910  corresponds to server  122  (FIG. 1) receiving information from the various network access points shown in FIG. 1. The wireless signal information referred to in block  910  may correspond to wireless signals transmitted from mobile network nodes and asset tags, such as mobile network node  120  and asset tag  142 . Further, the wireless signal information may include information describing multiple wireless signals received from a single mobile network node, such as mobile network node  500  (FIG. 5).  
     [0051] As shown in block  920 , an asset tag location is determined from the wireless signal information. This may be performed by resolving the location of the asset tag based on the information received from a plurality of network access point devices. The asset tag location may be resolved by triangulation. As shown in block  930 , the location of a network node is determined from the wireless signal information. This may be performed by triangulating the location of the mobile network node based on the information received from the plurality of network access points devices.  
     [0052] As shown in block  940 , the orientation of the network node is determined. This may be performed using many different possible mechanisms. For example, in some embodiments, the mobile network node transmits multiple signals from spatially diverse antennas. The antennas are spaced far enough apart such that the location of each can be determined separately, and the orientation of the network node may be determined therefrom. In other embodiments, the mobile network node includes an orientation unit that allows the mobile network node to determine its own orientation. Examples of such embodiments are described above with reference to FIG. 4. As shown in block  950 , information describing the orientation of the network node is sent to at least one of the plurality of network access point devices. This allows a network access point device to transmit the orientation information to a mobile network node, thereby allowing the mobile network node to determine the direction to a tracked asset and to display that direction correctly irrespective of the orientation of the mobile network node.  
     [0053]FIG. 10 shows a flowchart of a method for operating a mobile network node in a location-aware network. Method  1000  begins in Block  1010  when electromagnetic pulses are transmitted to a location-aware network. This corresponds to a mobile network node communicating with the network, such as mobile network node  120  transmitting signals to network access points (FIG. 1). In block  1020 , information describing an orientation of the mobile network node is retrieved. In some embodiments, this corresponds to reading a compass, and in other embodiments this corresponds to reading the status of an internally maintained accelerometer. In still further embodiments, this corresponds to receiving information from the location-aware network describing the orientation of the network node.  
     [0054] In block  1030 , information is received describing an asset tag location, and in block  1040  a direction to the asset tag is displayed. This corresponds to a mobile network node displaying tactile or visual data to aid a user in locating an asset.  
     [0055] It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.