HELICAL ANTENNAS IN LOCATION SYSTEMS

RELATED APPLICATIONS

This present invention claims priority to United States Patent Application No. 11/827,720 filed on July 12, 2007, which is a continuation-in-part of co-pending United States Patent Application No. 11/320,212 filed on December 27, 2005, the contents of which is incorporated by reference in its entirety.

BACKGROUND

It is useful to know the location of people or objects for several reasons. For example, knowledge about the location of a portable laptop computer combined with knowledge about the location of all the printers in a building can allow a system to automatically route a print job from the laptop computer to the nearest printer, thus saving time and aggravation.

Conventional location systems are generally based on one of two methods. In the first method, the amount of time is measured for a signal to travel from point A to point B, and then the distance between the two points A and B is calculated. In the second method, the conventional location systems calculate the distance between a transmitter and a receiver based on a received signal strength indication (RSSI). The RSSI is a function of distance and a path-loss factor: RSSI=k/d ^f where d is distance and f is the factor.

While the second method is conceptually simpler than the first method, the second method requires a transmitter or object identifier that has a consistent radiation power characteristic. The second method also requires a receiver that can receive signals consistently from the transmitter or object identifier. In the conventional location systems, the receiver employs a mono-pole or patch antenna that is either horizontally or vertically polarized. If the transmitter or object identifier is oriented such

that the transmitter antenna and receiver antenna are cross -polarized, the signals are significantly attenuated in the conventional location systems.

SUMMARY

There is a need for a receiver in location systems that can receive signals consistently and independently of the orientation or angle of a transmitter or object identifier relative to the receiver. The present invention provides a receiver that is able to receive signals with consistent sensitivity independently of the orientation or angle of a transmitter or object identifier relative to the receiver. The receiver may include a helical antenna that is circularly polarized to minimize the attenuation of the signals received from transmitter or object identifier. The helical antenna may receive signals from a transmitter or object identifier consistently so that the location of objects can be determined accurately.

In accordance with one aspect of the present invention, a receiver is provided for receiving signals from a transmitter. The receiver may include a helical antenna for receiving the signals from the transmitter. The receiver may also include a delta tap outputting signals from the helical antenna.

In accordance with another aspect of the present invention, an object location system is provided for identifying a location of an object. The location system includes an object identifier attached to an object for radiating a signal including information on a location of the object. The system also includes a receiver for receiving the signal consistently and independently of an orientation of the object identifier relative to the receiver. The receiver may include a helical antenna for receiving the signal from the transmitter. The helical antenna may include a delta-tap for outputting the signal from the helical antenna.

Brief Description of the Drawings

The aforementioned features and advantages, and other features and aspects of the present invention, will become better understood with regard to the following description and accompanying drawings, wherein:

Figure 1 illustrates an exemplary location system having an object identifier and a location determining module according to an exemplary embodiment;

Figure 2 illustrates an object identifier according to an exemplary embodiment; Figure 3 is a perspective view of an object identifier according to an exemplary embodiment;

Figures 4A-4C illustrate various methods of operation of an object identifier according to various embodiments;

Figure 5 illustrates a location determining module according to an exemplary embodiment;

Figure 6 illustrates a network connection element according to an exemplary embodiment;

Figure 7 depicts an exemplary helical antenna with a delta-tap. Figure 8 depicts a test environment for testing the exemplary helical antenna. Figure 9 depicts the results of the radiation test of the exemplary helical antenna.

Figure 10 depicts the standing wave ratio (SWR) of the exemplary helical antenna.

Figure HA illustrates a location resolver according to an exemplary embodiment; and

Figure HB provides a method of operation of a location resolver according to an exemplary embodiment.

DETAILED DESCRIPTION

An exemplary embodiment of the present invention may provide a location system that can be used to locate people or objects in a space, primarily indoors. In an exemplary embodiment, an array of sensors or receivers may pick up energy transmitted

from a device (tag), such as an object identifier and a transmitter, coupled to the people or objects. The examples of types of this energy may include infrared (IR), radio- frequency (RF) and ultrasonic (US). The location system may process the data obtained from the sensors or receivers using one or more computational techniques to determine the location of the people or objects. These computational techniques include, but are not limited to, triangulation, multilateration, signal strength and time-of-arrival calculations.

An exemplary embodiment may provide location systems that can receive signals consistently and independently of the orientation or angle of a transmitter or object identifier relative to a receiver. The receiver may include an antenna that is circularly polarized to be able to receive signals with consistent sensitivity independently of the orientation or angle of the transmitter or object identifier relative to the receiver. The circularly polarized antenna may minimize the attenuation of the signals received in the receiver so that the location of objects can be determined accurately. In an exemplary embodiment, the receiver may include a helical antenna with a delta-tap for outputting signals from the helical antenna.

Figure 1 is an exemplary location system 100 provided in an exemplary embodiment. The exemplary location system 100 may include an object identifier 200 and a location determining module 300. The object identifier 200 may be coupled to an object such that a location of the object corresponds to the location of the object identifier 200. The object identifier 200 may be any device capable of transmitting a signal for use in identifying a location of an object. In an exemplary embodiment, the object identifier 200 can be implemented in an electronic device. The electronic device may take many forms of, for example, a portable computer, a personal digital assistant, a communication device, such as a cellular phone, a receiver, a transmitter, an interface or any combination of these devices.

According to various embodiments, the object identifier 200 may transmit two identifiers, one identifier corresponding to the particular object identifier 200 and a second identifier which is a group designator. While the identifiers may be in many forms, some examples, according to various embodiments, include numbers, letters,

URLs, MAC addresses and IP addresses. The object identifier 200 will be described below in more detail with reference to Figures 2, 3, and 4A-4C.

According to an exemplary embodiment, the location determining module 300 may include any structure suitable for determining location. Examples include any device with intelligence to determine the location of one or more object identifiers. According to various embodiments, the location determining module 300 may include one or more, or combinations, of each of the following: a network connection element, a fixed location identifier, a location resolver, a database, topology data, an electronic device, a web interface, a network interface, a specialized network interface, an implementation interface, a database interface, a network and/or a specialized network, a receiver and/or a transmitter. According to various embodiments, the location determining module 300 may have only a receiver, only a transmitter, both a receiver and a transmitter, and additional hardware if desired. It will be apparent to one of ordinary skill in the art that one or more components may be distributed in a wide variety of configurations.

According to various embodiments, the present invention may be used to determine a location of an object with the location determining module 300, or of the module 300 itself. In such an exemplary embodiment, the location determining module 300 may be a mobile module, capable of determining its own location relative to one or more object identifiers. In such an exemplary embodiment, the object identifiers may be fixed. Optionally, the object identifiers may be moving. One example of the use of a mobile location determining module 300 involves a location system configured to determine locations within a large area. If such a large area is populated by a small number of objects, the components of such a location system may be more efficiently configured by providing functionality of a location determining module 300 with each object. In such a case, object identifiers could be distributed throughout the large area. The location determining module 300 could then be adapted to receive location signals from the object identifiers and thereby determine a location of the location determining module 300. In this embodiment, the location of the objects is determined relative to the location of one or more object identifiers, although the locations of the object identifiers

may be known, allowing locations of objects to be determined relative to other references or by name, such as a location on a map or a specific room.

The configuration above is contrasted with another embodiment, better suited to environments with a greater number of objects in a smaller area. In such an exemplary embodiment, each object may be provided with an object identifier. One or more location determining modules may then be located within the area to receive location signals transmitted by the object identifiers. In this embodiment, the location of the objects may be determined by determining the location of the object identifiers.

According to various embodiments, the location determining module 300 may be capable of performing additional functionality, such as receiving requests for information, providing information, storing information, commanding actions in response to location information, associating objects with other objects or with locations, establishing privacy conditions regarding availability of location information, interfacing directly with various network types, and the like. According to further embodiments, the location determining module 300 may include multiple, distributed receivers, some of which may be connected to a network, and others not connected to a network. According to various embodiments, the object identifier 200 and location determining module 300 may utilize both RF signals and IR signals for the determination of location.

According to an exemplary embodiment, the location determining module 300 may include one or more databases. The databases may store information relating to current location of object identifiers, fixed location identifiers and network connection elements. The databases will be described below in more detail with reference to Figure 6.

According to various embodiments, the location system 100 may be employed within an enclosed structure and hence can be applied to as an indoor positioning system. Enclosed structures include buildings, such as office buildings, exhibition halls, health care institutions, homes or other structures. According to other embodiments, the invention may be used outside of enclosed structures or may be used both concurrently within and outside enclosed structures.

Figure 2 is an exemplary object identifier 200 used in an exemplary embodiment. The object identifier 200 is provided with a controller 210 and controller support 220. The controller support 220 may include various items such as a power supply, such as a battery or other apparatus to provide electrical power, memory and/or various time keeping circuitry such as an oscillator. Controller support 220 may optionally include non-volatile memory. Various components of the controller support 220 may optionally be incorporated into the controller 210 or may be provided from an external source, outside the object identifier 200.

According to an exemplary embodiment, the object identifier 200 may be provided with an RF transmitter 230 and/or an IR transmitter 240 for transmitting RF and/or IR signals from the object identifier 200. According to another embodiment, the object identifier 200 may also be provided with an RF receiver 250 and/or an IR receiver 260 for receiving RF and/or IR signals in the object identifier 200. The RF transmitter 230 and/or the RF receiver 250 may be coupled to an antenna 290 for radiating or receiving the RF signals. The antenna 290 may be a loop antenna, which is described in more detail in co-pending United States Patent Application No. 11/320,212 filed on December 27, 2005.

The object identifier 200 may also be provided with an input device 270. Examples of input devices include buttons, switches, keypads, ports for electrical or optical communication with other devices, sensors, such as photocell cameras or microphones. Other types of input devices 270 may be apparent to one of ordinary skill in the art upon reading this disclosure and are to be considered within the scope of the invention. One or more input devices 270 are configured to provide input to the controller 210 in order to allow the controller 210 to take an action, not take an action, or to forward information outside the object identifier 200 by way of an RF transmitter 230 and/or an IR transmitter 240.

According to a further embodiment, an indicator 280 may be provided to enable the controller 210 to output information in the proximity of the object identifier 200. Examples of indicators 280 include visual, audio and vibration devices. Examples of

these include buzzers, bells, horns, LEDs, other forms of lights and/or displays. The indicator 280 may be configured to display or output information determined by the controller 210 or received by the controller 210 through the input device 270, RF receiver 250 and/or the IR receiver 260.

Figure 3 depicts a perspective view of an object identifier in an exemplary embodiment. The object identifier 200 is illustrated with two indicators 280 in the form of two LEDs. Three input devices 270 are also illustrated in the form of switches. Two switches are illustrated so as to correspond to the two indicators 280, while the third switch 270 is illustrated on an opposing surface of the object identifier 200. According to this exemplary embodiment, the input device 270 on the lower surface of the object identifier 200 is normally pushed in when the object identifier 200 is attached to an object. Upon removal from the object, the input device 270 extends, resulting in a change of position of the input device 270. This embodiment allows the controller 210 to be alerted when the object identifier 200 is removed from an object. Each of the indicators 280 may be configured to illuminate upon the activation of the corresponding switches, input devices 270, so as to allow visual confirmation of the activation of one of the switches. Various uses of these switches will become apparent to one of ordinary skill in the art. Several examples, by way of illustration, include panic alerts, causing the processor 210 to emit a specialized signal through at least one of the RF transmitter 230 and the IR transmitter 240. A further example may involve an ability to configure a portion of the location system 100 remotely by the activation of the input devices 270.

Figures 4A, 4B and 4C illustrate, according to various embodiments, various examples of a transmission of signals from the object identifier 200. A first method 402 is illustrated in Figure 4A according to an exemplary embodiment. An RF power level is set to Pn (step 404). An IR signal is transmitted (step 406). The delay of m seconds then occurs (step 408). An RF signal is transmitted (step 412). A further delay of x seconds occurs (step 414). Pn is then incremented (step 416). This method 402 provides a substantially consistent IR power level, while varying an RF power level.

Varying the RF power level may assist in determining a location of the object identifier 200 by enabling the location determining module 300, and in particular the network connection element 600 or location determining module 300 to receive less than all of

the RF signals. According to an exemplary embodiment, one or both of the IR and RF signals are also transmitting information. Examples of this information may include the signal strength being transmitted, the period between transmissions, the length of time of the transmissions, various identifiers, corresponding to the object identifier 200, information received from one or more input devices 270 and/or various status information, such as those pertaining to the controller 210 controller sport 220 or other components of the object identifier 200. According to one embodiment the RF signal is transmitted every ten seconds and the IR signal is transmitted every twenty seconds.

Determination of the frequency and length of the transmissions involves considerations including battery life precision of location, frequency of updates to location, interference among signal transmissions and network traffic.

A further method 422 of an exemplary embodiment is illustrated in Figure 4B. According to this embodiment, an RF signal is transmitted (step 424) and a delay occurs before the next transmission of an RF signal (step 426). Independently of the RF transmission, an IR signal is transmitted (step 428). The IR transmission may occur simultaneously with the transmission of the RF signal but this embodiment is not so limited. The transmission of the IR signal may occur at any time relative to the transmission of the RF signal. A delay of c seconds occurs before the next transmission of the RF signal (step 432).

According to a further embodiment, a further method 442 is illustrated by way of example in Figure 4C. According to this embodiment, an RF signal is transmitted (step 444) and an IR signal is transmitted (step 446). According to an alternative embodiment, a transmission in another medium may also occur (step 448). Examples of other mediums include ultra-sonic (US), visual light, or audible sound. According to the method 442 of Figure 4C, transmissions may be continuous, variable or occur at regular intervals. The transmissions among various mediums may be synchronized or random relative to transmissions in other mediums.

Figure 5 is a detailed block diagram of the location determining module 300 according to an exemplary embodiment. The object identifier 200 is in communication with the location determining module 300 that include at least a network connection

element 600. According to an exemplary embodiment, the object identifier 200 is physically coupled to an object so that the location of the object identifier 200 is considered to be the location of the object. According to another embodiment, the location of the object may be determined by locating one or more object identifiers 200 in an area and coupling a network connection element 600 to an object. In such an exemplary embodiment, the location of the network connection element 600, and hence the object, is determined relative to the one or more object identifiers 200. The network connection element 600 is configured to be coupled to a network 500. The network 500 may be a local area network (LAN), a wide area network (WAN), the Internet, an intranet, or a metropolitan network. The network may be a wireless network such as a Bluetooth network, a cellular network, a GSM based network, a hard wired network, or some other type of network. According to an optional embodiment, the network may be a wireless network. One or more object identifiers 200 may communicate to the network connection element 600. According to another embodiment, the network connection element 600 may communicate back to the object identifier 200.

According to a further embodiment, the location determining module 300 may include a fixed location identifier 510. Those of ordinary skill in the art will recognize that the fixed location identifier 510 can be separate from the module 300. The fixed location identifier 510 is configured to receive signals from one or more object identifiers 200 and to retransmit that information. The retransmitted information may be received by the network connection element 600. According to one embodiment, the retransmitted information includes the information provided by the object identifier 200, coupled with additional information to identify the fixed location identifier 510 that is re-transmitting the information. According to an exemplary embodiment, a plurality of network connection elements 600, fixed location identifiers 510 and object identifiers 200 may be provided in the location system 100. In such a case, the network 500 may provide communication among the network connection elements 600 in order to determine the location of one or more object identifiers 200 by one or more network connection elements 600 or by the use of other devices coupled to the network 500.

As shown by way of example, a location determining module 300, according to an exemplary embodiment, is illustrated, by way of example, as including the network connection element 600, the fixed location identifier 510 and the network 500. One or ordinary skill in the art will appreciate that the location determining module 300 may not include one or more of these elements in other embodiments.

According to an exemplary embodiment, the object identifier 200 and/or fixed location identifier 510 transmits various information. According to an exemplary embodiment, this information is transmitted over both RF and IR signals. Optionally, the information may be transmitted over only one signal. According to an exemplary embodiment, examples of the information transmitted may include one or all of the following: RF power level; IR power level; battery level; input device status; transmission frequency, e.g. repetition rate, for any or all types of transmissions, such as IR and/or RF; an identifier corresponding to the transmitting device; an identifier corresponding to a group to which the transmitting device is associated; any information received from another system component; status or condition information; or the like. According to an exemplary embodiment, some information may be repeated over multiple signal transmissions. Examples include transmitting input device status over ten transmissions to increase the likelihood of receipt by other components of the location system.

According to another embodiment, the location system 100 can include a location resolver 1100 provided for communication with the network connection element 600. In this embodiment, the location resolver 1100 communicates with one or more network connection elements 600, or if desired other system components, to obtain information pertaining to the location of one or more object identifiers 200 and one or more optional fixed location identifiers 510. The location resolver 1100 may be provided in the form of software or hardware or a combination of both. The location resolver 1100 may communicate with one or more network connection elements 600 over a network 500. The location resolver 1100 may directly be coupled to one or more network connection elements 600 in other embodiments.

As shown by way of example, the location determining module 300, according to an exemplary embodiment, is illustrated, by way of example, as including the network connection element 600, the location resolver 1100 and the fixed location identifier 510. In this embodiment, the network 500 is included in the location determining module 300, although this need not be the case, and the location resolver 1100 may communicate with the location determining module 300 directly or over the network 500. The location resolver 1100 will be described below in more detail with reference to Figures HA and HB.

Figure 6 depicts an example of a network connection element 600 according to an exemplary embodiment. A network connection element 600 can include one or more components similar to those of the object identifier 200 illustrated by way of example in Figure 2. A network connection element 600 is provided with a controller 610 and a controller support 620. Controller support 620 may optionally include non- volatile memory. Optionally, various embodiments may include an input device 670 and/or an indicator 680.

The network connection element 600 is adapted to receive signals from the object identifier 200. According to an exemplary embodiment, the network connection element 600 contains hardware and software capable of receiving signals from other components of the location system, such as an object identifier 200, other network connection elements 600. According to an exemplary embodiment, the network connection element 600 may have network connectivity software, a local web server, object identifier analysis software, software to transmit the results of an object identifier analysis to a remote server, DHCP software and local permanent storage. According to an exemplary embodiment, the network connection element 600 may also include configuration, service and debug applets to be used in the maintenance and configuration of the object identifier 200.

The network connection element 600, according to an exemplary embodiment, may further be provided with a web server 694. The web server 694 of network connection element 600 is able to provide or receive information or commands. In

various embodiments, the web server 694 may allow for control and configuration of any component of the location system.

According to a further embodiment, the network connection element 600 may be provided with a network interface 692. The network interface 692 is configured to couple the controller to a network 500. According to an exemplary embodiment, the network interface 692 is adapted to packetize buffered information received and send this information as a group, thereby providing more efficient network usage in some applications.

A further embodiment provides a database 696 in communication with then controller 610 of the network connection element 600. The database 696 may be provided within the network connection element 600 or may be provided on a network 500. According to alternative embodiment, the database 696 may be provided within the network connection element 600 and also in direct communication with the network 500.

According to an exemplary embodiment, the network connection element 600 may include an RF receiver 630, an IR receiver 640, an RF transmitter 650, an IR transmitter 660. The RF transmitter 650 and the IR transmitter 660 may transmit RF and IR signals from the network connection element 600. The RF receiver 630 and IR receiver 640 may receive RF and IR signals in the network connection element 600. The RF transmitter 650 and the RF receiver 630 may be coupled to an antenna 690 for radiating or receiving the RF signals. The antenna 690 may be a helical antenna, which will be described below in more detail with reference to Figures 7-10.

Figure 7 shows an exemplary helical antenna 710 that can be utilized in an exemplary embodiment. The body of the helical antenna 710 can be formed using a conducting wire coiled in the form of a helix or spiral. The direction of the coil determines the polarization of the antenna, while the space (S) between the coils and the diameter (D) of the coils determine the wavelength of the antenna. The polarization of an antenna refers to the polarization of the wave radiated by the antenna in a given

direction so that the polarization of an antenna can be determined by the wave radiated from the antenna.

As shown in Figure 7, the helical antenna 710 includes a delta-tap or delta-feed 720 for feeding signals to, or for receiving signals from, the helical antenna 710. Signals can be applied to or received from the helical antenna 710 through the delta-tap or delta- feed 720. The delta-tap 720 may be connected to circuitry, such as the RF transmitter 650 and the RF receiver 630 (Figure 6), to transmit and receive signals through the helical antenna 710. The helical antenna 710 can have either a clockwise (right-handed) or counter-clockwise (left-handed) polarization and receive signals with any type of plane polarization, such as horizontal or vertical polarization. That is, the helical antenna 710 can receive signals consistently and indepndently of the polarization of an antenna from which the signals are transmitted.

Figure 8 depicts an exemplary helical antenna that can radiate and receive signals consistently and independently of the polarization of the signals. The helical antenna 720 can be placed vertically so that the helical antenna has the z-axis as the axis of the antenna. The coils of the helical antenna are substantially parallel to the horizontal plane (x-y plane), which is substantially parallel to a ground plane. Signals are fed to or received from the helical antenna through the delta-tap or delta-feed 720.

A helical antenna may operate in a normal mode or in an axial mode. In a normal mode, radiation is most intense normal to the axis of the helical antenna (x-axis). The normal mode can occur when the diameter (D) of the coils is small compared to a particular wavelength. In an axial mode, the helical antenna may provide a maximum radiation along the axis of the antenna (z-axis). The axial mode can occur when the circumference of a coil is on the order of a wavelength. In a practical implementation, the helical antenna can be quite small when operating in the normal mode while the helical antenna may be of a larger size when operating in the axial mode. Those of ordinary skill in the art will appreciate that although an exemplary embodiment tests the helical antenna in a normal mode, the scope of the present invention is not limited to the normal mode and the helical antenna can operate in an axial mode.

Figure 9 depicts the results of a radiation test of the helical antenna operating at 443.65MHz. Figure 9 shows azimuthal radiation patterns plotted with a reference level of OdB at the outer ring and an elevation angle of zero degrees. The first plot 910 represents the total field of the radiation while the second plot 920 and the third plot 930 represent a horizontally polarized and a vertically polarized radiation pattern, respectively. In particular, the second plot 920 shows a gain of -5.03dB at an azimuth angle of 270 degrees and the third plot 930 shows a gain of -5.1 IdB at an azimuth angle of 90 degrees. In Figure 9, the plots 910, 920, 930 are relatively close to each other, which indicates that the helical antenna consistently radiates and receives signals independently of the polarization of the signals.

Although the foregoing test was performed at 443.65MHz in the exemplary embodiment, the helical antenna can operate across a wide spectrum or range of frequencies. Preferably, the helical antenna is useful in a UHF spectrum or range.

Figure 10 shows an exemplary standing wave ratio (SWR) of the helical antenna depicted in Figure 8. The SWR can be defined as the ratio of maximum power to minimum power to indicate reflected waves bouncing back to the signal source. An increase in SWR may correspond to an increase in power in the line beyond the actual transmitted power. The increased power may increase RF losses. A SWR of 1:1 may be ideal. Figure 10 shows that the helical antenna 710 with a delta feed 720 has low SWR around 443MHz and 444MHz, which are within the UHF spectrum.

Figure 11 depicts an example of the location resolver 1100 provided in an exemplary embodiment. As shown in Figure 11, a controller 1110 is provided in communication with a network interface 1120. The network interface 1120 is adapted to be coupled to the network 500. Controller support may also be optionally provided. A web server 1130 is provided in communication with a controller 1110. The web server 1130 of the location resolver 1100 is similar to the web server 694 of the network connection element 600, discussed herein.

According to an exemplary embodiment, the location resolver 1100 may be provided with a configuration capability to configure other components of the location system. For example, an exemplary embodiment of the location resolver 1100 may perform some or all of the following functions: reset system time; reset communications; disable all or selected input devices of all or selected components, such as object identifiers, fixed location identifiers, network connection elements; establish and/or cancel associations between all or selected components; establish and/or cancel privacy settings for specific location information; configure network communication protocols; configure receiver and/or transmitter configurations, altering or eliminating signals, signal types, such as RF, IR, ultrasonic, or the like, or transmission frequencies and the frequencies at which transmissions are expected; receive information on the location of the object identifier; determine or calculate the location of the object identifier 200.

An implementation interface 1140 is also provided in communication with controller 1110. The implementation interface 1140 is provided to communicate with other devices in order to allow for the communication of location information and/or initiation or response to commands as described herein. Various examples of implementation interfaces 1140 include XML and SMTP protocols, other examples may be apparent to those of ordinary skill in the art.

A database 1150 is also provided either within the location resolver 1100 or external the location resolver 1100. The database 1150 is adapted to store information relating to the location of one or more object identifiers 200 and/or optional fixed location identifiers 510 and/or network connection elements 600. According to various embodiments, the database 1150 may store current and/or previous location and status information of location system components, associations of location system components with each other or locations, privacy protocols and status, topology data indicating locations of some or all location system components relative to each other, or in other descriptive terms, such as room or location names or by a coordinate system.

A database interface 1155 may be provided in another embodiment in order to facilitate interaction between the database 1150 and the controller 1110. The database interface 1155 may be a network or other hardware or software to controller 1110 to

enable the controller 1110 to access the database 1150. Various examples of database interfaces 1155 include JDBC and ODBC, other examples may be apparent to those of ordinary skill in the art.

Figure HB is an example of a flow chart showing a method 1102 of operation of the location resolver 1100 in an exemplary embodiment. The location resolver 1100 initially waits for input from a receiver, such as the network connection element 600 (step 1104). The location resolver 1100 then determines whether an IR signal is received (step 1106). If an IR signal is received, data received from the transmitter and receiver's location is made available (step 1108). If an IR signal is not received, the location resolver 1100 checks to see if an RF signal is received (step 1112). Location resolver 1100 also checks to see if an RF signal is received after making any data available from the reception of an IR signal available. If an RF signal is not received, the location resolver 1100 according to an exemplary embodiment returns again to wait for further input from the network connection element 600. If an RF signal is received, the location resolver 1100 determines the strength of the received RF signal using the peak picking method provided in an exemplary embodiment (step 1113). The peak picking method is described in more detail in co-pending United States Patent Application No. 11/320,212 filed on December 27, 2005. If the strength of the received RF signal is determined, the location resolver 1100 determines whether the RF signal power is high (step 1114). If so, data received from the transmitter is made available with a message indicating that the object identifier is within a large radius of the network connection element 600 (step 1116). If the RF signal power is not high, the location resolver 1100 determines whether the RF signal power is medium (step 1118). If so, data received from the object identifier is made available with a message that the object identifier is within a smaller radius of the network connection element 600 (step 1122). If the RF signal power is not medium, the location resolver 1100 determines whether the RF signal power is low (step 1124). If so, data from the object identifier 200 is made available with an indication that the object identifier is within a smaller radius of the network connection element 600 (step 1126). The location resolver 1100 then returns to await further input from one or more of the network connection elements 600 (step 1104).

It is understood that the method 12 may be accomplished by using transmitters or object identifiers that vary in output power or by constant power output transmitters. In using constant power output transmitters, received signal strength is categorized according to signal strength, such as by the use of a histogram. According to an exemplary embodiment, the network connection element 600 classifies signal strength within specific ranges and may pass an indication of the appropriate range to other location system components. According to another embodiment, the network connection element 600 provides a signal strength value that may be passed to other location system components, such as the location resolver 1100, allowing more precise analysis of received signal strength information.

A method of operation of the location resolver 1100 involves multilateration. Multilateration determines location by determining range from a relative location. Multilateration can be performed by a single receiver, but is best accomplished by multiple receivers. An object can infer the location of another object by calculating its range from one or more beacons with known locations using some type of signal measurement. According to an exemplary embodiment RF signal strength is used to determine location. The consistent signal strength enables objects of all types and materials to be accurately tracked independently of mounting the object identifier on conductive objects.

According to a further embodiment both RF and IR are used to determine location. It is understood that an absence of a signal that is expected is considered a signal for purposes of determining location. For example, receipt of an RF signal but not an IR signal may indicate a transmitter is out of IR range but within RF range, or just out of line-of- sight if required for lower-powered IR transmissions. The receiver may be configured to expect both RF and IR transmissions at specific intervals generally or for a specific transmitter. This is one example of the use of both RF and IR for determination of location.

In addition to current signal information, other information may be used in determining location. Previous location information may also be used in determining current location. Locations of other location system components may also be used in

determining location. For example, locations of one or more network connection elements 600, one or more fixed location identifiers 510 and other object identifiers 200 may be used in determining location of a particular location system component. According to one embodiment, establishing relative distances between additional nearby components and the component for which location information is desired assist in establishing a location with greater particularity.

According to an exemplary embodiment, transmission rates may vary among different types of object identifiers. Transmission rates may be adjusted in relation to the type of object for which location information is desired. Examples include low transmission rates for objects typically stationary, such as equipment typically found in a particular room. Whereas people, or mobile equipment may be better tracked by more frequent signal transmissions.

Another method of determining location involves at least one Bayesian network.

A further method of determining location involves triangulation. An example of one or more of the foregoing methodologies are described, for example, in U.S. Patent No. 5,774,876, which is incorporated herein by reference. Bayesian networks are also described in Castro, Paul et al. "A Probabilistic Room Location Service for Wireless Networked Environments" In: Ubicomp 2001: Ubiquitous Computing, Third

International Conference, Atlanta, Georgia, USA, September 30 - October 2, 2001 Proceedings. Edited by G.D. Abowd, et al. Heidelberg, Germany: Springer- Verlag, 2001, LNCS 2201, p. 18 ff. This publication is incorporated herein by reference. Combinations of these methods or other methods of location determination may be apparent to one of ordinary skill in the art and are included within the scope of the invention.

Privacy conditions may be established regarding location information for one or more location system components. Privacy may be accomplished in a variety of ways. For example, privacy may be accomplished by not making location information available or by not determining location information. Privacy may be managed by an opt-out protocol, requiring an action to establish privacy. Privacy may be managed by an opt-in protocol, requiring an action to cancel privacy. A not-opt-out protocol may

also be used, preventing action from establishing privacy. Various protocols may be used in combination within a location system. Different location system components may subject to different protocols. Examples include various groups of object identifiers being subject to different protocols, such as some people able to select a privacy protocol or a privacy status, such as privacy or no privacy, while object identifiers used to locate equipment may be subject to a not-opt-out protocol. According to an exemplary embodiment, protocols or privacy status may be assigned through a batch- processing capability in a user interface. According to another embodiment, privacy status for opt-in or opt-out protocols may be accomplished by an input device incorporated in the location system component. Optionally, privacy status may be confirmed by an indicator incorporated in the location system component.

Associations associating objects with other objects or with locations may be established. Examples of the use of associations include: determining procedure times, room utilization, proximity alerts that may be used to alert a fall of a person, regulatory compliance, person & equipment associations, location & equipment associations, friend & foe associations, and automatic billing. According to an exemplary embodiment, association information may be stored in a database. Associations may be performed through a batch-processing capability in a user interface. According to another embodiment, associations may be accomplished by an input device incorporated in the location system component. Optionally, association status may be confirmed by an indicator incorporated in the location system component. One example involves activating an input device on an object identifier, fixed location identifier or network connection element. An indicator indicates, such as by an LED or sound, that association can be performed. An input device may then be activated within a limited time on another location system component, such as an object identifier, to establish an association between the components.

Events or actions may be initiated based on location information association information or input device status, or changes in any of these. One example involves sending information in response to an object identifier being within a range of locations or a specific location. An example includes paging a doctor when a specific patient enters a treatment area. Other examples of actions include entering information in a

database, sending XML data containing the current location data and status of a location system component onto the network. An example is the use of a cardiac monitoring application typically used in a health care institution for receiving a report of a cardiac arrest. The term health care institution, as used herein, includes a wide variety of facilities associated with providing health care or services. Examples include hospitals, managed care facilities, assisted care facilities and clinics. The location system according to an exemplary embodiment may be configured to receive a request for the location of a particular patient, or the cardiac monitoring equipment sounding the alarm. The location system can then automatically reply with location information to assist health care institution staff in locating the patient in need. A similar example could use the activation of an input device on an object identifier as a distress call by a patient, with the alert and location information forwarded to a health care institution communication system for prompt attention by health care institution staff. One embodiment may interface with a Winegard interface to unlock a door, or activate other security equipment, in response to location information or input device status. Other examples include pages, WAP messages, sending e-mails and activating or canceling alarms.

The present invention has been described by way of example, and modifications and variations of the described embodiments will suggest themselves to skilled artisans in this field without departing from the spirit of the invention. Aspects and characteristics of the above-described embodiments may be used in combination. The described embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is to be measured by the appended claims, rather than the preceding description, and all variations and equivalents that fall within the range of the claims are intended to be embraced therein.