Patent Publication Number: US-11665505-B2

Title: Identifying and locating users on a mobile network

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to remotely communicating with a mobile device such as a mobile telephone or a media player and more specifically, to cause a mobile device to perform a function through the transmission of one or more remote commands. 
     2. Introduction 
     Mobile devices have been adapted to a wide variety of applications, including computing, communication, and entertainment. Through recent improvements, mobile devices can now also determine their geographic location by either using a built-in global position system (GPS) antenna or extrapolating its location from the signals it receives through the network of fixed-location cellular antennas. Thus, a user may be able to use the mobile device to determine his or her location. 
     A mobile device user may wish to have friends or family members know of his or her location and likewise, he or she may like to know the location of his or her friends or family members. Several known systems perform such services. However, one drawback of such services is that determining locations, particularly when using GPS devices, may consume a lot of power. 
     Balancing battery life and mobile device performance is a chief concern for mobile device makers, and location aware programs are a big part of those concerns. Specifically, applications that must make frequent requests of a GPS device consume a lot of power. Such applications include mapping programs, and social location aware applications such as FOURSQUARE and GOOGLE LATITUDE, which allow a user to share his location with a server so that authorized friends can view the user&#39;s location on their mobile devices. Frequently, such services require an application running on the user&#39;s mobile device to periodically activate the GPS device, learn the user&#39;s location, and update the server. Such repeated use of the GPS device drastically reduces the battery life of the mobile device. 
     SUMMARY 
     Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or can be learned by practice of the herein disclosed principles. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the disclosure will become more fully apparent from the following description and appended claims, or can be learned by the practice of the principles set forth herein. 
     Disclosed are systems, methods, and non-transitory computer-readable storage media for determining the location of one or more mobile devices connected to a communications network. The present technology provides a system for allowing users to learn the location of other users whom have given permission to have their location shared. In a preferred embodiment a user can launch an application which allows a user to request permission from a friend to receive information describing their location. The application can list the friends whom have given their permission to a user to view their location information. 
     When a user desires to see the location of one or more friends, the application can request location information for each friend, or selected friends, from a system server. The server can receive and interpret the request to determine whether the application requires detailed location information or approximate location information. For example, if the application has requested location information for all friends, it would be interpreted as a request for only approximate information because, among other reasons, displaying all friends on a map on a computer screen only requires approximate locations. However, if the application recently received updated approximate information regarding a particular friend, but is now requesting additional location information on just that specific friend, it is likely that the application requires detailed location information. 
     The difference in detailed location information versus approximate location information is based in not only a threshold of tolerated variance of the location information but also time since updated location information was received by the server, and the power required to learn accurate location information by the friend&#39;s device. For example, detailed location information might require an accuracy of +/−3 m, and with present technology, such accuracy is most often obtained using a GPS device. Additionally, detailed location information might only be considered accurate for a duration of 1 minute or less. In contrast, approximate location information may only require a city level of accuracy (e.g., +/−1 km) and be deemed relevant for up to 15 minutes or more. 
     A request to locate a friend is processed by a central server. Upon receiving a request, the server may forward the request to the friend&#39;s device and wait for a response. Alternatively, the server may respond to the request without contacting the friend&#39;s device. For example, the server may have cached location information of the friend&#39;s device. Because location information is only relevant at certain accuracies and for a certain period of time, the server may compare the cached information with the request and/or any predetermined constraints before sending the cached location information rather than sending a request to the friend&#39;s device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only exemplary embodiments of the disclosure and are not therefore to be considered to be limiting of its scope, the principles herein are described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG.  1    illustrates an example system embodiment; 
         FIG.  2    illustrates an exemplary computing environment; 
         FIGS.  3   a  and  3   b    illustrate flow diagrams describing exemplary processes for locating a mobile device; 
         FIG.  4    illustrates a flow diagram describing an exemplary process for locating a mobile device and updating the location information; 
         FIG.  5    illustrates a flow diagram describing an exemplary process for sending an invitation to a mobile device user to share location information; 
         FIGS.  6 - 12    illustrate exemplary user interfaces depicting how a user may locate friends; 
         FIGS.  13 - 15    illustrate exemplary user interfaces depicting how a user may send to friends invitations to be located; 
         FIGS.  16 - 17    illustrate exemplary user interfaces depicting how a user may receive and respond to an invitation to be located; and 
         FIGS.  18 - 20    illustrate exemplary user interfaces depicting how a user may change his or her location information. 
         FIGS.  21 - 24    illustrate exemplary user interfaces depicting how an invitation to share location information until an expiration time may be configured and displayed. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the disclosure. 
     The present disclosure addresses the need in the art for a mechanism for transmitting location information of a user&#39;s mobile device and locating friends and family members through their respective mobile devices. A system, method and non-transitory computer-readable media are disclosed which locate a mobile device by sending a command to the device to determine its present location and report it back to the requestor. A brief introductory description of a basic general purpose system or computing device in  FIG.  1    which can be employed to practice the concepts is disclosed herein. A more detailed description of the methods and systems will then follow. 
     With reference to  FIG.  1   , an exemplary system  100  includes a general-purpose computing device  100 , including a processing unit (CPU or processor)  120  and a system bus  110  that couples various system components including the system memory  130  such as read only memory (ROM)  140  and random access memory (RAM)  150  to the processor  120 . The system  100  can include a cache  122  of high speed memory connected directly with, in close proximity to, or integrated as part of the processor  120 . The system  100  copies data from the memory  130  and/or the storage device  160  to the cache  122  for quick access by the processor  120 . In this way, the cache  122  provides a performance boost that avoids processor  120  delays while waiting for data. These and other modules can control or be configured to control the processor  120  to perform various actions. Other system memory  130  may be available for use as well. The memory  130  can include multiple different types of memory with different performance characteristics. It can be appreciated that the disclosure may operate on a computing device  100  with more than one processor  120  or on a group or cluster of computing devices networked together to provide greater processing capability. The processor  120  can include any general purpose processor and a hardware module or software module, such as module  1   162 , module  2   164 , and module  3   166  stored in storage device  160 , configured to control the processor  120  as well as a special-purpose processor where software instructions are incorporated into the actual processor design. The processor  120  may essentially be a completely self-contained computing system, containing multiple cores or processors, a bus, memory controller, cache, etc. A multi-core processor may be symmetric or asymmetric. 
     The system bus  110  may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. A basic input/output (BIOS) stored in ROM  140  or the like, may provide the basic routine that helps to transfer information between elements within the computing device  100 , such as during start-up. The computing device  100  further includes storage devices  160  such as a hard disk drive, a magnetic disk drive, an optical disk drive, tape drive or the like. The storage device  160  can include software modules  162 ,  164 ,  166  for controlling the processor  120 . Other hardware or software modules are contemplated. The storage device  160  is connected to the system bus  110  by a drive interface. The drives and the associated computer readable storage media provide nonvolatile storage of computer readable instructions, data structures, program modules and other data for the computing device  100 . In one aspect, a hardware module that performs a particular function includes the software component stored in a non-transitory computer-readable medium in connection with the necessary hardware components, such as the processor  120 , bus  110 , output device  170 , and so forth, to carry out the function. The basic components are known to those of skill in the art and appropriate variations are contemplated depending on the type of device, such as whether the device  100  is a small, handheld computing device, a desktop computer, or a computer server. 
     Although the exemplary embodiment described herein employs a storage device  160 , it should be appreciated by those skilled in the art that other types of computer readable media which can store data that are accessible by a computer, such as magnetic cassettes, flash memory cards, digital versatile disks, cartridges, random access memories (RAMs)  150 , read only memory (ROM)  140 , a cable or wireless signal containing a bit stream and the like, may also be used in the exemplary operating environment. Non-transitory computer-readable storage media expressly exclude media such as energy, carrier signals, electromagnetic waves, and signals per se. 
     To enable user interaction with the computing device  100 , an input device  190  represents any number of input mechanisms, such as a microphone for speech, a touch-sensitive screen for gesture or graphical input, keyboard, mouse, motion input, speech and so forth. An output device  170  can also be one or more of a number of output mechanisms known to those of skill in the art. In some instances, multimodal systems enable a user to provide multiple types of input to communicate with the computing device  100 . The communications interface  180  generally governs and manages the user input and system output. There is no restriction on operating on any particular hardware arrangement and therefore the basic features here may easily be substituted for improved hardware or firmware arrangements as they are developed. 
     For clarity of explanation, the illustrative system embodiment is presented as including individual functional blocks including functional blocks labeled as a “processor” or processor  120 . The functions these blocks represent may be provided through the use of either shared or dedicated hardware, including, but not limited to, hardware capable of executing software and hardware, such as a processor  120 , that is purpose-built to operate as an equivalent to software executing on a general purpose processor. For example the functions of one or more processors presented in  FIG.  1    may be provided by a single shared processor or multiple processors. (Use of the term “processor” should not be construed to refer exclusively to hardware capable of executing software.) Illustrative embodiments may include microprocessor and/or digital signal processor (DSP) hardware, read-only memory (ROM)  140  for storing software performing the operations discussed below, and random access memory (RAM)  150  for storing results. Very large scale integration (VLSI) hardware embodiments, as well as custom VLSI circuitry in combination with a general purpose DSP circuit, may also be provided. 
     The logical operations of the various embodiments are implemented as: (1) a sequence of computer implemented steps, operations, or procedures running on a programmable circuit within a general use computer, (2) a sequence of computer implemented steps, operations, or procedures running on a specific-use programmable circuit; and/or (3) interconnected machine modules or program engines within the programmable circuits. The system  100  shown in  FIG.  1    can practice all or part of the recited methods, can be a part of the recited systems, and/or can operate according to instructions in the recited non-transitory computer-readable storage media. Such logical operations can be implemented as modules configured to control the processor  120  to perform particular functions according to the programming of the module. For example,  FIG.  1    illustrates three modules Mod 1   162 , Mod 2   164  and Mod 3   166  which are modules configured to control the processor  120 . These modules may be stored on the storage device  160  and loaded into RAM  150  or memory  130  at runtime or may be stored as would be known in the art in other computer-readable memory locations. 
     Having disclosed some components of a computing system, the disclosure now turns to  FIG.  2   , which illustrates a general purpose mobile computing environment  200 . A communication network  210  connects the devices and applications hosted in the computing environment  200 . In this computing environment  200 , different devices may communicate with and send commands to each other in various ways. The server  230 , for example, may function as an intermediary between two or more user devices such as, computer  220 , mobile device  240 , and mobile device  245 . The server  230  may pass messages sent from one user device to another. For example, the server  230  may receive a request from device  240  (the “requesting device”) to locate another device  245  (the “requested device”). In response to such a request (preferably after appropriate authentication and authorization steps have been taken to ensure the request is authorized by the user of the requested device), the server  230  may send a request to the requested device  245  and receive a response containing information relating to its location. The requested device  245  may have obtained this location information based on signals it received from, for example, GPS satellites  260 . Having received a response, the server  230  may then send the information to the requesting device  240 . Alternatively, the server  230  does not send a request to the requested device  245  because it has recent location information relating to the requested device  245  cached. In such an embodiment, the server  230  may respond to a request by sending cached location information to the requesting device  240  without communicating with the requested device  245 . 
     The devices  220 ,  240 , and  245  preferably have one or more location aware applications that may run on them. Of these applications, some may have the functionality to send requests to other user devices to enable a requesting user to locate a friend&#39;s device. Upon receiving authorization to locate, a requesting device may then be able to send location requests to requested devices and receive responses containing the location of the requested device. Authorization is preferably managed at the server level, but may also be managed at the device level in addition or as an alternative. 
     Referring back to  FIG.  2   , the communication network  210  can be any type of network, including a local area network (“LAN”), such as an intranet, a wide area network (“WAN”), such as the internet, or any combination thereof. Further, the communication network  210  can be a public network, a private network, or a combination thereof. The communication network can also be implemented using any type or types of physical media, including wired communication paths and wireless communication paths associated with one or more service providers. Additionally, the communication network  210  can be configured to support the transmission of messages formatted using a variety of protocols. 
     A device such as a user station  220  may also be configured to operate in the computing environment  200 . The user station  220  can be any general purpose computing device that can be configured to communicate with a web-enabled application, such as through a web browser. For example, the user station  220  can be a personal computing device such as a desktop or workstation, or a portable computing device, such as a laptop a smart phone, or a post-pc device. The user station  220  can include some or all of the features, components, and peripherals of computing device  100  of  FIG.  1   . 
     User station  220  can further include a network connection to the communication network  210 . The network connection can be implemented through a wired or wireless interface, and can support bi-directional communication between the user station  220  and one or more other computing devices over the communication network  210 . Also, the user station  220  may include an interface application, such as a web browser or custom application, for communicating with a web-enabled application. 
     An application server  230  can also be configured to operate in the computing environment  200 . The application server  230  can be any computing device that can be configured to host one or more applications. For example, the application server  230  can be a server, a workstation, or a personal computer. In some implementations, the application server  230  can be configured as a collection of computing devices, e.g., servers, sited in one or more locations. The application server  230  can include some or all of the features, components, and peripherals of computing device  100  of  FIG.  1   . 
     The application server  230  can also include a network connection to the communication network  210 . The network connection can be implemented through a wired or wireless interface, and can support bi-directional communication between the application server  230  and one or more other computing devices over the communication network  210 . Further, the application server  230  can be configured to host one or more applications. For example, the application server  230  can be configured to host a remote management application that facilitates communication with one or more mobile devices connected with the network  210 . The mobile devices  240 ,  245  and the application server  230  can operate within a remote management framework to execute remote management functions. The application server  230  can be configured to host a notification service application configured to support bi-directional communication over the network  210  between multiple communication devices included in the computing system  200 . For example, the notification service application can permit a variety of messages to be transmitted and received by multiple computing devices. 
     In some implementations, the notification service can include a defined namespace, in which a unique command collection topic can be created for each subscribing mobile device. A unique identifier can be used to associate a subscribing mobile device with the corresponding command collection topic, such as an assigned number or address. The unique identifier also can be embedded in a Uniform Resource Identifier (URI) that is associated with a subscribed command collection topic. Further, one or more command nodes can be created below a command collection topic, such that each command node corresponds to a particular remote command type. For example, a command collection topic can include a separate command node for a location command. 
     Through the use of separate command nodes, multiple commands can be transmitted to one or more mobile devices substantially simultaneously. In some implementations, if multiple commands are received in a command collection topic, server time stamps can be compared to determine an order of execution. 
     Through the notification service, a publisher, such as a remote management application, can publish a remote command message to a command collection topic that is associated with a particular mobile device. When a remote command message is published to the command collection topic, a notification message can be transmitted to the one or more subscribing mobile devices. The mobile device can then access the subscribed topic and retrieve one or more published messages. This communication between the publisher and the mobile device can be decoupled. Further, the remote command message can be published to the appropriate command node of the command collection topic. Additionally, a mobile device receiving a remote command message can publish a response to a result topic hosted by a notification service. A publisher such as a remote management application, can subscribe to the result topic and can receive any published response messages. 
     Further, the computing environment  200  can include one or more mobile devices, such as mobile device  240  and mobile device  245 . These mobile devices are preferably smart phones such as an Apple iPhone® or post-pc device such as an Apple iPad®. Each of the mobile devices included in the computing environment  200  can include a network interface configured to establish a connection to the communication network  210 . For example, mobile device  240  can establish a cellular (e.g., GSM, EDGE, 3G, or 4G) network connection that provides data access to the communication network  210 . Such a connection may be facilitated by one or more cellular towers  250  located within the range of the mobile devices  240  and  245  and connected to the network  210 . Further, mobile device  245  can establish an IEEE 802.11 (i.e., WiFi or WLAN) network connection to the communication network  210 . Such a connection may be facilitated by one or more wireless network routers  255  located within the range of the mobile devices  240  and  245  and connected to the network  210 . Also, either one of these mobile devices  240 ,  245  or an additional device may connect to the network  210  through the IEEE 802.16 (i.e., wireless broadband or WiBB) standard. Again, the devices  240 ,  245  may employ the assistance of a cell tower  250  or wireless router  255  to connect to the communication network  210 . 
     Each of the mobile devices,  240  and  245  also can be configured to communicate with the notification service application hosted by the application server  230  to publish and receive messages. Further, each of the mobile devices  240  and  245  can be configured to execute a remote management application or a remote management function responsive to a remote command received through the notification service application. In some embodiments, the remote management application can be integrated with the operating system of the mobile device. 
     A mobile device can execute a remote command to perform one or more associated functions. For example the remote commands can include locate commands, notification commands, and message commands. A message command can be used to present a text-based message on the display of a mobile device. A locate command can be used to cause a mobile device to transmit a message indicating its location at the time the locate command is executed. The locate command may also command the mobile device to use certain resources, such as an embedded GPS system, to determine its location. 
     Additionally, each of the mobile devices  240  and  245  can include an input interface, through which one or more inputs can be received. For example, the input interface can include one or more of a keyboard, a mouse, as joystick, a trackball, a touch pad, a keypad, a touch screen, a scroll wheel, general and special purpose buttons, a stylus, a video camera, and a microphone. Each of the mobile devices  240  and  245  can also include an output interface through which output can be presented, including one or more displays, one or more speakers, and a haptic interface. Further, a location interface, such as a Global Positioning System (GPS) processor, also can be included in one or more of the mobile devices  240  and  245  to receive and process signals sent from GPS satellites  260  for obtaining location information, e.g., an indication of current location. In some implementations, general or special purpose processors included in one or more of the mobile devices  240  and  245  can be configured to perform location estimation, such as through base station triangulation or through recognizing stationary geographic objects through a video interface. 
     Having disclosed some basic system components and concepts, the disclosure now turns to exemplary method embodiments  300   a  and  300   b  shown in  FIGS.  3   a  and  3   b    respectively. For the sake of clarity, the methods are discussed in terms of an exemplary system  100  as shown in  FIG.  1    configured to practice the methods and operating environment shown in  FIG.  2   . The steps outlined herein are exemplary and can be implemented in any combination thereof, including combinations that exclude, add, or modify certain steps. 
       FIG.  3   a    shows a flow diagram illustrating an exemplary process executed by a server for servicing a request by a requesting device to locate one or more mobile devices (requested devices), such as mobile devices  240  and  245  in  FIG.  2   , connected to a communication network, such as communication network  210  in  FIG.  2   . The process may be performed by a server such as application server  230  in  FIG.  2   . 
     In a preferred embodiment, the server  230  may maintain data associated with the members of one or more services. The maintained data may include certain identification information relating to each member such as, for example, the member&#39;s username and other personal identification information, unique identification information relating to the member&#39;s phone, and the identification of other members that have chosen to give permission to share their location information with this member. The information may also include recent location information of each member. This location information may be caused to be updated by certain applications/processes on the member&#39;s mobile device and/or at the request of a requesting device. For example, an application on a mobile device such as a mapping service or other location aware application may be requested by the user to determine the location of the device and, whenever such a determination is made, the device may provide this information to the application server. The server may then retain this information in storage  335   a  for a length of time that has been deemed to still be representative of that device&#39;s location (such as, for example, 15 minutes or less). 
     In a preferred embodiment, a user/requester may have an application on his or her computer or mobile device that, when executed, initiates one or more locate requests to all of the devices whose members have agreed to share their location with the requester (the requestor&#39;s “friends”). In such embodiments, the application may initially present to the user/requester the location of all of the friends on a map or in a list. The locate request  310   a  may be received by a server such as application server  210  in  FIG.  2    for processing. 
     Upon receiving a location request from a mobile device  301   a  of a requesting user, the server may initially respond with the location data that it has cached in  335   a . As mentioned above, in a preferred embodiment, the application server may maintain and/or cache information relating to members of services including recent location information. Updates in location information preferably overwrite older location information. Thus, the server may first, in step  315   a , determine whether it is in possession of recent location information. As mentioned before, the server may have a set “time of life” for the location information it maintains. When it has decided that the location information is has is recent, in step  330   a , the server retrieves the last known location from storage  335   a . Again, in some instances such as when a person may be on the go, only very recent location information would be relevant. Thus, some embodiments, the time of life of the information may be adjusted based on the device&#39;s recent location activity. Some examples might include when the owner of the device has designated his/her location, such as home or work, where he/she typically remains for several hours at a time each day. Thus, if the server determines that it is in possession of location information of the requested mobile device deemed to be recent, it will provide that information to the requesting device in step  360   a.    
     The server also preferably maintains this location information at a relatively low level of accuracy. The reason for this is similar to why the location is only deemed relevant for a short period of time: the more accurate the location information is, the more likely the person has since moved from that specific location, thereby rendering the location incorrect. Thus, maintaining recent location information at a lower level of accuracy increases the likelihood that the location is still correct and, therefore, not requiring additional communication with the user device. 
     Alternatively, the server may determine, in step  315   a , that it does not have recent location information relating to the requested device. The server may, in step  320   a , send a location request to the one or more requested devices (i.e., those devices associated with the friends). In this step, the server transmits a location request message to each requested device. The message sent by the server may take on any number of forms but has the effect of commanding the requested mobile device to obtain its current location information and transmit it back to the server in the form of a response message. In some alternative embodiments, the server only sends a location request message to the cellular network system, which may continually maintain recent location information relating to the requested device. Such location information may include, for example, the coordinates of the cell sites deemed closest to the requested device. 
     Some time after sending the request in step  320   a , server receives responses in step  340   a . Depending on, for example, the location of the requested devices and the network traffic, the responses may arrive in any order and may take different amounts of time. The response messages from the devices preferably include information relating to the location of the responding device and the time at which the location was determined. 
     This location information may be determined by the device in any number of ways including but not limited to those that have been discussed above. This information may even be obtained indirectly (i.e., not directly from the requested device), such as from the cellular communications network to which the device is communicating. For example, obtaining location information from the cell tower identified as being closest to the mobile device. Although this option may be of lower accuracy, it oftentimes may result in a quicker response and a savings in battery life for the requested device. Accordingly, the level of accuracy of the location information may vary. Thus, the location information may therefore include accuracy information as well. 
     In some embodiments, the owner of the responding device may have the option to enter unique location identifiers or labels associated with a location. For example, a user may assign labels such as “home,” “work,” or “school” to such locations. The user&#39;s mobile device may preferably associate certain geographic coordinates with such a label and transmit location-based messages to the server including the associated label. 
     Upon receiving this information, in step  350   a , the server preferably updates the stored information  335   a , if any, that it maintains relating to the device&#39;s last known location so that it may be made available to the next requester. 
     Having received a response from a requested device, in step  360   a , the server may then send location information to the requesting device. This step may be performed for each response received by the server from the various requested devices. Although location information relating to some devices may have already been retrieved from cache  335   a  in step  330   a , the server may additionally request and send updated information to the requesting device. In some embodiments, the server may additionally have a step (not shown) to compare the “known location information” that it had initially sent to the requesting device with the location information that it just received from the requested device to determine if sending the recently received location information would be any different. In other words, some embodiments would only send location information to the requesting device if the location of the requested device has changed. In such embodiments, a reduction in the amount of data that needs to be communicated may be realized. 
     In addition to temporal accuracy, the server may also have logic to determine how to handle a location request having a certain geographic location accuracy.  FIG.  3   b    shows a flow diagram illustrating an exemplary process  300   b  executed by a server for servicing a request by a requesting device to locate one or more mobile devices within a certain level of accuracy. 
     In a preferred embodiment, in step  310   b , the server receives a request to acquire location information relating to a requested device at a certain acceptable level of accuracy (accuracy y). In a preferred embodiment, the server typically only maintains, in storage  335   b , location information relating to devices at one level of accuracy (accuracy x). After receiving the request, in step  315   b , the server determines whether the accuracy of the location information it has in storage  335   b  is greater than or equal to the accuracy requested by the requesting device (i.e., accuracy x≥accuracy y). If so, the level of accuracy is deemed acceptable and, in step  330   b , the server retrieves the stored location information and, in step  360   b , sends the location information to the requested device. 
     More typically, however, when the server receives a request for location information of a requested device, the requested accuracy (accuracy y) is greater than the accuracy of the information stored in  335   b  (accuracy x) (i.e., accuracy y&gt;accuracy x). When this is determined in step  315   b , the server sends a request to the requested device in step  320   b . This request may be in several different forms. For example, the server may simply transmit the contents of the request to the requested device, containing the requested accuracy information, and leave it to the requested device (through its hardware, operating system, and applications) to determine how to respond to the request. Alternatively, the server may have sufficient information relating to the capabilities of the requested device (such as it having a GPS antenna of a certain accuracy) and the message sent is simply a command to determine its location using its GPS antenna and send this information to the server. The server, in step  340   b , then receives the location information from the requested device. Again, this information may be in several different forms and may depend on the device information known by the server. For example, the response may include accuracy information provided by the requested device or may simply include the location and the means by which it was obtained. In the latter form, the server, preferably knowing the model features of the requested device, may then determine the accuracy provided by the requested device. Also, depending on the request sent by the server, the means information may not be provided in the response but may be implied by the server as the same as what was requested. Once the location information is received by the server, in step  350   b , it updates its stored location information,  335   b , and sends location information to the requesting device in step  360   b.    
     Generally, the location information that is handled is of a low accuracy, such as at a city level or within a few miles of accuracy. As mentioned above, such information may be obtained by the server indirectly by, for example, knowing the geographic location of the cell phone tower or ISP to which the requested device is communicating. It is generally understood that mobile phones communicating with a cellular communications network periodically seek out cell sites having the strongest signal. In many cases, the strongest signals are measured by those cells that are the shortest distance away. Thus, in an area where there is a cell-phone tower every 4 miles, for example, the location of the mobile device may be extrapolated to be within 2 miles of the closest cell tower. A more accurate method of determining the location of a mobile device may be by determining the time difference of arrival (TDOA). The TDOA technique works based on trilateration by measuring the time of arrival of a mobile station radio signal at three or more separate cell sites. Such a method may be based on the availability of certain equipment supplied by the cellular network which may not be universally available and is therefore only an alternative embodiment. In either case, the location/accuracy determination may be performed by the communications network rather than by the mobile device. Such low accuracy information may preferably be transmitted by the server to the requesting device initially to give the device user a quick read on where his or her friends are located. The actions associated with obtaining such low accuracy information is herein referred to as a “shallow locate.” 
     Such low accuracy (i.e., less accuracy) location requests are only approximations but are preferably made initially, as they may result in the fastest response and require fewer resources from the requested device. On the other hand, a “deep locate request” may be requested by a user of a requesting device to obtain location information of a relatively higher accuracy (i.e., more accurate) from the requested device. For example, a “deep locate request” may command the requested device to use its GPS location resources to obtain location information having a level of accuracy that may be greater than that of some of the other location methods discussed above. While using a device feature such as GPS may be more accurate, the time and resources required to obtain signals from a sufficient number of GPS satellites and calculate the location oftentimes may take longer and require more energy. Thus, the “deep locate request” option is preferably reserved for specific requests made by the user of the requesting device. 
     This concept of a “shallow locate request” and a “deep locate request” is further illustrated from the perspective of the requesting device, such as a mobile device, in exemplary method  400  of  FIG.  4   . In a preferred embodiment, method  400  begins with step  410  when the application is started on a mobile device. Initially, in step  420 , the device may request location information of all friends that are associated with the user. This initial request is preferably a “shallow locate request” that is sent out to all of the “friend” devices (i.e., devices whose owners have allowed the requester to obtain location information). This request is sent to the server where it may be passed onto the requested device or serviced by the server, or both, as discussed above. Requesting device may then, in step  430 , receive responses containing the shallow locations of its user&#39;s friends. As the responses are received, requesting device may display the locations of the friends to the user in step  440 . 
     As individuals are often on the go, it is of value to the requesting user to occasionally have the location information of friends updated from time to time. The updating or refreshing of location information, performed in step  450 , may be done automatically at predetermined intervals, such as every 15 seconds or 15 minutes, and/or may be done at the request of the user. These predetermined timing intervals may be consistently applied to every user or may be individually applied to each user differently based on the individual user&#39;s observed moment frequency in combination with the heuristics of observed general user-movement data (e.g., determine a shorter time interval for a user observed to be traveling on a highway but determine a longer time interval for a user who has “checked-in” to a location such as a restaurant). As is shown in method  400 , a refresh step  450  will operate to repeat a request for shallow location information of all of the user&#39;s friends. 
     In addition to requesting and obtaining shallow location information of all of the user&#39;s friends, the user may request and obtain more detailed or “deep” location information of one or more friends, beginning in step  460 . To perform a “deep locate request,” in a preferred embodiment the user may select a friend that has been presented to the user after a shallow locate request. In this preferred embodiment, a deep locate request is sent to the server which will send a command to the requested device to provide more detailed location information. This request may include commanding the device to obtain accurate location information from its GPS system. Upon the receipt of the response in step  470 , the requesting device may display the deep location of the friend to the user in step  480 . The accuracy of the deep location may also be displayed to the requesting user. 
     One way a user may gain authorization to obtain location information of a device associated with a friend is shown by method  500  in  FIG.  5   . In most embodiments, in order for a user to be able to locate a friend, that user must send an authorization request to the friend. A user may do this by, in step  510 , selecting a friend to request authorization. In a preferred embodiment, the locating application may refer to or rely upon other applications on the user&#39;s device to maintain information of the user&#39;s friends. One example may be an address book application that stores contact information of persons known by the device user. These persons may include, friends, family members, business contacts, and others whose contact information the user has obtained. In the case where the particular person is not in the user&#39;s address book, the user may be able to enter that person&#39;s contact information directly into the running application. Upon selecting/entering a contact to locate, in step  520 , an authorization request is prepared and sent from the user&#39;s device. 
     Upon receiving a request from a user, the requested person (i.e., “friend”) is preferably presented with a message explaining the nature of the request and where he or she may either accept the request or reject the request. When the friend accepts the request in step  530 , an acceptance response is sent from that friend&#39;s device in step  540 . Upon receiving an accepting response, the server may update the information it maintains on either or both the requesting user and accepting friend such that when the user sends a location request, the server will process that request in step  550 . In addition, a notice may be sent by the server back to the requesting user to indicate to the user and/or the user&#39;s device that the authorization request has been accepted. Accordingly, the user may now obtain location information relating to that friend. In a preferred embodiment, the friend may revoke the authorization given to the user at any time; thus, the friend maintains control over the privacy of his or her location information. 
     On the other hand, a friend who has received a request to authorize the user to locate him or her but has rejected or ignored the request in step  560  may not be able to obtain location information relating to that friend. Thus, if the user subsequently attempts to locate that friend, in step  570 , both the device and the server will not process that request. From the requesting user and device perspective, such a friend would be displayed as having a status of “awaiting a response,” location not available,” or simply will not be listed. Of course, in some embodiments, the user may be able to send another request to the friend subsequently. 
       FIGS.  6 - 20    show a series of “screen shots” of preferred embodiments of the present disclosure as they might be viewed on a mobile device, such as the iPhone® or iPad®, both by Apple, Inc. One skilled in the art will appreciate that while the preferred embodiments are shown on these particular Apple products, the location application may be employed on any type of mobile device, smart phone, post-pc device, laptop computer, or desktop computer. 
       FIG.  6    illustrates an interface window  600  that is presented to a user when he or she initially runs the location program. In this window, the user may be prompted to enter his or her user ID  610  and password  620  associated with an account that the user has presumably already established with the location service. After entering a user ID and password, the user may select the “sign in” button  630  to authenticate and run the program. If the user has not yet created an account, the user may do so by selecting button  640 . 
     As shown in  FIG.  7   , when the user logs in for the first time, he may be presented with a screen  700  prompting him or her to invite friends to share their location. To invite a friend to share their location, a user may tap on the “+” button  710  to open a screen to select friends to invite. A more detailed explanation of these actions is in the discussion associated with  FIGS.  11 - 16    below. 
     On the other hand,  FIG.  8    shows what a user may likely immediately see when logging in after having several friends accept the user&#39;s invitation to share their location. As shown in  FIG.  8   , a list of friends  800  is displayed to the user. Next to a displayed friend&#39;s information  810  is a locating status indicator  820 . In this case, the status is that the device has sent out location requests to all of the friends&#39; devices and is still waiting for responses from each of the devices. 
     After a brief time has elapsed and the device has received location information relating to the user&#39;s friends, the location information may be presented to the user in display interface  900 , as shown in  FIG.  9   . As can be seen in  FIG.  9   , the friend information  910  may now include the location  920  of the friend, the accuracy of the location information  930 , and the time at which the location information was obtained  940 . The location  920  may be presented in a number of ways. For example, location information  920  includes a label that was selected by the user. Alternatively, the location information may include the name of the town or an address at which the friend is located, as in  950 . Additionally, when a location request was not successful, the display  900  may present a message similar to that of  960 . 
       FIG.  10    shows an alternative embodiment of displaying location information of friends. As is shown in  FIG.  10   , map interface  1000  is presented. In a preferred embodiment, the initial scale of map interface  1000  may be determined by the identified locations of each of the user&#39;s friends such that all of the user&#39;s friends may be viewed on one screen. Thus, if all of the user&#39;s friends are located within a few miles from each other, the scale of map interface  1000  may be zoomed in such that only a few miles (i.e., a city level) are presented. On the other hand, if the user&#39;s friends are located across the country or in other countries, the scale of the map may be zoomed out such that map interface  1000  is covering hundreds or even thousands of miles (i.e., a state level). 
     Referring again to  FIG.  10   , the user is presented with locations of his or her friends on map  1000 . In a preferred embodiment, the locations of the friends are presented as dots  1010  and  1020 . However, any other icon or other reasonable method of indicating the location of a person on an interactive map may be used. When the user selects one of the dots, information relating to the friend at that location appears, as is shown in dot  1010 . Additionally, the accuracy information may also be graphically presented on the map in the form of a shaded circle surrounding the friend&#39;s dot with a radius equivalent to the level of accuracy provided, as is shown in dot  1010 . 
       FIGS.  11  and  12    show alternative embodiments of the present invention. Such embodiments may be ideal for use on a device that has a larger screen, such as an iPad, laptop, or desktop computer. In  FIG.  11   , interface  1100  displays both a listing of the user friends in a table format  1100  as well as their geographic location on a map  1120 . In interface  1100 , when a user selects one of his or her friends  1130  on the map  1120 , details relating to the location of the friend may appear at the bottom of the map  1140 . Similarly, in  FIG.  12   , which provides an interface in a different aspect ratio, interface  1200  presents to the user a map  1220  indicating the geographic locations of his or her friends  1225 . Overlaying the map is a list of the user&#39;s friends in table  1210 . Similar to interface  1100 , when the user selects one of his or her friends within table  1210 , details of that friend may be displayed at the bottom of the display  1240 . 
     When a user wishes to send to a friend an invitation to share their location, “Add Friend” interface  1300 , as shown in  FIG.  13   , may be used. In interface  1300 , the user may enter the contact information of the friend/invitee at  1310  and may also include an optional personal message at  1320 . As mentioned above, the contact information may be obtained from other services or applications located on the user&#39;s device, as is shown in contacts list  1400  in  FIG.  14   . 
       FIG.  15    shows a completed add friend request form  1500  with the name of the contact (preferably an embedded link to the contact&#39;s e-mail address, phone number, or other relevant contact information) entered at  1510 . Also shown is a brief personal message  1520 . 
       FIG.  16    shows one way a friend may be notified that he or she has received an invitation to share their location with the requesting user in window  1600 . As presented to the friend in window  1600 , the user may either view the invitation immediately by selecting button  1610  or may choose to view the invitation at a later time by selecting button  1620 . Note that this notification may preferably be in the form of a system-based message that provides notification regardless of any particular application currently running. 
     When the friend selects to view the invitation, he or she is presented with a request message  1700 , as shown in  FIG.  17   . In request message  1700 , the invitation preferably includes the name of the inviter  1710  and a brief personal message  1720 . In addition, the invitation may include an accept button  1730  and a decline button  1740 . 
     Referring now to  FIG.  18   , a mobile device user may maintain certain items associated with his or her account in interface  1800 . In interface  1800 , a user may, for example set a label  1810  to his or her present location in field  1820 . A user may also review the list of followers  1830  which include all of the friends whom he or she has accepted invitations to be followed. A user may additionally select to hide from all of his or her followers by toggling switch  1840 . 
     With respect to assigning labels to certain locations, interface  1900  of  FIG.  19    may be presented to a user for this purpose. In interface  1900 , a user may select one of the prepared labels  1910  or may add a custom label by entering text into field  1930 . The current label in use is shown in field  1920 . In addition to the prepared labels  1910  in interface  1900 , additional location-specific label options may be automatically added, as is shown in interface  2000  in  FIG.  20   . As is shown in  FIG.  20   , location label  2010  has been added to the list of prepared location labels. A label such as label  2010  may be added when the user is determined to be located in the vicinity of a Starbucks for example. 
     To further explain certain embodiments in this disclosure, the following use scenarios are presented to show how certain users of mobile devices may be able to use one or more embodiments in the disclosure to locate his or her friends. 
     One scenario may occur when a mobile device user is located somewhere, say downtown Palo Alto, at noon and wants to know if any of his friends are in the vicinity and are available for a quick lunch. The user may be able to use an embodiment in the present disclosure to see the location of his or her friends, identify one that is close by, and subsequently make contact. 
     A second scenario may arise when there is a need or desire by users of mobile devices to allow others to know where they are at certain times. One such situation is where a mobile device user may, for example, be training for a marathon and is outside running for miles each day. This user wishes to have her partner aware of her location during this period of time so that she can always be located in case something happens and may therefore benefit from embodiments in this disclosure. Also, when this person is actually participating in the marathon, her friends may want to know at what part of the course she has made it to so that they may be able to be present at certain locations during the race to cheer her on. In such a scenario, the user would benefit from embodiments of the disclosure having a map of the race course superimposed onto a street map of the area such that the users may be able to see the location of the runner and have some indication about the location where she will be heading to next. 
     A third scenario may arise when users of mobile devices wish to receive an indication that someone has reached a certain location. In such a scenario, one user of a mobile device may, for example, be embarking on a road trip and another person wants to be notified when he or she has arrived. Such a scenario might include a parent who is allowing her teenage son to take the family car on a holiday weekend to drive to visit his cousins that live several hours away. Although the parent has asked that the son call as soon as he arrives, he is often forgetful and does not do so. To overcome this, the parent or son may take advantage of an embodiment of the present disclosure where they may set an alert to automatically notify the parent when the son has arrived at the destination. In the interim, the parent may additionally use other embodiments to manually locate the son&#39;s mobile device to make sure that he has not gotten lost. 
     A fourth scenario may arise when users of mobile devices wish to receive a notification when someone has entered a certain geographic location. For example, a person commutes to and from the city using public transportation but does not live in walking distance to the train or bus stop. Rather than driving and parking, the person may rely on a spouse or partner to pick her up in the evenings or whenever there is inclement weather. As certain busses and train cars have rules and courtesies prohibiting talking on cell phones, the commuter may have to wait to call her spouse or partner until after she arrives and subsequently having to wait, for example, in the rain. The users would benefit from some embodiments of the disclosure that would allow for a way for the commuter&#39;s mobile device to notify her partner&#39;s device whenever she enters into a certain geographic region (i.e., is close to arriving at the bus or train stop) without requiring the commuter to place a call. Thus, the commuter and her partner may both arrive to the stop close to the same time. 
     Similarly, a fifth scenario includes users having certain household appliances that may be connected to a network and can perform certain tasks upon receiving a notification when a person enters a certain area. For example, when a person is traveling to her vacation home out in the mountains, certain appliances in the vacation home such as, for example, the furnace and front porch light, may turn on when the person enters into a certain geographic area (i.e., gets close to the home). An embodiment of this disclosure would enable a user to have and benefit from such a configuration. 
     A sixth scenario may arise when someone wishes to receive a notification when a mobile device user has left a certain geographic location. For example, a parent has asked his daughter to stay at home for the weekend to finish a school assignment that is due the following Monday. If the daughter leaves the neighborhood with her mobile device, the parent may be notified. Aspects of the disclosed technology would enable a parent to receive such notifications. 
     A seventh scenario may arise when some mobile device users wish to be located for only a brief period of time. For example, a person is on a business trip in a city and wants to be able to meet up for dinner with an old friend who lives in that city. Since she is not normally in that city and does not often interact with this old friend, she does not want the old friend to be able to locate her all the time. One embodiment of the disclosure employs a “day pass” which the person may send to the old friend to allow the old friend to locate her for the next 24 hours. After that time, the day pass is expired and the old friend may not be able to locate the person anymore. 
     In an eighth scenario, a user may select a number of persons in her contact list to all share location information with each other for a limited period of time. For example, a user is in town to attend a conference such as Apple&#39;s WWDC. The user knows that some people that she knows are also attending the conference and she would like to know their whereabouts during the event. One embodiment of the disclosure enables this user to send an invitation to the persons that she wants to locate at the conference. When the user&#39;s acquaintances accept her invitation, she and the acquaintances will be able to locate each other. Certain limits on this ability to locate each other may be set by a user, however, such as certain windows of time during the day (such as, only during the conference), or until an expiration time. 
       FIGS.  21 - 24    disclose the configuration of certain interfaces that may be used to share location information until an expiration time and may be used, for example, during a scenario such as the one explained in scenario eight.  FIG.  21    displays one embodiment of an invitation interface screen in which the user may configure and send an invitation to friends to share their location. The user may add friends to the invitation by tapping the “+” button  2120 , similar to the one described in  FIG.  7   . The friends that have been added to the invitation may be displayed on the screen  2110  to indicate that they have been added, similar to that of a “To:” line in a composed e-mail.  FIG.  21    shows that the user has added two friends to the invitation, as their names; “Jared Gosler” and “Susan Adams” are displayed. 
     In the exemplary interface shown in  FIG.  21   , the user may also, for example, relate the invitation to enter a particular event  2130  and set an expiration time  2140 . However other configuration options such as setting an applicable geographical area and other time constraints may also be offered. In  FIG.  21   , the user has related the invitation to the “WWDC” conference and set an expiration time to be “Fri, June 10 at 10 AM.” In some embodiments, the relating of the invitation to a particular event may enable the users to have access to certain maps and wireless access ports hosted by the particular event, which may, for example, offer more accurate non-GPS location information (i.e., specific conference rooms). The expiration time sets a limit on how long the user and the invited friends may share location information. 
       FIG.  22    shows an alert that an invited friend may receive upon receiving an invitation to share location information sent by the user. A message box  2210  may be displayed providing notification of the request to the friend. The text  2220  of the request may explain that the friend has been invited to share location information with the user and another person (Susan Adams) until the set expiration time. In this embodiment the message box  2210  includes buttons to enable the device user to close the message box or view the invitation. In other embodiments the message box may also include additional or different buttons to accept, ignore, or reject the invitation. 
       FIG.  23    shows an exemplary embodiment displaying an invitation. This invitation may include the related event  2310  and text  2320  explaining the details of the request to share location information including the set expiration time. The names of all parties invited to share location invitation and their response status  2330 ,  2340 , and  2350  may also be displayed. As illustrated, a check mark may be placed next to a person&#39;s name to indicate that the person has accepted the invitation. Similarly, a question mark may be displayed next to a person&#39;s name to indicate that the person has not yet replied to the invitation and so it is still uncertain whether they will accept the invitation. If a person declines the invitation, an X may be displayed next to their name to indicate their decision to not share location information. This may also indicate that the person is not in the geographic area of the conference and/or, in some cases, has not checked in. Upon receipt of an invitation, a device user may decline or accept by selecting one of the available options  2360  and  2370 . 
       FIG.  24    illustrates an embodiment showing what a user would likely see when the user selects to view the temporary friend  2460  and after invited friends have accepted a user&#39;s invitation to share limited-time location information. As shown in  FIG.  24   , there is an event  2410 , WWDC, associated with the sharing of this location information. As mentioned above, in some embodiments, certain additional features may become available when the locate is associate with a particular hosted event, like connecting to local geo-coded access ports and receiving notifications from the event organizer. Alternatively or in addition, entering the event name and associating the locate with an event may simply auto-fill information such as the end time of the conference or event. Here, the end time  2420  of the locate permission is shown to expire on June 10 at 10 am. Information relating to the friends that have accepted a temporary locate request is shown on this display  2430   a ,  2430   b . Similar to the embodiment shown in  FIG.  9   , the friend information may include, among other things, the name of the friend, their last known location and time of that last known location. Preferably specific to associating requests to a particular event, a user may be able to contact all of the other users on the list by clicking on a button to send a group message  2440 . This button, when selected, may allow the user to compose one message which will be sent to each friend who accepted the invitation to share location information. The user may also select a button to view a map  2450  which, when selected, may display an overhead map which indicates each friend&#39;s location upon it. As mentioned above, the map may be a typical location map or may be a map customized and associated with the related event (i.e., a map showing the rooms inside of the Moscone Center and Yerba Buena Center). 
     As described above, one aspect of the present technology is the gathering and use of data available from a user&#39;s mobile device. The present disclosure contemplates that in some instances, this gathered data may include personal information data that uniquely identifies or can be used to contact or locate a specific person. Such personal information data can include hardware information relating to the user device, location-based data, telephone numbers, email addresses, social media IDs such as TWITTER IDs, work and home addresses, friends, or any other identifying information. The user typically enters this data when establishing an account and/or during the use of the application. 
     The present disclosure recognizes that the use of such personal information data in the present technology can be used to the benefit of users. In addition to being necessary to provide the core feature of the present technology (i.e., locating users), the personal information data can also be used to better understand user behavior and facilitate and measure the effectiveness applications. Further, other uses for personal information data that benefit the user are also contemplated by the present disclosure. 
     The present disclosure further contemplates that the entities responsible for the collection, analysis, disclosure, transfer, storage, or other use of such personal information data should implement and consistently use privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining personal information data private and secure. For example, personal information from users should be collected for legitimate and reasonable uses of the entity and not shared or sold outside of those legitimate uses. Further, such collection should occur only after the informed consent of the users. Additionally, such entities would take any needed steps for safeguarding and securing access to such personal information data and ensuring that others with access to the personal information data adhere to their privacy and security policies and procedures. Further, such entities can subject themselves to evaluation by third parties to certify their adherence to widely accepted privacy policies and practices. 
     Despite the foregoing, the present disclosure also contemplates embodiments in which users selectively block the use of, or access to, personal information data. That is, the present disclosure contemplates that hardware and/or software elements can be provided to prevent or block access to such personal information data. For example, in the case of location aware services, the present technology can be configured to allow users to select to “opt in” or “opt out” of participation in the sending of personal information data. The present disclosure also contemplates that other methods or technologies may exist for blocking access to user&#39;s personal information data. 
     Embodiments within the scope of the present disclosure may also include tangible and/or non-transitory computer-readable storage media for carrying or having computer-executable instructions or data structures stored thereon. Such non-transitory computer-readable storage media can be any available media that can be accessed by a general purpose or special purpose computer, including the functional design of any special purpose processor as discussed above. By way of example, and not limitation, such non-transitory computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code means in the form of computer-executable instructions, data structures, or processor chip design. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or combination thereof) to a computer, the computer properly views the connection as a computer-readable medium. Thus, any such connection is properly termed a computer-readable medium. Combinations of the above should also be included within the scope of the computer-readable media. 
     Computer-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. Computer-executable instructions also include program modules that are executed by computers in stand-alone or network environments. Generally, program modules include routines, programs, components, data structures, objects, and the functions inherent in the design of special-purpose processors, etc. that perform particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures, and program modules represent examples of the program code means for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps. 
     Those of skill in the art will appreciate that other embodiments of the disclosure may be practiced in network computing environments with many types of computer system configurations, including personal computers, hand-held devices, multi-processor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, and the like. Embodiments may also be practiced in distributed computing environments where tasks are performed by local and remote processing devices that are linked (either by hardwired links, wireless links, or by a combination thereof) through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices. 
     The various embodiments described above are provided by way of illustration only and should not be construed to limit the scope of the disclosure. Those skilled in the art will readily recognize various modifications and changes that may be made to the principles described herein without following the example embodiments and applications illustrated and described herein, and without departing from the spirit and scope of the disclosure.