Abstract:
A wireless power transfer system is disclosed that includes multiple levels of authentication and several different options for implementing theft prevention. The power station can perform a first authentication procedure to collect billing information of the device to receive power. If the first authentication succeeds, the power station then performs a second authentication procedure in which it sends one or more test power signals to the receiving device. The power station estimates the amount of power that should actually be received by the receiving device and compares the estimate to a reported value sent from the receiving device to ensure that the reported value is within an acceptable margin of the estimate value. If either authentication fails, the power station can take power theft prevention methods to prevent the receiving device from acquiring free power.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 61/747,061, filed on Dec. 28, 2012, which is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The disclosure relates to a wireless charging station and wirelessly-chargeable receiver and specifically to the protection against power theft and foreign object detection in a wireless power transfer environment. 
         [0004]    2. Related Art 
         [0005]    Wireless power transfer stations, such as power pads, have recently become known. However, conventional wireless power transfer stations provide power indiscriminately to any capable device in its vicinity. Therefore, an unauthorized device can easily obtain power from conventional wireless power transfer stations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         [0006]    Embodiments are described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left most digit(s) of a reference number identifies the drawing in which the reference number first appears. 
           [0007]      FIG. 1  illustrates an exemplary wireless power transfer environment; 
           [0008]      FIG. 2  illustrates a block diagram of an exemplary wireless power transfer station; 
           [0009]      FIG. 3  illustrates a block diagram of an exemplary power station that is capable of preventing power skimming; 
           [0010]      FIG. 4  illustrates a plan view of an exemplary power station for using temperature sensing to detect foreign objects; 
           [0011]      FIG. 5  illustrates a top-down plan view of an exemplary power station for detecting foreign objects; 
           [0012]      FIG. 6  illustrates a block diagram of an exemplary method for transferring power from a power station to a chargeable receiving device; and 
           [0013]      FIG. 7  illustrates a block diagram of an exemplary general purpose computer system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    The following Detailed Description refers to accompanying drawings to illustrate exemplary embodiments consistent with the disclosure. References in the Detailed Description to “one exemplary embodiment,” “an exemplary embodiment,” “an example exemplary embodiment,” etc., indicate that the exemplary embodiment described may include a particular feature, structure, or characteristic, but every exemplary embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same exemplary embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an exemplary embodiment, it is within the knowledge of those skilled in the relevant art(s) to affect such feature, structure, or characteristic in connection with other exemplary embodiments whether or not explicitly described. 
         [0015]    The exemplary embodiments described herein are provided for illustrative purposes, and are not limiting. Other exemplary embodiments are possible, and modifications may be made to the exemplary embodiments within the spirit and scope of the disclosure. Therefore, the Detailed Description is not meant to limit the invention. Rather, the scope of the invention is defined only in accordance with the following claims and their equivalents. 
         [0016]    Embodiments may be implemented in hardware (e.g., circuits), firmware, software, or any combination thereof. Embodiments may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact results from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. Further, any of the implementation variations may be carried out by a general purpose computer, as described below. 
         [0017]    For purposes of this discussion, the term “module” shall be understood to include at least one of software, firmware, and hardware (such as one or more circuit, microchip, or device, or any combination thereof), and any combination thereof. In addition, it will be understood that each module may include one, or more than one, component within an actual device, and each component that forms a part of the described module may function either cooperatively or independently of any other component forming a part of the module. Conversely, multiple modules described herein may represent a single component within an actual device. Further, components within a module may be in a single device or distributed among multiple devices in a wired or wireless manner. 
         [0018]    The following Detailed Description of the exemplary embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge of those skilled in relevant art(s), readily modify and/or adapt for various applications such exemplary embodiments, without undue experimentation, without departing from the spirit and scope of the disclosure. Therefore, such adaptations and modifications are intended to be within the meaning and plurality of equivalents of the exemplary embodiments based upon the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by those skilled in relevant art(s) in light of the teachings herein. 
         [0019]    Those skilled in the relevant art(s) will recognize that this description may be applicable to many various charging and/or communication methods without departing from the spirit and scope of the present disclosure. 
         [0020]    An Exemplary Wireless Power Transfer Environment 
         [0021]      FIG. 1  illustrates an exemplary wireless power transfer environment  100 . The environment  100  includes a wireless power transfer station (hereinafter “power station”)  110 . The power station  110  includes at least one coil  115  ( 115 ( 1 )- 115 ( 8 ) in the example of  FIG. 1 ) arranged in a grid or matrix pattern. The coils send and receive signals between a wirelessly-chargeable device  150 . The exchanged signals can include data, commands and/or other communications, and can be used to transfer power from the power station  110  to the device  150 . In an embodiment, the coils  115  of the power station  110  may be used as secondary coils to a primary coil  120 , discussed in detail below. 
         [0022]    When a user of the device  150  seeks to wirelessly charge a battery or other power storage device within the device  150 , the user moves the device  150  to be within a proximity of the power station  110 . After an initialization and setup period, the power station  110  loads power transfer signals onto one or more of its coils  115  and transmits those signals to the device  150 . The device receives the signals from the coils  115  of the power station  110  and extracts power therefrom. In this manner, the power station  110  functions as a power transmitter and the device  150  functions as a power receiver. In embodiments, the wireless power transfer is implemented as a magnetic coil-to-coil power transfer using a transmit coil and a receive coil. The transmit coil is excited with an AC current to produce an alternating magnetic field, that induces a secondary AC current in the receive coil. The secondary current can then be rectified using a diode bridge so as to produce a DC voltage that can be stored in a battery or used to power receiver circuits. 
         [0023]    Exemplary Wireless Power Transfer Device and Functionality 
         [0024]      FIG. 2  illustrates a block diagram of an exemplary wireless power transfer station  200 . The power station  200  includes a controller module  210 , a coil driving module  220 , a coil module  230 , and an authorization module  240 , and may represent an exemplary embodiment of the power station  110 . It should be understood that the following descriptions of the structure, functions, and capabilities of the power station  200  described in  FIG. 2 , as well as with respect to the additional devices illustrated in  FIGS. 3-5  can be similarly applied in a multi-standard system and may employ out-of-band communications for carrying out communications operations. 
         [0025]    The coil module  230  may include one or more power transfer coils that are capable of being loaded with power transfer or other communication signals, and which are capable of receiving signals via load modulation or other communication standard. The coil driving module  220  drives one or more of the coils based on instructions received from the controller module  210 . 
         [0026]    When the power station  200  detects the presence of a chargeable device in its vicinity, the controller module  210  begins an initiation phase of power transmission. During the initiation phase, the controller module  210  causes the coil driving module  220  to drive the coil module  230  to transmit a small amount of power to the receiving device. This small amount of power should be limited to an amount sufficient to allow the receiving device to negotiate with the power station  200 . Ideally, the initiation power would be impractical for charging purposes. In this manner, an unauthorized device could not charge from the initiation charge. Alternatively, the initiation power can be sufficient for charging purposes, but only supplied for a limited amount of time. This amount of time is preferably only slightly longer than an expected authentication period. At the end of the initiation period, if the receiving device has not been authenticated, the supply of wireless power to the receiving device can be halted. 
         [0027]    During the initiation phase, the power station  200  exchanges information and/or instructions with the receiving device in order to acquire authentication information from the receiving device. In an embodiment, the authentication information includes identification and/or password or other access key information. In an embodiment, the authentication information includes billing information, such as bank account, credit card, or other electronic funds transfer information. As shown, for example, in  FIGS. 2 and 3 , the authentication information can be received by the coil module  230 / 330  using in-band communication protocols, and/or from the communication module  360  using out-of-band communications. 
         [0028]    The coil module  230  forwards the received authentication information to an authentication module  240 . The authentication module  240  carries out an authentication procedure, using the received authentication information. The authentication process results in allowing or restricting access to the nearby receiving device based on whether the authentication process succeeded or failed. 
         [0029]    Allowing and Restricting Access to Power 
         [0030]    If the authentication module  240  determines that the authentication process has succeeded, the authentication module  240  transmits an authentication success signal to the controller module  210 . The controller module  210  then instructs the coil driving module  220  to drive the one or more coils that correspond to the receiving device to transmit a charging power to the device. The charging power may be larger than the initiation power level and/or have a longer supply duration, and should be sufficient for the receiving device to charge its battery. 
         [0031]    If, on the other hand, the authentication module  240  determines that the authentication process has failed, the authentication module  240  transmits an authentication failed signal to the controller module  210 . The power station  200  can then institute one or more of several possible theft prevention methods. 
         [0032]    In an embodiment, upon a failed identification, the coil driving module  220  can decommission power to the one or more coils  115  corresponding to the receiving device  150 . These coils can be identified by the coil driving module  220  based on loads and other signals of those coils  115 . Once identified, the coil driving module  220  can then stop the supply of power signals to those coils  115 . 
         [0033]    In an embodiment, the coil module  220  can shift a transmission frequency and/or phase of the transmitted power signals. For example, in an environment where the power station  200  is capable of charging multiple devices at a given time, the power station  200  can privately set unique phase and/or frequencies for the power transmission signals. The authentication information can be obtained using a standard phase and/or frequency. Once authenticated, private phase and/or frequency information can be transmitted to the authenticated receiving devices. In this manner, each authenticated device will have a private power transmission channel on which to receive power from the power station  200 . 
         [0034]    Similarly, rather than transmitting a private single frequency to be used in communication, the power station  200  can provide a frequency hopping code to be used in a frequency-hopping algorithm. The power station  200  and the receiving device can then transfer power over a frequency-hopping algorithm defined by the private code or other notifier. With different coils, different frequency-hopping or other algorithms may be run on each to provide different power/power levels to different devices. 
         [0035]    When a device fails the authentication process, the coil driving module  220  can cause the coils  115  of the coil module  230  to shift frequency and/or phase without informing the receiving device  150  as to the new transmission information. In this manner, the unauthorized receiving device  150  will be unable to receive the signals being transmitted from the coil module  230 . 
         [0036]    In an embodiment, when the controller module  210  receives the authentication failed signal from the authentication module  240 , the controller module  210  can instruct the coil driving module  220  to stop all power transmission. This halt may last for a predetermined time, until a new receiving device is detected, until the power station  200  detects the absence of the unauthorized receiving device, or until the occurrence of another trigger within the spirit and scope of the present disclosure. 
         [0037]    In an embodiment, the coil driving module can simply continue transmitting at the low initiation power. As discussed above, this initiation power should be insufficient for practical charging purposes. Therefore, simply maintaining the initiation power may be a sufficient deterrent in some scenarios. 
         [0038]    In another embodiment, the power station  200  includes a plurality of coils in its coil module  230 . Upon detecting the presence of an unauthorized device, the power station  200  can next determine a location of the unauthorized device. For example, by monitoring load impedance incident of the various coils of the coil module  230 , the power station  200  can determine a relatively accurate position of the unauthorized device with respect to the various coils. Once this position has been determined, the controller module  210  can cause the coil driving module  220  to drive two or more of the various coils at calculated frequencies to cause spatial anti-phase mixing at the location of the unauthorized device. By controlling the frequencies of these coils, the power station  200  is able to cancel the magnetic field at the location of the unauthorized device. 
         [0039]    Alternatively, or in addition, to any of the above power theft prevention techniques, alarms can be used to notify relevant persons or monitoring system of the unauthorized device. For example, upon determining that the device is unauthorized, the power station  200  may generate an audible or visual alarm to notify a user or station manager of the unauthorized charging attempt. Similarly, the alarm may be transmitted via network/cloud to a remote location or monitoring authority. For example, local security may be informed of the attempted breach in order to respond and remedy the unauthorized attempt. 
         [0040]    Preventing Power Skimming 
         [0041]    After a device has been authenticated and given access to receiving power, there may be other ways for the receiving device to steal power from the power station. For example, in wireless transfer protocols, the amount of power loaded onto the coils of the power station if often different from the amount of power received by the receiving device. This differential can be explained by the efficiency of the system, which often is not perfect. 
         [0042]    In an embodiment, the amount of money charged for the power transferred to the receiving device is a function of the amount of power actually received by the receiving device. Therefore, it may be necessary to communicate with the receiving device in order to obtain a report of the amount of power actually received. However, if the receiving device falsifies or erroneously generates this report (e.g., reports an amount received that is lower than actual), the receiving device is able to acquire more power than that for which the user of the receiving device actually pays (“power skimming”). 
         [0043]      FIG. 3  illustrates an exemplary power station  300  that is capable of preventing power skimming. The power station  300  includes a power measurement module  350  and a communication module  360 , and may represent an exemplary embodiment of the power station  110 . 
         [0044]    In the power station  300 , the power being transmitted from the coil module  230  is measured by a power measurement module  350 . The power measurement module  350  forwards the measured amount of power to the authentication module  340  for analysis. 
         [0045]    The authentication module  340  can be programmed with a transfer function. The transfer function is a function for estimating an amount of power that should be received by the receiving device based on the amount of power loaded onto the coil module  230 . Therefore, using the received measured power value from the power measurement module  350 , the authentication module  340  can estimate the amount of power being received by the receiving device. 
         [0046]    In addition, the controller module  210  can control one or more of the coil module  230  and the communication module  360  to acquire a received power report from the receiving device. For example, the power station  300  can receive the received power report via load modulation of one or more of the coils within the coil module  230  or via any available wired or wireless communication method via the communication module  360 , including NFC, Bluetooth, Wi-Fi, etc. 
         [0047]    Once the authentication module  340  obtains the received power report from the receiving device, the authentication module  340  compares the amount of power reported by the receiving device to the estimated amount of power. Based on the comparison, the authentication module  340  then makes a determination as to whether the device remains authenticated for receiving power. 
         [0048]    For example, if the amount of power reported by the receiving device is greater than the estimated amount of power, the authentication module  340  determines that the receiving device is still authenticated, and takes no further action. If the reported amount of power is less than the estimate, the authentication module  340  compares the reported amount of a threshold value. The threshold value may be set as a percentage of the estimated value, for example. If the reported amount is above the threshold value, the authentication module  340  assumes the report is accurate and allows for the power transfer to continue. 
         [0049]    If, on the other hand, the reported value is less than the threshold value, the authentication module  340  assumes that the report is false or at least erroneous and notifies the controller module  210  that the receiving device is no longer authenticated for power transfer. Consequently, the controller module  210  controls the coil driving module  220  to halt or reduce power transfer to the receiving device. In this manner, the power station  300  is able to prevent power skimming by the receiving device. 
         [0050]    Power skimming can also be prevented at the outset of power transfer. For example, during the initial authentication process between the power station  300  and the receiving device  150 , the power station  300  can perform a power reporting authentication routine. As a part of this routine, the coil driving module  220  can drive the coil module  230  with several different power levels at different time intervals, and the communication module  360  can obtain received power reports from the receiving device after each interval. This allows the authentication module  340  to compare data for multiple different power levels in order to increase comparison accuracies, or to determine at the outset as to whether the receiving device is accurately reporting received power. 
         [0051]    In addition to transmitting at different power levels, the power station  300  can also instruct the receiving device via the communication module  360  and/or coil module  230  to employ different load for one or more of the transmitted test power signals. This change in load can be detected by the coil module  230  of the power station  300  in order to determine if the receiving device is complying with instructions. In addition, load data provides the authentication module  340  with an additional layer of data for use in its accuracy determinations. Using one or more of these procedures can even further improve protection against power skimming. 
         [0052]    Power skimming can also be prevented that would otherwise occur towards the end of power exchange. For example, in an embodiment, a device may be authenticated and billed for a predetermined amount of power/time. However, the receiving device may seek to extend its charging beyond those valued. Therefore, in an embodiment, reauthorization can be required after predetermined intervals or intervals set by earlier payment in order to prevent post-skimming of power. 
         [0053]    Foreign Object Detection 
         [0054]    Foreign objects in the vicinity of the power station can absorb power transmitted to the environment. This can greatly reduce efficiency of power transfer. In addition, foreign objects may heat up from the absorbed energy, which can be a safety hazard. Therefore, power stations should implement some form of foreign object detection in order to improve safety and to improve efficiency and authentication of power transfers. 
         [0055]    Conventionally, a power transmitter detects foreign objects by estimating an amount of power consumed by foreign objects, and comparing that amount to a threshold. Although this method may be effective for identifying foreign objects in some instances, the accuracy of the method is low, and therefore many foreign objects are often overlooked. 
         [0056]    In an embodiment, one option is increase the frequency at which the power signals are transmitted. For example, the coil driving module  220  can drive the coil module  230  at a high frequency. Eddy currents decrease at higher frequencies. Therefore, by increasing the transmission frequency of the power signals, the power station  300  can naturally reduce the effects of foreign objects. 
         [0057]    In an embodiment, the power station can utilize the receiving device to assist in the foreign object detection. For example, for a receiving device that has been authenticated, the power station can request received power statistics from the receiving device. Based on the known amount of power transmitted, and the reported amount of power received by the receiving device, the power station  300  can determine if foreign objects are present. For example, if the reported amount of received power is significantly lower than the amount of transmitted power, this would suggest that a foreign object is absorbing some of the transferred power. 
         [0058]    In an embodiment, the power station can detect foreign objects using sideband sensing. For example, such sideband sensing may include infrared sensing or temperature sensing to detect hot areas of the power station, which may be indicative of a foreign object. When infrared is used, the measured heat data will be compared to some baseline value in order to determine whether there are any hot spots on the power station. 
         [0059]      FIG. 4  illustrates a plan view of an exemplary power station  400  for using temperature sensing to detect foreign objects. The power station  400  includes a plurality of coils  420  disposed on a ferrite material plate  410 . A plurality of temperature sensors are attached to the ferrite material  410 . 
         [0060]    As the foreign objects absorb transmitted power, they will heat up, causing a temperature of the ferrite plate  410  to heat up in localized areas. The temperature sensors  430  detect the temperature of the ferrite plate  410  at these localized areas to determine whether a foreign object is present. In an embodiment, the temperature sensors  430  are disposed on a housing  440  that encases the ferrite plate  410 . In this configuration, the temperature sensors  430  detect the internal temperature of the power station  400  rather than the direct temperature of the ferrite material  410 . 
         [0061]      FIG. 5  illustrates a top-down plan view of an exemplary power station  500  for detecting foreign objects. The power station  500  includes a ferrite plate  505  and a plurality of temperature sensors  530 . The power station  500  further includes a primary coil  510  and a plurality of secondary coils  520 , and may represent an exemplary embodiment of the power station  110 . 
         [0062]    The power station  500  demonstrates multiple foreign object detection configurations that may or may not be used together. In an embodiment, the ferrite plate  505  is broken into multiple sections  505 A- 505 D. A temperature sensor  530 A- 530 D is provided to each of these sections, respectively, for detecting localized temperature changes in the ferrite material. 
         [0063]    In another embodiment, the temperature of the ferrite sections  505 A- 505 D can be determined by measuring the resistance changes of each of the those section. As the ferrite material  505  heats up, its resistance will change. By measuring a current passed through each corresponding ferrite material section  505 A- 505 D, temperature changes of those sections can be determined. 
         [0064]    In an embodiment, the coils  520 / 510  can be used to determine whether foreign objects are in the vicinity. The coils cover a large surface area of the power station  500 . Further, the coils  510 / 520  are metallic and can be constructed with materials that are good heat conductors. Similar to the ferrite material, when the metal of the coils  510 / 520  heats up, their resistances will change. By passing a known current through the coils  510 / 520  and measuring the voltage change, heat changes can be detected. 
         [0065]    The foreign object detection can be performed without interrupting power transfer to another device. For example, the primary coil  510  can be used to transmit power signals to a receiving device while the power station  500  measures voltage changes in each of the secondary coils  520 . Alternatively, the power station  500  can transmit power to a receiving device via one or more of the secondary coils  520 , while measuring voltage changes among the remaining secondary coils  520 . 
         [0066]    The power station  500  can temporarily energize the secondary coils to perform foreign object detection. Once the foreign object detection procedure has completed, the power station  500  can de-energize those same coils in order to save power. Further, in order to avoid interfering with the coils being used to charge the receiving device, the unused coils can be energized at a different frequency from the charging coils. 
         [0067]    Additional configurations may be available to detect the presence of foreign objects, such as for example video/still camera detection, laser scanning and pressure sensing, among others within the spirit and scope of the present disclosure. Using any of the above foreign object detection methods will allow for efficient power transfer and accurate authentication with a receiving device. 
         [0068]    In an embodiment, the power station  500  is capable of detecting and distinguishing between a foreign object and an unauthorized device. In doing so, the power station  500  measures power and/or impedances across multiple of its coils  520  and/or at multiple frequencies. By analyzing the results of these measurements, the power station  500  can characterize the object as an unauthorized device or foreign object. The power station  500  can then take different actions depending on its determination. For example, if the power station  500  determines that a foreign object is present, the power station  500  can stop any or nearby charging operations as a safety precaution. Alternatively, if the power station  500  determines that an unauthorized phone is present, the power station  500  may implement any of the power control methods described above. 
         [0069]    Exemplary Method for Wirelessly Transmitting Power 
         [0070]      FIG. 6  illustrates a block diagram of an exemplary method for transferring power from a power station to a chargeable receiving device. 
         [0071]    Initially, the power station receives authentication information from the receiving device ( 610 ). This information can be received via load modulation over the WPT standard, or using any other available communication standard, including NFC, WiFi, Bluetooth, etc. Based on the received authentication information, the power station determines whether the receiving device is authenticated for power transfer ( 620 ). 
         [0072]    If the power station determines that the receiving device is not authenticated ( 620 —N), the power station initiates a power theft prevention measure ( 630 ). This measure may include decommissioning power to coils corresponding to the receiving device, shifting frequencies of those coils, or shutting down the transmission, among others. 
         [0073]    If, on the other hand, the power station determines that the receiving device is authenticated ( 620 —Y), the power station transmits a report request as well as test power signals ( 640 ). The test power signals may be chosen at different power level, different frequencies, and for different loads. In response to the report request, the power station receives a received power report from the receiving device ( 650 ) that reports the amount of power actually received for the different test power signals. 
         [0074]    Based on the report, the power station determines whether the receiving device is authenticated ( 660 ). This second authentication may be performed by comparing the reported power levels to expected/estimated power levels. If the reported levels are too low compared to the estimated levels, then the power station determines that the receiving device failed the power report authentication ( 660 —N). When this occurs, the power station implements one or more of the power theft prevention measures detailed above ( 630 ). 
         [0075]    If, on the other hand, the power station determines that the reported power values are sufficient close to the estimated values, then the power station authenticates the receiving device ( 660 —Y). Once the receiving device has successfully passed the second authentication ( 660 —Y), the power station begins transmitting power ( 670 ). 
         [0076]    During power transmission ( 670 ), the power station can periodically request an updated received power report from the receiving device ( 640 ) in order to verify that proper tracking is being performed. When this occurs, the power station proceeds back through steps  650  and  660  before returning to power transmission ( 670 ). 
         [0077]    Those skilled in the relevant art(s) will recognize that the above method can additionally or alternatively include any of the functionality of the power station  110  discussed above, as well as any of its modifications. Further, the above description of the exemplary method should neither be construed to limit the method nor the description of the mobile device power station  110 . 
         [0078]    Exemplary Computer System Implementation 
         [0079]    It will be apparent to persons skilled in the relevant art(s) that various elements and features of the present disclosure, as described herein, can be implemented in hardware using analog and/or digital circuits, in software, through the execution of instructions by one or more general purpose or special-purpose processors, or as a combination of hardware and software. 
         [0080]    The following description of a general purpose computer system is provided for the sake of completeness. Embodiments of the present disclosure can be implemented in hardware, or as a combination of software and hardware. Consequently, embodiments of the disclosure may be implemented in the environment of a computer system or other processing system. An example of such a computer system  700  is shown in  FIG. 7 . One or more of the modules depicted in the previous figures can be at least partially implemented on one or more distinct computer systems  700 . 
         [0081]    Computer system  700  includes one or more processors, such as processor  704 . Processor  704  can be a special purpose or a general purpose digital signal processor. Processor  704  is connected to a communication infrastructure  702  (for example, a bus or network). Various software implementations are described in terms of this exemplary computer system. After reading this description, it will become apparent to a person skilled in the relevant art(s) how to implement the disclosure using other computer systems and/or computer architectures. 
         [0082]    Computer system  700  also includes a main memory  706 , preferably random access memory (RAM), and may also include a secondary memory  708 . Secondary memory  708  may include, for example, a hard disk drive  710  and/or a removable storage drive  712 , representing a floppy disk drive, a magnetic tape drive, an optical disk drive, or the like. Removable storage drive  712  reads from and/or writes to a removable storage unit  716  in a well-known manner. Removable storage unit  716  represents a floppy disk, magnetic tape, optical disk, or the like, which is read by and written to by removable storage drive  712 . As will be appreciated by persons skilled in the relevant art(s), removable storage unit  716  includes a computer usable storage medium having stored therein computer software and/or data. 
         [0083]    In alternative implementations, secondary memory  708  may include other similar means for allowing computer programs or other instructions to be loaded into computer system  700 . Such means may include, for example, a removable storage unit  718  and an interface  714 . Examples of such means may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM, or PROM) and associated socket, a thumb drive and USB port, and other removable storage units  718  and interfaces  714  which allow software and data to be transferred from removable storage unit  718  to computer system  700 . 
         [0084]    Computer system  700  may also include a communications interface  720 . Communications interface  720  allows software and data to be transferred between computer system  700  and external devices. Examples of communications interface  720  may include a modem, a network interface (such as an Ethernet card), a communications port, a PCMCIA slot and card, etc. Software and data transferred via communications interface  720  are in the form of signals which may be electronic, electromagnetic, optical, or other signals capable of being received by communications interface  720 . These signals are provided to communications interface  720  via a communications path  722 . Communications path  722  carries signals and may be implemented using wire or cable, fiber optics, a phone line, a cellular phone link, an RF link and other communications channels. 
         [0085]    As used herein, the terms “computer program medium” and “computer readable medium” are used to generally refer to tangible storage media such as removable storage units  716  and  718  or a hard disk installed in hard disk drive  710 . These computer program products are means for providing software to computer system  700 . 
         [0086]    Computer programs (also called computer control logic) are stored in main memory  706  and/or secondary memory  708 . Computer programs may also be received via communications interface  720 . Such computer programs, when executed, enable the computer system  700  to implement the present disclosure as discussed herein. In particular, the computer programs, when executed, enable processor  704  to implement the processes of the present disclosure, such as any of the methods described herein. Accordingly, such computer programs represent controllers of the computer system  700 . Where the disclosure is implemented using software, the software may be stored in a computer program product and loaded into computer system  700  using removable storage drive  712 , interface  714 , or communications interface  720 . 
         [0087]    In another embodiment, features of the disclosure are implemented primarily in hardware using, for example, hardware components such as application-specific integrated circuits (ASICs) and gate arrays. Implementation of a hardware state machine so as to perform the functions described herein will also be apparent to persons skilled in the relevant art(s). 
       CONCLUSION 
       [0088]    It is to be appreciated that the Detailed Description section, and not the Abstract section, is intended to be used to interpret the claims. The Abstract section may set forth one or more, but not all exemplary embodiments, and thus, is not intended to limit the disclosure and the appended claims in any way. 
         [0089]    The invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries may be defined so long as the specified functions and relationships thereof are appropriately performed. 
         [0090]    It will be apparent to those skilled in the relevant art(s) that various changes in form and detail can be made therein without departing from the spirit and scope of the disclosure. Thus, the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.