Abstract:
A mobile terminal, operational both to receive and transmit, may comprise a mobile antenna and an antenna controller that may be configured to control the mobile antenna at least for keeping it pointed towards the satellite, e.g. as the mobile terminal and/or the satellite move. Disclosed is a method that may be used by the antenna controller for optimizing the pointing of the mobile antenna, the method may be based on assessing both the reception quality and the transmission quality. This method may be used for overcoming degradation, mainly to transmission quality, that may result from squints between an optimal reception direction and an optimal transmission direction associated with the mobile antenna.

Description:
PRIORITY CLAIM 
       [0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 62/219,910, filed Sep. 17, 2015, and entitled “Mobile Antenna Tracking,” the disclosure of which is incorporated by reference herein in its entirety and made part hereof. 
     
    
     FIELD 
       [0002]    Aspects of the disclosure pertain to the field of satellite communications using mobile terminals. 
       BACKGROUND 
       [0003]    A mobile terminal for communication via satellite is typically equipped with a mobile antenna that keeps pointing towards the satellite while the terminal is in motion. A controller coupled with the antenna uses one or more devices, for example a GPS receiver, a compass, 3-D gyroscopes and accelerometers, for determining a direction of movement and corrects the antenna alignment in accordance with the determined direction of movement to keep the antenna pointing towards the satellite. However, compasses often suffer from large errors, whereas pointing data from gyroscopes and accelerometers tend to slowly drift. In order to compensate for the drift in pointing data and provide slow correction of the antenna pointing, the antenna controller often uses information related to the reception quality of a received signal, for example any one of Signal to Noise Ratio (SNR), Signal Strength, Receiver Signal Strength Indication (RSSI) and Bit Error Rate (BER). 
         [0004]    When the mobile terminal is operational both to receive and transmit, the transmitting (TX) antenna and the receiving (RX) antenna usually share the same reflector. Pointing the shared aperture (reflector) in accordance with a reception SNR at the mobile terminal is usually sufficient for achieving fairly accurate pointing, both for receiving and for transmitting. 
         [0005]    However, sometimes the direction of the TX antenna beam has a slight squint in reference to the direction of the RX antenna beam, even when both the TX antenna and the RX antenna share the same reflector. Sometimes, the RX antenna and the TX antenna have independent apertures. For instance, in phased array antennas, the TX antenna and the RX antenna usually have independent apertures and although the two antennas may be installed in parallel and the RX antenna pointing may be used for pointing the TX antenna as well, small inaccuracies lead to some squint between the pointing of the two antennas. 
         [0006]    In satellite communications, the transmission frequencies are higher than the reception frequencies. Consequently, where an RX antenna and a TX antenna share a common reflector the TX antenna has a narrower beam compared to the beam of the RX antenna. In order to use SNR readings of a received signal for mobile antenna tracking, the antenna is dithered around the pointing direction in order to estimate a gradient of the pointing error, which can then be used for determining the needed pointing correction. One dithering method includes moving the antenna in accordance with four corners of a square around the current pointing direction (e.g. lower-left, lower-right, higher-right, and higher-left). Another dithering method includes moving the antenna in accordance with a conical scan around the some pointing direction. Typically, this dithering or conical scan follows a −0.5 dB contour of the RX beam (the specific contour selection is a compromise between the need for low antenna gain loss and good antenna dynamics). As the TX antenna has a narrower beam, this dithering or scan corresponds to a more degraded contour (for example, a −1 dB contour) around the TX antenna pointing, causing greater loss in the terminal&#39;s TX link, even with no squint at all. When some squint is added, the loss in the terminal&#39;s TX link is even larger. 
       SUMMARY 
       [0007]    The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is intended neither to identify key or critical elements of the disclosure nor to delineate the scope of the disclosure. The following summary merely presents some aspects of the disclosure in a simplified form as a prelude to the description below. 
         [0008]    A satellite communication system may comprise at least a hub, a mobile terminal and a satellite. The mobile terminal may comprise a modem, a mobile antenna, an antenna controller and one or more sensors that may be configured to sense changes in a direction at which the mobile antenna may be pointing. The antenna controller may be configured to receive one or more indications from the modem and/or from the one or more sensors, and to generate one or more control signals towards the mobile antenna for at least the purpose of modifying the direction at which the mobile antenna may be pointing. 
         [0009]    According to aspects of the disclosure, the antenna controller may be configured to receive Local-SNR estimations corresponding to reception at the mobile terminal of a signal transmitted by the hub. The antenna controller may further be configured to receive Far-SNR estimations corresponding to reception at the hub of a signal transmitted by the mobile terminal. The Local-SNR estimations may correspond to a reception (RX) pointing quality of the mobile antenna. The Far-SNR estimations may correspond to a transmission (TX) pointing quality of the mobile antenna. In some embodiments, the Far-SNR estimations may be received by the antenna controller from the modem of the mobile terminal. The modem of the mobile terminal may be configured to generate the Far-SNR estimations based on corresponding Far-SNR estimations or based on Far-SNR telemetry data that the hub may be configured to send to the mobile terminal. 
         [0010]    According to aspects of the disclosure, the antenna controller may be configured to control the mobile antenna to perform a dithering movement (for example, a 360 degrees conical scan) around a tracked direction. The antenna controller may further be configured to record a plurality of Local-SNR estimations and a plurality of Far-SNR estimations while the dithering movement may be in progress. The antenna controller may further be configured to calculate an RX pointing error corresponding to the Local-SNR estimations. Additionally, or alternatively, the antenna controller may be configured to calculate a TX pointing error corresponding to the Far-SNR estimations. The antenna controller may further be configured to synchronize the calculated TX pointing error with the calculated RX pointing error by accounting for a (satellite path) delay in receiving Far-SNR estimations and calculate a weighted-sum of the RX pointing error and the TX pointing error to produce a calculated combined pointing error. 
         [0011]    According to aspects of the disclosure, the antenna controller may be configured to periodically repeat the dithering movement and to calculate a combined pointing error estimation for each dithering cycle, and generate pointing corrections for the mobile antenna based on the combined pointing error estimations while using an averaging loop-filter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Having thus described the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
           [0013]      FIG. 1  shows a satellite communication system in accordance with aspects of the disclosure; 
           [0014]      FIG. 2  shows a series of steps performed to maintain an antenna pointing towards a satellite; and 
           [0015]      FIG. 3  shows a series of steps performed to correct an antenna pointing direction. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    In reference to  FIG. 1 , a satellite communication system  100  may comprise at least a hub  110 , a mobile terminal  120  and a satellite  103 . In some embodiments, the satellite communication system  100  may comprise a plurality of terminals, wherein at least one terminal of the plurality of terminals may be the mobile terminal  120 . 
         [0017]    The hub  110  may comprise a hub modem  101  and a hub antenna  102 , wherein the hub modem  101  may be coupled to the hub antenna  102 . The mobile terminal  120  may comprise a terminal modem  105  and a mobile antenna  104 , wherein the terminal modem  105  may be coupled to the mobile antenna  104 . The mobile terminal  120  may further comprise an antenna controller  106  and one or more sensors  107 , wherein the antenna controller  106  may be coupled to the mobile antenna  104 , to the terminal modem  105  and to the one or more sensors  107 . The antenna controller  106  may comprise one or more circuits to interface with mobile antenna  104 , one or more circuits to interface with terminal modem  105 , and one or more circuits to interface with the one or more sensors  107 . In some embodiments, the one or more sensors  107  may comprise any of a GPS receiver, one or more gyroscopes, and one or more accelerometers. The antenna controller  106  may be configured to receive one or more indications from any of the terminal modem  105  and the one or more sensors  107 , and generate one or more control signals towards the mobile antenna  104 . The mobile antenna  104  may be configured to, upon receiving the one or more control signals, change at least one of an azimuth property and an elevation property in accordance with the received one or more control signals. The hub modem  101  may be configured to transmit, e.g. via the hub antenna  102 , at least one transmission to the mobile terminal  120 . The at least one transmission may be relayed via the satellite  103  to the mobile terminal  120 , where it may be received by the terminal modem  105  via the mobile antenna  104 . 
         [0018]      FIG. 2  shows a series of steps that may be performed to maintain an antenna pointing towards a satellite. At step  200 , the terminal modem  105  of mobile terminal  120  may transmit, via the mobile antenna  104 , a transmission to the hub  110 . The transmission by the mobile terminal modem  105  may be relayed via the satellite  103  to the hub  110 , where it may be received by the hub modem  101  via the hub antenna  102 . At step  201 , the hub modem  101  may be configured to receive the transmission from the mobile terminal  120 . The hum modem  101  may receive the transmission using a receiver that may be included in the hub modem  101 . 
         [0019]    At step  202 , the hub modem  101  may determine a Signal to Noise Ratio (SNR) estimation for the transmission received from the mobile terminal  120 . In some embodiments, the hub modem  101  may be configured to determine a plurality of SNR estimations for the transmission received from the terminal  120  in order to determine an SNR estimation for every preconfigured interval (or in accordance with an interval otherwise determined by the hub modem  101 ). At step  203 , the hub modem  101  may send at least one SNR estimation corresponding to the transmission received from the mobile terminal  120 . The hub modem  101  may be configured to send the at least one SNR estimation corresponding to the transmission received from the mobile terminal  102  in the at least one transmission that the hub modem  101  may be configured to transmit to the mobile terminal  120 . In some embodiments, the hub modem  101  may be configured to send a plurality of SNR estimations corresponding to the transmission received from the mobile terminal  120 . The hub modem may be configured to send an SNR estimation of the plurality of SNR estimations immediately or substantially immediately following a determining of the SNR estimation(s). 
         [0020]    At step  204 , the terminal modem  105  may receive from the hub  110  at least one SNR estimation corresponding to its transmission to the hub. In some embodiments, the terminal modem  105  may be configured to receive a plurality of SNR estimations corresponding to its transmission to the hub  110 . The terminal memory  105  may be configured to store, e.g. in a memory associated with the terminal modem  105 , one or more SNR estimations of the plurality of SNR estimations. In some embodiments, the terminal modem  105  may be configured to store the one or more SNR estimations corresponding to its transmission to the hub  110  as Far-SNR data. 
         [0021]    At step  205 , the mobile terminal  120  may keep the mobile antenna  104  pointed towards the satellite  103  by using a tracking algorithm. In some embodiments, the tracking algorithm may be implemented in software that may be executed by one or more processors that may be included in the antenna controller  106 . The software, when executed by the one or more processors, may cause the antenna controller  106  to control the pointing of the mobile antenna  104  in accordance with the tracking algorithm. For example, the one or more sensors  107  may be configured to sense a change in a direction at which the mobile antenna  104  may be pointing at. The one or more sensors  107  may indicate the sensed change to the antenna controller  106 . The antenna controller  106  may be configured to correct the antenna pointing direction using the tracking algorithm. 
         [0022]      FIG. 3  shows a series of steps that may be executed by the antenna controller to correct the antenna pointing direction using the tracking algorithm. At step  300 , the antenna controller  106  may receive, for example from the terminal modem  105 , one or more Local-SNR estimations that may correspond to the local reception of mobile terminal  120 . The one or more Local-SNR estimations may be based on the reception by mobile terminal  120  of the at least one transmission from the hub  110 . In some embodiments, the antenna controller  106  may receive from the terminal modem  105 , a plurality of Local-SNR estimations that may correspond to the local reception of mobile terminal  120 . The antenna controller  106  may be configured to receive the plurality of SNR estimations at equal intervals. 
         [0023]    At step  301 , the antenna controller  106  may receive, for example from the terminal modem  105 , one or more Far-SNR estimations. The one or more Far-SNR estimations may correspond to the one or more Far-SNR estimations that the terminal modem  105  may receive from the hub  110 . At step  302 , the antenna controller  106  may determine a reception (RX) pointing error of the mobile antenna  104  based on the one or more Local-SNR estimations (discussed in detail below). At step  303 , the antenna controller  106  may determine a transmission (TX) pointing error based on the one or more Far-SNR estimations (discussed in detail below). At step  304 , the antenna controller  106  may determine a correction for the antenna pointing based on the estimated RX pointing error and/or the estimated TX pointing error (discussed in detail below). The correction for the antenna pointing may be a correction in azimuth and/or in elevation. At step  305 , the antenna controller  106  may control the mobile antenna  104  in accordance with the determined correction for the antenna pointing. 
         [0024]    In some embodiments, antenna controller  106  may control the mobile antenna  104  in a manner that may cause the mobile antenna  104  to dither around a current or present pointing direction. In some embodiments, the antenna controller  106  may be configured to control the mobile antenna  104  in a manner that may cause the mobile antenna  104  to perform a conical scan around the mobile antenna&#39;s current or present pointing direction. In some embodiments, the antenna controller  106  may be configured to control the mobile antenna  104  to complete a full 360 degrees conical scan in a time interval T (e.g. in seconds). The antenna controller  106  may be further configured to receive from the terminal modem  105  and while the conical scan may be in progress, N Local-SNR estimations and N Far-SNR estimations. The N Local-SNR estimations and N Far-SNR estimations may be evenly spaced along the conical scan interval. For example, the antenna controller  106  may receive one Local-SNR estimation and one Far-SNR estimation every T/N. Each of the N Local-SNR estimations may be received at the antenna controller  106  with delay DLocal, whereas each of the Far-SNR estimations may be received at the antenna controller  106  with delay DFar. The delay DFar may be significantly longer than DLocal due to the round trip latency that may be introduced by the satellite  103  (for example, in case of a geostationary satellite, the round-trip latency may be in the excess of 500 milliseconds). 
         [0025]    For sake of simplicity, the descriptions above and/or herein may assume reception of the same number of Local-SNR estimations and Far-SNR estimations while the conical scan may be in progress (e.g. N). However, the method described herein may be easily adjusted to receiving a first number of Local-SNR estimations (e.g. NLocal) and a second number of Far-SNR estimations (e.g. NFar) while the conical search is in progress, wherein the first number may be different from the second number (e.g. NLocal≠NFar). Furthermore, while the description above and/or herein may refer to conical scan as a possible dithering pattern, the methods described herein may be usable also with other dithering patterns. 
         [0026]    When the pointing direction that may be associated with a center of the conical scan may comprise some pointing error, arranging a plurality of SNR estimations corresponding to the conical scan in a form of a graph may result in a graph that resembles a sine wave with a single period (cycle). Therefore, a process of determining a maximum SNR estimation among a plurality of SNR estimations corresponding to the conical scan may be equivalent to a process of estimating an unknown phase of single-period sine wave. An unknown phase of a single-period sine wave may be estimated by correlating samples of the single-period sine wave against sine and cosine waveforms of a single period. 
         [0027]    The antenna controller  106  may be configured to compute based on the received N Local-SNR estimations, a complex value that may correspond to the RX pointing error based on the following equations: 
         [0000]    
       
         
           
             
               
                 
                   
                     E 
                     
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         [0028]    In the above equations, Local_SNR may represent an array (a vector) containing the received N Local-SNR estimations, E i   _   Local  and E q   _   Local  may respectively represent a real part and imaginary part of the RX pointing error, and E Local  may represent the RX pointing error value. 
         [0029]    The antenna controller  106  may be configured to compute based on the received N Far-SNR estimations, a complex value that may correspond to the TX pointing error based on the following equations: 
         [0000]    
       
         
           
             
               
                 
                   
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                   5 
                 
               
             
             
               
                 
                   
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         [0030]    In the above equations, Far_SNR may represent an array (a vector) containing the received N Far-SNR estimations, E i   _   Far  and E q   _   Far  may respectively represent a real part and imaginary part of the TX pointing error, and E Far  may represent the TX pointing error value. 
         [0031]    It may be noted that both in the case of the RX pointing error value (e.g. E Local ) and in the case of the TX pointing error value (e.g. E Far ), the relevant complex value may correspond to an amplitude (e.g. in dB) and to a phase towards a gradient direction. In some embodiments, the real part of the complex value (e.g. E i   _   Local  and E i   _   Far ) may correspond to an azimuth direction and the imaginary part of the complex value (e.g. E q   _   Local  and E q   _   Far  may correspond to an elevation direction. 
         [0032]    However, as previously mentioned, for each pointing direction of the mobile antenna  104  during the conical scan the corresponding Far-SNR estimation may be received at the antenna controller  106  after a delay of D Far  and the corresponding Local-SNR estimation may be received at the antenna controller  106  after a delay of D Local  (e.g. wherein D Far &gt;D local ). Therefore, some compensation may be needed for at least the purpose of synchronizing the previously calculated complex values (e.g. E Local  and E Far ) with the antenna pointing direction during the dithering or with the conical scan phase. Given the conical scan duration T (e.g. in seconds), a delay D (e.g. also in seconds) in receiving SNR estimations may result in a phase associated with the relevant complex value (e.g. E Local  or E Far ) being rotated by an angle θ (e.g. in Radian): 
         [0000]    
       
         
           
             
               
                 
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                       T 
                     
                   
                 
               
               
                 
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                    
                   
                       
                   
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                   7 
                 
               
             
           
         
       
     
         [0033]    The antenna controller  106  may be configured to calculate a corrected TX pointing error value. The antenna controller  106  may calculate the corrected TX pointing error value by back-rotating a phase associated with the TX pointing error value in accordance with the delay associated with receiving Far-SNR estimations (e.g. D Far ). Additionally, or alternatively, the antenna controller  106  may be configured to calculate a corrected RX pointing error value. The antenna controller may be configured to calculate a corrected RX pointing error value by back-rotating a phase associated with the RX pointing error value in accordance with the delay associated with receiving Local-SNR estimations (e.g. D Local ). The corrected TX pointing error value and corrected RX pointing error value may be calculated as follows: 
         [0000]    
       
         
           
             
               
                 
                   
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                       Far 
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                       Corrected 
                     
                   
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                     Local 
                   
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                         Local 
                       
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                       Local 
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                       Corrected 
                     
                   
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                       Local 
                     
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                           Local 
                         
                       
                     
                   
                 
               
               
                 
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                   11 
                 
               
             
           
         
       
     
         [0034]    In the above equations, D Far  and D local  may respectively represent delays associated with receiving the Far-SNR estimations and Local-SNR estimations, T may represent a conical scan duration, θ Far  and θ Local  may respectively represent phase rotates associated with the TX pointing error value (E Far ) and the RX pointing error value (E Local ), and E Far   _   Corrected  and E Local   _   Corrected  may respectively represent a phase-corrected TX pointing error value and a phase-corrected RX pointing error value. 
         [0035]    In some embodiments, where the delay associated with receiving Local-SNR estimations may be sufficiently short in comparison to the conical scan interval (T), the corresponding correction angle (e.g. θ Local ) may be quite small and perhaps lead to a negligible correction (e.g., e jθ     Local   ≈1). In such embodiments (for example, when the delay associated with receiving Local-SNR estimations is smaller than a delay threshold value), the corrected RX pointing error value may be set to the same value as the RX pointing error value without performing the corrective rotation calculation (e.g. E Local   _   Corrected =E Local ). 
         [0036]    The antenna controller  106  may be configured to, after calculating the corrected RX pointing error value (e.g. E Local   _   Corrected ) and the corrected TX pointing error value (e.g. E Far   Corrected ), optimize (i.e. correct) the mobile antenna  104  pointing in accordance with the calculated pointing error values. In some embodiments, the antenna controller  106  may be configured to optimize the mobile antenna  104  pointing only in accordance with reception performance, e.g. by optimizing the mobile antenna  104  pointing only in accordance with the corrected RX pointing error value. In some embodiments, the antenna controller  106  may be configured to optimize the mobile antenna  104  pointing only in accordance with transmission performance, e.g. by optimizing the mobile antenna  104  pointing only in accordance with the corrected TX pointing error value. In some embodiments, for example where the mobile antenna  104  may comprise a single aperture (or reflector), the antenna controller  106  may be configured to optimize the mobile antenna  104  pointing in accordance with both reception performance and transmission performance. The antenna controller  106  may be configured to optimize the mobile antenna pointing by optimizing the mobile antenna  104  pointing in accordance with both the corrected RX pointing error value and the corrected TX pointing error value. The antenna controller  106  may linearly combine the corrected RX pointing error value and the corrected TX pointing error value in order to generate an antenna pointing error value (e.g. E). The antenna controller  106  may control the mobile antenna  104  in accordance with the antenna pointing error value E so that the mobile antenna  104  may be pointed in a direction that may be associated with a compromise between a transmission (TX) only optimization and a reception (RX) only optimization. For example, the antenna controller  106  may be configured to calculate the antenna pointing error value using a predefined or a configurable weight parameter α (e.g. 0≦α≦1): 
         [0000]        E=αE   Far   _   Corrected +(1−α) E   Local   _   Corrected    Equation 12
 
         [0037]    In the above equations, E Far   _   Corrected  and E Local   _   Corrected  may respectively represent a phase-corrected TX pointing error value and a phase-corrected RX pointing error value, α may represent a weight parameter, and E may represent an antenna pointing error value. 
         [0038]    In some embodiments, the antenna controller  106  may be configured to optimize the mobile antenna  104  pointing in accordance with both reception performance and transmission performance (as previously described) when both Far-SNR estimations and Local-SNR estimations are received from the terminal modem  105 , and to optimize the mobile antenna  104  pointing only in accordance with reception performance when only Local-SNR estimations are received (i.e. when Far-SNR estimations are not available). In a first example, Far-SNR estimations might not be available when the mobile terminal  120  may not be allowed to transmit (e.g. following a powering up of the mobile terminal and for as long as the mobile antenna  104  is not pointing (e.g. with sufficient accuracy) towards the satellite  103 ). In a second example, Far-SNR estimations might not be available if for any reason the transmission from mobile terminal  120  is not received by the hub  110  (e.g. as the Far-SNR estimations may also indicate whether a receiver, which may be included in the hub modem  101 , is locked on the mobile terminal&#39;s transmission). 
         [0039]    The antenna controller  106  may be configured to periodically repeat the conical scan process described above. The antenna control  106  may periodically repeat the conical scan process for as long as the mobile terminal  120  may be operative, such that the mobile antenna  104  is kept on track during the duration of the operation of the mobile terminal  120 . However, the delay for obtaining Far-SNR estimations may also determine an interval between a time of completing a conical scan and a time at which a next conical scan may start. In order to obtain Far-SNR estimations that may be relevant to an updated mobile antenna pointing, a next conical scan may not be started for a duration of at least D Far  since the mobile antenna  104  pointing may have been updated. 
         [0040]    In some embodiments, the antenna controller  106  may be configured to, after completing a conical scan, update the mobile antenna  104  pointing and/or a center for a next conical scan in accordance with a direction that may be indicated by the antenna pointing error value (E) calculated during the completed conical scan. In some embodiments, the antenna controller  106  may be configured to determine an updated mobile antenna pointing and/or an updated center for a next conical scan by using an optimal pointing that may be suggested by the antenna pointing error value (E). In some embodiments, the antenna controller  106  may be configured to determine an updated mobile antenna pointing and/or an updated center for a next conical scan using an averaging loop-filter. For example, the loop-filter may be configured in accordance with an averaging parameter as follows: 
         [0000]        Az ( n+ 1)= Az ( n )+ K *Real( E )   Equation 13
 
         [0000]        El ( n+ 1)= El ( n )+ K *Image( E )   Equation 14
 
         [0041]    In equations 13 and 14, E may correspond to the antenna pointing error value, Az may correspond to the antenna azimuth, El may correspond to the antenna elevation, Real may be a function that returns the real part of a complex value, Image may be a function returning the imaginary part of a complex value, K may represent the averaging parameter, n may represent a current step and n+1 may represent a next step. In some embodiments, the averaging parameter (e.g. K) may be set to a small fraction for at least the purpose of prolonging the averaging time, wherein the averaging time may be in the excess of T/K and T may represent the conical scan duration. 
         [0042]    In some embodiments, the antenna controller  106  may be configured to modify the way the mobile antenna  104  pointing is optimized simply by changing the weight parameter (α) that may be used for combining the corrected RX pointing error value and the corrected TX pointing error value in to an antenna pointing error value (e.g. E). The antenna controller  106  may be configured to modify the weight parameter (α) in small steps, to determine the effect of each value of the weight parameter (α) on the corrected TX pointing error values and/or on the corrected RX pointing error values (e.g. that may be computed for a plurality of conical scans that may be performed for each value of the weight parameter (α)), and to determine an optimum value for the weight parameter (α) in accordance with one or more criteria. 
         [0043]    Various aspects of the disclosure may be embodied as one or more methods, systems, apparatuses (e.g., components of a satellite communication network), and/or computer program products. Accordingly, those aspects may take the form of an entirely hardware embodiment, an entirely software embodiment, an entirely firmware embodiment, or an embodiment combining firmware, software, and/or hardware aspects. Furthermore, such aspects may take the form of a computer program product stored by one or more computer-readable storage media having computer-readable program code, or instructions, embodied in or on the storage media. Any suitable computer readable storage media may be utilized, including hard disks, CD-ROMs, optical storage devices, magnetic storage devices, and/or any combination thereof. In some embodiments, one or more computer readable media storing instructions may be used. The instructions, when executed, may cause one or more apparatuses to perform one or more acts described herein. The one or more computer readable media may comprise transitory and/or non-transitory media. In addition, various signals representing data or events as described herein may be transferred between a source and a destination in the form of electromagnetic waves traveling through signal-conducting media such as metal wires, optical fibers, and/or wireless transmission media (e.g., air and/or space). 
         [0044]    Modifications may be made to the various embodiments described herein by those skilled in the art. For example, each of the elements of the aforementioned embodiments may be utilized alone or in combination or sub-combination with elements of the other embodiments. It will also be appreciated and understood that modifications may be made without departing from the true spirit and scope of the present disclosure. The description is thus to be regarded as illustrative instead of restrictive on the present disclosure.