Patent Publication Number: US-8995939-B2

Title: Method and apparatus for power cutback in a simultaneous dual frequency band call

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This patent application is a continuation of U.S. patent application Ser. No. 13/221,430 filed Aug. 30, 2011 by Dean E. Thorson and entitled “Method and Apparatus for Power Cutback in a Simultaneous Dual Frequency Band Call.” This related application is hereby incorporated by reference herein in its entirety, and priority thereto for common subject matter is hereby claimed. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure is directed to a method and apparatus for power cutback in a simultaneous dual frequency band call. More particularly, the present disclosure is directed to power cutback for a cellular call in a first frequency band simultaneous with a second frequency band. 
     2. Introduction 
     Wireless communication devices used in today&#39;s society include mobile phones, personal digital assistants, portable computers, gaming devices, and various other electronic communication devices. Such devices employ multiple transceivers that allow a device to transmit and receive signals on different wireless networks. For example, a device can include a Code Division Multiple Access (CDMA) transceiver, a Long Term Evolution (LTE) transceiver, a Universal Mobile Telecommunications System (UMTS) transceiver, a Global Positioning System (GPS) receiver, an 802.11-based transceiver, and/or other transceivers. 
     Unfortunately, nonlinearities in a device&#39;s radio frequency circuitry can cause receiver desensitization on certain channel combinations. For example, desensitization can occur when both the LTE and CDMA transmitters are on and are at or close to full power. This receiver desensitization can be a reduction in receiver sensitivity due to the presence of a high-level off-channel signal overloading the radio frequency amplifier or mixer stages. As a further example, receiver desensitization can occur when a strong off-channel signal overloads a receiver front end and thus reduces the sensitivity to weaker on-channel signals. One other example is when non-linearity in the transmitter circuitry can cause the transmit signals to mix, creating strong signals that fall within the device&#39;s receive frequency bands. 
     Hardware design has been implemented to minimize desensitization in a simultaneous dual frequency band call. However, with present technology, desensitization cannot be completely eliminated without degrading performance of the individual transceivers when they are operating alone. 
     Thus, there is a need for a method and apparatus for power cutback in a simultaneous dual frequency band call. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which advantages and features of the disclosure can be obtained, various embodiments will be illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the disclosure and do not limit its scope, the disclosure will be described and explained with additional specificity and detail through the use of the drawings in which: 
         FIG. 1  illustrates an example diagram of a system in accordance with a possible embodiment; 
         FIG. 2  illustrates an example block diagram of an apparatus in accordance with a possible embodiment; 
         FIG. 3  shows a sample flowchart illustrating the operation of the apparatus of  FIG. 2  in accordance with a possible embodiment; and 
         FIG. 4  shows a sample flowchart illustrating the operation of the apparatus of  FIG. 2  in accordance with a possible embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A method and apparatus for power cutback in a simultaneous dual frequency band call is disclosed. The method can operate on a dual frequency band transmit device. The method may include determining if a transmit frequency in a first frequency band from the device combined with a transmit frequency in a second frequency band from the device causes receiver desensitization at the device. The method may include determining if the transmit power in the first frequency band is above a threshold power. The method may include reducing maximum transmit power in the second frequency band by an amount proportional to transmit power in the first frequency band and transmit signal bandwidth in the second frequency band. 
       FIG. 1  is an example block diagram of a system  100  according to one possible embodiment. The system  100  can include a terminal  110 , a network  120 , a first base station  130 , a second base station  135 , and a network controller  140 . 
     The terminal  110  can be a wireless communication device including cellular and/or other wireless communication circuitry, such as Code Division Multiple Access (CDMA) circuitry, Long Term Evolution (LTE) circuitry, Universal Mobile Telecommunications System (UMTS) circuitry, Time Division Multiple Access (TDMA) circuitry, Frequency Division Multiple Access (FDMA) circuitry, Bluetooth circuitry, Wi-Fi circuitry, Global Positioning System (GPS) circuitry, and/or other wireless communication circuitry. For example, the terminal  110  can be a mobile phone, a personal digital assistant, a laptop computer, a tablet, or any other communication device that allows a user to communicate or perform applications using the terminal  110 . As a further example, the terminal  110  can be a wireless communication device, such as navigation device, gaming device, entertainment device, a wireless telephone, a cellular telephone, a personal digital assistant, a pager, a selective call receiver, or any other device that is capable of sending and receiving communication signals on an electronic network 
     The base stations  130  and  135  may be cellular base stations, a wireless local area network access points, or any other devices that provides access between a wireless device and a network. For example, the base station  130  can be a CDMA base station and the base station  135  can be a LTE or UMTS base station. 
     In an exemplary embodiment, the network controller  140  is connected to the network  120 . The controller  140  may be located at a base station, at a radio network controller, or anywhere else on the network  120 . The network  120  may include any type of network that is capable of sending and receiving signals, such as wireless signals. For example, the network  120  may include a wireless telecommunications network, a cellular telephone network, a CDMA network, a LTE network, a UMTS network, a TDMA network, an FDMA network, a satellite communications network, and other like communications systems. Furthermore, the network  110  may include more than one network and may include a plurality of different types of networks. Thus, the network  120  may include a plurality of data networks, a plurality of telecommunications networks, a combination of data and telecommunications networks and other like communication systems capable of sending and receiving communication signals. 
     In operation, the terminal  110  can determine if a transmit frequency in a first frequency band from the terminal  110  combined with a transmit frequency in a second frequency band from the terminal  110  causes receiver desensitization at the terminal  110 . The terminal  110  can determine if the transmit power in the first frequency band is above a threshold power. The terminal  110  can reduce maximum transmit power in the second frequency band by an amount proportional to transmit power in the first frequency band and transmit signal bandwidth in the second frequency band. 
     For example, the first frequency band can be a CDMA frequency band or other frequency band. The second frequency band can be a LTE frequency band, a UMTS frequency band, or other frequency band. The maximum LTE output power can be cut back when certain channel combinations are encountered during a Simultaneous CDMA Voice/LTE Call (SVLTE). A method for cut back power can be performed using the following information: 1. The fact that the terminal  110  is in an SVLTE call; 2. The CDMA channel number; 3. LTE uplink Resource Block (RB) allocation, such as the number of RBs and RB location; 5. The CDMA output power, which can be calculated from open loop and/or closed loop power control; 6. Non-volatile memory location elements dictating the minimum CDMA power at which LTE cutback will start; and/or other useful information. 
     The calculation for LTE power cutback can be as fast as open loop power control because de-sensitization can otherwise occur in the receiver until the LTE power is cutback if the phone goes into a deep fade where CDMA power suddenly increases above the threshold. 
     LTE output power can be cut back starting at a given CDMA output power which can be dependent upon the phone design, such as dependent on front end losses, Surface Acoustic Wave (SAW) Duplex Filter Intercept Point3 (IP3), attenuation of LTE/CDMA Diplexer, antenna isolation for dual antenna configuration, and other information. Three non-volatile memory location elements can be used. Two elements can be used for the threshold CDMA output power at which LTE output power can be cut back to avoid either CDMA de-sensitization or LTE de-sensitization and one element can be used that gives the bandwidth, such as in tens of Khz, around the receive CDMA channel to be protected. Embodiments can scale the cutback according to the number of assigned uplink RBs. As more uplink RBs are assigned, the LTE output power can be spread, and consequently, LTE power may not have to be cut back as much. 
     According to some embodiments, the algorithm can disable the maximum power cutback for LTE de-sensitization and can ignore limitations created by Signal Absorption Radio (SAR) and antenna constraints, to allow for minimal implementation impact on the CDMA and LTE sub-systems. 
     The following terms can be used for the following example embodiment:
     LTE_PWR_RED_SVLTE: The amount of power cutback that can be applied to the uplink LTE output power from max LTE output power.   P_MIN_CDMA_LTE: The threshold CDMA output power that can give the desired LTE sensitivity at max LTE power during SVLTE. Any CDMA power higher than this may degrade LTE sensitivity.   P_MIN_CDMA_CDMA: The threshold CDMA output power that can give the desired CDMA sensitivity at max LTE power during SVLTE. Any CDMA power higher than this may degrade CDMA sensitivity.   P_CDMA: CDMA uplink output power that is currently being transmitted from the terminal.   NUM_OF_RB: Number of uplink RBs to be transmitted.   CHANNEL_NUMBER: CDMA Channel Number.   INT_BW: Bandwidth of the interferer (in tens of KHz). Default can be 264, which is equivalent to 2,640,000 Hz.   RB_NUM_LOW: The lowest RB number for a given CDMA channel, CHANNEL_NUMBER, which might require LTE power cutback.   RB_NUM_HIGH: The highest RB number for a given CDMA channel, CHANNEL_NUMBER, which might require LTE power cutback.   

     According to some embodiments, the following procedure can be implemented at a terminal MODEM:
         1. Procedures for CDMA Side.
           a. When any of the following messages are received, compare the CHANNEL_NUMBER contained in the message to the current operating channel. If different, then send a message from the CDMA sub-system to the LTE sub-system containing the new CHANNEL_NUMBER and the P_MIN_CDMA_CDMA information. The new CHANNEL_NUMBER can be the CHANNEL_NUMBER contained in the message. For example, the message can contain an updated channel number, if it has changed. According to some examples, the message may always contain the active CDMA channel number, because it can be simpler to always include that data.
               i. Channel Assignment Message   ii. Extended Channel Assignment Message   iii. Handoff Direction Message   iv. Extended Handoff Direction Message   v. Global Handoff Direction Message   
               b. When transmitting above P_MIN_CDMA_CDMA in Band Class 0 and when
               1≦CHANNEL_NUMBER≦313 or   991≦CHANNEL_NUMBER≦1023,   
                set the General Purpose Input Output X1 (GPIOX1) to inform the LTE sub-system that a potential interference problem exists. The channel numbers can correspond to frequencies where a previous calculation has determined interference can exist if the LTE system is transmitting the wrong resource blocks. The state of GPIOX1 shall be held until the modem stops transmitting for any of the reasons noted below.
               i. The CDMA sub-system sends a Release Order to the network.   ii. The CDMA sub-system receives a Release Order from the network.   iii. The call is dropped through signal loss from the network.   
               c. When GPIOX1 is set, the CDMA sub-system can send the measured transmit power (P_CDMA) to the LTE sub-system once every 5 milliseconds over the UART connecting the two modems. For example, that the power control groups in CDMA can operate on 1.25 millisecond boundaries, while those in LTE can operate on 1 millisecond boundaries. The choice of 5 milliseconds can allow the two sub-systems to adjust their power on fixed boundaries. This can induce a possible error of 4 power control adjustments on the CDMA side and 5 on the LTE side.
               i. The data can be transmitted in signed integer format (8 bit field) that ranges from +127 to −128 dBm, with valid powers within the range +30 to −64 dBm.   
               
           2. Procedures for LTE Side
           a. When the CHANNEL NUMBER and PMIN CDMA CDMA information message is received from the CDMA sub-system, the LTE sub-system can calculate the resource block limitations (RB_NUM_LOW and RB_NUM_HIGH) based upon the formula below.
               i. IF 1≦N≦799 (where N=the operational CDMA channel)
 
RB_NUM_LOW=INT[(3*CHANNEL_NUMBER−INT_BW+241)/18]
 
RB_NUM_HIGH=INT[(3*CHANNEL_NUMBER+INT_BW+241)/18]
   ii. ELSEIF 991≦N≦1023
 
RB_NUM_LOW=INT[(3*CHANNEL_NUMBER−INT_BW−2828)/18]
 
RB_NUM_HIGH=INT[(3*CHANNEL_NUMBER+INT_BW−2828)/18]
    where INT_BW=264, which corresponds to a 2.64 MHz interference bandwidth.   
               b. When GPIOX1 is set, the LTE sub-system can receive the measured CDMA transmit power, P_CDMA, from the CDMA sub-system over the Universal Asynchronous Receiver/Transmitter (UART) connection.
               i. If any resource blocks fall within the range    RB_NUM_LOW≦RB≦RB ≦ NUM_HIGH,    then the LTE sub-system can calculate the power cutback for bearer resource blocks per the following formula:
 
LTE_PWR_RED_SVLTE_CDMA=2*(P_CDMA−P_MIN_CDMA_CDMA)−10*log (NUM_OF_RB)
    According to one example, this formula can be determined based on the fact that the interference can be third order and proportional to twice the CDMA transmit power and proportional to 1× the LTE transmit power. Furthermore, the power can be proportional to the LTE operating bandwidth, which can be defined by the number of active resource blocks. Note that if any resource blocks fall within the interference range, then the power reduction calculation can be based upon the number of resource blocks (NUM_OF_RB) that fall within the RB_NUM_LOW≦RB≦RB_NUM_HIGH limits.   ii. The LTE sub-system can reduce the maximum transmit power of the resource blocks that fall within the interference range (RB_NUM_LOW≦RB≦RB_NUM_HIGH) per the following constraints.
                   1. Resource blocks that contain signaling may not have their maximum transmit power reduced.   2. Resource blocks that do not contain signaling may have their maximum transmit power reduced by LTE_PWR_RED_SVLTE_CDMA. Note that the power reduction limitation can be with respect to the maximum transmit power of the device and not necessarily the dynamic transmit power of the LTE sub-system. The overall effect of the reduction in many cases may result in no change in the LTE transmit power, as this can change the maximum power limit.   
                   
               
               

     As an example for Conversion of Channel Number to Frequency for Band Class 0, if the terminal CDMA channel number is 1≦N≦799, the CDMA center frequency can be 0.030 N+825.000 MHz. If the terminal CDMA channel number is 991≦N≦1023, the CDMA center frequency can be 0.030 (N−1023)+825.000 MHz. If the base station CDMA channel number is 1≦N≦799, the CDMA center frequency can be 0.030 N+870.000 MHz. If the base station CDMA channel number is 991≦N≦1023, the CDMA center frequency can be 0.030 (N−1023)+870.000 MHz. 
     As an example for Conversion of Resource Block Number to Frequency for Band 13, if the terminal LTE Resource Block (RB) number is 1≦RBt≦50, that LTE Resource Block center frequency can be 0.18 RBt+777.590 MHz. If the base station LTE Resource Block (RB) number is 1≦RBr≦50, that LTE Resource Block center frequency can be 0.18 RBr+746 MHz. 
       FIG. 2  is an example block diagram of a wireless communication device  200 , such as the terminal  110 , according to a possible embodiment. The wireless communication device  200  can include a housing  210 , a controller  220  located within the housing  210 , audio input and output circuitry  230  coupled to the controller  220 , a display  240  coupled to the controller  220 , a first transceiver  250  coupled to the controller  220 , a first antenna  255  coupled to the first transceiver  250 , a second transceiver  252  coupled to the controller  220 , a second antenna  257  coupled to the second transceiver  252 , a user interface  260  coupled to the controller  220 , and a memory  270  coupled to the controller  220 . The wireless communication device  200  can also include a power cutback module  290 . The power cutback module  290  can be coupled to the controller  220 , can reside within the controller  220 , can reside within the memory  270 , can be an autonomous module, can be software, can be hardware, or can be in any other format useful for a module for a wireless communication device  200 . 
     The display  240  can be a liquid crystal display (LCD), a light emitting diode (LED) display, a plasma display, a touch screen display, a projector, or any other means for displaying information. Other methods can be used to present information to a user, such as aurally through a speaker or kinesthetically through a vibrator. The transceivers  250  and/or  252  may include transmitters and/or receivers. The audio input and output circuitry  230  can include a microphone, a speaker, a transducer, or any other audio input and output circuitry. The user interface  260  can include a keypad, buttons, a touch pad, a joystick, an additional display, a touch screen display, or any other device useful for providing an interface between a user and an electronic device. The memory  270  can include a random access memory, a read only memory, an optical memory, a subscriber identity module memory, flash memory, or any other memory that can be coupled to a wireless communication device. 
     In operation, the first transceiver  250  can transmit in a first frequency band. The second transceiver  252  can transmit in a second frequency band. The controller  220  can control operations of the wireless communication device  200 . The power cutback module  290  can determine if a transmit frequency in the first frequency band combined with a transmit frequency in the second frequency band causes receiver desensitization. The power cutback module  290  can determine if the transmit power in the first frequency band is above a threshold power. The power cutback module  290  can reduce the maximum transmit power in the second frequency band by an amount proportional to transmit power in the first frequency band and transmit signal bandwidth in the second frequency band if the transmit frequency in the first frequency band combined with the transmit frequency in the second frequency band causes receiver desensitization at the device  200  and if the transmit power in the first frequency band is above the threshold power. 
     The power cutback module  290  may reduce the maximum transmit power in the second frequency band in only the portion of the second frequency band where a resultant frequency component can cause desensitization. The power cutback module  290  may also reduce the maximum transmit power in the second frequency band in only the portion of the second frequency band where a resultant frequency component can cause desensitization in the sub-portion of that second frequency band that does not contain signaling. The power cutback module  290  can reduce the maximum power in the second frequency band based on a formula including: two multiplied by (first frequency band transmit power minus a threshold) minus (an amount inversely proportional to the bandwidth of transmit bandwidth in the second frequency band). For example, the power cutback module can reduce the maximum power in the second frequency band based on a formula including: 2*(Tx 1 −Th)−(1/BW 2 ), where Tx 1  comprises a first frequency band transmit power, where Th comprises a threshold for the first frequency band transmit power, and where 1/BW 2  comprises an amount inversely proportional to the bandwidth of transmit bandwidth in the second frequency band. The power cutback module  290  can calculate an interfering bandwidth between the first frequency band and the second frequency band and can reduce the maximum transmit power in the second frequency band based on the calculated interfering bandwidth. For example, the power adjustment can depend upon the calculated interfering bandwidth, the part of a LTE waveform that creates interference can be calculated, and then the power can be adjusted appropriately for that bandwidth. The interference calculation can be performed on the active portion of the LTE waveform and a determination can be made that no real interference exists if the active portion, such as the portion including allocated resource blocks, does not actually create interference. The transmit power in the second frequency band can be inversely proportional to a number transmitted of resource blocks. 
     The controller  220  can operate the wireless communication device  200  in a simultaneous call in the first frequency band and in the second frequency band. The power cutback module  290  can determine receiver sensitization while operating the device  200  in a simultaneous call in the first frequency band and in the second frequency band. The first frequency band can be a CDMA radio frequency band and the second frequency band can be LTE radio frequency band. The power cutback module  290  can determine if the transmit frequency in the first frequency band from the device  200  combined with a simultaneous transmit frequency in the second frequency band from the device  200  causes receiver desensitization at the device  200 . 
       FIG. 3  illustrates an example flowchart  300  illustrating the operation of the wireless communication device  200  according to one possible embodiment. For example, the flowchart  300  can illustrate a method of operating a dual frequency band transmit device. As a further example, the method can be performed in a LTE modem at a baseband level before transmission. The method can reduce transmit power in a frequency band by an amount proportional to transmit signal bandwidth. At  310 , the flowchart can begin. 
     At  320 , a determination can be made whether a transmit frequency in a first frequency band from the device combined with a transmit frequency in a second frequency band from the device causes receiver desensitization at the device. According to one embodiment, the first frequency band can be a CDMA radio frequency band and the second frequency band can be a LTE radio frequency band. The frequency bands can be other cellular wireless technology frequency bands. For example, the second frequency band can be a UMTS frequency band. Receiver desensitization can be a reduction in receiver sensitivity due to the presence of a high-level off-channel signal overloading the radio-frequency amplifier or mixer stages. 
     For example, receiver desensitization can occur when a strong off-channel signal overloads a receiver front end and thus reduces the sensitivity to weaker on-channel signals. For example, receiver desensitization can occur when two off-channel signals combine in a non-linear device to create an on-channel signal that reduces the receiver front end&#39;s sensitivity to on-channel signals. Determining receiver desensitization can include determining if transmitting at the transmit frequency in the first frequency band from the device combined with simultaneous transmitting at the transmit frequency in the second frequency band from the device causes receiver desensitization at the device. 
     If the combination of transmit frequencies causes receiver desensitization, at  330 , a determination can be made whether transmit power in the first frequency band is above a threshold power. At  340 , if transmit power in the first frequency band is above the threshold power, a maximum transmit power can be reduced in the second frequency band by an amount proportional to transmit power in the first frequency band and transmit signal bandwidth in the second frequency band. Reducing can include reducing the maximum transmit power in the second frequency band in only the portion of the second frequency band where a resultant frequency component can cause desensitization. Reducing can include reducing the maximum transmit power in the second frequency band in only the portion of the second frequency band where a resultant frequency component can cause desensitization and signaling is not being transmitted. Reducing can include reducing the maximum power in the second frequency band based on a formula including: 2*(first frequency band transmit power−threshold)−(an amount inversely proportional to the bandwidth of transmit bandwidth in the second frequency band). The transmit power in the second frequency band can be inversely proportional to a number of transmitted resource blocks. At  350 , the device can transmit a call in the second frequency band simultaneous with reduced maximum transmit power and in the first frequency band. 
     At  350 , the flowchart  300  can end. According to some embodiments, all of the blocks of the flowchart  300  may not be necessary. Additionally, the flowchart  300  or blocks of the flowchart  300  may be performed numerous times, such as iteratively. For example, the flowchart  300  may loop back from later blocks to earlier blocks. Furthermore, many of the blocks can be performed concurrently or in parallel processes. 
       FIG. 4  illustrates an example flowchart  400  illustrating the operation of the wireless communication device  200  according to one possible embodiment. At  410 , the flowchart  400  begins. At  420 , an interfering bandwidth between a first frequency band and a second frequency band can be calculated. 
     At  430 , the maximum transmit power in the second frequency band can be reduced based on the calculated interfering bandwidth. For example, the power adjustment can depend upon the calculated interfering bandwidth. The part of the LTE waveform that creates interference can be calculated, and then the power can be adjusted appropriately for that bandwidth. The interference calculation can be performed on the active portion of the LTE waveform and a determination can be made that no real interference exists if the active portion, such as the portion including allocated resource blocks, does not actually create interference. 
     At  440 , the device can operate in a simultaneous call in the first frequency band and in the second frequency band. For example, the first frequency band can be transmitted using a first frequency band transmitter and the second frequency band can be transmitted using a second frequency band transmitter. Determining receiver sensitization can be performed before operating the device in a simultaneous call in the first frequency band and in the second frequency band and/or can be performed while or after operating the device in a simultaneous call in the first frequency band and in the second frequency band. 
     Elements of the flowchart  400  can be combined with elements of the flowchart  300 . For example, elements of the flowchart  400  can be added to the flowchart  300  as described in earlier embodiments. According to some embodiments, all of the blocks of the flowchart  400  may not be necessary. Additionally, the flowchart  400  or blocks of the flowchart  400  may be performed numerous times, such as iteratively. For example, the flowchart  400  may loop back from later blocks to earlier blocks. Furthermore, many of the blocks can be performed concurrently or in parallel processes. 
     The methods of this disclosure may be implemented on a programmed processor. However, the operations of the embodiments may also be implemented on non-transitory machine readable storage having stored thereon a computer program having a plurality of code sections that include the blocks illustrated in the flowcharts, or a general purpose or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a hardware electronic or logic circuit such as a discrete element circuit, a programmable logic device, or the like. In general, any device on which resides a finite state machine capable of implementing the operations of the embodiments may be used to implement the processor functions of this disclosure. 
     While this disclosure has been described with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added, or substituted in the other embodiments. Also, all of the elements of each figure are not necessary for operation of the disclosed embodiments. For example, one of ordinary skill in the art of the disclosed embodiments would be enabled to make and use the teachings of the disclosure by simply employing the elements of the independent claims. Accordingly, the embodiments of the disclosure as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure. 
     In this document, relational terms such as “first,” “second,” and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The term “coupled,” unless otherwise modified, implies that elements may be connected together, but does not require a direct connection. For example, elements may be connected through one or more intervening elements. Furthermore, two elements may be coupled by using physical connections between the elements, by using electrical signals between the elements, by using radio frequency signals between the elements, by using optical signals between the elements, by providing functional interaction between the elements, or by otherwise relating two elements together. Also, relational terms, such as “top,” “bottom,” “front,” “back,” “horizontal,” “vertical,” and the like may be used solely to distinguish a spatial orientation of elements relative to each other and without necessarily implying a spatial orientation relative to any other physical coordinate system. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “a,” “an,” or the like does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. Also, the term “another” is defined as at least a second or more. The terms “including,” “having,” and the like, as used herein, are defined as “comprising.”