Patent Publication Number: US-11664854-B2

Title: System and method for augmenting transmission with data streams from transmission/reception points

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY 
     The present application claims priority to U.S. Provisional Patent Application Ser. No. 63/192,357, filed on May 24, 2021. The content of the above-identified patent document is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to wireless communication systems and, more specifically, the present disclosure relates to a system and method for augmenting transmission with data streams from transmission/reception points. 
     BACKGROUND 
     Coordinated Multipoint (CoMP) is a suite of techniques introduced in LTE Advanced (3GPP Rel 11) to enhance coverage and throughput particularly at the cell edge. In a legacy cellular network, a UE connects to a single node (e.g., an eNB or gNB), and different nodes perform scheduling and precoding independently. In a CoMP-enabled network, however, the UE connects to multiple nodes, or transmit-receive points (TRPs), forming a CoMP cluster, that collaborate to improve performance by providing diversity or multiplexing gains and interference reduction among other measures. 
     Joint Transmission (JT) is a CoMP technique where multiple coordinating TRPs transmit streams of data, or layers, to a UE in the same resources. When JT is used, the TRPs can transmit identical data streams to improve the power and quality of the received signal, effectively providing diversity gain. Alternatively, the TRPs can transmit non-identical data streams to enhance the data rate, effectively providing multiplexing gain. This last technique is referred to as Multiplexing Joint Transmission, or Mux-JT for short. 
     SUMMARY 
     The present disclosure relates to wireless communication systems and, more specifically, to a system and method for augmenting transmission with data streams from other transmission/reception points. 
     In one embodiment, a method includes obtaining one or more channel quality and performance indicators of a user equipment (UE) from multiple transmit-receive points (TRPs) in a coordinated multipoint (CoMP) cluster. The method also includes generating a set of performance metrics from the one or more channel quality and performance indicators. The method also includes determining a number of helping layers for multiplexing joint transmission (Mux-JT) in the CoMP cluster based on the set of performance metrics. The method also includes selecting a modulation and coding scheme (MCS) for the Mux-JT based on at least one channel quality indicator (CQI) of the UE. 
     In another embodiment, a coordinator device includes a memory configured to store instructions. The coordinator device also includes a processor operably connected to the memory. The processor is configured when executing the instructions to: obtain one or more channel quality and performance indicators of a UE from multiple TRPs in a CoMP cluster; generate a set of performance metrics from the one or more channel quality and performance indicators; determine a number of helping layers for Mux-JT in the CoMP cluster based on the set of performance metrics; and select a MCS for the Mux-JT based on at least one CQI of the UE. 
     In yet another embodiment, a non-transitory computer readable medium includes a plurality of instructions. The plurality of instructions, when executed by at least one processor, is configured to cause the at least one processor to: obtain one or more channel quality and performance indicators of a UE from multiple TRPs in a CoMP cluster; generate a set of performance metrics from the one or more channel quality and performance indicators; determine a number of helping layers for Mux-JT in the CoMP cluster based on the set of performance metrics; and select a MCS for the Mux-JT based on at least one CQI of the UE. 
     Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims. 
     Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “transmit,” “receive,” and “communicate,” as well as derivatives thereof, encompass both direct and indirect communication. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrase “associated with,” as well as derivatives thereof, means to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The term “controller” means any device, system, or part thereof that controls at least one operation. Such a controller may be implemented in hardware or a combination of hardware and software and/or firmware. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C. 
     Moreover, various functions described below can be implemented or supported by one or more computer programs, each of which is formed from computer readable program code and embodied in a computer readable medium. The terms “application” and “program” refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer readable program code. The phrase “computer readable program code” includes any type of computer code, including source code, object code, and executable code. The phrase “computer readable medium” includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. A “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links that transport transitory electrical or other signals. A non-transitory computer readable medium includes media where data can be permanently stored and media where data can be stored and later overwritten, such as a rewritable optical disc or an erasable memory device. 
     Definitions for other certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
         FIG.  1    illustrates an example wireless network according to embodiments of the present disclosure; 
         FIG.  2    illustrates an example gNB according to embodiments of the present disclosure; 
         FIG.  3    illustrates an example UE according to embodiments of the present disclosure; 
         FIG.  4 A  illustrates a high-level diagram of an orthogonal frequency division multiple access transmit path according to embodiments of the present disclosure; 
         FIG.  4 B  illustrates a high-level diagram of an orthogonal frequency division multiple access receive path according to embodiments of the present disclosure; 
         FIG.  5    illustrates an example antenna according to embodiments of the present disclosure; 
         FIG.  6    illustrates an example wireless network in which Mux-JT can be performed according to embodiments of the present disclosure; 
         FIGS.  7  through  9    illustrate details of different example processes for augmenting transmission with data streams from helping TRPs according to embodiments of the present disclosure; and 
         FIG.  10    illustrates a flow chart of a method for augmenting transmission with data streams from helping TRPs according to embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1  through  10   , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged system or device. 
     Aspects, features, and advantages of the disclosure are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the disclosure. The disclosure is also capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. The disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. 
     The present disclosure covers several components which can be used in conjunction or in combination with one another, or can operate as standalone schemes. 
     To meet the demand for wireless data traffic having increased since deployment of 4G communication systems and to enable various vertical applications, efforts have been made to develop and deploy an improved 5G/NR or pre-5G/NR communication system. Therefore, the 5G/NR or pre-5G/NR communication system is also called a “beyond 4G network” or a “post LTE system.” The 5G/NR communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 28 GHz or 60 GHz bands, so as to accomplish higher data rates or in lower frequency bands, such as 6 GHz, to enable robust coverage and mobility support. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beam forming, large scale antenna techniques are discussed in 5G/NR communication systems. 
     In addition, in 5G/NR communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation and the like. 
     The discussion of 5G systems and frequency bands associated therewith is for reference as certain embodiments of the present disclosure may be implemented in 5G systems. However, the present disclosure is not limited to 5G systems or the frequency bands associated therewith, and embodiments of the present disclosure may be utilized in connection with any frequency band. For example, aspects of the present disclosure may also be applied to deployment of 5G communication systems, 6G or even later releases which may use terahertz (THz) bands. 
       FIGS.  1 - 4 B  below describe various embodiments implemented in wireless communications systems and with the use of orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA) communication techniques. The descriptions of  FIGS.  1 - 4 B  are not meant to imply physical or architectural limitations to the manner in which different embodiments may be implemented. Different embodiments of the present disclosure may be implemented in any suitably-arranged communications system. 
       FIG.  1    illustrates an example wireless network according to embodiments of the present disclosure. The embodiment of the wireless network shown in  FIG.  1    is for illustration only. Other embodiments of the wireless network  100  could be used without departing from the scope of this disclosure. 
     As shown in  FIG.  1   , the wireless network includes a gNB  101  (e.g., base station, BS), a gNB  102 , and a gNB  103 . The gNB  101  communicates with the gNB  102  and the gNB  103 . The gNB  101  also communicates with at least one network  130 , such as the Internet, a proprietary Internet Protocol (IP) network, or other data network. 
     The gNB  102  provides wireless broadband access to the network  130  for a first plurality of UEs within a coverage area  120  of the gNB  102 . The first plurality of UEs includes a UE  111 , which may be located in a small business; a UE  112 , which may be located in an enterprise (E); a UE  113 , which may be located in a WiFi hotspot (HS); a UE  114 , which may be located in a first residence (R); a UE  115 , which may be located in a second residence (R); and a UE  116 , which may be a mobile device (M), such as a cell phone, a wireless laptop, a wireless PDA, or the like. The gNB  103  provides wireless broadband access to the network  130  for a second plurality of UEs within a coverage area  125  of the gNB  103 . The second plurality of UEs includes the UE  115  and the UE  116 . In some embodiments, one or more of the gNBs  101 - 103  may communicate with each other and with the UEs  111 - 116  using 5G/NR, LTE, LTE-A, WiMAX, WiFi, or other wireless communication techniques. 
     Depending on the network type, the term “base station” or “BS” can refer to any component (or collection of components) configured to provide wireless access to a network, such as transmit point (TP), transmit-receive point (TRP), an enhanced base station (eNodeB or eNB), a 5G/NR base station (gNB), a macrocell, a femtocell, a WiFi access point (AP), or other wirelessly enabled devices. Base stations may provide wireless access in accordance with one or more wireless communication protocols, e.g., 5G/NR 3GPP new radio interface/access (NR), LTE, LTE advanced (LTE-A), high speed packet access (HSPA), Wi-Fi 802.11a/b/g/n/ac, etc. For the sake of convenience, the terms “BS” and “TRP” are used interchangeably in this patent document to refer to network infrastructure components that provide wireless access to remote terminals. Also, depending on the network type, the term “user equipment” or “UE” can refer to any component such as “mobile station,” “subscriber station,” “remote terminal,” “wireless terminal,” “receive point,” or “user device.” For the sake of convenience, the terms “user equipment” and “UE” are used in this patent document to refer to remote wireless equipment that wirelessly accesses a BS, whether the UE is a mobile device (such as a mobile telephone or smartphone) or is normally considered a stationary device (such as a desktop computer or vending machine). 
     Dotted lines show the approximate extents of the coverage areas  120  and  125 , which are shown as approximately circular for the purposes of illustration and explanation only. It should be clearly understood that the coverage areas associated with gNBs, such as the coverage areas  120  and  125 , may have other shapes, including irregular shapes, depending upon the configuration of the gNBs and variations in the radio environment associated with natural and man-made obstructions. 
     As described in more detail below, one or more of the UEs  111 - 116  include circuitry, programming, or a combination thereof for implementing a system and method for augmenting transmission with data streams from helping transmission/reception points. In certain embodiments, and one or more of the gNBs  101 - 103  includes circuitry, programming, or a combination thereof for implementing a system and method for augmenting transmission with data streams from helping transmission/reception points. 
     Although  FIG.  1    illustrates one example of a wireless network, various changes may be made to  FIG.  1   . For example, the wireless network could include any number of gNBs and any number of UEs in any suitable arrangement. Also, the gNB  101  could communicate directly with any number of UEs and provide those UEs with wireless broadband access to the network  130 . Similarly, each gNB  102 - 103  could communicate directly with the network  130  and provide UEs with direct wireless broadband access to the network  130 . Further, the gNBs  101 ,  102 , and/or  103  could provide access to other or additional external networks, such as external telephone networks or other types of data networks. 
       FIG.  2    illustrates an example gNB  102  according to embodiments of the present disclosure. The embodiment of the gNB  102  illustrated in  FIG.  2    is for illustration only, and the gNBs  101  and  103  of  FIG.  1    could have the same or similar configuration. However, gNBs come in a wide variety of configurations, and  FIG.  2    does not limit the scope of this disclosure to any particular implementation of a gNB. 
     As shown in  FIG.  2   , the gNB  102  includes multiple antennas  205   a - 205   n , multiple RF transceivers  210   a - 210   n , transmit (TX) processing circuitry  215 , and receive (RX) processing circuitry  220 . The gNB  102  also includes a controller/processor  225 , a memory  230 , and a backhaul or network interface  235 . 
     The RF transceivers  210   a - 210   n  receive, from the antennas  205   a - 205   n , incoming RF signals, such as signals transmitted by UEs in the network  100 . The RF transceivers  210   a - 210   n  down-convert the incoming RF signals to generate IF or baseband signals. The IF or baseband signals are sent to the RX processing circuitry  220 , which generates processed baseband signals by filtering, decoding, and/or digitizing the baseband or IF signals. The RX processing circuitry  220  transmits the processed baseband signals to the controller/processor  225  for further processing. 
     The TX processing circuitry  215  receives analog or digital data (such as voice data, web data, e-mail, or interactive video game data) from the controller/processor  225 . The TX processing circuitry  215  encodes, multiplexes, and/or digitizes the outgoing baseband data to generate processed baseband or IF signals. The RF transceivers  210   a - 210   n  receive the outgoing processed baseband or IF signals from the TX processing circuitry  215  and up-converts the baseband or IF signals to RF signals that are transmitted via the antennas  205   a - 205   n.    
     The controller/processor  225  can include one or more processors or other processing devices that control the overall operation of the gNB  102 . For example, the controller/processor  225  could control the reception of UL channel signals and the transmission of DL channel signals by the RF transceivers  210   a - 210   n , the RX processing circuitry  220 , and the TX processing circuitry  215  in accordance with well-known principles. The controller/processor  225  could support additional functions as well, such as more advanced wireless communication functions. For instance, the controller/processor  225  could support beam forming or directional routing operations in which outgoing/incoming signals from/to multiple antennas  205   a - 205   n  are weighted differently to effectively steer the outgoing signals in a desired direction. Any of a wide variety of other functions could be supported in the gNB  102  by the controller/processor  225 . 
     The controller/processor  225  is also capable of executing programs and other processes resident in the memory  230 , such as an OS. The controller/processor  225  can move data into or out of the memory  230  as required by an executing process. 
     The controller/processor  225  is also coupled to the backhaul or network interface  235 . The backhaul or network interface  235  allows the gNB  102  to communicate with other devices or systems over a backhaul connection or over a network. The interface  235  could support communications over any suitable wired or wireless connection(s). For example, when the gNB  102  is implemented as part of a cellular communication system (such as one supporting 5G/NR, LTE, or LTE-A), the interface  235  could allow the gNB  102  to communicate with other gNBs over a wired or wireless backhaul connection. When the gNB  102  is implemented as an access point, the interface  235  could allow the gNB  102  to communicate over a wired or wireless local area network or over a wired or wireless connection to a larger network (such as the Internet). The interface  235  includes any suitable structure supporting communications over a wired or wireless connection, such as an Ethernet or RF transceiver. 
     The memory  230  is coupled to the controller/processor  225 . Part of the memory  230  could include a RAM, and another part of the memory  230  could include a Flash memory or other ROM. 
     Although  FIG.  2    illustrates one example of gNB  102 , various changes may be made to  FIG.  2   . For example, the gNB  102  could include any number of each component shown in  FIG.  2   . As a particular example, an access point could include a number of interfaces  235 , and the controller/processor  225  could support routing functions to route data between different network addresses. As another particular example, while shown as including a single instance of TX processing circuitry  215  and a single instance of RX processing circuitry  220 , the gNB  102  could include multiple instances of each (such as one per RF transceiver). Also, various components in  FIG.  2    could be combined, further subdivided, or omitted and additional components could be added according to particular needs. 
       FIG.  3    illustrates an example UE  116  according to embodiments of the present disclosure. The embodiment of the UE  116  illustrated in  FIG.  3    is for illustration only, and the UEs  111 - 115  of  FIG.  1    could have the same or similar configuration. However, UEs come in a wide variety of configurations, and  FIG.  3    does not limit the scope of this disclosure to any particular implementation of a UE. 
     As shown in  FIG.  3   , the UE  116  includes an antenna  305 , a radio frequency (RF) transceiver  310 , TX processing circuitry  315 , a microphone  320 , and RX processing circuitry  325 . The UE  116  also includes a speaker  330 , a processor  340 , an input/output (I/O) interface (IF)  345 , a touchscreen  350 , a display  355 , and a memory  360 . The memory  360  includes an operating system (OS)  361  and one or more applications  362 . 
     The RF transceiver  310  receives, from the antenna  305 , an incoming RF signal transmitted by a gNB of the network  100 . The RF transceiver  310  down-converts the incoming RF signal to generate an intermediate frequency (IF) or baseband signal. The IF or baseband signal is sent to the RX processing circuitry  325 , which generates a processed baseband signal by filtering, decoding, and/or digitizing the baseband or IF signal. The RX processing circuitry  325  transmits the processed baseband signal to the speaker  330  (such as for voice data) or to the processor  340  for further processing (such as for web browsing data). 
     The TX processing circuitry  315  receives analog or digital voice data from the microphone  320  or other outgoing baseband data (such as web data, e-mail, or interactive video game data) from the processor  340 . The TX processing circuitry  315  encodes, multiplexes, and/or digitizes the outgoing baseband data to generate a processed baseband or IF signal. The RF transceiver  310  receives the outgoing processed baseband or IF signal from the TX processing circuitry  315  and up-converts the baseband or IF signal to an RF signal that is transmitted via the antenna  305 . 
     The processor  340  can include one or more processors or other processing devices and execute the OS  361  stored in the memory  360  in order to control the overall operation of the UE  116 . For example, the processor  340  could control the reception of DL channel signals and the transmission of UL channel signals by the RF transceiver  310 , the RX processing circuitry  325 , and the TX processing circuitry  315  in accordance with well-known principles. In some embodiments, the processor  340  includes at least one microprocessor or microcontroller. 
     The processor  340  is also capable of executing other processes and programs resident in the memory  360 , such as processes for beam management. The processor  340  can move data into or out of the memory  360  as required by an executing process. In some embodiments, the processor  340  is configured to execute the applications  362  based on the OS  361  or in response to signals received from gNBs or an operator. The processor  340  is also coupled to the I/O interface  345 , which provides the UE  116  with the ability to connect to other devices, such as laptop computers and handheld computers. The I/O interface  345  is the communication path between these accessories and the processor  340 . 
     The processor  340  is also coupled to the touchscreen  350  and the display  355 . The operator of the UE  116  can use the touchscreen  350  to enter data into the UE  116 . The display  355  may be a liquid crystal display, light emitting diode display, or other display capable of rendering text and/or at least limited graphics, such as from web sites. 
     The memory  360  is coupled to the processor  340 . Part of the memory  360  could include a random access memory (RAM), and another part of the memory  360  could include a Flash memory or other read-only memory (ROM). 
     Although  FIG.  3    illustrates one example of UE  116 , various changes may be made to  FIG.  3   . For example, various components in  FIG.  3    could be combined, further subdivided, or omitted and additional components could be added according to particular needs. As a particular example, the processor  340  could be divided into multiple processors, such as one or more central processing units (CPUs) and one or more graphics processing units (GPUs). Also, while  FIG.  3    illustrates the UE  116  configured as a mobile telephone or smartphone, UEs could be configured to operate as other types of mobile or stationary devices. 
       FIG.  4 A  illustrates a high-level diagram of an orthogonal frequency division multiple access (OFDMA) transmit path  400  according to embodiments of the present disclosure.  FIG.  4 B  illustrates a high-level diagram of an OFDMA receive path  450  according to embodiments of the present disclosure. In  FIGS.  4 A and  4 B , for downlink communication, the transmit path  400  may be implemented in a base station (gNB)  102  or a relay station, and the receive path  450  may be implemented in a user equipment (e.g., user equipment  116  of  FIG.  1   ). In other examples, for uplink communication, the receive path  450  may be implemented in a base station (e.g., gNB  102  of  FIG.  1   ) or a relay station, and the transmit path  400  may be implemented in a user equipment (e.g., user equipment  116  of  FIG.  1   ). 
     The transmit path  400  comprises channel coding and modulation block  405 , serial-to-parallel (S-to-P) block  410 , Size N Inverse Fast Fourier Transform (IFFT) block  415 , parallel-to-serial (P-to-S) block  420 , add cyclic prefix block  425 , and up-converter (UC)  430 . The receive path  450  comprises down-converter (DC)  455 , remove cyclic prefix block  460 , serial-to-parallel (S-to-P) block  465 , Size N Fast Fourier Transform (FFT) block  470 , parallel-to-serial (P-to-S) block  475 , and channel decoding and demodulation block  480 . 
     At least some of the components in  FIGS.  4 A and  4 B  may be implemented in software, while other components may be implemented by configurable hardware or a mixture of software and configurable hardware. In particular, it is noted that the FFT blocks and the IFFT blocks described in this disclosure document may be implemented as configurable software algorithms, where the value of Size N may be modified according to the implementation. 
     Furthermore, although this disclosure is directed to an embodiment that implements the Fast Fourier Transform and the Inverse Fast Fourier Transform, this is by way of illustration only and may not be construed to limit the scope of the disclosure. It may be appreciated that in an alternate embodiment of the present disclosure, the Fast Fourier Transform functions and the Inverse Fast Fourier Transform functions may easily be replaced by discrete Fourier transform (DFT) functions and inverse discrete Fourier transform (IDFT) functions, respectively. It may be appreciated that for DFT and IDFT functions, the value of the N variable may be any integer number (i.e., 1, 4, 3, 4, etc.), while for FFT and IFFT functions, the value of the N variable may be any integer number that is a power of two (i.e., 1, 2, 4, 8, 16, etc.). 
     In the transmit path  400 , the channel coding and modulation block  405  receives a set of information bits, applies coding (e.g., LDPC coding) and modulates (e.g., quadrature phase shift keying (QPSK) or quadrature amplitude modulation (QAM)) the input bits to produce a sequence of frequency-domain modulation symbols. The serial-to-parallel block  410  converts (i.e., de-multiplexes) the serial modulated symbols to parallel data to produce N parallel symbol streams where N is the IFFT/FFT size used in the BS  102  and the UE  116 . The Size N IFFT block  415  then performs an IFFT operation on the N parallel symbol streams to produce time-domain output signals. The parallel-to-serial block  420  converts (i.e., multiplexes) the parallel time-domain output symbols from the Size N IFFT block  415  to produce a serial time-domain signal. The add cyclic prefix block  425  then inserts a cyclic prefix to the time-domain signal. Finally, the up-converter  430  modulates (i.e., up-converts) the output of the add cyclic prefix block  425  to RF frequency for transmission via a wireless channel. The signal may also be filtered at baseband before conversion to RF frequency. 
     The transmitted RF signal arrives at the UE  116  after passing through the wireless channel, and reverse operations to those at the gNB  102  are performed. The down-converter  455  down-converts the received signal to baseband frequency, and the remove cyclic prefix block  460  removes the cyclic prefix to produce the serial time-domain baseband signal. The serial-to-parallel block  465  converts the time-domain baseband signal to parallel time-domain signals. The Size N FFT block  470  then performs an FFT algorithm to produce N parallel frequency-domain signals. The parallel-to-serial block  475  converts the parallel frequency-domain signals to a sequence of modulated data symbols. The channel decoding and demodulation block  480  demodulates and then decodes the modulated symbols to recover the original input data stream. 
     Each of gNBs  101 - 103  may implement a transmit path that is analogous to transmitting in the downlink to the UEs  111 - 116  and may implement a receive path that is analogous to receiving in the uplink from the UEs  111 - 116 . Similarly, each one of the UEs  111 - 116  may implement a transmit path corresponding to the architecture for transmitting in the uplink to the gNBs  101 - 103  and may implement a receive path corresponding to the architecture for receiving in the downlink from the gNBs  101 - 103 . 
       FIG.  5    illustrates an example beamforming architecture  500  according to embodiments of the present disclosure. The embodiment of the beamforming architecture  500  illustrated in  FIG.  5    is for illustration only.  FIG.  5    does not limit the scope of this disclosure to any particular implementation of the beamforming architecture  500 . In certain embodiments, one or more of gNB  102  or UE  116  can include the beamforming architecture  500 . For example, one or more of antenna  205  and its associated systems or antenna  305  and its associated systems can be configured the same as or similar to the beamforming architecture  500 . 
     Rel.14 LTE and Rel.15 NR support up to 32 CSI-RS antenna ports which enable an eNB to be equipped with a large number of antenna elements (such as 64 or 128). In this case, a plurality of antenna elements is mapped onto one CSI-RS port. For mmWave bands, although the number of antenna elements can be larger for a given form factor, the number of CSI-RS ports—which can correspond to the number of digitally precoded ports—tends to be limited due to hardware constraints (such as the feasibility to install a large number of analog-to-digital converts/digital-to-analog converts (ADCs/DACs at mmWave frequencies)). 
     In the example shown in  FIG.  5   , the beamforming architecture  500  includes analog phase shifters  505 , an analog beamformer (BF)  510 , a hybrid BF  515 , a digital BF  520 , and one or more antenna arrays  525 . In this case, one CSI-RS port is mapped onto a large number of antenna elements in antenna arrays  525 , which can be controlled by the bank of analog phase shifters  505 . One CSI-RS port can then correspond to one sub-array which produces a narrow analog beam through analog beamforming by analogy BF  510 . The analog beam can be configured to sweep  530  across a wider range of angles by varying the phase shifter bank  505  across symbols or subframes. The number of sub-arrays (equal to the number of RF chains) is the same as the number of CSI-RS ports NC SI-PORT. A digital BF  515  performs a linear combination across NCSI-PORT analog beams to further increase precoding gain. While analog beams are wideband (hence not frequency-selective), digital precoding can be varied across frequency sub-bands or resource blocks. 
     Since the above system utilizes multiple analog beams for transmission and reception (wherein one or a small number of analog beams are selected out of a large number, for instance, after a training duration—to be performed from time to time), the term “multi-beam operation” is used to refer to the overall system aspect. This includes, for the purpose of illustration, indicating the assigned DL or UL transmit (TX) beam (also termed “beam indication”), measuring at least one reference signal for calculating and performing beam reporting (also termed “beam measurement” and “beam reporting”, respectively), and receiving a DL or UL transmission via a selection of a corresponding receive (RX) beam. 
     Additionally, the beamforming architecture  500  is also applicable to higher frequency bands such as &gt;52.6 GHz (also termed the FR4). In this case, the beamforming architecture  500  can employ only analog beams. Due to the O2 absorption loss around 60 GHz frequency HO decibels (dB) additional loss @100 m distance), larger number of and sharper analog beams (hence larger number of radiators in the array) will be needed to compensate for the additional path loss. 
     As discussed above, Joint Transmission (JT) is a CoMP technique where multiple coordinating TRPs transmit streams of data, or layers, to a UE in the same resources. When JT is used, the TRPs can transmit identical data streams to improve the power and quality of the received signal, effectively providing diversity gain. Alternatively, the TRPs can transmit non-identical data streams to enhance the data rate, effectively providing multiplexing gain. This last technique is referred to as Multiplexing Joint Transmission, or Mux-JT for short. 
     Mux-JT can provide significant rate gains over conventional transmission techniques by augmenting the layers sent by the serving TRP with layers from other TRPs in the CoMP cluster. However, the uneducated augmentation of layers can significantly deteriorate the transmission rate instead of improving it. Therefore, it can be important to use a UE&#39;s channel quality and performance, as seen from the perspectives of the cooperating TRPs, as a criterion to trigger Mux-JT. 
     To address these and other issues, this disclosure provides a system and method for augmenting transmission with data streams from helping TRPs. As described in more detail below, the disclosed embodiments include a coordinating entity that determines whether to trigger Mux-JT by evaluating a number of metrics that are a function of the UE&#39;s channel quality and performance indicators as determined by the TRPs of the CoMP cluster. In some embodiments, the coordinating entity determines the UE&#39;s eligibility for Mux-JT, obtains indicators of the channel quality and performance of the UE from TRPs in the CoMP cluster, builds a set of metrics, and determines the number of helping layers by successively evaluating and comparing these metrics, one at a time, to a target range of values. Note that while some of the embodiments discussed below are described in the context of use in consumer electronic devices, such as smartphones or tablet computers, these are merely examples. It will be understood that the principles of this disclosure may be implemented in any number of other suitable contexts. 
       FIG.  6    illustrates an example wireless network  600  in which Mux-JT can be performed according to embodiments of the present disclosure. The embodiment of the wireless network  600  shown in  FIG.  6    is for illustration only. Other embodiments of the wireless network  600  could be used without departing from the scope of this disclosure. 
     As shown in  FIG.  6   , the wireless network  600  includes two TRPs  601 - 602  and a UE  611 . The TRPs  601 - 602  are gNBs and can represent (or be represented by) one or more of the gNBs  101 - 103  of  FIG.  1   . Each TRP  601 - 602  has a corresponding coverage area  621 - 622 . The coverage areas  621 - 622  can form a CoMP cluster for performing CoMP. The UE  611  can represent (or be represented by) one or more of the UEs  111 - 116  of  FIG.  1   . 
     In legacy (i.e., non Mux-JT) transmission, a UE is served with streams of data by a single TRP. The TRP is referred to as the serving TRP, and the UE is referred to as the served UE. In Mux-JT in the wireless network  600 , the UE  611  is served by multiple TRPs—the TRP  601  and the TRP  602 —with non-identical streams of data, R S  and L H . As Mux-JT is a CoMP operation, the transmission is performed by TRPs of the same CoMP cluster. The roles of the multiple TRPs  601 - 602  performing Mux-JT are distinguished through the following terminology. The TRP  601 , which the UE  611  associates with, is referred to as the serving TRP. The TRP  602 , which contributes to Mux-JT, is referred to as a helping TRP. 
     The TRPs  601 - 602  forming the CoMP cluster share information about the UE  611  to be used by the serving TRP  601  to decide whether to perform legacy transmission or Mux-JT. This information can include the channel state information (CSI) between the UE  611  and the TRPs  601 - 602 , which includes the Channel Quality Indicator (CQI) and Rank Indicator (RI) obtained in the feedback report sent by the UE  611  to each TRP  601 - 602  that requests one. The shared information can also include the Precoding Matrix Indicator (PMI) when PMI precoding is used, and the Sounding Reference Signal (SRS) transmitted by the UE  611  and measured by every TRP  601 - 602  when SRS precoding is used. Other information can include channel quality indicators such as the Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ) for every TRP-UE channel. Still other information can include performance indicators such as data rate, block error rate (BLER), code rate, modulation order, the number of retransmissions, and the like. 
     The information that is shared among the TRPs  601 - 602  can be instantaneous, averaged over a finite history, or averaged over the entire history. In some embodiments, the shared information can also be a statistic of a time series of a channel quality and performance indicator, such as the median or other percentile. In this disclosure, the variable x t  is defined as the channel quality and performance of the UE  611  as measured by TRP t, where t=1 is reserved for the serving TRP  601 . For example, x 1  can include the CQI in the feedback report requested by the serving TRP  601 , the SRS power as computed by the serving TRP  601 , and the moving average of the data rate for the UE  611 . 
     The task of deciding whether to perform legacy transmission or Mux-JT can be performed by a coordinator  630  that has access to the channel quality and performance information {x t } t=1   T  that is determined by the T TRPs  601 - 602  of the CoMP cluster. The coordinator  630  can be the serving TRP  601 , a device or entity residing therein, or a device or entity that is physically separated from the TRP  601 . In some embodiments, the coordinator  630  is a computing device (e.g., a server) that includes one or more processors  631  or other processing devices that control the overall operation of the coordinator  630 . Each processor  631  is capable of executing programs and other processes resident in a memory  632 , such as an OS. Each processor  631  can move data into or out of the memory  632  as required by an executing process. The coordinator  630  can implement one or more algorithms, processes, or techniques to determine whether to perform legacy transmission or Mux-JT, as described in greater detail below. 
     Although  FIG.  6    illustrates one example of a wireless network  600  in which Mux-JT can be performed, various changes may be made to  FIG.  6   . For example, other numbers of TRPs, coverage areas, and UEs could be included in the wireless network  600 . Also, various components in  FIG.  6    could be combined, further subdivided, or omitted and additional components could be added according to particular needs. 
       FIG.  7    illustrates details of an example process  700  for augmenting transmission with data streams from helping TRPs according to embodiments of the present disclosure. The embodiment of the process  700  shown in  FIG.  7    is for illustration only. Other embodiments of the process  700  could be used without departing from the scope of this disclosure. 
     As shown in  FIG.  7   , the process  700  includes multiple operations that can be performed by one or more coordinators in a CoMP cluster. For ease of explanation, the process  700  will be described as being performed by the coordinator  630  of the wireless network  600 . In the following description, the network  600  will be referred to as a CoMP cluster  600 . In the process  700 , the number of serving layers L S  refers to the number of layers to be transmitted by the serving TRP  601 , and the number of helping layers L H  refers to the number of layers to be sent by the helping TRP  602 . 
     At operation  701 , the number of helping layers L H  is initialized to zero. 
     At operation  702 , the coordinator  630  determines if the UE  611  is a CoMP UE, i.e., a UE that is suitable for a CoMP operation. To determine if the UE  611  is a CoMP UE, the coordinator  630  defines and evaluates an eligibility metric g(x 1 , . . . , x T ) that is a function of multiple channel quality and performance parameters {x t } t=1   T . Here, T represents the number of channel quality and performance parameters that are evaluated. The coordinator  630  compares the value of the eligibility metric against a reference set of acceptable values. In one example, T=2 and g(x 1 , x 2 ) is the difference of CQI values of the feedback reports obtained by the serving TRP  601  and the helping TRP  602 . In another example, g(x 1 , . . . , x T ) is the standard deviation of the SRS power as determined by the T TRPs. In yet another example, g(x 1 , x 2  . . . , x T )=g(x 1 , Ø, . . . , Ø) is the RSRQ of the UE  611  as measured by the serving TRP  601  alone. After determining the eligibility metric g, the coordinator  630  compares the value of the eligibility metric against a predetermined range of acceptable reference values and determines whether the UE  611  is eligible for a CoMP operation, i.e., Mux-JT. For example, if the eligibility metric is within the range of acceptable values, then the coordinator  630  can determine that the UE  611  is eligible for Mux-JT. 
     At operation  703 , the coordinator  630  determines the number of serving layers L S . The number of serving layers can be equal to the RI that is reported by the UE  611  to the serving TRP  601 . Alternatively, the number of serving layers can be determined from the multi-layer SRS channel if the UE  611  supports Transmit Antenna Switching (TAS). If L S =1, the process  700  continues to operation  704 , where the coordinator  630  determines the number of helping layers L H . Otherwise, if L S ≠1, the coordinator  630  determines that no helping TRP should contribute streams of data, and that effectively legacy transmission should be performed. In some embodiments, the coordinator  630  need not perform Mux-JT only when L S =1, but rather allow Mux-JT even when L S &gt;1. 
     At operation  704 , the coordinator  630  computes a set of M performance metrics {f m (x)} m=1   M . Each performance metric is a function of the UE  611 &#39;s channel quality and performance indicators as determined by the helping TRP  602  in the CoMP cluster. Here x=(x 1 , . . . , x T ). For example, one performance metric f 1 (x) can be chosen to be the instantaneous feedback CQI the UE  611  reports to the serving TRP  601 ; another performance metric f 2  (x) can be the moving average of the UE  611 &#39;s BLER. Having defined M performance metrics, the coordinator  630  allows for a maximum of M helping layers. The coordinator  630  determines the number of helping layers by successively comparing the performance metrics, one at a time, to a target range of values A m  and B m . At operation  705 , the coordinator  630  increments L H  by one (i.e., adds a layer) every time a performance metric falls within its target range, i.e., if A m &lt;f m (x)&lt;B m . Acceptable values for A m  and B m  for each performance metric f m (x) can be determined empirically, e.g., via simulation. 
     At operation  706 , the coordinator  630  sets the total number of layers L as the sum of the number of serving layers L S  and the number of helping layers L H . The layers L can be used during Mux-JT. 
     Although  FIG.  7    illustrates one example of a process  700  for augmenting transmission with data streams from helping TRPs, various changes may be made to  FIG.  7   . For example, while the process  700  is described as involving only one helping TRP that helps only one UE, other embodiments could include more than one helping TRP or UE. Also, while shown as a series of steps, various steps in  FIG.  7    could overlap, occur in parallel, occur in a different order, or occur any number of times. 
       FIG.  8    illustrates details of another example process  800  for augmenting transmission with data streams from helping TRPs according to embodiments of the present disclosure. The embodiment of the process  800  shown in  FIG.  8    is for illustration only. Other embodiments of the process  800  could be used without departing from the scope of this disclosure. 
     As shown in  FIG.  8   , the process  800  includes multiple operations that can be performed by one or more coordinators in a CoMP cluster. Some of the operations are the same as, or similar to, corresponding operations of the process  700 . For ease of explanation, the process  800  will be described as being performed by the coordinator  630  of the wireless network  600 , also referred to as the CoMP cluster  600 . 
     At operation  801 , the number of helping layers L H  is initialized to zero. 
     At operation  802 , the coordinator  630  determines if the UE  611  is a CoMP UE, i.e., a UE that is suitable for a CoMP operation. The operation  802  can be the same as, or similar to, the operation  702 , in which the coordinator  630  defines and evaluates an eligibility metric g(x 1 , . . . , x T ), compares the value of the eligibility metric against a predetermined range of acceptable reference values, and determines whether the UE  611  is eligible for Mux-JT. 
     At operation  803 , the coordinator  630  determines the number of serving layers L S . The operation  803  can be the same as, or similar to, the operation  703 , in which the number of serving layers can be equal to the RI that is reported by the UE  611  to the serving TRP  601 , or the number of serving layers can be determined from the multi-layer SRS channel if the UE  611  supports TAS. If L S =1, the process  800  continues to operation  804 , where the coordinator  630  determines the number of helping layers L H . Otherwise, if L S ≠1, the coordinator  630  determines that no helping TRP should contribute streams of data, and that effectively legacy transmission should be performed. In some embodiments, the coordinator  630  need not perform Mux-JT only when L S =1, but rather allow Mux-JT even when L S &gt;1. 
     At operations  804  and  805 , the coordinator  630  computes the number of helping layers L H  by framing a single performance metric f (x) between successive steps of a ladder of target values. In the example shown in  FIG.  8   , there is a total of K steps. In particular, the coordinator  630  defines and evaluates the performance metric f (x), which can be the CQI that the UE  611  feeds back to the serving TRP  601 . The performance metric f (x) is then framed between successive steps of a ladder of target values {A 1 , A 2 , . . . , A K }. Acceptable values for the target values {A 1 , A 2 , . . . , A K } can be determined empirically. Steps toward the top end of the ladder favor the addition of more helping layers, and steps toward the bottom favor the addition of fewer helping layers. The performance metric f(x) need not be the CQI reported by the UE  611  to the serving TRP  601 . Instead, the performance metric f(x) can be the arithmetic mean of the CQI the UE  611  reports to the serving TRP  601  and the CQI the UE  611  reports to the helping TRP  602 , the arithmetic mean of the RIs reported to the TRPs  601 - 602 , or other simple or hybrid metrics that indicate benefit in adding layers. If the performance metric f(x) is taken to be the feedback CQI, the coordinator  630  frames its value in a ladder that can start at 5 dB with steps of 10 dB. Of course, these values are merely examples; other combinations of values are possible and within the scope of this disclosure. The higher the CQI, the more layers the coordinator  630  chooses to augment from the serving TRP  601 . 
     At operation  806 , the coordinator  630  sets the total number of layers L as the sum of the number of serving layers L S  and the number of helping layers L H . The layers L can be used during Mux-JT. 
     Although  FIG.  8    illustrates one example of a process  800  for augmenting transmission with data streams from helping TRPs, various changes may be made to  FIG.  8   . For example, while the process  800  is described as involving only one helping TRP that helps only one UE, other embodiments could include more than one helping TRP or UE. Also, while shown as a series of steps, various steps in  FIG.  8    could overlap, occur in parallel, occur in a different order, or occur any number of times. 
       FIG.  9    illustrates details of yet another example process  900  for augmenting transmission with data streams from helping TRPs according to embodiments of the present disclosure. The embodiment of the process  900  shown in  FIG.  9    is for illustration only. Other embodiments of the process  900  could be used without departing from the scope of this disclosure. 
     As shown in  FIG.  9   , the process  900  includes multiple operations that can be performed by one or more coordinators in a CoMP cluster. Some of the operations are the same as, or similar to, corresponding operations of the process  700 . For ease of explanation, the process  900  will be described as being performed by the coordinator  630  of the wireless network  600 , also referred to as the CoMP cluster  600 . 
     At operation  901 , the number of helping layers L H  is initialized to zero. 
     At operation  902 , the coordinator  630  determines if the UE  611  is a CoMP UE, i.e., a UE that is suitable for a CoMP operation. The operation  902  can be the same as, or similar to, the operation  702 , in which the coordinator  630  defines and evaluates an eligibility metric g(x 1 , . . . , x T ), compares the value of the eligibility metric against a predetermined range of acceptable reference values, and determines whether the UE  611  is eligible for Mux-JT. 
     At operation  903 , the coordinator  630  determines the number of serving layers L S . The operation  903  can be the same as, or similar to, the operation  703 , in which the number of serving layers can be equal to the RI that is reported by the UE  611  to the serving TRP  601 , or the number of serving layers can be determined from the multi-layer SRS channel if the UE  611  supports TAS. If L S =1, the process  900  continues to operation  904 , where the coordinator  630  determines the number of helping layers L H . Otherwise, if L S ≠1, the coordinator  630  determines that no helping TRP should contribute streams of data, and that effectively legacy transmission should be performed. 
     At operations  904  and  905 , the coordinator  630  determines the number of helping layers L H  by comparing a single performance metric f (x) to a single threshold. In particular, the coordinator  630  defines and evaluates the performance metric f (x), which can be the CQI that the UE  611  feeds back to the serving TRP  601 , or a channel quality or performance indicator determined by a TRP  601 - 602 , or a combination of these. The performance metric f (x) is then compared to a predetermined threshold value A. In some embodiments, the threshold value A may be a passing threshold, e.g., 5-15 dB. If the performance metric f (x) is greater than the threshold value A, then the coordinator  630  increments L H  by one, i.e., adds a layer. As shown in  FIG.  9   , the process  900  restricts the augmentation of helping layers to a single layer from the helping TRP  602 . That is, the coordinator  630  makes a one-step decision to perform Mux-JT by comparing the performance metric f (x) to a threshold. 
     At operation  906 , the coordinator  630  sets the total number of layers L as the sum of the number of serving layers L S  and the number of helping layers L H . The layers L can be used during Mux-JT. 
     Although  FIG.  9    illustrates one example of a process  900  for augmenting transmission with data streams from helping TRPs, various changes may be made to  FIG.  9   . For example, while the process  900  is described as involving only one helping TRP that helps only one UE, other embodiments could include more than one helping TRP or UE. Also, while shown as a series of steps, various steps in  FIG.  9    could overlap, occur in parallel, occur in a different order, or occur any number of times. 
     Selection of Modulation and Coding Scheme 
     In some embodiments, selecting the appropriate Modulation and Coding Scheme (MCS) is very important when performing Mux-JT. In legacy transmission, the serving TRP determines the MCS that is commensurate with the channel between the served UE and the serving TRP. The TRP computes the MCS as a function of a CQI such as the feedback CQI. With Mux-JT, however, the different data streams transmitted by the coordinating TRPs observe different channels. Single-codeword (CW) transmission thus entails the use of an MCS that is supported by the different channels linking the UE to the TRPs. Too high of an MCS would lead to many errors. Too low of an MCS would tie down the rate. The following describes different techniques for the coordinator to select the MCS according to various embodiments. 
     In one example, the network allows a CoMP cluster set with a maximum size of two, meaning that there are two TRPs in the CoMP cluster: one serving TRP from the perspective of a UE and one helping TRP (such as the CoMP cluster shown in  FIG.  6   ). Additionally, the TRPs use a single codeword for the multi-layer transmission. The coordinator (e.g., the coordinator  630 ) can combine, in different ways, the CQIs reported by the UE to the two TRPs to determine the MCS: 
     Minimum CQI: The smaller of the CQI reported to the serving TRP and the CQI reported to the helping TRP is used to determine the MCS. 
     Maximum CQI: The larger of the CQI reported to the serving TRP and the CQI reported to the helping TRP is used to determine the MCS. 
     Serving CQI: The CQI reported to the serving TRP is used. 
     Layer-weighted CQI: The CQIs C S  and C H  reported to the serving TRP and the helping TRP, respectively, are weighted by the number of serving and helping layers and normalized by the total number, as represented by the following: 
     
       
         
           
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     Rank-weighted CQI: The CQIs C S  and C H  are weighted by the ranks R S  and R H  reported to the serving TRP and the helping TRP, respectively, and normalized by the total number of layers, as represented by the following: 
     
       
         
           
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     Effective Exponential Signal-to-Noise Ratio Mapping (EESM) averaging of the CQIs reported to the serving TRP and the helping TRP. 
       FIG.  10    illustrates a flow chart of a method  1000  for augmenting transmission with data streams from helping TRPs according to embodiments of the present disclosure, as may be performed by a coordinator device (e.g., the coordinator  630  as illustrated in  FIG.  6   ). An embodiment of the method  1000  shown in  FIG.  10    is for illustration only. One or more of the components illustrated in  FIG.  10    can be implemented in specialized circuitry configured to perform the noted functions or one or more of the components can be implemented by one or more processors executing instructions to perform the noted functions. 
     As illustrated in  FIG.  10   , the method  1000  begins at step  1002 . At step  1002 , a coordinator device obtains one or more channel quality and performance indicators of a UE from multiple TRPs in a CoMP cluster. This could include, for example, the coordinator  630  obtaining one or more channel quality and performance indicators of the UE  611  (e.g., CQI, RI, PMI, SRS, RSRP, RSRQ, data rate, BLER, code rate, modulation order, the number of retransmissions, and the like) from the TRPs  601 - 602 . 
     At step  1004 , the coordinator device determines eligibility of the UE for CoMP communication based on at least one of the one or more channel quality and performance indicators. This could include, for example, the coordinator  630  performing operation  702  to determine the eligibility of the UE  611  for CoMP communication. 
     At step  1006 , the coordinator device determines a number of serving layers for Mux-JT in the CoMP cluster. This could include, for example, the coordinator  630  performing operation  703  to determine the number of serving layers L S . 
     At step  1008 , the coordinator device generates a set of performance metrics from the one or more channel quality and performance indicators. This could include, for example, the coordinator  630  performing operation  704  to compute the set of M performance metrics {f m (x)} m=1   M . 
     At step  1010 , the coordinator device determines a number of helping layers for Mux-JT in the CoMP cluster based on the set of performance metrics. This could include, for example, the coordinator  630  performing operations  704  and  705  to determine the number of helping layers L H . 
     At step  1012 , the coordinator device selects a MCS for the Mux-JT based on at least one CQI of the UE. This could include, for example, the coordinator  630  selecting the MCS based on one or more of maximum CQI, minimum CQI, serving CQI, layer-weighted CQI, rank-weighted CQI, or EESM averaging of the CQIs. 
     Although  FIG.  10    illustrates one example of a method  1000  for augmenting transmission with data streams from helping TRPs, various changes may be made to  FIG.  10   . For example, while shown as a series of steps, various steps in  FIG.  10    could overlap, occur in parallel, occur in a different order, or occur any number of times. 
     Although the present disclosure has been described with exemplary embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims. None of the description in this application should be read as implying that any particular element, step, or function is an essential element that must be included in the claims scope. The scope of patented subject matter is defined by the claims.