Abstract:
Described herein is a system and method for enhanced channel access in existing communication networks. The system comprising: a first enhanced node comprising a first processor, the first processor configured to: transmit a legacy frame header of a physical layer protocol data unit (PPDU), the legacy frame header comprising an indicator indicating that sub-PPDUs will be transmitted during a duration associated with transmission of a legacy PPDU; a second enhanced node comprising a second processor configured to receive the legacy frame header; and a third enhanced node comprising a third processor configured to receive the legacy frame header.

Description:
TECHNICAL FIELD 
     The present application generally relates to communications between networked devices, more specifically, to systems and methods for enabling channel access enhancements in existing communication networks. 
     BACKGROUND 
     Networked nodes typically communicate with one another using a communication protocol, for example the 802.11 series of protocols commonly known as WiFi, HomePlug® protocols for power-line communication, or other protocols for communication between nodes. Some protocols are contention based allowing many nodes to share a single communication medium. Contention based protocols may transmit data on the communication medium using protocol data units (PDU). In a contention based protocol using the open systems interconnection (OSI) model, various layers may have PDUs associated with them. Each PDU may require header information or other overhead information to allow transmission of the PDU. Each transmission on the communication medium incurs a certain amount of channel access overhead, i.e., data that is not payload data for an intended recipient. Physical layer PDUs (PPDU) are typically more efficient as they increase in size, due to a decrease in the overhead required relative to the size of the payload. Therefore, multiple smaller PPDUs typically require more overhead than a single larger PPDU, thereby decreasing the efficiency of the transmission medium. However, smaller PPDUs are becoming more common as enhancements are made to communication protocols to increase maximum throughput of the communication medium. In some cases, a node may have significant impact on the overall network throughput by transmitting many small PPDUs. A node transmitting at a low rate to multiple nodes may further reduce the overall throughput by transmitting many small PPDUs to multiple nodes. Still further, nodes used as repeaters may each transmit the same PPDU multiple times, thereby incurring additional overhead with each repeat transmission and further impacting the throughput. 
     SUMMARY 
     Described herein are various embodiments of systems and methods for enabling channel access enhancements in existing communication networks. A node may communicate with other nodes using PPDUs. In legacy networks, a PPDU is transmitted between two nodes. An enhanced node described herein may transmit or receive between multiple nodes using a single enhanced PPDU. Legacy devices may recognize the enhanced PPDU and remain synchronized with the network as if the enhanced PPDU were a legacy PPDU. The enhanced PPDU may enable multiple enhanced nodes to share a single PPDU, thereby decreasing the amount of overhead that may be required for communication, as compared to using multiple legacy PPDUs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the following detailed description, taken in conjunction with the accompanying drawings. It is emphasized that various features may not be drawn to scale and the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion. Further, some components may be omitted in certain figures for clarity of discussion. 
         FIG. 1  is a diagram of a an embodiment of a network comprising enhanced nodes and a legacy node; 
         FIG. 2  is a diagram of an embodiment of a legacy point-to-point transmission; 
         FIG. 3  is a diagram of an embodiment of a legacy bi-directional transmission; 
         FIG. 4  is a diagram of an embodiment of an enhanced multi-destination transmission; 
         FIG. 5  is a diagram of an embodiment of an enhanced multi-source transmission; 
         FIG. 6  is a diagram of an embodiment of an enhanced repeating transmission; 
         FIG. 7  is a diagram of an embodiment of an enhanced repeating transmission using constructive interference; 
         FIG. 8  is a flow diagram of an embodiment of a method for enhanced multi-destination transmissions; 
         FIG. 9  is a flow diagram of an embodiment of a method for enhanced multi-source transmissions; 
         FIG. 10  is a flow diagram of an embodiment of a method for enhanced repeating transmissions; and 
         FIG. 11  is a flow diagram of an embodiment of a method for enhanced repeating transmissions. 
     
    
    
     Although similar reference numbers may be used to refer to similar elements for convenience, it can be appreciated that each of the various example embodiments may be considered distinct variations. 
     DETAILED DESCRIPTION 
     In some embodiments, efficiency of a contention based network may be improved by usage of an enhanced PPDU that comprises several smaller sub-PPDUs to be transmitted to or received from several enhanced nodes. The enhanced PPDU may be formatted similarly to a legacy PPDU to allow legacy devices to remain synchronized with the transmission medium of the network. In other words, the enhanced PPDU may appear to be a legacy PPDU to legacy nodes, while enhanced nodes recognize that the enhanced PPDU comprises sub-PPDUs for several different nodes. 
       FIG. 1  is a diagram of a network  100  comprising enhanced nodes and a legacy node. Network  100  may comprise several enhanced nodes: node A  110 , node B  120 , node C  130 , and node D  140 . Network  100  may also comprise a legacy node  150  and a transmission medium  160 . Node A  110  may comprise a processor  112 , memory  114 , and an I/O module  116 . Node B  120  may comprise a processor  122 , memory  124 , and an I/O module  126 . Node C  130  may comprise a processor  132 , memory  134 , and an I/O module  136 . Node D  140  may comprise a processor  142 , memory  144 , and an I/O module  146 . Legacy Node  150  may comprise a processor  152 , memory  154 , and an I/O module  156 . Each of the nodes may communicate with one another via the transmission medium  160 . While four enhanced nodes and one legacy node are depicted, embodiments may include any number of legacy and enhanced nodes. The transmission medium  160  may be wired and/or wireless in accordance with the communication protocol used by network  100 . 
     As used herein, processors may control the functions of a node. Any actions described as being taken by a processor may be taken by the processor alone or by the processor in conjunction with one or more additional components. Additionally, while only one processor may be shown in certain devices, multiple processors may be present. Thus, while instructions may be discussed as being executed by a processor, the instructions may be executed simultaneously, serially, or otherwise by one or multiple processors. A processor may be implemented as one or more CPU chips and may be a hardware device capable of executing computer instructions. The processor may execute instructions, codes, computer programs, or scripts. The instructions, codes, computer programs, or scripts may be received from an I/O module or from memory. 
     As used herein, an I/O module may include modems, modem banks, Ethernet devices, universal serial bus (USB) interface devices, serial interfaces, token ring devices, fiber distributed data interface (FDDI) devices, wireless local area network (WLAN) devices, radio transceiver devices such as code division multiple access (CDMA) devices, global system for mobile communications (GSM) radio transceiver devices, universal mobile telecommunications system (UMTS) radio transceiver devices, long term evolution (LTE) radio transceiver devices, worldwide interoperability for microwave access (WiMAX) devices, and/or other well-known devices for connecting to networks. I/O modules may also include liquid crystal displays (LCDs), touch screen displays, keyboards, keypads, switches, dials, mice, track balls, voice recognizers, card readers, paper tape readers, printers, video monitors, or other well-known input/output devices. 
     As used herein, memory may include random access memory (RAM), read only memory (ROM), or various forms of secondary storage. RAM may be used to store volatile data and/or to store instructions that may be executed by a processor. ROM may be a non-volatile memory device that may have a smaller memory capacity than the memory capacity of a secondary storage. ROM may be used to store instructions and/or data that may be read during execution of computer instructions. Access to both RAM and ROM may be faster than access to secondary storage. Secondary storage may be comprised of one or more disk drives or tape drives and may be used for non-volatile storage of data or as an over-flow data storage device if RAM is not large enough to hold all working data. Secondary storage may be used to store programs that may be loaded into RAM when such programs are selected for execution. 
     Turning now to  FIG. 2 , a diagram of a legacy point-to-point transmission is provided. A legacy node  150  may determine that it may transmit based upon data contained in the priority resolution slots  230 . As used herein priority resolution slots may be any identifier that indicates to a node that it may transmit during a contention period. Contention periods may be durations of time or portions of transmission medium used by nodes for transmitting. Legacy node  150  may transmit and receive during contention period  250 . During contention period  250 , legacy node  150  may transmit a PPDU  210  to a second node, for example, node A  110 . PPDU  210  may comprise a sync portion  212 , a frame header  214 , and a payload  216 . As used herein sync portion may be data used by a node to remain synchronized with a network. Frame headers may contain data used for routing payloads, identifying types of payloads, and or other header data. Upon receiving PPDU  210 , node A  110  may transmit an acknowledgment PPDU  220 . Acknowledgment PPDU  220  may comprise a sync portion  222  and a response portion  224 . Each time a legacy node transmits, the transmission may include a sync and header portion. If multiple nodes are transmitting relatively small payloads, then the many sync portions and frame headers required for each PPDU may result in inefficient use of the transmission channel. 
     In some legacy systems, efficiency may be increased by transmitting payload rather than an acknowledgment PPDU as shown in  FIG. 3 .  FIG. 3  is a diagram of a legacy bi-directional transmission. In this case, communication of payloads may occur between a pair of nodes during a contention period  350  assigned to one of the nodes. After a legacy node  150  determines it may transmit based on priority resolution  340 , the legacy node  150  may transmit a PPDU  310  to node A  110 , or some other node. PPDU  310  may comprise a sync portion  312 , a frame header  314 , and a payload  316 . In response to the PPDU  310  from the legacy node  150 , node A  110  (or some other node that receives the PPDU  310 ) may transmit a responsive PPDU  320 . Responsive PPDU  320  comprises a sync portion  322 , frame header  324 , and payload  326 . In this case, the responsive PPDU  320 , indicates to the legacy node  150 , that node A  110  has received the initial transmission from legacy node  150 . The responsive PPDU functions as an acknowledgment while also delivering payload, i.e., the payload and ACK are piggybacked. Lastly, legacy node  150  may transmit an acknowledgment PPDU  330  to node A  110  to indicate that legacy node  150  has received the transmission from node A  110 . Acknowledgment PPDU  330  may comprise a sync portion  332  and a response portion  334 . 
       FIG. 4  is a diagram of an enhanced multi-destination transmission. An enhanced node, for example node A  110 , may determine that it may transmit during contention period  410  based upon priority resolution indictors  420 . A legacy PPDU may occupy the timing indicated by duration  430 . During duration  430 , node A may transmit a sync portion  432  and frame header  434 . Sync portion  432  and frame header  434  may appear as a legacy PPDU to legacy nodes. However, frame header  434  may utilize a legacy field and/or indicator to indicate to other enhanced nodes that an enhanced PPDU is being transmitted. For example, the source and destination address in the frame header  434  may be set to the same value. In this case, a legacy node would ignore the PPDU because the destination address is not the address of the legacy PPDU. However, an enhanced node would check both the source address and destination address to see if they match. In the case where the source address and destination address match, the enhanced node would further read the enhanced PPDU to determine if there is a sub-PPDU addressed to it within the enhanced PPDU. While source address and destination address are used in this example, other embodiments may use other existing fields or indicators within the frame header  434  to indicate the presence of sub-PPDUs. 
     After transmitting frame header  434 , node A  110  may transmit a sub-PPDU comprising a sync portion  436  and payload  438  to node B  120 . While sync portion  436  is pictured here, certain embodiments may not require sync portion  436 . In those embodiments, node B  120  may use the sync information provided in sync portion  432  instead. Node A  110  may then transmit a sub-PPDU comprising a sync portion  440  and payload  442  to node C  130 . While sync portion  440  is pictured here, certain embodiments may not require sync portion  440 . In those embodiments node C  130  may use the sync information provided in sync portion  432  instead. Node A  110  may then transmit a sub-PPDU comprising a sync portion  444  and payload  446  to node D  140 . While sync portion  444  is pictured here, certain embodiments may not require sync portion  444 . In those embodiments, node D  140  may use the sync information provided in sync portion  432  instead. While  FIG. 4  shows an embodiment where a node is transmitting to three enhanced nodes, the node may transmit to any number of enhanced and/or legacy nodes. 
     Upon receiving payload  438 , node B  120  may transmit sync portion  450  and frame header  452 . Sync portion  450  and frame header  452  may be compatible with legacy nodes and may identify that enhanced PPDUs may be transmitted as previously described. Node B  120  may then transmit a sub-PPDU comprising sync portion  454  and response portion  456  as an acknowledgment that payload  438  was received. Node C  130  may then transmit a sub-PPDU comprising sync portion  458  and response portion  460  as an acknowledgment that payload  442  was received. Node D  140  may then transmit sync portion  470  and response portion  472  as an acknowledgment that payload  446  was received. Sync portion  470  and frame header  452  may be compatible with legacy nodes and may indicate the end of contention period  410 , and may further allow legacy nodes to remain synchronized. 
       FIG. 5  is a diagram of an enhanced multi-source transmission. An enhanced node, for example node A  110 , may determine that it may transmit during contention period  520  based upon priority resolution indictors  510 . A legacy PPDU may occupy the timing indicated by duration  530 . During duration  530 , node A  110  may transmit a sync portion  532  and frame header  534 . Sync portion  532  and frame header  534  may appear as a legacy PPDU to legacy nodes. However, frame header  534  may utilize a legacy field and/or indicator to indicate to other enhanced nodes that an enhanced PPDU is being used and that the enhanced nodes may transmit sub-PPDUs to node A  110  during duration  530 . Multiple enhanced nodes may transmit to node A  110  based upon data contained in frame header  534  or based upon some other predetermined timing sequence. 
     After receiving frame header  534 , node B  120  may transmit a sub-PPDU comprising sync portion  536  and payload  538  to node A  110 . After receiving frame header  534 , node C  130  may transmit a sub-PPDU comprising sync portion  540  and payload  542  to node A  110 . After receiving frame header  534 , node D  140  may transmit a sub-PPDU comprising sync portion  544  and payload  546  to node A  110 . 
     Node A  110  may acknowledge receipt of the payloads  538 ,  542 ,  546 . Node A  110  may transmit sync portion  550  and frame header  552 . Sync portion  550  and frame header  552  may be compatible with legacy nodes and may identify that enhanced PPDUs may be transmitted to or from node A  110  as previously described. Node A  110  may then transmit acknowledgment that payload  538  was received from node B  120  using a sub-PPDU comprising sync portion  554  and response portion  556 . Node A  110  may then transmit acknowledgment that payload  542  was received from node C  130  using a sub-PPDU comprising sync portion  558  and response portion  560 . Node A  110  may then transmit sync portion  570  and response portion  572  as an acknowledgment that payload  546  was received. Sync portion  570  and frame header  552  may be compatible with legacy nodes and may indicate the end of contention period  520 . 
       FIG. 6  is a diagram of an enhanced repeating transmission. An enhanced node, for example node A  110 , may determine that it may transmit during contention period  610  based upon priority resolution indictors  620 . A legacy PPDU may occupy the timing indicated by duration  630 . During duration  630 , node A  110  may transmit a sync portion  632  and frame header  634 . Sync portion  632  and frame header  634  may appear as a legacy PPDU to legacy nodes. However, frame header  634  may utilize a legacy field and/or indicator to indicate to other enhanced nodes that an enhanced PPDU is being used to facilitate a repeating transmission. A repeating transmission may be used when a node that is not the intended recipient of a transmission is used to repeat the transmission to the intended recipient. 
     After transmitting frame header  634 , node A  110  may transmit a sub-PPDU comprising sync portion  636  and payload  638  to node C  130 . In this case, the payload  638  may be intended to be delivered to node B  120 , using node C  130  as a repeater. After node C  130  receives payload  638 , node C  130  may transmit a sub-PPDU comprising sync  640  and payload  642  to node B  120 . Payload  642  may be the same as payload  638 . Upon receiving payload  642 , node B  120  may transmit sync portion  644  and response  646  to node A  110  and/or node C  130  as an acknowledgment of receiving payload  642 . 
       FIG. 7  is a diagram of an enhanced repeating transmission using constructive interference. An enhanced node, for example node A  110 , may determine that it may transmit during contention period  710  based upon priority resolution indictors  720 . A legacy PPDU may occupy the timing indicated by duration  730 . During duration  730 , node A  110  may transmit a sync portion  732  and frame header  734 . Sync portion  732  and frame header  734  may appear as a legacy PPDU to legacy nodes. However, frame header  734  may utilize a legacy field and/or indicator to indicate to other enhanced nodes that an enhanced PPDU is being used to facilitate a repeating transmission using constructive interference. As described above, a repeating transmission may be used when a node that is not the intended recipient of a transmission is used to repeat the transmission to the intended recipient. Constructive interference may occur when multiple nodes transmit the same transmission simultaneously. Thereby increasing the perceived transmission strength of the intended recipient. 
     After transmitting frame header  734 , node A  110  may transmit a sub-PPDU comprising sync portion  736  and payload  738  to node C  130  and node D  140 . In this case, the payload  738  is intended to be delivered to node B  120 , using node C  130  and node D  140  as repeaters. After node C  130  and node D  140  received payload  638 , node C  130 , node D  140 , and node A  110  may each simultaneously transmit a sub-PPDU comprising sync portion  740  followed by payload  742  to node B  120 . Payload  742  may be the same as payload  738 . Upon receiving payload  742 , node B  120  may transmit sync portion  744  and response  746  to node A  110  and/or node C  130  and/or node D  140  as an acknowledgment of receiving payload  742 . 
       FIG. 8  is a flow diagram of an embodiment of a method for enhanced multi-destination transmissions. The flow begins at step  810  when an enhanced node may transmit a legacy sync portion and a legacy frame header to a plurality of nodes within a network. The legacy frame header may comprise information to allow legacy nodes in the network to remain synchronized. The frame header may also comprise information indicating to enhanced nodes that a multi-destination PPDU may be transmitted comprising one or more sub-PPDUs. At step  820 , the enhanced nodes and/or legacy nodes in the network may determine a legacy PPDU duration. The legacy PPDU duration may be a predetermined transmission duration assigned to a legacy PPDU transmitted within the network. 
     At step  830 , the enhanced node may transmit to a plurality of other enhanced nodes during the legacy PPDU duration using a plurality of sub-PPDUs. Each sub-PPDU transmitted by the enhanced node may be transmitted to a different enhanced node. The other enhanced nodes may know when their respective sub-PPDUs are transmitted based upon information contained in the frame header. This information may be found in fields of the frame header that are not needed by legacy devices. 
     At step  840 , the enhanced node may receive enhanced acknowledgments from the other enhanced nodes, all but one of the other enhanced nodes may transmit acknowledgments using a piggyback ACK scheme or some other scheme allowing multiple acknowledgment to be transmitted in sub-PPDUs. At step  850 , the enhanced node may receive a legacy acknowledgment from the last other enhanced node. Reception of the legacy acknowledgment enables legacy nodes in the network to remain synchronized. 
       FIG. 9  is a flow diagram of an embodiment of a method for enhanced multi-source transmissions. The flow begins at step  910  when an enhanced node may transmit a legacy sync portion and a legacy frame header to a plurality of nodes within a network. The legacy frame header may comprise information to allow legacy nodes in the network to remain synchronized. The frame header may also comprise information indicating to enhanced nodes that a multi-source PPDU may be transmitted comprising one or more sub-PPDUs. At step  920 , the enhanced nodes and/or legacy nodes in the network may determine a legacy PPDU duration. The legacy PPDU duration may be a predetermined transmission duration assigned to a legacy PPDU transmitted within the network. 
     At step  930 , the enhanced node may receive several sub-PPDUs from other enhanced nodes during the legacy PPDU duration. Each sub-PPDU received by the enhanced node may be received from a different enhanced node. The other enhanced nodes may know when their respective sub-PPDUs are to be transmitted based upon information contained in the frame header. This information may be found in fields of the frame header that are not needed by legacy devices. 
     At step  940 , the enhanced node may transmit enhanced acknowledgments to the other enhanced nodes, all but one of the other enhanced nodes may receive enhanced acknowledgments using a piggyback ACK scheme or some other scheme allowing multiple acknowledgments to be transmitted in sub-PPDUs. At step  950 , the enhanced node may transmit a legacy acknowledgment to the last other enhanced node. Transmission of the legacy acknowledgment enables legacy nodes in the network to remain synchronized. 
       FIG. 10  is a flow diagram of an embodiment of a method for enhanced repeating transmissions. The flow begins at step  1010  when an enhanced node may transmit a legacy sync portion and a legacy frame header to a plurality of nodes within a network. The legacy frame header may comprise information to allow legacy nodes in the network to remain synchronized. The frame header may also comprise information indicating to enhanced nodes that a multi-source PPDU may be transmitted comprising one or more sub-PPDUs. At step  1020 , the enhanced nodes and/or legacy nodes in the network may determine a legacy PPDU duration. The legacy PPDU duration may be a predetermined transmission duration assigned to a legacy PPDU transmitted within the network. 
     At step  1030 , the enhanced node may transmit a sub-PPDU to a repeater enhanced node. After receiving the sub-PPDU at the repeater enhanced node, the repeater enhanced node may transmit a sub-PPDU comprising payload identical to the received sub-PPDU to the destination enhanced node. Each sub-PPDU may be transmitted during the legacy PPDU duration. The destination enhanced node may transmit a legacy acknowledgment at step  1050  to indicate successful reception of the sub-PPDU. Transmission of the legacy acknowledgment enables legacy nodes in the network to remain synchronized. 
       FIG. 11  is a flow diagram of an embodiment of a method for enhanced repeating transmissions. The flow begins at step  1110  when an enhanced node may transmit a legacy sync portion and a legacy frame header to a plurality of nodes within a network. The legacy frame header may comprise information to allow legacy nodes in the network to remain synchronized. The frame header may also comprise information indicating to enhanced nodes that a multi-source PPDU may be transmitted comprising one or more sub-PPDUs. At step  1120 , the enhanced nodes and/or legacy nodes in the network may determine a legacy PPDU duration. The legacy PPDU duration may be a predetermined transmission duration assigned to a legacy PPDU transmitted within the network. 
     At step  1130 , the enhanced node may transmit a sub-PPDU to several repeater enhanced nodes. After receiving the sub-PPDU at the repeater enhanced nodes, the repeater enhanced nodes may simultaneously transmit a sub-PPDU comprising payload identical to the received sub-PPDU to the destination enhanced node. Each sub-PPDU may be transmitted during the legacy PPDU duration. The destination enhanced node may transmit a legacy acknowledgment at step  1050  to indicate successful reception of the sub-PPDU. Transmission of the legacy acknowledgment enables legacy nodes in the network to remain synchronized. Simultaneous transmission of the sub-PPDUs may result in constructive interference. 
     As used herein, networks may represent any form of communication network between connected machines and any other network elements, and may also represent a collection of machines or virtual machines operable to provide cloud computing services to users. Networks may include a public cloud or a private cloud. Networks may include routers, hubs, switches, firewalls, content switches, gateways, call controllers, and/or any other suitable components in any suitable form or arrangement. Networks may include, in whole or in part, one or more secured and/or encrypted Virtual Private Networks (VPNs) operable to couple one or more network elements together by operating or communicating over elements of a public or external communication network. 
     Nodes may include any device with a network interface, which includes, but is not limited to, network components, desktop computers, laptops, or mobile devices. A node may be a virtual machine, computer, device, instance, host, or machine in a networked computing environment. 
     While various embodiments in accordance with the disclosed principles have been described above, it should be understood that they have been presented by way of example only, and are not limiting. Thus, the breadth and scope of the embodiments should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the claims and their equivalents issuing from this disclosure. Furthermore, the above advantages and features are provided in described embodiments, but shall not limit the application of such issued claims to processes and structures accomplishing any or all of the above advantages. 
     Various terms used herein have special meanings within the present technical field. Whether a particular term should be construed as such a “term of art,” depends on the context in which that term is used. “Connected to,” “in communication with,” or other similar terms should generally be construed broadly to include situations both where communications and connections are direct between referenced elements or through one or more intermediaries between the referenced elements, including through the Internet or some other communicating network. “Network,” “system,” “environment,” and other similar terms generally refer to networked computing systems that embody one or more aspects of the present disclosure. These and other terms are to be construed in light of the context in which they are used in the present disclosure and as those terms would be understood by one of ordinary skill in the art would understand those terms in the disclosed context. The above definitions are not exclusive of other meanings that might be imparted to those terms based on the disclosed context. 
     Words of comparison, measurement, and timing such as “at the time,” “equivalent,” “during,” “complete,” and the like should be understood to mean “substantially at the time,” “substantially equivalent,” “substantially during,” “substantially complete,” etc., where “substantially” means that such comparisons, measurements, and timings are practicable to accomplish the implicitly or expressly stated desired result. 
     Additionally, the section headings herein are provided for consistency with the suggestions under 37 C.F.R. 1.77 or otherwise to provide organizational cues. These headings shall not limit or characterize the embodiments set out in any claims that may issue from this disclosure. Specifically and by way of example, although the headings refer to a “Technical Field,” such claims should not be limited by the language chosen under this heading to describe the so-called technical field. Further, a description of a technology in the “Background” is not to be construed as an admission that technology is prior art to any embodiments in this disclosure. Neither is the “Summary” to be considered as a characterization of the embodiments set forth in issued claims. Furthermore, any reference in this disclosure to “embodiment” in the singular should not be used to argue that there is only a single point of novelty in this disclosure. Multiple embodiments may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the embodiments, and their equivalents, that are protected thereby. In all instances, the scope of such claims shall be considered on their own merits in light of this disclosure, but should not be constrained by the headings herein.