Abstract:
A system and method for physical layer device enabled power over Ethernet (PoE) processing. A digital PoE control module is included within a physical layer device and is designed to complement an analog PoE control module within a power sourcing equipment. The inclusion of the digital PoE control within the physical layer device reduces the complexity of the power sourcing equipment without sacrificing PoE control features.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to power over Ethernet (PoE) and, more particularly, to a system and method for physical layer device enabled PoE processing. 
         [0003]    2. Introduction 
         [0004]    In a PoE application such as that described in the IEEE 802.3af (which has now part of the IEEE 802.3 revision and its amendments) and 802.3at specifications, a power sourcing equipment (PSE) can deliver power to a powered device (PD) over Ethernet cabling. Various types of PDs exist, including voice over IP (VoIP) phones, wireless LAN access points, Bluetooth access points, network cameras, computing devices, etc. 
         [0005]    In accordance with IEEE 802.3af, a PSE can deliver up to 15.4 W of power to a single PD over two wire pairs. In accordance with IEEE 802.3at, on the other hand, a PSE may be able to deliver up to 30 W of power to a single PD over two wire pairs. Other proprietary solutions can potentially deliver higher or different levels of power to a PD. A PSE may also be configured to deliver power to a PD using four wire pairs. 
         [0006]    In the PoE process, a valid device detection is first performed. This detection process identifies whether or not a PSE is connected to a valid PD to ensure that power is not applied to non-PoE capable devices. After a valid PD is discovered, the PSE can optionally perform a power classification. In a conventional 802.3af allocation, for example, each PD would initially be assigned a 15.4 W power classification after a Layer  1  discovery process is implemented. 
         [0007]    After a valid PD is identified and possibly classified, power can be allocated to the port. In this allocation process, a determination can be made as to the amount of power that can be delivered to the PD relative to the amount of power available to the PSE. Typically, a PSE can distribute a fixed pool of power amongst a plurality of PDs that are each coupled to a network element such as a switch. 
         [0008]    The allocation of power to a PD can be based on a power budget, which can identify the amount of power allocated to the port to which the PD is coupled. In one example, the power budget allocated to the port can also consider the power loss attributable to the cable. In one embodiment, the amount of power allocated to the port can be fixed or dynamic. In one example, dynamic budgeting of power to a PD can be based on current or anticipated changes in the power consumed by the PD. 
         [0009]    Beyond the allocation of power budgets to the PD, further monitoring functions can be implemented to manage the PD. What is needed therefore is a mechanism that enables efficient control of the various PoE processes. 
       SUMMARY 
       [0010]    A system and method for physical layer device enabled power over Ethernet processing, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    In order to describe the manner in which the above-recited and other advantages and features of the invention can be obtained, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
           [0012]      FIG. 1  illustrates an embodiment of a PoE system. 
           [0013]      FIG. 2  illustrates an embodiment of physical layer device enabled PoE control. 
           [0014]      FIG. 3  illustrates a flowchart of a process of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Various embodiments of the invention are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the invention. 
         [0016]      FIG. 1  illustrates an example of a PoE system. As illustrated, the PoE system includes PSE  120  that transmits power to PD  140  over two wire pairs. Power delivered by PSE  120  to PD  140  is provided through the application of a voltage across the center taps of a first transformer that is coupled to a transmit (TX) wire pair and a second transformer that is coupled to a receive (RX) wire pair carried within an Ethernet cable. In general, the TX/RX pairs can be found in, but not limited to structured cabling. The two TX and RX pairs enable data communication between Ethernet PHYs  110  and  130  in accordance with 10BASE-T, 100BASE-TX, 1000BASE-T, 10GBASE-T and/or any other PHY technology. 
         [0017]    As is further illustrated in  FIG. 1 , PD  140  includes PoE module  142 . PoE module  142  includes the electronics that would enable PD  140  to communicate with PSE  120  in accordance with a PoE specification such as IEEE 802.3af (PoE), 802.3at (PoE Plus), legacy PoE transmission, or any other type of PoE transmission. PD  140  also includes controller  144  (e.g., pulse width modulation (PWM) DC:DC controller) that controls power transistor (e.g., FET)  146 , which in turn provides constant power to load  150 . 
         [0018]    In implementing the basic PoE system of  FIG. 1 , various PoE architectures can be used. In one example, the PSE is designed with low-cost analog hardware having a register map interface that facilitates network-based management. This architecture is optimized for low-cost, high-volume PoE production, where the analog hardware is designed to support basic analog functions such as detection, classification, soft start, FET control, disconnect, current/voltage/temperature monitoring, etc. 
         [0019]    While the low-cost analog hardware PSE implementation provides production benefits, PoE control features are limited. For example, a PSE having low-cost analog hardware is not designed to implement power budgeting (e.g., power level thresholds), enhanced monitoring (e.g., power consumption measurements, PD policing, etc.), and feature rich software controls (e.g., port-specific configuration, dynamic power adjustments, etc.). 
         [0020]    To facilitate these expanded PoE control features, another PoE architecture has the PoE subsystem incorporating a processor to implement the digital control functions that extend beyond the conventional analog control functions. In one embodiment, the processor is incorporated in the PSE. In another embodiment, the processor is incorporated in a separate PoE controller device that is shared by a plurality of PSEs. The variations in this type of PoE architecture are based on the tradeoffs in processing bandwidth, cost, and die considerations. 
         [0021]    Die considerations are significant especially when considering the incorporation of the processor within the PSE. This results from the different requirements of the analog control functions as compared to the digital control functions, which necessitate a multi-die package or a larger die size. As would be appreciated, either of these manufacturing options would have a significant impact on PoE cost, and hence a significant impact on the competitiveness of the PoE product in the marketplace. Notwithstanding the increase in costs in manufacturing and implementation, the incorporation of processing capability in the PSE can be accepted in light of the corresponding increase in PoE service functionality. 
         [0022]    In accordance with the present invention, PoE service functionality can be increased with a relatively small increase in manufacturing cost.  FIG. 2  illustrates an embodiment of such a solution that provides PHY enabled PoE processing. 
         [0023]    As illustrated in  FIG. 2 , PHY  210  is coupled to two transformers that are respectively coupled to two wire pairs. Specifically, a first transformer is coupled to a transmit (TX) wire pair and a second transformer is coupled to a receive (RX) wire pair carried within an Ethernet cable. The two TX and RX wire pairs enable data communication by PHY  210  with a PHY in a peer device. As illustrated, PSE  220  transmits power to a PD over the same two wire pairs through the application of a voltage across the center taps of the two transformers. 
         [0024]    PSE  220  includes analog PoE control  222 , which is a module designed to support the analog functions of the PSE. As noted above, these conventional analog functions include detection, classification, soft start, FET control, disconnect, current/voltage/temperature monitoring, etc. Unlike other conventional architectures, the digital process control has been removed from PSE  220  and implemented in PHY  210  as digital PoE control  212 . As noted above, the digital process control can implement power budgeting, enhanced monitoring, and other feature rich software controls. This list of controls are not intended to limiting as they can extend into other areas. For example, the digital process control can be used to run a state machine that controls the PoE discovery and/or disconnect process. 
         [0025]    The inclusion of digital PoE control  212  into PHY  210  comes with minimal impact to PHY  212 . First, many modern PHYs already incorporate some form of processing capability, which capability can be used, for example, in cable diagnostics, line equalization, energy efficient Ethernet control policy, etc. As compared to current processing needs of a conventional PHY (e.g., 10GBASE-T), the processing needs of digital PoE control  212  is relatively small. Incorporation of the digital logic within PHY  210  to support the digital PoE control features therefore comes with relatively small increase in the number of gates required in the die package. Moreover, as the digital PoE control  212  would not represent a need for mixed signal processing within PHY  210 , digital PoE control  212  can be simply added onto a single die. 
         [0026]    As illustrated in  FIG. 2 , the mixed processing between digital PoE control  212  in PHY  210  and the analog PoE control  222  in PSE  220  would be facilitated by opto-isolator  230 , which facilitates communication between PHY  210  and PSE  220  through an isolation boundary. This feature of the present invention would obviate the need for a multi-die package or larger die within PSE  220 . As would be appreciated, isolation techniques other than an opto-isolator can be used to produce an isolation boundary. 
         [0027]    It should also be noted that some application environments need not require the use of an isolation boundary. Examples of such an application environment are cases where the entire system is floating (e.g., a plastic VoIP phone), PHY enhancements exist, the PHY and PoE embodied in a multi chip module (MCM), and an analog PHY and PoE are on the same die. 
         [0028]    Having described an example embodiment of a PHY enabled PoE processing system, reference is now made to  FIG. 3 , which illustrates an example method for using the PHY enabled PoE processing system. In the following description, it should be noted the specific interplay between analog PoE control  222  and digital PoE control  212  would be implementation dependent and that the example is not intended to be limiting on the scope of the present invention. Moreover, the flowchart of  FIG. 3  is only one example application of how the PHY enabled PoE processing system can be used. Other applications of the control enabled by such a PHY enabled PoE processing system would be evident to one of ordinary skill in the relevant art. 
         [0029]    As illustrated, the process begins at step  302  where the PSE detects the signature resistance of the PD. This detection process can be performed under the control of the analog PoE control within the PSE. The optional classification process of the PD can also be performed under the control of the analog PoE control within the PSE. 
         [0030]    At step  304 , the PHY enabled PoE system allocates power to the PD. In this process, the digital PoE control within the PHY can determine a power budget applicable to the PD. In one example, this power budget can be based on a power classification of the PD in additional to power loss estimates for the cabling. As would be appreciated, the power loss estimates for the cabling can be determined using cable measurements by the PHY that enable a determination of cable length, type, resistance, temperature, etc. As the digital PoE control is contained within the PHY, the digital PoE control can easily leverage cabling measurements (e.g., TDR, insertion loss, cross talk, etc.) taken by the PHY for data transmission configuration. 
         [0031]    Next, at step  306 , a determined amount of power is delivered to the PD. In one example, power budget information determined by the digital PoE control in the PHY can be used to generate a current limit that can be used by the analog PoE control in the PSE that controls the actual delivery of power to the PD. As would be appreciated, various forms of interaction between the digital PoE control in the PHY and the analog PoE control in the PSE can be used to effect a power allocation or other control on a functional aspect of the delivery of power to the PD. 
         [0032]    After power is delivered to the PD at step  306 , it is then determined at step  308  whether a reallocation of power is needed for that PD. In one embodiment, this process can represent a dynamic control that can alter the amount of power delivered to the PD based on factors such as actual usage, scheduling, anticipated needs, etc. In this process, the digital PoE control can be used to monitor and effect a feature rich control mechanism that can modify the allocation of power to the PD. If a reallocation is needed, then the reallocation can be effected at step  304 , whereas if a reallocation is not needed, then power can continue to be delivered to the PD at step  306 . 
         [0033]    In the above example, an example application of a PHY enabled PoE processing system has been provided. This example is not intended to be limiting on the potential features of either the digital PoE control, analog PoE control, or the interplay between them. One of the aspects of significance of the present invention is that complex controls can be implemented in the PoE system by leveraging the processing capabilities of the PHY, instead of incorporating such complex control mechanisms within the PoE subsystem. Such a feature reduces the complexity of the PoE subsystem complexity without sacrificing any of the application features that can be provided by the PoE subsystem. 
         [0034]    As would be appreciated, the principles of the present invention can be applied to various two-pair and four-pair PoE applications, or to various PHY data transmission systems. In one embodiment, the principles of the present invention can be applied to midspans with PHY intelligence. 
         [0035]    These and other aspects of the present invention will become apparent to those skilled in the art by a review of the preceding detailed description. Although a number of salient features of the present invention have been described above, the invention is capable of other embodiments and of being practiced and carried out in various ways that would be apparent to one of ordinary skill in the art after reading the disclosed invention, therefore the above description should not be considered to be exclusive of these other embodiments. Also, it is to be understood that the phraseology and terminology employed herein are for the purposes of description and should not be regarded as limiting.