HK1191770A - Cable imbalance diagnostics between channels that include wire pairs for power over ethernet transmission - Google Patents

Abstract

The present invention is directed to cable imbalance diagnostics between channels that include wire pairs for power over Ethernet transmission. In one embodiment, measurements of one or more characteristics of a first channel that includes a first of four twisted wire pairs in a network cable are performed along with measurements of one or more characteristics of a second channel that includes a second of the four twisted wire pairs in the network cable. A determination is then made as to whether the measured one or more characteristics of the first channel and the measured one or more characteristics of the second channel indicate an imbalance between the first channel and the second channel. Adjustments such as isolation, reporting or compensation can then be made in response to the determination.

Description

Cable imbalance diagnostic between channels including line pairs for power over ethernet transmission

Cross-reference to related applications this application claims priority from U.S. provisional application No. 61/679,175 filed on 3/8/2012 and U.S. patent application No. 13/890,596 filed on 9/5/2013, which are incorporated herein by reference in their entirety.

Technical Field

The present invention relates generally to network power systems and methods, and more particularly to cable imbalance diagnostics between channels including pairs of wires for power over ethernet transmission.

Background

Power over ethernet (PoE) provides an architecture for transferring power from a Power Sourcing Equipment (PSE) to a Power Device (PD) over an ethernet cable. There are various types of PDs including voice over IP (VoIP) phones, wireless LAN access points, bluetooth access points, webcams, computing devices, and the like.

In PoE applications such as described in IEEE802.3af and 802.3at (now part of the IEEE802.3 revision and modifications thereof), the PSE may transfer up to 25.5W of power to the PD over two of four wire pairs within the ethernet cable.

Disclosure of Invention

The invention provides a method, comprising the following steps: measuring one or more characteristics of a first channel comprising a first of four twisted pairs within a network cable and one or more characteristics of a second channel comprising a second of the four twisted pairs, wherein the four twisted pairs are used to transfer power from a power supply device to a power device; determining, by the power supply device, whether the measured one or more characteristics of the first channel and the measured one or more characteristics of the second channel represent an imbalance between the first channel and the second channel; and adjusting operation of the power supply apparatus when delivering power to the power device in response to the determination.

In the above method, the measuring comprises measuring impedances of the first channel and the second channel.

In the above method, the determining comprises determining a difference in impedance between the first channel and the second channel.

In the above method, the imbalance is an inductive or capacitive imbalance.

The method further includes generating a message reporting the determined imbalance.

In the above method, said adjusting comprises compensating for said imbalance.

In the above method, the adjusting includes limiting operation of the power supply apparatus to deliver power to the power device through two wire pairs.

In the above method, the measuring comprises measuring one or more characteristics of a magnetic element within the first channel.

The method wherein measuring comprises measuring one or more characteristics of a connector within the first channel.

In the above method, the measuring comprises measuring one or more characteristics of a patch cable other than the network cable.

In the above method, the measuring comprises measuring using a physical layer device.

In the above method, the measuring includes measuring using a power supply device.

In the above method, the measuring includes determining a classification type of an ethernet cable of the network cable.

The present invention provides a power supply device including: a port for delivering power to a power device via four twisted wire pairs within a network cable; and a controller configured to receive diagnostic information based on measurements of one or more characteristics of a first channel comprising a first of the four twisted pairs within a network cable and one or more characteristics of a second channel comprising a second of the four twisted pairs, determine whether the received diagnostic information represents an imbalance between the first channel and the second channel, and adjust operation of the power supply apparatus in delivering power to the power device in response to the determination.

In the above power supply apparatus, the measurement is an impedance measurement.

In the above power supply apparatus, the controller is configured to generate a message reporting the determined unbalance.

In the above power supply apparatus, the controller is configured to compensate for the unbalance.

In the above power supply apparatus, the controller is configured to limit the operation of the power supply apparatus to transmit the electric power to the electric power device through two wiring pairs.

Drawings

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 to be 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:

fig. 1 shows one example of a link between a power supply apparatus and a power device;

fig. 2 shows a first example of transferring power from a power supply apparatus to a power device via four wire pairs;

FIG. 3 illustrates one example circuit for transferring power from a power supply apparatus to a power device via four wire pairs;

fig. 4 shows a second example of transferring power from a power supply apparatus to a power device via four wire pairs;

FIG. 5 shows a flowchart of an exemplary process according to the present invention;

FIG. 6 illustrates one example of one embodiment of a PHY configured to perform diagnostics in accordance with the present invention.

Detailed Description

Various embodiments of the invention are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other elements and configurations may be used without parting from the spirit and scope of the invention.

Power over ethernet (PoE) may be used to transfer power from a Power Sourcing Equipment (PSE) to a Power Device (PD) via a twisted pair ethernet cable. In a four-pair PoE system, an imbalance may occur between two different pairs of wires. One problem caused by such imbalance is that the effective resistance of the path for transmitting power via a set of parallel pairs of wires increases. Since a larger portion of the power budget is now caused by the losses of the cable itself, this increase in the effective resistance of the path used to transfer power may cause power transfer inefficiencies. In the present invention, it is believed that mismatches may be caused based on the characteristics of the cable itself, the connectivity (e.g., patch cords, patch panels, connectors, etc., for structural routing), the magnetic elements, the Printed Circuit Board (PCB) traces, or any other component that is part of the channel for transmitting power over the network.

In one embodiment, measuring one or more characteristics of a first channel of a first of four twisted pairs included in the network cable is performed while measuring one or more characteristics of a second channel of a second of the four twisted pairs included in the network cable. Subsequently, it may be determined whether the measured one or more characteristics of the first channel and the measured one or more characteristics of the second channel represent an imbalance between the first channel and the second channel. Adjustments, such as isolation, reporting, or compensation, may then be made in response to the determination. As described above, the particular characteristics of the channel being measured may include one or more characteristics of network cables, connectors, jumpers, magnetics, PCB traces, and the like.

The principles of the present invention are not limited to an imbalance between pairs of wires. In other embodiments, these imbalances may be measured within a single wire pair. In general, the principles of the present invention are directed to any imbalance that may be generated within the channel used to transfer power to the PD.

Fig. 1 shows one example of a link for providing power to a PD via a network. In this illustrated example, the principles of the present invention provide a process that may be incorporated into one or more of the PSE110 and PD120 to identify and respond to channel imbalances. In one embodiment, the PSE110 is a midspan PSE.

Channel imbalance may occur in various environments where the theoretical framework of network powering is applied in practical network applications where less than ideal components and installations are encountered. Despite these network deficiencies, efficient delivery of network power is still achievable through appropriate diagnostics and proper measurements. In the event that proper diagnostics and proper measurements are not achieved, network performance will be unnecessarily compromised, thereby increasing the overall cost of managing the network.

As shown in fig. 1, the PSE110 may be connected to the PD120 via a link comprising a plurality of link segments. These multiple link segments include one or more patch cables (patch cables) 140 and a network cable 130. Typically, additional link segments will dictate the use of additional connectors and/or magnetic elements.

In various embodiments, patch cables 140 may be used to facilitate organized transfer of power and communication via a cross-connect system, wall outlets, and the like. Patch cables 140 and network cables 130 are also coupled to various connectors along the length of the link. While multiple patch cables and connectors are added for structural deployment to provide network services, the increased number of components within a channel creates additional opportunities for channel imbalance to occur. In the present invention, it is believed that increased structural cable system complexity should be met with increased diagnostics to eradicate instances of increased network defects.

In the PoE installation of fig. 1, the PD120 may include a PoE module 122, which PoE module 122 includes electronics that will enable the PD120 to communicate with the PSE110 in accordance with PoE specifications (such as ieee802.3af, 802.3 at), conventional PoE transmissions, or any other type of PoE transmissions. The PD120 also includes a controller 124 (e.g., a pulse width modulated DC: DC controller) that controls a power transistor 126, which in turn provides constant power to the load. In another aspect, the PSE110 includes one or more power sources (not shown) and a controller 114, the controller 114 facilitating detection, classification, powering, disconnection, etc. of the PD120 and diagnosis and corresponding response to channel imbalance.

In one example, four pairs of PoE power supplies are used to transfer higher power levels (e.g., greater than 15.4W) from the PSE to the PD. In this example, each of these four wire pairs within the network cable and any patch cables is used to transfer power from the PSE to the PD. Fig. 2 shows a first example of transferring power from the PSE210 to the PD220 via four wire pairs included in four channels. As shown, a single PSE210 transfers power to a PD220 via channels 1-4. The power transmitted by the PSE210 to the PD220 is provided by applying voltages on the center taps of the data transformers coupled to channels 1 and 2 and the data transformers coupled to channels 3 and 4. At the other end of the network link, power is received by the PD220 through the center tap of the data transformer. In this context, it should be noted that each channel is intended to represent an end-to-end link and will include all elements (e.g., network cables, patch cables, connectors, magnetics, etc.) between power insertion and extraction points at the PSE and PD, respectively.

An effective circuit for such a scenario for transferring power from the PSE210 to the PD220 is shown in fig. 3, where R₁Representing the resistance, R, of a first channel comprising a wiring pair 1₂Representing the resistance, R, of a second channel comprising a wiring pair 2₃Representing the resistance of a third channel comprising the wiring pair 3, and R₄Representing the resistance of the fourth channel comprising the pair of wires 4. More generally, the principles of the present invention may be applied to links having capacitive and inductive imbalances. Here, equivalent inductance and capacitance imbalances may be caused by the channel, end-to-end as defined or any related parasitics. In one example, an imbalance may result due to differences in the windings of the transformer.

In this context, it is again believed that any imbalance between channels comprising different pairs of wires of a network cable may lead to inefficiencies in power transmission. This is especially true when higher power levels are considered for transmission in next generation PoE systems. In particular, four-pair PoE systems suffer from imbalances between the different channels comprising the wire pairs, since these systems are designed to transmit power levels significantly higher than two-pair PoE systems.

In the context of fig. 3, it can be seen that imbalance in the resistance of the channels comprising the wire pairs can result in inefficient power transfer. In a simple example, consider the following scenario: resistance R₁And R₂Approximately equal to 10 omega (i.e. approximately 100 meters of the third type of cable). And R₂Parallel R₁The effective resistance of (d) will thus be (10 Ω x 10 Ω)/(10 Ω +10 Ω) =5 Ω. If R is₁And R₂Is unbalanced so that R₁=15 Ω and R₂If =10 Ω, then with R₂Parallel R₁The effective resistance of (d) will thus be (15 Ω x 10 Ω)/(15 Ω +10 Ω) =6 Ω. Since this difference can be multiplied by 2 to represent the entire circuit of fig. 3, the effective imbalance will be 10 Ω to 12 Ω. It will be appreciated that a 20% increase in resistance resulting from an imbalance may create significant inefficiencies when transferring power.

For example, consider transmitting 700mA of power over a network cable. In this example, the power loss due to the extra 2 Ω resistance due to channel imbalance would be Power Loss (PL) = i²R=(700mA)²2 Ω = 0.98W. In essence and naturally, the additional 0.98W power loss caused by channel imbalance may not seem significant. For a 20W PD, the power loss that may be caused by channel imbalance represents 5% of the power consumed by the PD. For the cable itself, the additional 20% increase in resistance caused by the imbalance produces a power loss of 5.9W in the channel compared to the 4.9W ideal power loss for the channel. In the present invention, it is believed that the effect of channel balancing inefficiency becomes more pronounced when multiplied between percentages of a large number of PSE ports.

Although inefficiencies arise from the additional power loss in an unbalanced channel, the increased resistance on one channel can also cause an increase in heat on that channel. The heat in the channel will increase only when the current level increases. Unnecessary increases in channel heat may also affect data communications when the cable is near or above a temperature rating. This temperature effect will also accumulate on a bundle of cables in an enterprise installation. More specifically, increased heat in a bundle of cables may translate into a reduction in the overall subset of ports that may be powered and/or a reduction in the maximum operating current (i.e., reduced functionality) for all ports that keep the heat low. The effect of channel imbalance cannot be underestimated.

FIG. 4 illustrates another example of transferring power from a PSE to a PD via four wire pairs. As shown, two PSEs 410A, 410B transfer power to PD420 via four channels including wire pairs 1-4. In one example, two PSEs power a single PD, where current sharing occurs at the PD. In another example, the two PSEs may represent an implementation of one logical PSE powering one PD, where current sharing occurs at the PD and/or at the PSE. In yet another example, there may be a "bonded port" where two PSEs power two PDs, where the two PDs are included within a single device. In one case, the two PSEs may be located on one logical PHY port or a portion of two ports (e.g., two pairs on each 1000BASE-T channel).

Generally, the effect of these and other variations is that, due to having an imbalance, more power can be pushed through one leg of the channel than through another leg of the channel. In addition to current limiting, other effects include less efficient power transfer, additional heat generation, more complex current sharing circuitry required at the PD and/or PSE adding additional complexity, the effect of voltage at the PD when the voltage drop is affected by effective resistance within the channel, additional heat generation within elements (e.g., magnetic elements, FETs, and/or power supply circuitry), and the like. The effects of these different effects cause accelerated degradation of the device and channel over time.

Power delivered by PSE410A to PD420 is provided by applying a voltage on the center tap of the data transformer coupled to channels 1 and 4, while power delivered by PSE410B to PD420 is provided by applying a voltage on the center tap of the data transformer coupled to channels 2 and 3. Further, it should be noted that each channel is intended to represent an end-to-end link, and all elements (e.g., network cables, patch cables, connectors, magnetics, etc.) will be included between power insertion and extraction points at the PSE and PD, respectively. In this example, a system resistance mismatch of only a few ohms between the two PSEs may affect the current provided by the two PSEs. Here, the current offset caused by the two PSEs may place one PSE within current limits, which may cause a shutdown on the port.

Generally, when considering the cumulative effect of powering multiple PDs, the resulting imbalance between PSEs will affect the efficiency of operating different power sources. Ideally, each power supply operates at nearly peak capacity to enable the power supply to operate efficiently. Based on the supply assumption of having a defect, when there is a significant change in the amount of power delivered by the individual power sources, the efficiency of power delivery by the group of power sources will correspondingly decrease, resulting in increased management costs.

As described above, imbalances caused by mismatches within channels including wiring pairs of network cables, wiring pairs of patch cables, connectors, magnetics, PCB traces, etc., can affect the performance of PoE systems in a variety of ways. It is therefore a feature of the present invention that a cable imbalance diagnosis between channels for power over ethernet transmission may be provided to identify and potentially correct such imbalance.

To illustrate various features of the present invention, reference is made to the flow chart of FIG. 5, which illustrates the processing of the present invention. As shown, the process begins at step 502, where one or more characteristics of a first channel comprising a first pair of wires and a second channel comprising a second pair of wires are measured. In one embodiment, the measurements may be made by a diagnostic module within a physical layer device (PHY) (e.g., time domain reflectometry, insertion loss, crosstalk, etc.). Typically, these measurements may be mapped into one or more characteristics of the channel.

FIG. 6 illustrates one example of one embodiment of a PHY configured to perform diagnostics in accordance with the present invention. As shown, transceiver 612 within PHY610 is coupled to wire pair 1 and wire pair 2 via a set of data transformers. PSE620 is shown coupled to the center tap of the set of data transformers to transfer power to the PD via wire pair 1 and wire pair 2. This set of configurations is similar to the configuration shown in the four-pair power scenario of fig. 2. It is understood that PHY610 will be coupled to four pairs of wires communicating with PHYs within link partners according to communication standards (such as 10GBASE-T, 100BASE-TX, 1000BASE-T, 10GBASE-T, 40 GBASE-T) and any future speeds (such as 100G, 400G, etc.). For simplicity, PHY610 is shown coupled only to wire pair 1 and wire pair 2. In operation, under the control of the controller 616, the diagnostic module 614 may be configured to perform relative diagnostics between channels comprising wire pair 1 and wire pair 2, respectively. Typically, the measurement may be a single ended measurement or a double ended measurement. The presence of more measurement points yields more accurate results. Some baseline measurements may also be shared between ports.

In one embodiment, the diagnostic module 614 may be designed to measure one or more characteristics that enable determination of the impedance of the first channel. For example, the diagnostic module 614 may be designed to measure one or more characteristics indicative of cable type, cable length, temperature, number of connectors, etc. within different channels.

In another embodiment, one or more characteristics may be measured by the PoE system (i.e., PSE and/or PD). For example, PoE systems can take current-voltage (I-V) measurements at various points in the PoE process (e.g., before detection, after detection, before power, after power, etc.) to exploit the characteristics of different channels. In another example, the PSE and PD may cooperate in this process when communicating measurement data over the link via a protocol, such as Link Layer Discovery Protocol (LLDP).

Based on the measured values of the one or more characteristics, the PoE system can then determine whether an imbalance exists between the different channels at step 504. In one embodiment, the one or more measurements are used to calculate or determine the impedance of the different channels. Thus, a comparison of different channel impedances may provide an indication of the level of mismatch or imbalance. In one embodiment, one or more measurements may be used to infer the presence of a mismatch or imbalance with reference to tabulated data. For example, direct measurements or differences between measurements may be compared to the list reference data to determine if a threshold difference has been exceeded. In another embodiment, one or more measurements may be applied to the algorithmic reference data to infer that a mismatch exists. For example, through a defined imbalance formula, the direct measurements or the difference between the measurements may be processed to determine if a threshold difference has been exceeded. It will be appreciated that the particular determination mechanism will depend on the measured characteristic or characteristics. In one embodiment, the location of the imbalance may also be determined outside of the PoE subsystem (e.g., the measurements are calculated). For example, the determination may be made within the processor and/or the PHY and/or a switching system coupled to the PHY.

Finally, at step 506, based on the determination made in step 504, operation of the power transmission of the PoE system can be adjusted. Various types of adjustments may be made in response to the determination made in step 504. In one example, a message may be generated that alerts IT personnel of the imbalance. Since an alarm may be generated as part of the automated process, the alarm message is part of the system process that identifies the power transfer installation that represents an efficiency risk. In response to such an alarm, IT personnel may correct the problem by repairing or replacing one or more components within the affected channel.

In another example, the imbalance may be addressed by isolation. Here, by limiting the power transfer, the identified mismatch may be resolved. For example, the PSE may be configured to limit the ports to two pairs of power, limit the output power on ports with imbalances, and so on. In yet another example, by compensating, the imbalance may be addressed. Here, hardware and/or software compensation mechanisms may be used to counteract the imbalance. For example, a compensation mechanism may be used to balance the currents between mismatched channels. This balancing mechanism may ensure that no undesirable excessive thermal effects are generated within a particular wire pair. In other examples, a current sharing circuit may be activated, a voltage may be adjusted at the PD and/or the PSE, a voltage may be adjusted over one set of pairs with another set of pairs (e.g., one pair may have its greater voltage relative to the other pair such that if the PD has isolated taps that are not tied at RX but are further down, the voltage drop produced across them is the same), a PD power consumption may be adjusted, one or more PSE current limits may be adjusted (if separated on each branch), and so on.

As described above, the combination of system mechanisms for identifying and resolving channel imbalances is used to increase the efficiency of an enterprise network when power is provided to multiple PDs in an efficient manner. Channel imbalance may have undesirable consequences such as excessive heat, which are not accounted for using standard power models. Although the above description focuses on distributing power over a cable over twisted pair ethernet, the principles of the present invention are also applicable to Digital Subscriber Line (DSL) technology, power over data line (PoDL) technology, power over ethernet (poe) technology, etc.

Another embodiment of the present invention may provide a machine and/or computer readable storage and/or medium having stored thereon a machine code and/or a computer program having at least one code section executable by a machine and/or computer to cause the machine and/or computer to perform the steps described herein.

These and other aspects of the present invention will become apparent to those skilled in the art upon review of the foregoing detailed description. While a number of the salient features of the invention have been described above, the invention is capable of other embodiments and of being practiced and carried out in various ways which will be apparent to those skilled in the art upon reading the disclosure and, therefore, the above description should not be taken as excluding these other embodiments. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

Claims (10)

1. A method, comprising:

measuring one or more characteristics of a first channel comprising a first of four twisted pairs within a network cable and one or more characteristics of a second channel comprising a second of the four twisted pairs, wherein the four twisted pairs are used to transfer power from a power supply device to a power device;

determining, by the power supply device, whether the measured one or more characteristics of the first channel and the measured one or more characteristics of the second channel represent an imbalance between the first channel and the second channel; and

in response to the determination, adjusting operation of the power supply apparatus when delivering power to the power device.

2. The method of claim 1, wherein the imbalance is an inductive or capacitive imbalance.

3. The method of claim 1, wherein the adjusting comprises limiting operation of the power supply apparatus to delivering power to the power device over two wire pairs.

4. The method of claim 1, wherein the measuring comprises measuring one or more characteristics of a magnetic element within the first channel.

5. The method of claim 1, wherein the measuring comprises measuring one or more characteristics of a connector within the first channel.

6. The method of claim 1, wherein the measuring comprises measuring one or more characteristics of a patch cable different from the network cable.

7. The method of claim 1, wherein the measuring comprises determining a classification type of an ethernet cable of the network cable.

8. A power supply apparatus comprising:

a port for delivering power to a power device via four twisted wire pairs within a network cable; and

a controller configured to receive diagnostic information based on a measurement of one or more characteristics of a first channel comprising a first of the four twisted pairs within a network cable and one or more characteristics of a second channel comprising a second of the four twisted pairs, determine whether the received diagnostic information represents an imbalance between the first channel and the second channel, and adjust operation of the power supply apparatus in delivering power to the power device in response to the determination.

9. The power supply apparatus of claim 8, wherein the controller is configured to compensate for the imbalance.

10. The power supply apparatus of claim 8, wherein the controller is configured to limit operation of the power supply apparatus to delivering power to the power device over two wire pairs.