Variable power over Ethernet based on link delay measurement

1. An apparatus, comprising:

a controller configured to:

receive one or more network data packets from a powered device over a network link, the one or more data packets indicating a network delay associated with the network link;

determine an amount of power to be supplied to the powered device based on the network delay indicated by the one or more network data packets received from the powered device; and

control a power supply to supply the determined amount of power to the powered device through the network link.

2. The apparatus of claim 1 , wherein determining the amount of power comprises:

estimating a length of the network link based on the received network delay;

selecting a first amount of power to be supplied to the powered device when the length satisfies a first threshold; and

selecting a second amount of power to be supplied to the powered device when the length satisfies a second threshold.

3. The apparatus of claim 2 , wherein the controller is further configured to:

receive one or more network data packets from the powered device indicating a requested power to be supplied to the powered device;

wherein the amount of power to be supplied to the powered device is determined based on the requested power and the estimated length of the network link.

4. The apparatus of claim 3 , wherein the first threshold is greater than or equal to a predetermined threshold length and the second threshold is less than or equal to the predetermined threshold length.

5. The apparatus of claim 4 , wherein the second amount of power is less than the first amount of power.

6. The apparatus of claim 1 , wherein the network link comprises an Ethernet cable.

7. The apparatus of claim 6 , wherein the controller is further configured to:

receive an electronic signature from the powered device though the network link;

recognize the powered device as a Power over Ethernet device based on the received electronic signature; and

determine a power requirement of the powered device based on the received electronic signature;

wherein the amount of power is determined based on the power requirement and the received network delay.

8. The apparatus of claim 1 , wherein the received network delay is based on a message exchange between the apparatus and powered device through the network link.

9. The apparatus of claim 8 , wherein the controller is further configured to:

receive a delay request message from the powered device through the network link; and

return a delay response message and a delay response follow-up message to the powered device through the network link, the delay response message including a receipt time of the delay request message, and the delay response follow-up message including an internal transmission time of the delay response message;

wherein the received network delay is based on a difference between the receive time and the internal transmission time.

10. The apparatus of claim 1 , wherein the message exchange is at least part of a synchronization message exchange between the apparatus and the powered device in accordance with IEEE 802.1.

11. The apparatus of claim 1 , further comprising:

a communication port configured to send and receive network data packets over the network link to the powered device when the communication port is operably connected to the powered device by the network link, wherein the power supply is operably connected to the communication port and configured to supply power to the powered device through the communication port and the network link when the communication port is operably connected to the powered device.

12. A method for supplying power to a device, comprising:

receiving, at a first device, one or more network data packets from a second device when the first device is operably connected to the second device by a network link, the one or more network data packets indicating a network delay associated with the network link;

determining, by the first device, an amount of power to be supplied to the second device based on the network delay indicated by the one or more network data packets received from the second device; and

supplying, by the first device, the determined amount of power to the second device through the network link.

13. The method of claim 12 , further comprising:

receiving one or more network data packets from the second device indicating a requested power to be supplied to the second device;

estimating a length of the network link based on the received network delay;

wherein the amount of power to be supplied to the second device is determined based on the requested power and the estimated length of the network link.

14. The method of claim 12 , further comprising:

estimating a length of the network link based on the received network delay;

selecting a first amount of power to be supplied to the second device when the length satisfies a first threshold; and

selecting a second amount of power to be supplied to the second device when the length satisfies a second threshold.

15. The method of claim 14 , wherein the first threshold is greater than or equal to a predetermined threshold length and the second threshold is less than or equal to the predetermined threshold length.

16. The method of claim 15 , wherein the second amount of power is less than the first amount of power.

17. The method of claim 12 , wherein the network link comprises an Ethernet cable.

18. The method of claim 17 , further comprising:

receiving an electronic signature from the second device though the network link;

recognizing the second device as a Power over Ethernet device based on the received electronic signature; and

determining a power requirement of the second device based on the received electronic signature;

wherein the amount of power is determined based on the power requirement and the received network delay.

19. A system, comprising:

a transceiver configured to send and receive network data packets over a network link to a power source device when operably connected to the power source device by the network link, the transceiver configured to receive power from the power source device through the network link; and

a controller operably connected to the transceiver and configured to, when the transceiver is operably connected to the power source device:

initiate a message exchange with the power source device through the network link;

determine a network delay associated with the message link based on the message exchange;

send one or more network data packets to the power source device indicating the network delay associated with the network link; and

receive an amount of power from the power source device through the network link contemporaneous with an exchange of data packets through the network link, the received amount of power based on the network delay sent to the power source device in the one or more network data packets.

20. The system of claim 19 , wherein the controller is further configured to:

send one or more network data packets to the power source device indicating a requested amount of power;

wherein the received amount of power is based on the requested amount of power and the network delay sent to the power source device.