1. Field of the Invention
The present invention relates generally to detection protocols. More particularly, the present invention relates to protocols for remote sensing of a PD-side voltage in 4-pair PoE applications for estimating cable resistance.
2. Background Art
Power over Ethernet (also known as PoE) technology allows electronic devices such as IP telephones, wireless LAN Access Points, Security network cameras and other IP-based terminals to receive power, in parallel to data, over an existing Ethernet infrastructure without the need to make modifications to the infrastructure. However, implementation of PoE solutions involves numerous challenges. Specifically, as PoE technology continues to advance and proliferate, there is an increasing need to ensure efficiency in the allocation and distribution of power to these devices.
In a conventional PoE arrangement a power sourcing equipment device (PSE) is connected to a powered device (PD) via an Ethernet cable. The Ethernet cable serves as the data/power interface between Ethernet elements, for example between a PSE and a PD. It is the responsibility of the PSE to allocate and distribute power to one or more connected PDs. Because a certain amount of power is lost due to such factors as cable resistance, such losses must be budgeted for when determining relative allocation of power by a PSE.
However, to avoid overtaxing a PSE supply, conventional PoE design has typically budgeted for cable losses by allocating a standard-wide, maximum power loss based on an assumed maximum cable length at an assumed cable resistance per meter. Thus, actual losses on a particular cable are not actually estimated by a conventional PSE. Consequently and especially in high power applications, conventional PoE power allocation and delivery protocols under-utilize the power distribution capacity of a PSE where assumed cable losses are budgeted for at inaccurately high levels.
Accordingly, there is a need to overcome the drawbacks and deficiencies in the art by providing a physical design and associated detection protocol that is relatively inexpensive and simple to implement while allowing an accurate estimation of the actual cable resistance, and hence, actual cable loss in a particular PoE application.