Heating effects on channel performance for PoE applications



Heating effects on channel performance for PoE applications

Abstract

The potential impact of heating on Ethernet cabling performance has constrained the Power over Ethernet (PoE) market for a while now, but the good news is that, numerous activities have been planned & implemented, in order to improve the efficiency of the technology. Cost and other benefits, of the existing PoE standards, have rallied a wide range of power applications. Therefore, efforts have been made to increase power from 25.5W to a minimum of 49W, available at the powered device load. With the emergence of new PoE application areas, there is a need to evaluate the effect of overheating on the channel performance.

Several dozens of Ethernet cables are bundled together in the walls. The notion of natural cooling may not eradicate the concerns of excessive heating. It is because cooling is limited within the walls. Therefore, excessive heating can have adverse effects on the Ethernet performance. The transmission line parameters experience adverse modifications. This paper investigated the effect of heating on secondary cable parameters, such as attenuation, Insertion loss, NEXT and FEXT. The results indicate that significant changes are observed with attenuation.

I. INTRODUCTION

Power over Ethernet (PoE) and its higher power derivatives (PoE+), is an established technology [1][2]. The technology allows power and data to be transmitted concurrently, on the same Ethernet cable. In other words, it does not require a separate electrical power outlet. The collective transmittance, of power & data, has allowed cost effective solutions. Also, it has made installation easy & quick.

In the PoE Technology, the power is transmitted from the Power Sourcing Equipment (PSE) to the powered device (PD), after active device detection and power classification. This has become the preferred method of powering networked devices [3]. Under type 1 (IEEE802.3af), the power sourcing equipment (PSE) is capable of delivering up to 12.95W to the powered devices, while type 2 (IEEE802.3at) allows power of up to 25.5W per pair. The maximum acceptable operating environment for cable type 1 is 600C, with a derating factor of 100C, while all pairs are energized. However, a reduction of 50C in the maximum ambient temperature for two pair powering is required. For this reason, it is necessary to transmit DC cable current that would keep the temperature within these limits.

Due to the increasing demand for power enhancement (above 25.5 Watts), a new IEEE802.3 working group has been set up. The group aims to work towards the standardization of 4-pair Power over Ethernet (PoE) [5]. The main idea is to utilize whole 4-pairs in the Ethernet cable, for delivering a minimum of 49W to PD. The working on 4-pair PoE standard would support new PoE applications (see fig.1). The idea has not been realized practically, as the group is still working towards the associated constraints [5]. The standardization of 4-Pair PoE instead of 2-pair will lower channel resistance, leading to reduction in power loss of the delivery channel. Also, it will improve efficiency of both the ...