PoE vs. PoE+

It all comes down to how much power you need

BY JEFFREY BAUSCH

Power over Ethernet, or PoE, distributes power and data safely over an Ethernet cable to a targeted device (or network of devices). It’s often used where universal serial buses (USB) are unsustainable and ac power is inconvenient, expensive or infeasible to supply (think wireless LAN access points, IP phones, surveillance cameras).

An added perk of PoE is that it gets powered over longer runs of cable than what the USB permits. Also, it doesn’t have to deal with the major topology and cable limitations that USB and power lines are faced with.

PoE has been in use for a while now, but as businesses have continued to invest in their data network infrastructure over the years, the need for higher power PoE systems became a growing demand. Devices like VoIP phones, WLAN access points, Web cameras and security cameras with pan, tilt and zoom capabilities are good examples of new devices that needed more power. The result of this need – PoE+.

Before comparing the two, it should be noted that the networking industry, IEEE, holds power delivery systems to a set of standards in order to reduce energy consumption and keep everyone in check. As such, both PoE and PoE+ fall under two separate standards:

To save you some confusion when reading other reports on these technologies, PoE is sometimes referred to as IEEE802.3AF and PoE+ as IEEE802.3AT. To save myself my own confusion, I just refer to them here as PoE and PoE+.

Why choose PoE?

It’s simple. PoE uses standard CAT 3 or CAT 5 Ethernet cables, so in terms of installation, it’s really no different than setting up a regular network. The only specialized equipment needed is a PoE-compliant switch.

It’s really convenient having multiple power devices over a single network. This eliminates the need for separate power and data cables, which makes for seamless installation and easy maintenance.

Furthermore, having a centralized power supply for all of the power sourcing equipment eliminates the call for each powered device to have its own ac/dc convertor or uninterruptible power supply.

It offers great flexibility. PoE can be installed anywhere, which means power devices can be placed wherever they’re needed, whether or not they’re near an existing power source. And since they don’t need to be located near an ac outlet, devices (and even entire systems) can be moved and adapted to suit any changing need of an application.

Unbeatable savings! There are two ways that you’ll save with PoE: network installation and energy management. We already covered the installation part, which saves on materials, labor and installation time, but PoE offers even greater savings through its effective energy management capabilities. That’s because most PoE switches support simple network management protocol (SNMP), which gives the administrator the ability to monitor and manage power consumption from a remote location.

Being able to so easily control your network’s power efficiency allows you to decide if and when to put a device (or system) into low-power or sleep mode (e.g. during off-peak hours like nights and weekends).

Terrific reliability. PoE allows for centralized power back-up solutions which, in turn, helps ensure constant availability of powered devices. When every power sourcing equipment is combined with this capability, the network is fully optimized for continuous operation, all but eliminating any chance of power interruptions and downtime. What’s more, the combination of the aforementioned SNMP and control logic allows the administrator to troubleshoot, restart, shut down and/or put measurement equipment into a safe state if ever the need should arise.

Due to all of these convenient features, PoE is largely used today in home office and consumer equipment like digital camcorders, MP3 players, DVD players, and musical instruments.

So then what’s the big deal about PoE+?

To put it simply, PoE+ offers pretty much everything that PoE has, plus a few additional conveniences:

Did I mention it has more power? PoE+ power sourcing equipment provides 50 to 57 Vdc – an increased and much tightened range compared to 44 to 57 Vdc for PoE. Also, consider this: the current for PoE is 350mA, while the current for PoE+ is a whopping 600mA. This provides as much as 25W at the powered device after allowing for cable voltage drops.

It’s even simpler. PoE+ uses standard cabling (Cat 5) and works with common Ethernet interfaces, so there’s no real need for “new wires”. This means that existing network cabling infrastructures can be utilized without running high-voltage ac power or a separate power connection for every embedded device.

It provides greater efficiency. IEEE standards require that PoE+ utilize a Cat 5 cable only. That’s because this particular cable features more wires internally (eight, as opposed to Cat 3’s four), which lowers the chance of possible impedance and reduces power dissipation. Also, Cat 5 cables are required to operate at an ambient temperature, going no higher than 50 degrees Celsius, which reduces the need for a high-performance cooling system, thus cutting back on the need for additional power.

Better reliability. Similar to PoEs, a network’s power sourcing equipment offers sophisticated control and management that can be accessed over the network via SNMP (or other means). This convenience, coupled with the advancements offered in PoE+’s updated technology, allows network administrators greater capabilities such as providing new remote power diagnostics, status reporting and PD power management (including remote power cycling of embedded devices).

PoE+ provides dynamic power allocation, optimized power distribution and supreme power-supply utilization. Naturally, this means increased system efficiency and heavily reduced costs for businesses that choose to utilize this technology.

So, which one should you choose?

Let’s keep things simple:

If you’re setting up a home network, you can’t go wrong with the simple and cost-effective PoE.

If you’re putting together a network of devices for a business, you can’t afford to not go with the convenient and super reliable, PoE+. ■