PoE Powering WLAN Growth

By Ed Sutherland

February 06, 2004

Tearing your hair out over how to get AC power to access points? That's what Power over Ethernet is for.

Are you getting your daily stretching while searching for a nearby power outlet for your new Wi-Fi access point, or buying Rogaine in bulk as you tear out your hair over the costs of installing new APs? Enterprises seeking to solve the problems surrounding powering Wi-Fi gear are increasingly turning to PoE -- Power over Ethernet.

Power over Ethernet, once hidden in the confusing jungle of proprietary PBX solutions, is now reborn as 802.3af, a new IEEE standard making its way into a plethora of network based gadgets. The recent Consumer Electronics Showin Las Vegas was dominated by vendors displaying wireless products, nearly all sporting support for PoE. Why?

"Because it's a pain without it," is the short answer from In-Stat/MDR analyst Allen Nogee. Although running Ethernet cable through ceilings to an AP isn't a big deal, "to get power there is another matter," says Nogee.

Brad McCoy, the IT chief at Purdue University in West Lafayette, Ind., is a believer in PoE making life easier for installing Wi-Fi. McCoy helped install more than 1,000 APs throughout the 40,000-student campus. He says PoE saved the university up to $1,000 per AP. You do the math.

"You typically need a licensed electrician to install outlets near each access point, and this can be very costly," says Nogee.

Not only can installing new APs be costly, the spots chosen do not lend themselves to an electrical outlet. McCoy said he had to fit APs in the middle of classrooms, in cafeterias and along hallways in 140 buildings. Depending on the Wi-Fi technology used -- 802.11a, 802.11g or 802.11b -- finding the correct spacing can become a real headache.

"With PoE, an IT person can hook the power up near an existing outlet in a closet or computer room and power all the access points without the need for an electrician," says Nogee.

Because of the advantages to using PoE in a WLAN, Nogee believes "802.3af will cause an increase in the number of APs than an enterprise may deploy."

Vernier Networks , a vendor targeting wireless companies, says incorporating PoE into WLANS also "means that enterprises no longer need to weigh the benefits of wireless networking, against the expense and inconvenience of installation issues," according to their Website.

There are two ways to deliver 48 volts of DC power over Ethernet cables: mid-span and end-span.

So-called mid-span power supply equipment can be an ideal option for bringing PoE features to 'legacy' WLANs.

"The unit is inserted into the LAN between the Ethernet switch and the peripherals," according to PowerDsine , an Isreali-based company which supplies mid-span equipment.

Purdue chose the mid-span option to update their existing local area network. On the downside, using mid-span equipment to introduce PoE in WLANs involves increased adding more cables to your wiring closet and additional costs.

The second option, end-span is becoming more popular as enterprises purchase Wi-Fi switches with built-in support for PoE, such as those from Aruba Networks.

PowerDsine now offers PoE on a chip, a move the industry hopes will further reduce costs of making the Ethernet cable a future universal power supply.

"The RJ-45 [Ethernet outlet] is the only standard power outlet in the world," says Igal Rotem, PowerDsine CEO.

PowerDsine is one of the founding members of the PoE Coalition, a collection of vendors with hopes of ensuring compatibility among the growing number of devices claiming compliance with the 802.3af standard.



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