PowerNOC Wireless Bridge

Equipment Review

©3/5/2004

Mike McArthur

http://www.mikemcarthur.net



Not long ago, I received a call from a man who had been contracted to provide computers and set up a network for an event at the Mississippi State Fairgrounds in Jackson. One thing that he needed to accomplish was setting up a network connection between two buildings, which are separated from each other by a parking lot.

He thought that some sort of wireless bridge would be ideal for this, and I agreed with him. He had already gotten a quote for $3000 on some BreezeCom wireless bridge equipment, but the budget for this project could not support such an expense.

I agreed to look into the issue for him, and a bit of Googling convinced me that $3000 wasn't a bad price for a brand-name wireless bridge setup. I also stumbled across the PowerNOC Wireless Bridge , sold on the web for $213 each.

The good news, I told the customer, was that I had found a cheaper solution for him. The bad news was that (unlike the BreezeCom or Aironet products) I had never installed one before, nor seen one in action.

The order-of-magnitude difference in price convinced him to go for it, and a few days later the brown truck of happiness visited my house, leaving 2 small packages.


Kit Contents


When I opened the boxes from PowerNOC, I was pleasantly surprised to find that each included a rather comprehensive installation kit. In addition to the device itself, and the “wall-wart” power supply, each wireless bridge kit included:


An 8 dB “patch” antenna is available as a $10 option, and higher-gain antennas are also available.

Somebody had obviously given a lot of thought to the installation requirements, and it was much appreciated.


The Wireless Bridge


The device itself is a sturdy metal box, 6” x 5.75” x 2”. Full specs for it can be found here. Below is a picture of the device with the antenna attached:



Illustration 1 -- Exterior View of the PowerNOC Wireless Bridge




The other side of the device is a mounting plate, which is held onto the electronic parts with 2 small screws. Removing the device from the mounting plate exposes 4 LED indicators labeled “Power”, “Diagnostic”, “Ethernet”, and “Wireless.”



Illustration 2 -- PowerNOC Bridge removed from mounting plate
Illustration 3 -- Closeup, showing status LED's



All the switches, cable connections, and antenna connections are on the “bottom” of the device. When the bridge is mounted to something, this side is intended to face downward, in order to protect the connectors from rain and dust.



Illustration 4 -- All connectors and switches are on the bottom of the device



Poor Man's Power-Over-Ethernet (Hey! Why didn't I think of that?)


One problem that is often encountered when installing a wireless access point or bridge, is that there often isn't a source of AC power anywhere near the place where you want to install it. (especially outdoors or in a warehouse/factory environment) And installing an AC outlet can be good deal more difficult and expensive than running a LAN drop, especially outdoors.

Equipment manufacturers have come up with many different ways to remedy this by using the spare pairs on Cat5 wiring to send power to the device. The “Elegant” way to do this is the recent IEEE 802.3af Power-Over-Ethernet standard. It definitely has its advantages in large-scale Wi-Fi and VOIP deployments.

The PowerNOC installation instructions recommend the more mundane expedient of cutting the cord attached to the “wall-wart,” and splicing the power cord to the brown pair of the Cat5 cable (using the included 3M Scotchlok splice). You will need to splice the other end of the Cat5 cable to the “connector” end of the power cord, and plug the connector into the device. You will need to splice both ends of the cable, because the PowerNOC wireless bridge will not receive power through its RJ-45 jack. (I tried) Not as elegant as the Cisco/PoweredSine/802.3af solution, but it gets the job done. Here is how it looks in practice, before wrapping the splices with electrical tape.



Illustration 5 -- Brown pair of the Cat5 cable spliced into power supply connector


I found the included 3M Scotchlok splices to be ideal for this purpose. They did not require stripping insulation off the wires and contained a silicone jelly sealant to make the splice weatherproof. I wish the installation kit had contained more of them.


Configuration


The PowerNOC's web-based configuration utility was pretty straightforward, and included all the options one would expect in a typical 802.11 client device.



Illustration 6 -- PowerNOC configuration utility, as seen from the Konqueror Web Browser



The PowerNOC Wireless Bridge is strictly a client device and cannot be setup as an access-point. (I later contacted PowerNOC, and was disappointed to find out that they don't sell an access-point.) The bridge can be configured for ad-hoc networking, though, which allows 2 or more devices to communicate without the need for an access-point.

I configured the 2 bridges that I had for ad-hoc networking and 128-bit WEP encryption, then verified that they could communicate across my living room.

It was now time to see how they would work in the field.


Field Test


The buildings are separated by about 150 yards of parking lot. Previous solutions to connecting them had involved running an aerial cable (coax or Cat5 UTP) across the parking lot, with a temporary tower of scaffolding keeping the cale from sagging enough to be a nuisance. Including the wiring within the buildings, the cable run had been nearly 800 feet long, and required line drivers at each end of the cable.

The site contact ran Cat5 cable from inside each building to where we planned to install the wireless bridges. I spliced DC power into the cables using the procedure mentioned above, and we mounted the devices where they would have clear line-of-sight to each other.



Illustration 7 -- The PowerNOC Bridge is the white square on top of the column
Illustration 8 -- The other Bridge was placed on top of the low roof in front of the Coliseum

The rest of the story is pretty much uneventful. The devices came up, we had an 11Mbps connection between the buildings, and the end user had no network problems for the duration of the event.

The site contact also thanked me for sparing him the hassle of running a cable between the two buildings, and I will definitely consider using PowerNOC equipment in the future for any application that requires outdoor, long-range wireless connectivity at low cost.