Imagine 1,000 Wi-Fi users in a conference room or airport connected to a single device and not hearing complaints about their connection speed. That's the heart of the Xirrus XS-3900, a wireless switch with 16 discrete access points encased in a ceiling-mounted housing. The set of integrated access points connected via internal switching aims to give a 2G bit/sec. (full-duplex Gigabit Ethernet ) transmission vehicle for dense Wi-Fi needs.

We tested the XS-3900 and found that it will support more than 1,000 concurrent users, but only if you can spread a majority of 802.11a-capable clients/users with them. We found some very good features, yet some downsides (including one security hole) that concern us.

Giant smoke alarm or UFO?

The XS-3900 is an appliance that looks like an overgrown smoke alarm (even Xirrus uses this analogy) with LEDs that give it an extraterrestrial feel. The unit we tested supports 802.11a/b/g, and needs the 802.11a component because of overlapping channels in 802.11b/g . Four simultaneous 802.11a/b/g access points with dedicated channels are supported, joined to 12 802.11a access points with dedicated channels. The 802.11a access points have antennas with 60-degree dispersion and two layers offset for six channels on each layer. In our tests this gave very good 802.11a coverage. External 802.11a/b/g Wi-Fi antennas can add to the unit's range and coverage, but this wasn't tested.

The four 802.11a/b/g antennas, which have 180-degree dispersion, are overlapped by 90 degrees for additional coverage, and can all share the same Service Set Identifier (SSID) or have independent ones for each band (two total SSIDs). The 16 antennas, when used together, provide a large radial/axial coverage area, with focused high-gain antennas that also push dispersion (the signal) farther than regular access points. The XS-3900 is designed to handle 1,024 users, or 64 users per IAP. In theory, the bandwidth afforded to each user within this context at Gigabit Ethernet rates should yield 128M bit/sec.

Installation

The lightweight unit (less than10 pounds) is designed for ceilings, but because of its power drain cannot use Power Over Ethernet and needs an AC or DC (different units sold separately) power connection. The LEDs, easily understood by their position, give a visual indication of what's going on, including power status, traffic activity and errors. The unit's power switch, hidden for security reasons, becomes inaccessible when the unit is installed.