Electronic Design

Have Your LAN Cake And Eat It Too

You need all the advantages you can get when you're designing and building a wireless local-area network (WLAN). You want maximum range, the widest coverage,-optimized throughput, low cost, low power consumption, the greatest reliability, and minimum installation hassle. Yet even the most successful designs require some compromises. Then again, maybe they don't.

The Xirrus XS-3900 is the ultimate WLAN access point (AP). This array combines 16 IEEE 802.11a/b/g radios with high-gain multisector antennas in a unique circular enclosure packaged with an integrated switch and controller (Fig. 1 and 2). It includes 12 802.11a transceivers and four 802.11b/g transceivers, all with directional gain antennas covering specific sectors of its 360° view.

One of those 802.11b/g radios may be designated as an RF monitor. The 12 802.11a antennas provide 60° overlapping coverage, while the four 802.11b/g radios have 180° overlapping coverage, all for redundancy and fallover. A 2-Gbit/s switch fabric and 16-port media-access controller (MAC) manage the wireless traffic.

The XS-3900 fully covers a 100- by 300-ft office area. The gain antennas greatly extend each radio's range and improve the data rate. Greater signal strength means the radio can ratchet up to the higher data speeds reliably. And with only one unit to install, the amount of cable pulling is reduced to a minimum. Maybe you don't need the vaunted speed and range of 802.11n with multiple input/multiple output (MIMO)—yet.

The Tolly Group, an independent testing and consulting organization, performed indoor tests in line-of-sight and obstructed settings to evaluate the range and data rate with standard wireless notebook PCs using 802.11a/b/g cards. The XS-3900 provided 2.5 times the range, a throughput of three times the typical rate at 100 ft, and a Transmission Control Protocol (TCP) throughput-13 times better than a leading enterprise AP.

The XS-3900 also makes it possible to support the treasured triple play of voice, video, and data over the LAN. It includes Wi-QoS (802.11e), which provides a switched Wi-Fi solution to tag each wireless packet with 802.11Q virtual LAN and 802.1p prioritization at the source of each packet's transition to the wired network.

ON THE JOB
With the XC-3900, an enterprise can extend its existing wired quality-of-service policies to the WLAN to allow for discrete tagging and prioritization of mission-critical applications between the wired and wireless parts of the network. Each Xirrus LAN array is capable of realtime, load-balanced discrete classification and prioritization between the wired and wireless network.

Additionally, each array can support 180 simultaneous voice calls and 45 simultaneous standard-definition TV (SDTV) video streams. They support wireless fast Ethernet back-haul links between arrays and fast roaming between radios with an array or between arrays as well. The total maximum bandwidth is 864 Mbits/s.

The XS-3700 offers eight radios (four 802.11a, four 802.11b/g). The XS-3500 has four radios (802.11a/b/g). The XM-3300 management platform can handle up to 500 WLAN arrays.

Xirrus will handle the networking chores for the Interop conference in New York City. The company also just received a design patent for its WLAN array housing, one of several patents pending for this product.

Xirrus Inc.
www.xirrus.com
The Tolly Group
www.tolly.com

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