Wireless expert cautions against mixing Wi-Fi, DAS

Cisco is one vendor who has given the thumbs-down to WLAN traffic running over a distributed antenna system.

May 21st, 2010

In a recent post on The Cabling Blog, Oberon Inc.'s director of engineering and co-founder Scott Thompson discussed dos and don'ts of in-building distributed antenna systems. Cabling Installation & Maintenance reported in its April issue that in-building DAS are growing in popularity as wireless-device users demand connectivity everywhere, including inside buildings constructed of materials that can interfere with the wireless antenna systems residing indoors.

In his post, Thompson notes, "Clearly as people become more dependent on mobile voice and data services, there is a growing expectation for network connectivity everywhere, indoors and outdoors. DAS and related in-building wireless systems provide a means to match this expectation, even in the most challenging indoor environments."

He stresses, though, that a DAS is a different architecture than the 802.11-based wireless LAN architecture deployed within buildings. 802.11 systems comprise distributed access points with connected antennas, rather than distributed antennas. And he further cautions users not to give in to the temptation to include private wireless LAN traffic over the DAS. "Generally speaking," he says, "when you use something in a way for which it was not intended, you don't get the results you want." He also points out that Cisco has issued a positioning statement indicating the company "does not certify, endorse, or provide RF support for Wi-Fi deployments over any distributed antenna system.

"Although not specifically precluding the use of Cisco wireless LAN products in a DAS, the statement recommends special consideration of signal coverage, client-to-access-point density, client roaming, location-based services, and the impact on the 802.11n antennas used by 802.11n access points," Thompson says in the blog.

View the entire blog entry here.

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