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Creating a switched RF environment with MIMO

May 17, 20042 mins
Cellular NetworksNetwork SecurityWi-Fi

* Multiple smart antennas make APs more like switches

It can be pretty challenging to offer predictable wireless LAN services, given the generally volatile nature of the radio-frequency medium. In the wireless environment, communications traffic is prone to rebounding off of certain types of materials (an effect called “multi-path”), as well as interference from other traffic in the same frequency.

Advanced antenna technology can help tame the impact of multi-path and interference on WLAN performance.

Last week, at the NetWorld+Interop trade show in Las Vegas, for example, WLAN start-up Airespace announced access points with smart antennas to help enhance security, performance, and reliability of WLANs in ways that the company compares to that of switched Ethernet in wired LANs.

Airespace says its Intelligent RF Access Point (IRAP), due to ship in the third quarter and supporting 802.11a/b/g, uses Multiple Input Multiple Output (MIMO) smart antenna technology to better accommodate the stringent WLAN requirements of enterprises.

MIMO uses multiple antennas to make a single access point, which usually operates as a shared-medium hub or bridge, behave more like a predictable wired LAN switch. To do this, MIMO actually takes advantage of the fact that RF signals propagate in multiple directions when they hit common obstacles, such as walls and people.

Multi-path typically degrades WLAN performance (when only a single antenna per band is present) by offering up multiple inefficient path options to wireless client devices. By contrast, says Airespace, IRAP uses multi-path to its advantage. It samples all available paths and then switches between the paths that are most optimal for communications with each wireless user at any given time.

The Airespace IRAP is also said to reduce interference between access points and clients by filtering out unnecessary paths.

Next time: A bit more on the MIMO landscape.