Software Innovation Opens DFS Channels
In June, Summit announced a software upgrade that makes the 5 GHz frequency band more attractive for business-critical mobile devices. Enhancements in the new version of Summit software can greatly reduce the time that it takes a mobile device to roam between Wi-Fi infrastructure endpoints, or access points (APs), in an environment where some channels require dynamic frequency selection (DFS).
Before it roams, a client must scan all channels on which APs may be operating. Active scanning, where the client probes for an AP, takes about 20 milliseconds per channel. Passive scanning, where the client listens for an AP beacon, can take hundreds of milliseconds per channel. DFS channels require passive scanning because those channels may be used by military or weather radar. Unless passive scanning can be accelerated, the use of DFS channels for highly mobile devices is discouraged because the long scan times lead to long roam times that cause failures in mission-critical applications.
“The most attractive aspect of the 5 GHz band is its support for up to 23 non-overlapping channels versus three in the 2.4 GHz band,” said Chris Bolinger, Summit’s VP of Sales and Marketing. “Most 5 GHz channels, however, require DFS. If you turn off DFS channels for mobile clients, then you are left with eight channels in North America and only four in the rest of the world.”
One of the Summit software enhancements enables an administrator to shorten the time that a Summit Wi-Fi radio listens for an AP beacon on each DFS channel. By making passive scanning nearly as fast as active scanning, the new Summit software enables Summit-enabled devices to roam quickly, even when all 5 GHz channels are scanned. Administrators no longer have to restrict highly mobile devices to non-DFS channels.
The enhancements are in version 3.2 of Summit software, which will be generally available in September. The enhancements work with Summit 10 Series and 15 Series radio modules as well as 20 Series and 22 Series radio cards.