Wi-Fi (a commercial trademark) is a set of technologies for enabling the sending of data packets across a wireless local area network (WLAN), similar to the use of Ethernet cable in wired LANs. It makes use of radio frequencies that are suitable for short-distance communications, and by international agreement are not required to be licensed as (for example) the broadcasting frequencies are. However, the permitted uses of these frequencies are subject to local regulations that vary across the world, so that all Wi-Fi equipment must be sold using channels within those permitted for the country of sale.
Early equipment under the Wi-Fi standard was sold using the 2.4GHz frequency band (channels 1 to 11, and up to 13 or 14 depending on the country). More recently, new Wi-Fi standards have included the 5GHz frequency band, with generally shorter range but higher capacity for data transmission. The newer standards also improve transmission by using the available bandwidth more efficiently and changing frequencies automatically to minimise interference.
Some of these wireless ranges are intensively used, as can be seen by the number of SSIDs that nowadays can be detected in any neighborhood, but Wi-Fi is also competing with other uses of the same frequencies. In the 2.4GHz range, interference can include cordless telephones, Bluetooth devices and radiation leakage from other electronics. Radar for aeronautical and weather-forecasting use share the 5GHz range. In addition, the wireless mesh that connects a VeeaHub network operates on 5GHz, and other proprietary networks may also do so.
This article covers some VeeaHub features that mitigate these problems, Automatic Channel Selection (ACS) and Dynamic Frequency Selection (DFS).
Automatic Channel Selection (ACS)
ACS is a feature on the VeeaHub that sets the wireless access points (APs) to the best frequency channel for each, based on a number of metrics that take account of such problems as interference from external wireless sources and the communications with other VeeaHubs in the network.
ACS is the default option on the VeeaHub, whenever available. ACS then chooses the best frequency for each AP when it is started or restarted; the frequency is not changed while the AP is running. In Enterprise Center or VeeaHub Manager, there is the option to override this and set a single channel from the list of available channels.
ACS frequency scan
To select the best channel, the ACS function carries out a scan of the available channels on the frequency range. This scan ranks the channels in order of preference, and the auto selected frequency is the highest ranked. The ranking is based on a combination of the following measurements, along with other interference data not displayed. Note: the VHC05 does not display scan results.
-
#BSS: the number of basic service sets (Wi-Fi SSIDs) detected on this channel
-
Min/Max RSSI for BSS: The minimum and maximum Received Signal Strength Indicator for the SSIDs on this channel
-
Noise Floor / dBm: The noise floor on this channel
-
Load: A measure of the time the channel is occupied
These measurements are combined to select a best channel for the ACS. Because additional interference metrics not displayed here are used in the auto channel selection algorithm, it is on occasion possible for the ranking to appear to not choose the best channel. This results from a limit on the ability to display all factors used to choose the best channel, and it is not erroneous algorithm behaviour. However, if all channels show poor results, then moving the VeeaHub to another position should be considered.
Channel bonding
The standard bandwidth of a Wi-Fi channel is 20MHz. This can be increased by ‘bonding’ it to neighboring channels, which can result in higher data throughput. The VeeaHub can use 40MHz and 80MHz when this is technically possible. You can select these values by setting 20/40 or 20/40/80 for the Bandwidth option in the Radio tab for the access point.
If you set 20/40 or 20/40/80 when ACS is active, then you must ensure that the channels that are used for the bonding are all in the Auto Channel Whitelist, otherwise the bandwidth will revert to a lower value. If in doubt, select all available channels for the whitelist.
Node Manager
ACS settings appear on the Wi-Fi Radio tabs in Node Manager whenever ACS is an option. ACS is in operation whenever Channel is set to Auto, and this is the default. If you do not wish to use ACS, set the value to the channel you wish to specify. The Channel in Use is the actual channel, whether auto or manually selected.
The Auto Channel Whitelist enables you to select or exclude particular channels for the automatic selection.
VeeaHub Manager
ACS settings appear on the Wi-Fi Radio tabs in Node Manager whenever ACS is an option. ACS is in operation whenever Channel is set to Auto, and this is the default. If you do not wish to use ACS, set the value to the channel you wish to specify. The Channel in Use is the actual channel, whether auto or manually selected.
The Auto Channel Whitelist drop-down enables you to select or exclude particular channels for the automatic selection.
Dynamic Frequency Selection (DFS)
DFS is a feature that enables Wi-Fi operation on an extended set of channels in the 5GHz frequency range, the so-called DFS channels. It enables the WLAN functionality in the 5GHz band to switch frequency channels dynamically in response to detected interference from external sources, such as radar. The channels and the operation of DFS vary with location in accordance with national regulations.
If this feature is available for your VeeaHub model, then it is configured by default when DFS channels are selected. To remove DFS channels from ACS operation, select the Exclude DFS channels option (if available). When using DFS channels, whether by manual channel selection or with ACS operation, then Auto Channel Whitelist defines the set of channels to dynamically switch to if interference from radar sources is detected.
There are no DFS requirements for 2.4GHz WLAN operation, so the feature is not applicable to radios operating in this frequency band.
Note that if DFS is enabled, the automatic change of channel may cause a brief interruption in connectivity. When the VeeaHub is powered on, there is a brief period while the channels are scanned before an AP becomes available.
DFS is not available on the VHC05.