Best Practice for highly mobile/intense roaming devices

The recommendations in this article should not be strictly seen as requirements, but rather as something that can be described as the optimal conditions for mobile device which needs to utilize a wireless network.

It’s ideal to follow in cases where there are issues with the WiFi, for example if poor roaming is experienced. In this case, following all the recommendations mentioned here could function as a “best possible” benchmark, and after establishing this, the WiFi performance could be re-evaluated. If better, then you can start reenabling features one by one, while still monitoring performance. This should enable you to identify the deciding factor(s).

Frequency band

Stick with 2.4GHz if possible – even though the bandwidth is higher with 5GHz, the range is limited, so more AP’s are needed for same coverage. In some scenarios 5GHz may prove better, for example if there are many users on the 2.4 GHz band and thus a lot of “noise”. But 2.4GHz should always be tested as well before deciding.

Hidden SSID

Hidden SSID is not a security option and will increases the roaming time of a client between multiple access points. Non-broadcast SSIDs are not a valid security measure and actually make it easier for the SSID to be discovered since it forces clients to continuously probe for it.

The 802.11 standard does not define SSID hiding, and therefore, all implementations of a closed network are vendor specific. As a result, incompatibility can potentially cause connectivity problems when using cards from different vendors on your own network.

Multiple SSID

General recommendations when deploying multiple SSIDs on a single physical AP:

- No more than 3 SSIDs should be enabled on any single AP.

- Only enable an SSID on an AP if needed.

- Each SSID should be configured to tag a separate VLAN.

Consequences of Multiple SSIDs -> Overhead from Management Frames

Beacons and probe response are two types of required wireless management frames that can increase channel utilization. Beacon frames are used by the VAP (Each SSID that is enabled on a given AP is called a VAP (Virtual AP)) to advertise the SSID and inform connected clients that frames are waiting for delivery. Each VAP must send a beacon every 100ms at the lowest supported data rate so all clients can receive it.

TX Power Level of 5GHz (802.11a)

Mismatched AP and client power: --> the best solution is to ensure that all of the access points transmit power settings match the client transmit power.

Fixed TX-power level assignment (max 17dBm EIRP = transmitter output power plus antenna gain)

With a fixed channel and TX power assignment the system has a stable RF propagation pattern.

802.11a UNII 2 and 2 extended channels (DFS/TPC, Radar Channels)

Avoid the usage of the UNII 2 band and UNII 2 extended band 802.11a DFS and TPC cannels (Radar channels) as they are not supported by some handheld terminals.

Fast Roaming

Some handheld terminals do not support the new Fast Roaming standards. 802.11r, 802.11k and 802.11v, so this option should not be enabled if in doubt.  

Disable Load Balancing    

This feature is vendor specific and designed for high density environments with less roaming devices, and thus not ideal for the typical setup for highly mobile handheld terminals in a warehouse environment and should also be disabled.

Disable Band Steering    

If the service areas of the 2.4GHz and the 5GHz radios are not similar or equal of each access point then the vendor specific feature is preventing the clients to roam as expected.

example: depends on FSPL ( 6dB free space path lost of 5Ghz compared to 2.4GHz) fixed 2.4GHz TX power level at 11dBm and fixed 5GHz TX power level at 17dBm