Spectralink 84-Series Series Wireless Telephones Administration Guide
1725-86984-000_P.docx
September 2016
241
If this preference is not configured, the 84-Series handset performs inter-band roaming between
the 2.4GHz and 5GHz bands if both bands are enabled without any preference to one band
over the other. The band of the access point with the strongest signal strength, as measured by
the handset, is used.
Band steering is the use of a preferred band when selecting an AP. The handset uses the
preferred band as long as telephone performance is not degraded by staying on the preferred
band instead of using the non-preferred band.
Table 11-4: Band steering parameters
Parameter
Permitted Values
Default
preferredBandRoaming.band
noPreference
prefer2_4GHz
prefer5GHz
noPreference
The configuration parameter,
preferredBandRoaming.band
, selects the preferred inter-band roaming mode.
Allowable values are
noPreference
(the default value),
prefer2_4GHz
, or
prefer5GHz
. For inter-band
roaming to function, both 2.4GHz and 5GHz bands must be enabled using existing
device.wifi.radio
parameters.
preferredBandRoaming.threshold
-65 to -40 db
-65
The 84 Series handset makes band selections based on signal strength for three different conditions; strong signal
strength, moderate signal strength, and low signal strength.
If the measured signal strength on a channel in the preferred band is above
preferredBandRoaming.threshold
+ 10db, the handset stays on the preferred band regardless of how much
better the signal strength on the non-preferred band may be. There is no degradation in performance as long as
the signal strength is strong so there is no reason to roam to the non-preferred band. The 84 Series handset may
still roam between APs on the preferred band. The threshold is set by
preferredBandRoaming.threshold
which may be configured for RSSI signal strengths from -65db to -40db.
While the default is -65db, Spectralink recommends that users experiment with values between -65db and -55db.
The +10db is added the threshold to prevent it from ping-ponging between two APs.
On the other end of the signal strength range is the point where signal strength is so low the wireless performance
is impacted. Below this threshold, the handset uses the access point with the best signal strength regardless of
which band is available (i.e. uses the rules that existed prior to adding the band steering feature). Any user
configured preference is ignored. This threshold is -75db and is not configurable.
preferredBandRoaming.bias
0 to 10 db
0
The lower end of the signal strength range is the point where signal strength is so low the wireless performance is
impacted. Below this threshold, the handset uses the access point with the best signal strength regardless of
which band is available. Any user configured preference is ignored. This threshold is -75db and is not configurable.
When the signal strength on the preferred band is moderate, between -75db and
preferredBandRoaming.threshold
+ 10db, the 84 Series handset MAY use the preferred band. The handset
uses the non-preferred band if the signal strength is significantly better than the preferred band. If the signal
strength on the non-preferred band is only slightly better than on the preferred band, the 84 Series handset uses
the preferred band.
The handset software has 10db built into the roaming algorithm to prevent the telephone from constantly switching
between two APs with similar signal strength. The handset will switch from a non-preferred band AP to a preferred
band AP if the preferred band AP signal strength is greater than the signal strength of the non-preferred band AP.
But to switch back to the non-preferred band AP, the non-preferred band AP must be at least 10db better than the
preferred band AP. This amount can be increased up to 20db by using the bias parameter, thus strengthening the
preferred band criteria. The
preferredBandRoaming.bias
is added to the preferred band signal strength
before comparing it to the non-preferred band AP.
