SpectraLink NetLink Wireless Telephones Best Practices White Paper Wireless Telephone - Manual (Page 7)

White Paper
Page 6
The maximum number of simultaneous telephone calls an AP can
support is determined by dividing the total available bandwidth by the
percentage of bandwidth used for each individual call. Approximately 20-
40% of the AP bandwidth is reserved for channel negotiation and
association algorithms, so 60-80% of the total available bandwidth
should be used for calculating the maximum call capacity per AP. Lower
overall bandwidth is available when there are a greater number of
devices associated with an AP. For example if all calls on an AP are
using a theoretical 4.5% of the bandwidth at 11 Mb/s, the actual number
of calls expected at that rate would be about 13 (60% of bandwidth
available / 4.5% theoretical bandwidth utilized per call). The actual
number of calls expected at 2 Mb/s using the NetLink Telephony
Gateway and a 20 ms sample rate is about 7 (70% of bandwidth
available / 10% theoretical bandwidth utilized per call).
Even with all of the known variables, there are many other vendor-
specific characteristics associated with individual access points that
make it difficult to quantify the concurrent calls per AP without thoroughly
testing specific configurations. As a general rule based on lab tests and
experience, wireless LAN designs for NetLink Wireless Telephones
should consider no more than 12 simultaneous calls at 11 Mb/s or no
more than 7 calls at 2 Mb/s using either G.711 or NetLink Telephony
Gateways. Using the G.729 codec will yield roughly 50% more calls at
these mentioned data rates, but the general performance of NetLink
Wireless Telephones using this codec on various APs has not been well
tested.
To allow for bandwidth to be available for data traffic, SpectraLink
provides the ability to limit the number of calls per access point within the
NetLink Telephony Gateway and SVP Server. The “Calls per Access
Point” setting will limit the number of active NetLink Wireless Telephone
calls on each access point. Wireless Telephones are free to associate
with other APs within range that have not reached the set maximum
number of calls. SpectraLink recommends this setting be equal to or
below the maximum number of calls discussed in the previous
paragraph.