Installation guide

TD 92408EN

9 December 2011 / Ver. G

System Planning

Ascom VoWiFi System

11 Known Problems

b/g/n

802.11 operates in the 2.4GHz Industrial Scientific Medical (ISM) band. This

band is

unlicensed and many different wireless equipment uses this band with various radio

techniques.

As described in 6.1 Clear Channel Assessment, CCA on page 22

, the CCA makes 802.11

equipment sensitive to other transm

issions. This applies to all RF signals, not only other

802.11 equipment.

If CCA problems occur, it will affect the transmission pa

rt of the link between the AP and the

VoWiFi Handset. If the uplink speech (from the VoWiFi Handset) drops, the problem is near

the VoWiFi Handset. Check for nearby equipment such as wireless surveillance cameras,

Bluetooth gadgets, WiDi devices, ZigBee/Z-wave for HVAC controls, Light controls,

automation etc.

a/n

DFS channels.

Data traffic in a b/g/n network with large aggregated packet

s m

ight delay voice traffic.

802.11n

A full-blown 802.11n AP will also saturate the wired li

nk to the Ethenet switch since it can

easily pump out more than 100 Mbps of data. Thus to benefit from the 802.11n standard

the link to the switch must be upgraded to support Gigabit, otherwise the AP will have to

queue data frames and eventually throw away packets.

If the wired network contains a lot of APs connected to the same switch or if

wireless traffic

has to be route to a common device like a WLAN controller on the wired LAN, the switch

itself or the common device may become a bottleneck.