Although Communication Manager supports wideband transmission for from two to 30 channels, the most common transmissions are at the H channel rates:
H Rate
Speed
# 64-Kbps Channels
H0
384 Kbps
6
H11
1.536 Mbps
24
H12
1.920 Mbps
30
When considering how many trunks to put in a trunk group that supports wideband call activity, remember:
Every wideband call must be carried on a single DS1 interface. That is, when the bandwidth on one interface is insufficient for the call, another interface must be found that can accommodate the entire call. The bandwidth for the call cannot be spread over 2 or more interfaces. The chances for finding enough bandwidth on a single interface are far less than finding the bandwidth on several interfaces.
Some far end switches (for example, the 4ESS) require the bandwidth for a call be contiguous. That is, not only must the call be carried over a single interface, but the channels over which the call is carried must be consecutively numbered. The chances for finding contiguous bandwidth are far less than for finding the bandwidth on a single interface alone.
To increase the chances of providing the bandwidth a wideband call requires, either put as many trunks as possible in the trunk groups you have designated for wideband call usage or put as many trunk groups as possible in the wideband routing pattern.
