Zhone Technologies IMACS Network Device - Manual (Page 101)

Zhone Technologies, Inc. IMACS Product Book, Version 4
March 2001 Page 97
IMACS with LBRV is suited to carrier networks and service organizations where downtime is unacceptable.
Examples include call centers; help desks, and inter-exchange trunks. IMACS with LBRV offers high reliability
through:
- Hardware redundancy
- Environmental ruggedness
- No moving parts
- Path redundancy (with FRS). It can be achieved through Backup PVC feature, which switches to an
alternate path upon either Loss of LMI [loss of FR administration connection or WAN CGA alarm (T1/E1
failure)]
•
Carrier networks requiring specialized Telco interfaces.
IMACS has specialized Telco interfaces found in carrier environments such as :
- Coin phone (12/16 kHz or battery reversal)
- 64 kbps G.703 co- / contra-directional
- BRI & PRI ISDN voice
- T1 and E1 interface
The IMACS equipped with the LBRV Server card offers cost-effective applications including:
- Bulk voice compression for remote call center
- Back-hauling voice for new carriers (e.g. centralized voice mail)
- Extending voice access network over VSAT
Call Center Application
In the application shown in Figure 41, customer calls originating from the PSTN, are compressed by the LBRV
server for efficient transmission on the leased E1 trunk, using frame relay. Up to three LBRV servers are used per
up to 8 IMACS terminals to compress up to 192 voice channels from the PSTN. Groups of two IMACS terminals
are combined. The first IMACS terminal of each pair uses 3 128 Kb/S channels each carrying 8 compressed voice
sub-channels (9.646 Kb/S per channel), effectively using only 77.16 Kb/S out of 128 Kb/S. The 3 channels are
inserted into the second IMACS terminal over a local T1 link. The second IMACS terminal combines its 3 128Kb/S
channels and the other 3 128 Kb/S channels into a single T1 link feeding into another IMACS terminal equipped
with the Frame Relay server. Ultimately, 4 T1 links bring the compressed voice signal from all 192 PSTN ports to
the frame relay IMACS. Although the total occupied bandwidth on all 4 T1 links is 3073 Kb/S (6 x 4 x 128 Kb/S)
the effective bandwidth used is only about 1852 Kb/S (4 x 2 x 3 x 8 x 9.646). The Frame Relay server takes the
advantage of this and combines only the effective bandwidth over an E1 unstructured transmission link. This still
leaves 128 Kb/S of the total E1 bandwidth (1984 Kb/S) for data traffic from a router attached to the IMACS
terminal via an HSU card. The Frame Relay server IMACS is used at the hub locations to send voice and data
traffic on a single leased E1 trunk.