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DEFINITY AUDIX System Release 4.0
System Description Pocket Reference
585-300-214
Issue 1
May 1999
Capacity and Sizing
3-2
Voice Ports
The system’s GOS represents the fraction of calls to the port group that
are delayed more than 10% of the length of an average session during
the busiest hour of the day. Session times vary with subscribers’ feature
use, but session times average 60 to 100 seconds when all subscribers
access features through a single port group. All services on the system,
such as Automated Attendant, Call Answer, Voice Mail, and Bulletin
Board, usually share the voice ports.
Tab le 3-2
lists the DEFINITY AUDIX system’s port capacities in Erlangs
at .01 to .10 GOS .
Two examples from Tab le 3-2 will help demonstrate the significance of
using Erlangs to compare voice port GOS.
A system with a voice port capacity that falls in the top left cell of the
table would have 4 active voice ports on the DEFINITY AUDIX system.
Operating at .01 GOS, only 1% of the calls to those 4 ports would be
delayed longer than10 seconds during the busiest hour of the day. Thus,
the system would be operating at 0.89 Erlangs, which means that an
average of 0.89 of the customer’s 4 voice ports would be in use at any
one time. In this configuration, all callers would be assured an open
voice port to the DEFINITY AUDIX system.
On the other hand, a system whose voice port capacity falls in the
bottom right cell of Tab le 3-2
would have 12 active voice ports on the
DEFINITY AUDIX system. This system would be operating at .10 GOS,
meaning that 10% of the calls to the voice ports would be delayed more
than 10 seconds during the busiest hour. The system would then be
operating at 8.08 Erlangs, meaning that an average of 8.08 of the
customer’s 12 voice ports would be in use at any one time. In this
configuration, most callers could access one of the DEFINITY AUIDX
system’s voice ports. But at times when use is unusually heavy, some
subscribers may have to wait for service.
Table 3-2. Port Capacities in Erlangs
GOS
.01 .02 .03 .04 .05 .06 .08 .10
4 0.89 1.09 1.22 1.34 1.43 1.51 1.65 1.78
6 1.92 2.24 2.44 2.60 2.74 2.86 3.06 3.22
Ports 8 3.14 3.53 3.81 4.00 4.17 4.33 4.58 4.78
10 4.44 4.92 5.25 5.50 5.69 5.89 6.17 6.42
12 5.83 6.39 6.78 7.06 7.28 7.47 7.81 8.08