Lucent Technologies Release 4.0 manual Capacity and Sizing Voice Ports, Port Capacities in Erlangs

DEFINITY AUDIX System Release 4.0	Issue 1
System Description Pocket Reference 585-300-214	May 1999
Capacity and Sizing
Voice Ports	3-2

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.

Table 3-2 lists the DEFINITY AUDIX system’s port capacities in Erlangs at .01 to .10 GOS .

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

Two examples from Table 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 Table 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.