The purpose in determining voice circuit requirements for an E9-1-1 Trunk Group is to provide a transmission Grade of Service (GOS) for each 9-1-1 caller that is at least P.01 (probability that no more than one call out of 100 attempts made during the average busy hour will be blocked) and that, where available, physically diverse routing is being used between nodes.
In no case is it ever recommended that voice circuits be designed at less than P.01 Grade of Service (GOS). Note that P.01 can also be described as P0.01 in the industry. In this document that are to be considered as synonymous.
This document is intended to provide information and straightforward instructions to determine the number of trunks required in a 9-1-1 trunk group to provide a P.01 Grade of Service (GOS). This method will apply between any of the following: End Office to Selective Router (SR); SR to PSAP; E9-1-1 gateway to the SR; Mobile Switching Center (MSC) to SR.
While this document is primarily targeted to the PSAP Manager community, the methodology described herein applies to all entities involved in the provision of 9-1-1 emergency service. Any network service provider (including but not limited to traditional wireline, wireless and VoIP) who claims compliance with NENA standards will engineer 9-1-1 trunk groups to not less than a P.01 Grade of Service (unless otherwise negotiated with the PSAP authority) using industry accepted methodologies like those described in this document, and detailed further in NENA 03-006 NENA Standards for E9-1-1 Call Congestion Management
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| 03-506_20070413.pdf | 169.1 KB |