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Wireless E911 Guide CG-EWCG-001
BellSouth Wireless E9–1–1/SS7 Interconnection
Guide Issue 3, January 6, 2004
regard to how they are used in this document. There may be significant impact to Wireless E9-1-1 service
if the Wireless Engineer fails to understand these differences during establishment of initial interconnection
using SS7/ISUP for wireless E9-1-1.
Generally speaking, the term CAS (Callpath Associated Signaling) means the same thing in Wireless
Phase 1 and Phase 2. In each case, ALL of the FCC mandated data is carried directly from the WSPs
MSC through the BellSouth E9-1-1 Tandem to the PSAP. In Phase 1, CAS includes two (significant)
data elements, the CBN and the pANI. In Phase 2, CAS includes those two elements as well as the
longitude/latitude coordinates of the caller (aka: x, y) when they dialed 9-1-1 on their wireless device.
Phase 2 CAS requires SS7/ISUP between the MSC and the BellSouth E9-1-1 Tandem, and ISDN to the
PSAP. As of 3Q2002 Phase 2 CAS is NOT supported in BellSouth. (ISUP Initial Address Message
Parameter Contents for CAS are fully described in J-STD-036-A, Annex-D, Section D.1.3)
In Phase 1, NCAS includes two (significant) data elements: the pANI and the CBN. In Phase 1 NCAS,
ONLY the pANI is sent directly from the WSPs MSC through the BellSouth E9-1-1 Tandem to the PSAP
(with the callpath). The CBN is added to the existing pANI record in the BellSouth ALI-DB by the WSP
or their agent during call setup, using an out-of-band signaling path (hence NCAS). The updated pANI
ALI record including the CBN & cell/sector address data is delivered to the PSAP through the BellSouth
ALI database using the BellSouth Standard ALI format. (The various NCAS architectures are beyond the
scope of this document. See J-STD-034 and each NCAS vendor’s own documents for details.)
In Phase 2, NCAS includes those same two (significant) data elements as well as the longitude/latitude
coordinates of the caller when they dialed 9-1-1 on their wireless device (and potentially can include
updated data upon demand). However, in Phase 2, NCAS (as defined in J-STD-036-A, Annex-D,
Section D.1.2) includes BOTH the CBN and the pANI being sent directly from the WSPs MSC through
the BellSouth E9-1-1 Tandem to the PSAP. In this instance the PSAP obtains the longitude/latitude
coordinates through the BellSouth ALI database (using the BellSouth Extended ALI format) via the
WSPs E2 interface. (The various E2 interface architectures are beyond the scope of this document. See J
STD-036-A and Intrado’s "BellSouth SR/ALI to MPC Interface Specifications for TCP/IP Implementation
of TIA/EIA/J-STD-036 E2" for details).
In Phase 2 there is an alternative method of data delivery that J-STD-036-A refers to as Wireline
Compatibility Mode (WCM), which ONLY sends the pANI (ESRK) directly from the WSPs MSC
through the BellSouth E9-1-1 Tandem to the PSAP (Sounds like Phase 1 NCAS doesn’t it? Hence the
terminology confusion!). In WCM the CBN and the longitude/latitude coordinates are added to an existing
pANI record in the BellSouth ALI-DB during the call by the WSP or their agent using an out-of-band
signaling path defined as an E2 interface. An updated Phase 2 compliant pANI ALI record including the
CBN, cell/sector address data and longitude/latitude coordinates is delivered to the PSAP through the
BellSouth ALI database using the BellSouth Extended ALI response format. If the x, y coordinates of
the caller are unknown at the time the updated pANI ALI record is created, the WSP (or their agent) is
expected to fall back to a Phase 1 compliant record that would include the CBN & cell/sector address data.
(The E2 interface architecture and operations are beyond the scope of this document. See J-STD-036-A,
and Intrado’s "BellSouth SR/ALI to MPC Interface Specifications for TCP/IP Implementation of
TIA/EIA/J-STD-036 E2" for details.)
In BellSouth there is another alternative method of data delivery that is structured upon the J-STD-036-A
NCAS Solution in Phase 2, or on J-STD-034 CAS in Phase 1. In either case it is a 20 digits to the PSAP
type solution. However, this 20 digit solution can be used between the MSC and the NDET even if the
PSAP is not capable of receiving 20 digits from the NDET. This is accomplished by using the BellSouth
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