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Wireless E911 Guide CG-EWCG-001
MSAG Maintenance and ESN Assignment Issue 3, January 6, 2004
For areas with existing E911 service, existing ESN numbers should be assigned for wireless call routing.
Any of the currently assigned ESN numbers for a specific PSAP can be selected and placed in the
corresponding MSAG entries for the cell site addresses as described in the next section. The PSAP should
identify which ESNs should be used.
4.3 MSAG Maintenance and Validation
The Master Street Address Guide (MSAG) is the portion of the E911 database which contains the address
and ESN information. The MSAG associates the appropriate ESN to the pseudo-ANI number based on the
address on the data record provided by the Wireless Carrier.
It is the responsibility of the E911 Customer to assign, maintain and resolve discrepancies in MSAG data
for their service area. The E911 Customer is also responsible for providing new address information and
changes to address information to the BST data vendor for updating to the MSAG database.
It is the responsibility of all telcos (wireless and wireline) participating in an E911 service area to ensure
that all data records sent to the E911 host database have an MSAG valid address. Each telco will work
directly with the E911 Customer to resolve any address discrepancies.
The Wireless Carrier and E911 Customers must agree on the formatting of the Wireless Carrier data
records. Some wireless solutions require that each antenna face or PSAP, depending on the wireless
solution implemented, be assigned an MSAG valid address. The carrier and E911 Customer must work
together and agree on how the address and cell site sector location information should be formatted and
to ensure the addresses exist in the MSAG database with the appropriate ESN to route 911 calls to the
agreed upon PSAP. For some solutions, each antenna face should be assigned unique pseudo-ANI (pANI)
numbers by the Wireless Carrier to identify the specific cell site sector location. In other solutions, each
PSAP is assigned unique pANI numbers. Pseudo-ANI numbers must be geographically valid for the E911
selective routing tandem used to route the calls to PSAPs. The Wireless Carrier must create SOIR data
records for the cell sites or PSAPs containing the MSAG valid street address previously agreed upon with
the E911 Customer. If the street address in the SOIR data record is not formatted exactly to match the
MSAG entries, the SOIR data record will be in error and returned to the Wireless Carrier for correction.
Refer to tab "TN Database Updates" for detailed information on providing data for the E911 database.
For some solutions, the address used for the cell site is the address that has been assigned to the structure
where the tower is located. Or, if the tower is being constructed where there is no existing structure, it is
the E911 address assigned by the County to the new tower location.
If all antenna faces for a tower will route calls to the same PSAP, the one address may be shown for each
pseudo-ANI number associated with that tower. If it is determined that one or more of the pseudo-ANI
numbers will need to route to a different PSAP, then different addresses for each face must be obtained
from the E911 Customer. Prior to sending the pseudo-ANI data record to the E911 host, the cell site
address should be validated with the E911 customer’s MSAG in an effort to minimize error fallout and
ensure proper ESN assignment for call routing. If the address(es) to be used are not currently in the
MSAG, then the E911 Customer should send a MSAG ledger document to the BST data vendor to add the
address to the MSAG database. The pseudo-ANI data records for that cell site should not be transmitted by
the wireless carrier until the address has been added to the MSAG database.
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