Content for  TR 22.952  Word version:  17.0.0

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A  Region specific aspectsp. 34

This Annex describes region specific aspects of Priority Service.

A.1  U.S.A. specific aspectsp. 34

This subclause describes U.S.A region specific aspects of Priority Service.

A.1.1  Priority level assignmentp. 34

The sequence of events involved in receiving a Priority Service priority level assignment is as follows:
  • A Service User submits a request to their Authorizing Agent for the lowest applicable priority level necessary.
  • The Authorizing Agent forwards the request with a recommendation for approval or denial to the national designated authority.
  • The National Designated Authority returns the final priority level assignment to the Authorizing Agent as well as provides the Service User information (including assigned priority level) to the Service Provider.
  • The Authorizing Agent forwards the final priority assignment information to the Service User to complete the feedback loop.
See [13] for descriptions of Authorizing Agent and National Designated Authority.

A.1.2  Call origination / invocationp. 34

Within U.S. networks, a Priority Service call is invoked by dialling *SC + Destination Number, with a Service Code (SC) of "272".
Within U.S. networks, a Service User is assigned one or more Access Classes in the range of 12 - 14 to receive priority access to the network, in addition to an assigned Access Class in the range of 0-9.

A.1.3  Mapping of priority indicatorsp. 34

Within the U.S., there are five Priority Service priority levels. Table A.1 indicates the relationship among Service User Priority Assignment, TS 22.011 Access Classes, TS 22.067 eMLPP Priority Level, TS 48.008 Priority Level, TS 48.008 queuing allowed (qa) Value, and Precedence Level in the ISUP Precedence Parameter for Priority Service.
Service User Priority Assignment Access Class(es) eMLPP Priority Level 48.008 Priority Level 48.008 qa Value Precedence Level in ISUP Precedence Parameter
1 (highest)14 and 13 and 12B210
214 and 13 and 120311
313 and 121412
413 and 122513
5 (lowest)123614
0-104Implementation dependent, in the range of 7-14Implementation Dependent
Access Classes 11 and 15 may be used for network internal use.
eMLPP Priority Level A may be used for network internal use.
TS 48.008 Priority Level 1 may be used for network internal use.

A.1.4  Signalling of priority indicatorsp. 35

Priority assignment for ISUP messages is specified in ANSI T1.111.5, Annex A [10]. For a Priority Service call, MTP message priority of 1 is used for ISUP IAM messages signalled to establish the call.
A Priority Service call invokes the High Probability of Completion (HPC) Network Capability as described in T1.631 [11]. The HPC Network Capability sets Calling Party's Category parameter to "NS/EP call" in the ISUP IAM message to indicate that the call has been authorized to receive priority treatment. In the U.S., Service Providers use the "NS/EP call" value and not the IEPS value. For a Priority Service call, the Calling Party's Category parameter value of "NS/EP call" is propagated through the network and signalled to any interconnected network.
Service Provider transit nodes are expected to receive and pass the ISUP IAM message unaltered for all Priority Service calls. This explicitly includes the Calling Party's Category (CPC) parameter, the MTP Priority of the ISUP IAM message, and the ISDN MLPP Precedence Parameter.
For a Priority Service call, the ISUP Precedence parameter is encoded as indicated in Table A.2.
Field Description Value
Look Ahead for BusyIndicates whether look ahead for busy is allowed or whether the path has been reserved Binary "10" (Look Ahead for Busy not allowed)
Precedence Level Calling Party's Priority Level Binary, 4 bits "0000" through "0100", based on Calling Party's Priority Level, as assigned to the Service User: Service User priority 1 =
Precedence Level 0 (highest priority)
Service User priority 2 =
Precedence Level 1
Service User priority 3 =
Precedence Level 2
Service User priority 4 =
Precedence Level 3
Service User priority 5 =
Precedence Level 4 (lowest priority)
Network IdentityTelephone Country Code of the originating network Binary Coded Decimal, 4 digits, "0100" (indicating networks in the U.S.A.)
MLPP Service DomainPriority Service Domain Binary, 3 octets:
NCS Wireless Priority Service-1 (Decimal 4194891)
0100 0000 
0000 0010 
0100 1011
NCS Wireless Priority Service-2 (Decimal 4194892)
0100 0000
0000 0010 
0100 1100
NCS Wireless Priority Service-3 (Decimal 4194893)
0100 0000 
0000 0010 
0100 1101
NCS Wireless Priority Service-4 (Decimal 4194894)
0100 0000 
0000 0010 
0100 1110
NCS Wireless Priority Service-5 (Decimal 4194895)
0100 0000 
0000 0010 
0100 1111
The Precedence parameter includes the Look Ahead for Busy field to indicate whether a TCAP message may be sent prior to call setup to determine whether the called party's line is busy. Recognizing the call setup may be delayed, Priority Service does not support this functionality and the Precedence parameter is encoded accordingly.
The Network Identity (NI) field identifies the network or country which administers the service, not the country from which the call originates. Each digit is coded in binary coded decimal representation from 0 to 9. The first digit of this field is coded 0. The TCC (Telephone Country Code) follows in the second to fourth NI digits (the most significant TCC digit is in the 2nd NI digit). If the TCC is one or two digits long, the excess digit(s) is inserted with the code for the Recognized Operating Agency (ROA) or network identification, if necessary. If the 3rd and 4th NI digits are not required, they are coded all zeros.
The MLPP Service Domain is a 3-octet subfield that carries a code expressing in binary representation the number allocated to an MLPP Service Domain. These numbers are allocated in accordance with the procedures in Annex B, T1.113.3 [12]. The MLPP Service Domain values assigned to the National Communications System (NCS), the National Designated Authority as named in [13], correspond to Service User priority, i.e., NCS Wireless Priority Service-1 is used for a Service User priority of 1, etc. Therefore, there is no MLPP service interaction among the various levels of Service User priority nor between Priority Service and other services using the Precedence parameter.
For a Priority Service call, it is desirable that all TCAP messages sent during initial call setup associated with the Priority Service call are sent with MTP message priority 2.

A.1.5  Feature interactionsp. 37

A.1.5.1  eMLPPp. 37

For priority treatment, a Service User receives treatment that is compliant with eMLPP service capabilities with the following exceptions, extensions, or clarifications:
  • Support for the eMLPP Pre-emption capability is not required and is not supported for Priority Service.

A.1.6  Software access controlp. 37

Priority Service in the U.S. and U.S. territories is restricted to authorized individuals. Therefore, Service Providers do not implement Priority Service in their networks without an arrangement with the National Designated Authority. To support this restriction, the MSC/VLR should provide the capability to control access to, and activation of, the Priority Services software in the GSM BSS, MSC/VLR and HLR.

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