GA/T 1364-2017 Police digital trunking communication system - Technical specifications for interconnection
1 Scope
This standard specifies the interconnection interface protocol architecture, pSIP syntax, DNS extension provisions, RTP extension provisions and protocol process of police digital trunking (PDT) communication system.
This standard is applicable to the design, manufacturing and engineering acceptance of police digital trunking (PDT) communication system.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GA/T 1056-2013 Police digital trunking communication system - General technical specifications
GA/T 1058-2013 Police digital trunking communication system - Technical specifications for call control layer of air interface
GA/T 1059-2013 Police digital trunking communication system - Security technical specifications
YD/T 1522.1-2006 Technical requirements for session initiation protocol - Part 1: Basic session initiation protocol
YD/T 1936-2009 Technical Requirements for session description protocol
RFC 1035 Domain names - Implementation and specification
RFC 3550 RTP: A transport protocol for real-time applications
RFC 3551 RTP profile for audio and video conferences with minimal control
NMEA 0183 Protocol
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
user agent
logical functional entity supporting the SIP protocol, which acts as a UAC where a request is generated and as a UAS where a request is received and a response is generated
3.1.2
user agent client
functional entity that sends a session request with client transaction status machine in the process of SIP session establishment
3.1.3
user agent server
functional entity that receives, rejects or forwards the corresponding session request, and sends this response with the server transaction status machine in the process of SIP session establishment
3.1.4
transaction
client and server event that shall range from the first request sent by the client to the server to the last (non-1xx) termination response sent by the server to the client
3.1.5
transaction user
protocol layer on top of the SIP transaction layer
3.1.6
session
point-to-point SIP connection between two UAs that lasts for a period of time and records the relevant content on the two UAs already connected
3.2 Abbreviations
For the purposes of this document, the following abbreviations apply.
BNF Backus-Naur Form
DNS Domain Name Service
ENUM Telephone Number Mapping
GH_MSC Group Home Mobile Switching Center
H_MSC Home Mobile Switching Center
HSS Home Subscriber Sever
IP Internet Protocol
MFID Manufacturer's Specific FID
MS Mobile Station
MSC Mobile Switching Center
O_MSC Original Mobile Switching Center
P_MSC Participant Mobile Switching Center
pSDP PDT Session Description Protocol
pSIP PDT Session Initiation Protocol
PDT Police Digital Trunking
RTP Real-time Transport Protocol
SDP Session Description Protocol
SIP Session Initiation Protocol
UA User Agent
UAC User Agent Client
UAS User Agent Server
UDP User Datagram Protocol
URI Universal Resource Identifier
V_MSC Visit Mobile Switching Center
XML Extensible Markup Language
4 Overview
4.1 Interconnection function
The interconnection between PDT systems is based on all-IP softswitch technology and shall meet the following requirements:
——The user mobility management between PDT systems includes functions of roaming registration/de-registration, cross-system authentication, stunning/reviving roaming users, killing roaming users and user group management;
——Call control functions between PDT systems include individual call, group call, PTT authorization, multi-site handover and speaker identification;
——Data services between PDT systems include cross-system short messages, status information and satellite positioning information;
——Support dynamic group number assignment (DGNA) function;
——The maximum transmission delay of the link between PDT systems is less than 100 ms, the transmission jitter is less than 25 ms, and the packet loss rate is less than 10-3, the bandwidth of each session is not less than 32 kbps;
——The cross-system group calling establishment time is not more than 500 ms.
4.2 Interconnection architecture
The PDT communication system shall have the national networking capability, as well as the multi-level network management capability of ministries, provinces and cities. Therefore, the flat IP network is divided into virtual multi-level interconnection management system, as shown in GA/T 1056-2013. The interconnection between any two PDT systems in the flat IP network adopts a completely peer-to-peer system interconnection architecture, as shown in Figure 1.
Keys:
pSIP control signaling;
RTP voice service.
Figure 1 Completely peer-to-peer system interconnection architecture
A pSIP protocol shall be used for interconnection control signaling between PDT systems, a RTP protocol for voice transmission between PDT systems, and a DNS protocol between PDT systems and domain name servers (DNS). A DNS is a database with distributed architecture, which completes number and domain name address parsing and mapping to IP addresses.
The PDT system supports users to roam across the country. The home system shall decide whether the mobile station can roam to the remote system according to the user's roaming authority, and the system of visited area can decide the calling authority of roaming users according to the local roaming authority control policy. If ordinary roaming users roam in the visited area to access the network, the system of visited area only opens the lower call authority by default. If the system resources of visited area are busy, the local user may preempt the roaming user's call service channel. The system of visited area may also pre-configure the policy to reserve the calling authority of the home system for roaming users from some remote systems as appropriate, and the roaming users may enjoy the equivalent or higher calling authority as the local users.
The roaming authority is configured by the local municipal network management system according to the work demands, and it is required to enable the roaming authority only for users who need to roam; if users without roaming authority need to roam across systems, they shall contact the home network management to activate roaming authority. The roaming authority control policy of the system of visited area is configured by the local network manager or the senior network manager.
4.3 Interconnection protocol
The interconnection protocol between PDT systems is divided into control plane and user plane, and the hierarchical structure of the interconnection protocol is shown in Figure 2.
Figure 2 Hierarchical structure of interconnection protocol
The interconnection control plane interface between PDT systems uses the pSIP protocol for mobile management, call control and network maintenance, etc. The pSIP protocol also includes the pSDP protocol for media stream control, MAP protocol for user data definition and NMEA protocol for satellite positioning information. The basic syntax rules of pSIP shall meet the requirements of YD/T 1522.1-2006 and YD/T 1936-2009.
The interconnection user plane interface between PDT systems uses the RTP protocol and it shall meet the following requirements:
——The format of the RTP header shall conform to RFC 3550, and the format of the media information carried by the RTP shall conform to RFC 3551;
——The RTP extension header can carry information such as LC, PI and EMS of wireless air interface voice;
——The PDT system shall be capable of transmitting air interface voice information with channel coding transparently.
If the MSC needs to obtain the IP address of the H_MSC to which the MS belongs or the IP address of the GH_MSC to which the group user belongs, the relevant data may be obtained from the DNS server through the DNS query protocol.
The layers of the pSIP protocol stack have the following meanings:
——Application layer: providing various application services between PDT systems;
——Session layer: completing various session service processes between PDT systems, such as call control and roaming registration;
——Transaction layer: divided into client transaction and server transaction. The client transaction is responsible for accepting the request from the upper entity and reliably sending the request to the server transaction; receiving responses and transmitting them to upper entities, while filtering duplicate responses and some illegal responses. The server transaction is responsible for receiving requests from the transport layer and sending them to upper entities, while filtering repeatedly received requests; receiving responses from upper entities and reliably sending responses to client transactions;
——pSIP signaling compression layer: completing the syntax parsing, signaling encoding and decoding, and signaling compression functions of pSIP protocol;
——Transport layer: UDP protocol is used for completing end-to-end data transport;
——Network layer: IP protocol is used for completing the routing from source address to destination address.
5 PDT session initiation protocol (pSIP)
5.1 pSIP protocol architecture
The pSIP protocol stack is divided into application layer, session layer, transaction layer, compression layer, transport layer and network layer. The transport layer uses UDP protocol, and the port number is 5060 by default.
Foreword i
1 Scope
2 Normative references
3 Terms, definitions and abbreviations
4 Overview
5 PDT session initiation protocol (pSIP)
6 Domain name service (DNS) extension provisions
7 Real-time Transport Protocol (RTP) extension provisions
8 Interconnection protocol processes
Annex A (Normative) Description of domain name
Annex B (Informative) Example of ENUM transformation relationship
Annex C (Informative) Example of DNS lookup
Annex D (Informative) Description of message sequence diagram
