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Voice Feature Guide 01

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
The Principles of ISDN BRA

The Principles of ISDN BRA

Figure 1-111 and Figure 1-112 show the principles of the ISDN BRA.

Figure 1-111 H.248 protocol principles of the ISDN BRA

Figure 1-112 SIP protocol principles of the ISDN BRA

User Access

Entering the AN from the MG side, the BRA user call from the deactivated state experiences four stages: activation, TEI application, Layer 2 link setup, and Layer 3 call control. If the port terminal is activated, the TEI is distributed, or the Layer 2 link is set up, skip to next stage.

Call Control

  • For the H.248 protocol or the MGCP protocol:
    • According to the signaling round-trip control, the call signaling on the MG is sent to the softswitch through the IUA (as the green line in the figure). The softswitch delivers the media control information through the H.248 protocol/MGCP protocol, and controls the resources on the MG (as the blue line in the figure), such as the B channel, context, and terminal.The gateway does not process the primitive Q.931 but takes out the primitive terminal Q.931 from the Q.921 message, encapsulates the Q.931 to the IUA message, and then sends to the softswitch. Resources are not assigned to the primitive Q.931.
      The context is supported only when the protocol is H.248.
    • Create an IUA service environment on the MG and MGC sides. Bear the Q.931 signaling on the ISDN BRA service board to the SCTP link, pack the signaling through the IUA protocol stack, and then send the packet to the MGC. Switch the Q.931 signaling on the MGC side. The MGC sends the Q.931 signaling to the peer end through the SCTP link to perform ISDN signaling call.
  • For the SIP protocol:
    • The ISDN service is provisioned in the IMS network by mapping and interaction between the SIP signaling and the DSS1 signaling.
    • The gateway converts the ISDN message to the SIP message and then the ISDN uses the SIP protocol for call control. The gateway between the ISDN terminal and the IMS implements signaling conversion and service control. Specifically, the gateway translates the DSS1 signaling to the SIP signaling and then sends the signaling to the IMS. Generally, the IMS transparently transmits the SIP signaling to the peer ISDN user. Then, the peer ISDN user translates the SIP signaling to the DSS1 signaling and then sends the signaling to the ISDN terminal. This process enables two ISDN terminals to be connected with each other and therefore the ISDN service is provisioned.

Working Mode

The BRA working modes include point to multipoint (P2MP) and point to point (P2P).
  • In the P2MP mode, one NT1 can connect to multiple terminals. Multiple Layer 2 links can be created at the same time, and up to two users can call simultaneously. If no call service exists, the system can be deactivated automatically to save the power and it also supports longtime activation.
  • In the P2P mode, one NT1 can connect to one terminal only. The Layer 2 link is always set up to ensure the service bearing at any moment. No matter whether the call service exists, the link is activated.

Terminal Power Supply Mode

The BRA power supply is to provide power for the terminal. Two terminal power supply modes are provided:
  • Local power supply: The terminal applies battery or connects to the power supply.
  • NT1 power supply: The terminal uses the NT1 power supply only. The NT1 power supply falls into two categories:
    • Local power supply: The NT1 connects to the local power supply.
    • Gateway power supply: Configure the remote power supply attribute of the BRA port on the gateway.

Terminal Identifier Distribution

In the P2MP mode, if the physical line of the BRA user is activated, one BRA port can connect multiple terminals. A terminal equipment identifier (TEI) is needed to identify the terminal.

The TEI can be specified by the terminal, or distributed on the network side.
  • The TEI that the terminal specifies ranges 0-63.
  • The TEI on the network side is distributed by the subscriber board, ranging 64-126.
  • The 127, as a multicast TEI, is used when the BRA user is called (all the users under the same port share the same telephone number). When the destination terminal is unknown, the connections to all the terminals are initiated.
  • In the P2P mode, the terminal TEI is 0.
Updated: 2019-02-22

Document ID: EDOC1100067358

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