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Voice Feature Guide 01

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Voice Feature Overview

Voice Feature Overview

Access devices support the following basic voice features to help carriers provide high-quality voice services.

Table 1-1 Basic voice features

Basic Feature



Voice protocols are used for communication between an access device and an upper-layer gateway control device. The access device supports H.248, Media Gateway Control Protocol (MGCP), and Session Initiation Protocol (SIP). You can run the display protocol support command to query the protocol used on the device. If the protocol used on the device is different from the planned protocol, run the protocol support command to switch the protocol.




Access Mode

A voice access mode is based on terminal type and service requirements. The access device supports POTS, ISDN, and R2 access modes. Voice communication also supports fax and modem services.
  • A POTS network is a connection-oriented circuit switched network based on timeslot switching. Each circuit connection uses a timeslot in a pulse code modulation (PCM) group. That is, the circuit switched rate is 64 kbit/s.
  • The ISDN access can be basic rate access (BRA) or primary rate access (PRA). The BRA access provides 2 B channels and 1 D channel. The rates of B and D channels are 64 kbit/s and 16 kbit/s, respectively. The PRA access provides 30 B channels and 1 D channel. The rates of B and D channels are both 64 kbit/s.
  • In R2 access mode, the access device connects to a private branch exchange (PBX), which communicates with the access device through R2 signaling.






Key Techniques for Improving Voice Service Quality

The VoIP technology provides a series of technologies, such as codec, echo cancellation (EC), and voice activity detector (VAD) to improve the voice quality.

Key Techniques for Improving Voice Service Quality

Table 1-2 Voice service features

Service Type



The VoIP service uses the IP packet switched network for transmission after the traditional analog voice signals are compressed and packetized, to lower the cost of the voice service.


The modem over Internet Protocol (MoIP) refers to the modem service provided on the IP network or between the IP network and the traditional PSTN network.


The fax over Internet Protocol (FoIP) refers to the fax service provided on the IP network or between the IP network and the traditional PSTN network.

Line hunting

Line hunting is a feature that allows a group of ports to share a group of called party numbers by specifying a hunting group and hunting policy. Only the SIP protocol supports this feature.


To configure an IP SPC, configure the data (including the local IP address, local UDP port, remote IP address, and remote UDP port), set up an IP direct connection between the two ends of the voice service. In this manner, the voice media data can be directly transmitted to the peer end.

Table 1-3 Voice security features



Device authentication

Device authentication is a method to improve the security of the core network and prevent illegal devices from registering with the core network device.

For the SIP protocol:
For the H.248 protocol:
For the MGCP protocol:


Dual homing is an NGN (Next Generation Network) total solution. Based on this solution, when the active softswitch or the link from the MG to the active softswitch is faulty, the MG need be switched to the standby softswitch immediately to prevent call services of users connected to the softswitch and the MG from being affected.


As an enhancement of dual-homing, multi-homing is a configuration in which a media gateway (MG) is homed to the primary media gateway controller (MGC), secondary MGC, and disaster-recovery MGC.

Emergency standalone

Emergency standalone is a solution in which the users on the same MG can call each other even when the interface between the MG and the softswitch is interrupted.

Table 1-4 POTS port maintenance and test features

Troubleshooting Method


A POTS user loop line test is used to test the electrical indicators of the line from the test device (an access node) to a phone. When users' POTS services are faulty, POTS user loop line tests can be performed to test the performance and electrical indicators of the loop line to diagnose whether the loop line is faulty.

POTS User Loop Line Test

A POTS user circuit test is used to check whether the chip of a POTS board functions normally. If the POTS services are faulty and the loop line works normally, POTS user circuit tests can be used to test the functions (such as the ringing and power feeding) and some parameters (such as the feeding voltage and ringing voltage) of the board circuit to check whether the circuit works normally.

POTS User Circuit Test

A POTS port loop test is used to test the hardware and configurations related to POTS services during device installation or before POTS service provisioning. It helps reduce the number of site visits and minimize maintenance costs.

POTS Port Loop Test

A search tone test is a simple line fault locating function intended for maintenance engineers. In a search tone test, the test module sends voice signals with the specific frequency and amplitude to a line, and then maintenance engineers use a receiver or a dedicated device to detect the signals on the line. In addition, search tone tests can help maintenance engineers pinpoint the specific line among multiple user lines.

Search Tone Test

In a signal tone test, the system sends the signal tone signals to a specific port of a POTS board and makes the port loop back the signals, and then checks whether the loopback signals can be detected. This test function helps maintenance engineers check whether the system can normally process the detection of the user off-hook and signal tone and locate hardware faults related to the user off-hook and signal tone playing.

Signal Tone Test

A call emulation test emulates call functions to verify data configuration for the voice service. The call emulation test can also be used to locate voice service faults.

Call Emulation Test

Updated: 2019-02-22

Document ID: EDOC1100067358

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