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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).
R2 Principles

R2 Principles

R2 signaling is inter-office channel associated signaling, and applies to international/national networks. R2 signaling is specified on both analog and digital transmission systems. R2 signaling contains line signaling and register signaling. Line signaling is available in three forms: DC line signaling, inband single-frequency pulse line signaling, and digital line signaling. For multi-end route transmission, the link-by-link forwarding mode is used. Register signaling can be transmitted in multi-frequency compelled (MFC) mode and dual tone multiple frequency (DTMF) mode.

Line Signaling

Line signaling is primarily used for monitoring the occupation, release and congestion states of a trunk line. Line signaling is classified into analog line signaling and digital line signaling. The MA5600T/MA5603T/MA5608T supports only the digital line signaling which will be described in detail in the following paragraph.

The digital line signaling uses timeslot 16 of the PCM for transmitting line signaling at a rate of 2048 kbit/s. To transmit line signaling of 30 voice channels, 16 frames form a multiframe. Timeslot 16 of frame 0 in the multiframe is used for multiframe synchronization. The first four bits of timeslot 16 in frame 1 correspond to the first voice channel, while the last four bits correspond to the 16th voice channel and so on.

Register Signaling

Register signaling is the signaling transmitted over a voice channel after the line signaling occupies the voice channel. Register signaling, including the selection signaling and service signaling, is used to transmit the control signals for a voice channel connection, such as managing the telephone network and selecting the route and the called party. The MFC register signaling will be described in detail.

The MFC register signaling includes the forward signaling and backward signaling, both of which are consecutive. The forward signaling is used to transmit the address information and control the indication information, while the backward signaling is used for acknowledgement and control. When transmitting a number, the transmit end stops transmitting the forward signaling only after receiving the acknowledgement from the backward signaling. Similarly, the receive end stops transmitting the backward signaling only after confirming that the transmission of the forwarding signaling is stopped. A control period can be divided into four steps, which is listed as follows:
  • Step 1: The user side sends the forward signaling.
  • Step 2: The network side receives the forward signaling and returns the backward signaling.
  • Step 3: The user side receives the backward signaling and stops sending forward signaling.
  • Step 4: The network side finds that the transmission of forward signaling is stopped, and stops sending the backward signaling.
The MFC register signaling uses the arithmetic frequency with 120 Hz as the common difference. This section takes the definition in Q.441 as an example, the forward signaling uses the high-frequency group (1380 Hz to 1980 Hz) and selects two out of six frequencies (1380 Hz, 1500 Hz, 1620 Hz, 1740 Hz, 1860 Hz, and 1980 Hz) for encoding. Up to 15 signaling combinations can be formed. The backward signaling uses the low-frequency group (780 Hz to 1140 Hz) and selects two out of four frequencies (780 Hz, 900 Hz, 1020 Hz, and 1140 Hz) for encoding. Up to six signaling combinations can be formed. To expand the signaling capability, the forward signaling is divided into group I forward signaling and group II forward signaling, while the backward signaling is divided into group A backward signaling and group B backward signaling.
  • Register signaling must always start with group I forward signaling. Group I forward signaling includes the information of the country code, echo suppressor indicator (I-11) and address signal (number: 1-9).
  • Group II forward signaling is the calling party's category signaling sent by an outgoing R2 register. It is used to reply to backward signal A-3 (the address-complete signal) or A-5 (the request signal for a calling party's category), and send the national or international calling information.
  • Group A backward signaling is used to acknowledge the group I forward signaling and under some conditions, group II forward signaling, such as acknowledging the calling party's type and group II forward signals.
  • Any group B backward signaling acknowledges the group II forward signaling and is always preceded by the address-complete signal A-3. Signal A-3 indicates that the incoming R2 register has received all the required forward signals from the outgoing R2 register.

Register signaling is the in-band signaling (the frequency is within the voice frequency band). Therefore, the register signaling is transmitted over the voice channel.

R2 Application in Access Networks

A PBX is connected to the next generation network (NGN) through R2 signaling. Interfaces between an MG and an MGC/IMS use the H.248/SIP protocol, and interfaces between an MG and a PBX use the R2 protocol. Figure 1-113 shows the networking of connecting the R2 PBX to the NGN network.

To connect a PBX to the NGN network through R2 signaling, MGs need to perform the conversion between R2 signaling and H.248/SIP signaling.
  • In the upstream direction, the MA5600T/MA5603T/MA5608T terminates R2 signaling transmitted from the PBX, converts R2 signaling to H.248/SIP signaling, and sends the converted signaling to the softswitch.
  • In the downstream direction, the MA5600T/MA5603T/MA5608T terminates H.248/SIP signaling transmitted from the softswitch, converts H.248/SIP signaling to R2 signaling, and sends the converted signaling to the PBX.
Figure 1-113 Network example of connecting the R2 PBX to the NGN network

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Updated: 2019-02-22

Document ID: EDOC1100067358

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