No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>Search

Reminder

To have a better experience, please upgrade your IE browser.

upgrade

Voice Feature Guide 01

Rate and give feedback :
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).
Classification of FoIP

Classification of FoIP

Fax over IP (FoIP) is a faxing service provided over an IP network or between an IP network and a traditional PSTN network. The fax machine can be regarded as a special Modem. In the FoIP negotiation, the Modem negotiation is performed before the fax negotiation. FoIP services can be classified based on the transmission real-time performance, or based on the transmission mode.

Classification Based on Transmission Real-time Performance

Based on the real-time performance, FoIP can be classified in store-and-forward FoIP and real-time FoIP. The difference between the two modes lies in whether communication between the gateway and the fax machine is real-time on the IP side. On the PSTN side, communication of the two FoIP modes is real-time.
  • Store-and-forward FoIP: In this mode, fax information is stored and then forwarded to the IP network, as defined in the T.38 protocol.
  • Real-time FoIP: In this mode, communication during the entire fax process is carried out in real time, as defined in the T.38 protocol.
NOTE:
Huawei access gateway (AG) supports real-time FoIP.

Classification Based on Transmission Mode

According to the transmission protocol used, there are two modes of fax services carried over the IP network: the T.30 transparent transmission mode and the T.38 transmission mode.

T.30 transparent transmission mode

In this mode, T.30-defined fax messages and data are transparently transmitted in an AG or between AGs. Figure 1-117 shows the T.30 transparent transmission mode.
Figure 1-117 T.30 transparent transmission mode
The advantages and disadvantages of the T.30 transparent transmission mode are as follows:
  • Advantages: consumes less DSP resources, and is less dependent on the softswitch/IMS.
  • Disadvantages: weak resistance against interference from the network, and does not provide reliable guarantee for fax quality. Stability of the T.30 transparent transmission mode can be improved using the RFC 2198 and 10-ms packetization technologies. For more details, see Fax/Modem Quality Enhancement.

T.38 transmission mode

The T.38 transmission mode is shown in Figure 1-118. T.38 fax supports two rate negotiation modes: end-to-end negotiation and local negotiation. The difference between the two negotiation modes lies in whether the rate training signals need to be transmitted from the transmitting AG to the receiving AG.
  • When the rate training signals need to be transmitted from the transmitting AG to the receiving AG, it is end-to-end negotiation.
  • When the rate training signals are terminated and generated by the transmitting AG, it is local negotiation. If the local negotiation mode is used, the maximum rate supported by the AG should be considered. That maximum rate is reflected by the maximum fax rate supported by the digital signal processor (DSP).
Figure 1-118 T.38 transmission mode
The advantages and disadvantages of the T.38 transmission mode are as follows:
  • Advantages: provides a redundancy mechanism for transmitting data packets, and does not have strict requirements on network quality (able to process the fax service even with a 20% packet loss rate on the network).
  • Disadvantages: The DSP chip of the AG needs to participate in parsing the T.38 signals. Because there are various types of terminals on the network, interoperability problems may occur.

Differences Between High-speed Fax and Low-speed Fax

The main differences between high-speed fax and low-speed fax include the following:
  • Standards applied. High-speed fax applies the V.8 data transmission process, while low-speed fax applies a fax process defined by the T.30 protocol. In addition, some low-speed fax terminals may use earlier standards.
  • Range of rates supported. High-speed fax supports a rate range of 2400 bit/s-33600 bit/s, while low-speed fax supports a rate range of 2400 bit/s-14400 bit/s.
  • Upstream transmission modes used. High-speed fax can use only the T.30 transparent transmission mode. In other words, for an AG, only the high-speed Modem T.30 transparent transmission mode can be used for fax services. Low-speed fax can use the T.30 transparent transmission mode or T.38 transmission mode, according to data configuration of the fax terminal.
  • Error correction requirements. For high-speed fax, the error correction function is a mandatory requirement; for low-speed fax, the error correction function is optional.
  • Echo cancellation (EC) requirements. High-speed fax requires the EC function to be disabled because a high-speed fax terminal already has an inherent EC mechanism; low-speed fax requires the EC function to be enabled.
Translation
Download
Updated: 2019-02-22

Document ID: EDOC1100067358

Views: 13052

Downloads: 123

Average rating:
This Document Applies to these Products
Related Documents
Related Version
Share
Previous Next