Voice compression and IP online voice (VoIP) technology

In the fully transparent networking scheme using IP network or leased line to realize voice switch, in addition to adopting the most advanced signaling system, the built-in voice compression platform and its IP network voice are integrated in the switching system.

VOIP Technology and Gateway technology are the key to achieve high quality voice communication. The built-in speech compression technology provides a new set of solutions for the connections between nodes, and can reduce the communication cost of the enterprise private network. The speech compression scheme can increase the traffic passing ability among the switching nodes without changing the existing network construction conditions. Speech compression can be used for leased lines like voice and data multiplexer . A 64kbit/s leased line is used to connect two voice exchange nodes, which can transmit multiple voice channels and a private network signaling data channel during the 64KBIT/S bandwidth.

In the most advanced networking solution, it is possible to implement a VPN scheme with a real compression function without the need for a permanent network signaling channel. The network signaling can be transmitted in B channel, and this B-channel is established on demand only when there is a traffic between two nodes, that is, to establish a special network network to provide all the special network services. Another application of voice compression is to reduce communication costs between two high traffic companies. This function is also known as the second call free business. This free second call is also built on demand. With built-in speech compression platform and voice gateway, voice Exchange node can transmit voice Voip on IP network.

First, speech compression platform technology

At present, the voice compression platform built in advanced voice switch is realized by the Link optimization function module in the system. The specific choice of which function board is determined by how the switching nodes connect to the network. The connections between switching nodes can be leased lines, ISDN switching networks, frame relays, and IP networks. The so-called compressed platform is actually a multiplex multiplexer for voice and data. There are always three items involved in a multiplexer: Voice access, network signaling and data, and networking via wide area networks (also known as hybrid channels).

1. Voice Access is part of the advanced built-in speech compression platform used by the compression algorithm for G723. 1, the compression rate is about 6. 4 kbit/s, which is also the default compression standard for low speed VoIP, Microsoft's Communications applications Network conferencing netmeeting also adopted this standard.

G723. 1 of the Mass by M. O. S The average judgment score  the quantity. 5 indicates the best quality, G71164k voice is set to 4. 2,g723. The 1 algorithm was contracted to 3. The G729 of the 9,8kbit/s was also 3. 9,GSM is 3. 5. Because the compression will cause delay, the built-in echo cancellation technology. The third type of fax is supported at a maximum rate of 9600bit/s, and faxes will be demodulated and modulated to avoid the use of WAN 64kbit/s bandwidth. Modem call does not go through the compression device. The translation, coding and reconstruction of the MFQ23 code are also done on the other end. This avoids the distortion of the signal q23 receiver is very sensitive . Missing frame patching prevents the loss of speech frames. This feature is useful in frame relay networks, where frames are discarded when the network is saturated. Speech detection, mute suppression, and mute regeneration are only sent when it occurs, which means that bandwidth is dynamically distributed, 50% of the time is saved, and can be reassigned to other traffic such as data. In order to lose as little speech as possible, even if the voice is transferred between several switching nodes, only one compression and decompression is performed.

2. The data part is very important to the speech compression platform, so the network signaling can be exchanged between nodes. At the same time the low speed rate HDLC data is also supported. The private network signaling is in fact also the HDLC data, which includes not only the call processing signal, but also the communication management, routing, monitoring and other information. The advanced speech compression platform adopts dynamic bandwidth management, and if there is no voice signal, bandwidth is used to transmit the special network signaling and data.

3. A wide area network (WAN) portion of a WAN can be a leased line, an ISDN channel, a Frame relay permanent virtual circuit, or an IP network. Speech and data are reused before the WAN network is transmitted. There are two ways to reuse and manage WAN bandwidth: Time division Multiplexing, frame/letter or package.

The TDM method orders a fixed bandwidth for each channel. The advantages of the delay and delay jitter is very small. The disadvantage is that bandwidth is wasted, which is not acceptable when using low speed access 64kbit/s128kbit/s because bandwidth cannot be used by other traffic such as data when the channel is not in use or there is no voice traffic. In the switching node of the built-in speech compression platform, use frame mode. This means that the allocation of bandwidth is dynamic. When one or more voice channels are not established or are in the gap phase of the call, bandwidth can be used by the private network signaling or data. This means that, for example, at night, there is no voice traffic, and billing can be transmitted using the vast majority of bandwidth.

The problem of frame mode reuse is the delay and how to manage the priority of traffic, to overcome these problems, advanced switching nodes can take the following measures: Data frame segmentation, user data frame may be very long, when there is a very long frame to send, in order to avoid long delay, the long frame is divided into small segments The frame is regularly sent by the minimum delay and the delay, the speech first, the voice information is sent to WAN in the frame, and the remaining part of the bandwidth sends the special net signaling and the user data. Delay in the network: Two nodes end to end sound call delay is 40~90 MS, each transmission increases 10~40ms.

4. Link optimization speech compression module with Alcatel OMNIPCX 4400 Integrated Services Broadband multimedia Exchange Platform for example, the implementation of speech compression platform by the LIOX series module implementation: LIOP, LIOB, Liox. Each board has 6 speech compression modules, and each module dynamically processes a voice or fax. The difference is in the external interface: LIOP with a PRA interface, LIOB with a serial port and 4 bra network interfaces, Liox no external interface. LIOP coupling plate. The LIOP is 2-in-1, Liox plus the PRA plate. The PRA interface can be connected to a public ISDN network. The special network traffic  on the need to establish the channel  and the public network telephone service uses the same interface. PRA can also be connected to the g703/g704 portion of the rate E1 leased line. Applicable to the high traffic volume requirements between the two places.

LIOB coupling plate. LIOB is liox plus 4 bra network interfaces plus 1 serial interfaces. LIOB can be applied to new systems or installed systems that are based on serial port requirements. The serial port on the LIOB board can be either x24/v11 or V36. A leased line 64bit/s,128kbit/s or Frame relay network with a small capacity can be connected; The LIOB serial interface cannot be used as a connection terminal. This interface is connected to the network. And the compression on the serial port can only be using LIOB, not the Liox plus sync terminal adapter, bra can connect to the T0 interface on the ISDN network. This interface can be used for the transfer of private and public traffic, the bra interface can not connect S0 extension or S0 PC board, bra interface only to connect T0, can not connect S0. LIOX coupling plate. The LIOX board does not have an external interface, LIOX can be used as an extension board for LIOP or LIOB boards  users do not need more external interfaces, only additional voice compression resources ;liox can be installed on bra 4400 systems that already have a PRA or OMNIPCX board. In the concentration of speech compression resources, voice compression resources are concentrated in one node and can be shared in all directions. The advantages are: security, some compressed resources failure does not affect the global, the central node to compress resources more than the requirements of the remote node. The loss rate should be very low.