Four parts about the composition of the voip system

The market advantage of VoIP is obvious. This voice technology, developed by the long-distance method, has impacted the market at its ultra-low price. How is the system of voice character completed by means of network? Now let's talk about the components of the VoIP system.

Due to many developments and technical breakthroughs in related hardware, software, protocols and standards, the widespread use of VoIP will soon become a reality. Technological advances and developments in these fields contribute to the creation of a more effective, functional, and interoperable VoIP network. The main developments in these fields are briefly listed. The technical factors driving the rapid development of VoIP and its wide application can be summarized into the following aspects.

VoIP system composition 1. Digital Signal Processor

Advanced Digital Signal Processor (DSP) is a computing intensive component required for speech and data integration. DSP processes digital signals for complex computing. Otherwise, these computing tasks may have to be executed by the general CPU. The combination of their specialized processing capabilities and low costs makes DSP well suited for implementing signal processing functions in VoIP systems.

The computing overhead of G.729 voice compression on a single speech stream is very high, with a requirement of 20 MIPS. If a central CPU is required to process multiple speech streams, it also implements the routing and system management functions, this is unrealistic. Therefore, you can use one or more DSPs to detach the computing tasks of the complex voice compression algorithm from the central CPU. In addition, DSP is also suitable for Speech Activity Detection and echo cancellation, so it is difficult for them to process voice data streams in real time and quickly access the memory on the board. This section describes in detail how to implement the Speech Encoding and echo cancellation functions on the TMS320C6201DSP platform.

VoIP system composition 2. Advanced dedicated Integrated Circuit

Application-Specific Integrated Circait (ASIC), an Integrated circuit dedicated for advanced IC, has developed a faster, more complex, and more powerful ASIC. ASIC is a dedicated application chip that executes a single application or a small set of functions. Because they are concentrated on narrow application goals, they can be highly optimized for specific functions. Generally, the dual-universal CPU is one or several orders of magnitude faster.

Just like the simplified instruction set computer RSIC) chips focus on fast throttling operations, ASIC is pre-programmed to allow it to execute a limited number of functions faster. Once the development is complete, the cost of ASIC batch production is not high. It is used for network devices such as routers and switches to perform routing lookup, grouping and forwarding, grouping classification and inspection, and queuing. The use of ASIC improves the performance of the device at a lower cost. They provide increased bandwidth and better QoS support for the network, so they play a major role in promoting the development of VoIP.

VoIP system composition 3. IP Address Transmission

Most transmission telecommunication networks adopt the time-division multiplexing mode. The Internet must adopt the statistical multiplexing and variable-length group switching mode. Compared with the two, the latter has a high utilization rate on network resources, interconnection is simple and effective, and is very suitable for data services, which is one of the important reasons for the rapid development of the Internet. However, broadband IP network communication requires unlimited QoS and latency. Therefore, the development of the technology of variable-length group switching for statistical multiplexing is a concern. At present, in addition to the new generation of IP protocol IPV6, the world Internet Engineering Task Group IETF has proposed Multi-Protocol Label Switching (MPLS ), this is a kind of tag/Tag Switching Based on Network Layer Routing. It can improve the flexibility of routing, expand the network layer Routing Capability, simplify the integration of routers and Cell Exchange, and improve network performance.

MPLS can be used as an independent routing protocol and compatible with existing network routing protocols. It supports various operations, management, and maintenance functions of IP networks, this greatly improves the QoS, routing, signaling, and other performance of the IP network communication, and achieves or approaches the statistical reuse of fixed-length group switching ATM. It is simpler, more efficient, cheaper, and more suitable than ATM. IETF is also focusing on new grouping management techniques to achieve QoS selection. The "tunneling technology" is being studied to achieve one-way link broadband transmission. In addition, how to select an IP network transmission platform is also an important area of research in recent years. Several technologies have emerged, such as IP over ATM, IP over SDH, and IP over DWDM.

The first layer is the basis for providing high-speed data transmission backbone. The IP layer provides IP access services with high quality and guaranteed service to IP users. The user layer provides access form IP Access and broadband access) and service content form. In the basic layer, Ethernet is the physical layer of an IP network. However, IP overDWDM has the latest technology and has great development potential.

Dense Wavelength Division MultipLexing Dense Wave Division MultipLexing, DWDM) injects new energy into the fiber network and provides amazing bandwidth in the laying of new fiber trunk networks by telecom companies. DWDM technology utilizes Optical Fiber capabilities and advanced optical transmission equipment. The name of wavelength division multiplexing is obtained by transmitting multiple wavelengths of optical LASER from a single optical fiber. The current system can send and recognize 16 wavelengths, and the future system can support 40 ~ 96 wavelength. This is important, because each time a wavelength is added, a message flow is added. So we can expand the 2.6 Gbit/sOC-48) network by 16 times without having to lay new optical fibers.

Most of the new optical fiber networks run OC-192 at 9.6 Gbit/s), generating a capacity of more than 150 Gbit/s on a pair of optical fibers when combined with DWDM. In addition, DWDM provides interface protocols and speed-independent features, and supports transmission of ATM, SDH, and Gigabit Ethernet signals at the same time in a single optical fiber, in this way, it can be compatible with the various existing networks. Therefore, DWDM can protect existing investment and provide more powerful backbone networks for ISPs and telecom companies with its huge bandwidth, and lower bandwidth costs and stronger access, which provides strong support for the bandwidth requirements of VoIP solutions. The increased transmission rate not only provides more coarse pipelines, but also reduces the latency. Therefore, QoS requirements on IP networks can be greatly reduced.

VoIP system composition 4. Broadband Access Technology

User Access to IP networks has become a bottleneck restricting the development of the whole network. From the perspective of long-term development, the ultimate goal of user access is fiber-to-user FTTH ). In a broad sense, optical access networks include optical digital loop carrier systems and passive optical networks. The former is mainly in the United States. Combined with the open port V5.1/V5.2, the former transmits its Integrated System on the optical fiber, showing great vitality. The latter is mainly in Japan and Germany. Japan has made unremitting efforts to tackle the problem for more than a decade. It has adopted a series of measures to reduce the cost of Passive Optical Networks to a level similar to copper and metal twisted pair wires, and has been widely used. In particular, in recent years, ITU has proposed an ATM-based Passive Optical Network (APON). The advantages of the ATM and the passive optical network are complementary, and the access rate can reach 622 Mbit/s, which is very beneficial to the development of broadband IP multimedia services, in addition, the failure rate and number of nodes can be reduced to expand coverage. At present, ITU has completed the standardization work, and manufacturers are actively developing and goods will soon be listed, which will become the main development direction of Broadband Access Technology for the 21st century.