The Next Generation Network (NGN) is a platform that supports a wide range of services, such as voice, video, SMS, collaborative work, integration with the Web, etc., allowing upper-layer application developers to take advantage of such The technical and business functions of the network platform have been used to develop a variety of customized applications. NGN adopts a layered, fully open network with an independent modular structure. It is a business-driven network. Business and call control are completely separated, and calls and bearers are completely separated. It is a packet network system based on a unified protocol. Its three major characteristics are multimedia, personalization and diversification.
Multimedia is to provide users with a wide range of interactive communication and information services with sound, video, pictures and text. It requires network broadband and huge multimedia business processing capabilities; personalization means that this network can Provide users with "anytime, anywhere" services according to personal wishes, while the previous generation of telecommunications services were basically impersonal; diversification means developing a large number of applications on the network service platform that can adapt to all walks of life and in various forms. The service methods of the Internet have shown us that in the 21st century, humans will create new ways of working, managing, commerce, finance, exchanging ideas, cultural education, medical care, and consumption and lifestyles online. These new methods will correspond to many applications.
The next generation network (NGN) is a network characterized by business drive. It separates the business from the bearer network and flexibly builds it on a unified open platform. Due to the openness and standardization of the platform, , the developers of future services may be operators or third parties, which can greatly enrich the types of services.
In order to speed up the research and standardization process of NGN, ITU-TSG13 held a joint meeting of NGN project rapporteurs and a plenary meeting of the research group in January and February 2004, following the meeting in September 2003. Twelve NGN standard drafts were launched, aiming to put forward overall requirements for NGN research directions, framework systems, business requirements, network functions, interworking, service quality, mobility management, manageable IP networks and NGN evolution methods, etc., and provide Communication operators and equipment manufacturers around the world provide ideas and basis for network development and product research and development.
After intense debate, the meeting gave the definition of NGN: NGN is a packet-based network that can provide telecommunications services; it uses a variety of broadband capabilities and QoS guaranteed transmission technologies; its business-related functions Independent of its delivery technology. In addition, NGN allows users to freely access different service providers and supports universal mobility.
Although there is still a lot of controversy about the next generation network, the pace of NGN research has not stagnated. Changes are inevitable, but how to evolve and implement them still requires in-depth research and discussion.
1. The driving force for the development of next-generation telecommunications networks
1. Revolutionary technology currently
The telecommunications industry is facing a great change that has not been seen in a century. , the progress of opening up the market and introducing competition has been significantly accelerated, and the reform of the telecommunications regulatory system has been significantly intensified. Especially in recent years, the new technological revolution represented by the Internet is profoundly changing the traditional telecommunications concepts and system framework. Its rapid development is the fastest among all industries in human history. Although its annual growth rate has gradually slowed down, its growth rate itself, especially the accumulated business growth, is still very impressive. Most experts believe that microelectronics technology will continue to develop according to Moore's Law (doubling in 18 months) and can last for 10 to 15 years; optical transmission capacity is developing according to Super Moore's Law (doubling in 9 months) and can last at least 10 years. The cost The distance factor in wireless network is gradually dying; wireless capacity is also developing beyond Moore's Law (doubling in 9 months) and is expected to last for several years. The number of users will exceed the number of wired users in the next 2 years or so. High-performance router technology has also made important progress, and service quality issues are expected to be basically solved.
2. The trend of network convergence as technical conditions mature
Network convergence is becoming a major trend in telecommunications development.
The first is the rapid development and comprehensive adoption of digital technology, which enables telephone, data and image signals to be transmitted and exchanged through unified coding; the second is the development of optical communication technology, which provides the necessary bandwidth and bandwidth for the comprehensive transmission of various business information. Transmission quality is an ideal platform for the services of the three networks; and the development of software technology enables the three major networks and their terminals to ultimately support the features, functions and services required by various users through software changes; and the last and most important thing It is the universal adoption of the unified TCP/IP protocol that enables various IP-based services to interoperate on different networks. For the first time, mankind has a unified communication protocol that can be accepted by the three major networks, which technically lays the solid foundation for the integration of the three networks.
3. Market opening and market competition
When the technical conditions are ready, deregulation and the need for market competition become key factors. Worldwide deregulation is only a matter of time. . Changes in market demand, market competition and regulatory policies have become the external driving force for the integration of the three networks. Since then, the information industry has entered an era of comprehensive competition, and the final integration of the three networks has become unstoppable.
With the opening up of the telecommunications market, new competitors have entered the telecommunications market. Their network construction often adopts a high starting point and directly builds next-generation integrated telecommunications networks. Facing competition, traditional telecommunications companies are also transforming their networks and gradually evolving and integrating with next-generation telecommunications networks. Obviously, with different backgrounds and competitive strategies, the evolution routes and characteristics of next-generation telecommunications networks are also different.
4. The needs of the new situation
Understanding of the new situation Under the above-mentioned macro trends, the telecommunications industry could have made rapid and steady progress towards the above-mentioned established goals. However, due to. Com companies and the media's excessive hype, coupled with the laissez-faire regulatory policies of some Western countries, have caused the downstream links in the information industry's survival chain to lose their ability to think calmly. They have borrowed and invested heavily to form emerging telecommunications companies and blindly build new networks, leading to Excessive competition, over-investment and large-scale blind construction of network infrastructure have resulted in a massive waste of network resources. along with. Com company's bubble burst, and the entire downstream links of the information industry's survival chain, including the telecommunications industry, fell into unprecedented difficulties. Vicious competition caused circuit prices to plummet, telecommunications companies' profits disappeared, and huge debts could not be repaid.
In response to the above-mentioned new situation, telecommunications companies began to shrink their front lines, adjust and slow down the construction of network infrastructure, and gradually shift their focus to business revenue and business development. However, one thing should not be doubted or shaken, that is, the strategic transformation trend towards next-generation networks faced by telecommunications companies is irreversible. It is driven by the needs of the external competitive environment, business development drivers and internal technology development laws. decided. The current difficulties have only slowed down this shift to a certain extent, but will never and cannot reverse this development trend.
2. Evolution direction of next-generation network
1. Evolution to next-generation switching network with soft switching as the core
Traditional circuit switches will transmit switching hardware , call control and switching, as well as business and application functions are combined into a single expensive switch device. It is a vertically integrated, closed and single-vendor dedicated system structure. The development of new services is also based on special equipment and special software as the carrier, resulting in Development costs are high, time is long, and it is unable to adapt to the current rapidly changing market environment and diverse user needs. Softswitch breaks the traditional closed switching structure and adopts a completely different horizontal combination model, using open interfaces and common protocols to form an open, distributed and multi-vendor application system structure with decentralized hardware, business control and Business logic is relatively centralized. This allows service providers to flexibly choose the best and most economical equipment combination to build a network. Not only is the cost of network construction low, the network is easy to upgrade, but it is also convenient to accelerate the development, generation and deployment of new services and new applications, quickly realizing low-cost broadband. domain business coverage and promote the integration of voice and data. The key feature of softswitch is that it adopts an open architecture to realize distributed communication and management, and has good structural scalability.
The main disadvantage of using softswitch is that the technology is not yet mature and there is a lack of experience in large-scale field applications, especially in multi-vendor interoperability, QoS guarantee of real-time services, unified and effective management of the network, and service generation and Business application revenue capabilities and other aspects.
2. Evolution to the next generation mobile communication network represented by 3G
In order to maximize the realization of global unified frequency bands, unified standards and seamless roaming, and develop new spectrum resources, To cope with the market demand for medium-to-high-speed data and multimedia services and to further improve spectrum efficiency, increase capacity, and reduce costs, the development of mobile communications towards 3G is an inevitable trend.
Since 2003, WCDMA and CDMA2000, the two FDD standards of 3G, have shown good development momentum. Some of the core networks have begun to implement the R4 version with the concept of soft switching structure. It is certain that both WCDMA and CDMA2000 standards are basically mature, and their technology and business capabilities are not much different. In addition to the differences in core network signaling, chip rate, base station synchronization method and pilot structure, they have other technical parameters. The performance is relatively close, and the voice capacity, data capacity and coverage are basically the same, and the economic performance is not much different. In the near future, CDMA2000 is leading the market; in the long term, WCDMA has the support of a wider range of equipment manufacturers, chip developers and business application developers, and has advantages such as global roaming capabilities, and may gradually become the dominant application standard.
On the other hand, as the TDD standard of 3G, the development of TD-SCDMA obviously lags behind WCDMA and CDMA2000. This situation has its historical reasons, but the fundamental reason is that the standard does not receive widespread global support, resulting in an absolute disadvantage in terms of financial investment and R&D manpower investment. In addition, the cost of setting up a large network independently under the TDD standard is high, the interference is high, and international roaming is limited, which are also issues that operators are very concerned about. However, TD-SCDMA is a technology proposed by China and has major patents on the physical layer. This standard comprehensively applies three multiple access technologies: time division, code division and space division, as well as a series of new technologies such as smart antennas, joint detection and uplink synchronization. technology has natural advantages in spectrum efficiency and spectrum flexibility. The TD-SCDMA and WCDMA standards are completely consistent in the core network, and the high-level protocols in the wireless network part are also the same. They can complement the advantages of the WCDMA standard and form a hybrid network, focusing on covering hot spots and supporting data services. The bundled application method will also enable roaming. Ability greatly enhanced.
In addition to technical factors, the development of 3G also depends to a large extent on services, service deployment and service architecture. In order to adapt to the development of data services, the requirements of new industrial chains and business models, and to increase the speed of new business generation, developing an open, horizontally structured comprehensive service platform is the key to expanding 3G services, and the most critical one is to implement unified Configuration, unified billing and unified security management. It should be noted that there is an important basic point in business development that cannot be ignored: for a long time, connection services based on voice and narrowband data will still be the main business income of mobile operators. Content business is just a growing supplementary business.
With the commercialization of 3G, post-3G or 4G technologies with higher speeds, higher spectrum efficiency, better coverage and stronger business support capabilities have also begun to enter the pre-research stage. From a development perspective, the performance-price ratio of mobile communications should still have great potential. With the further development of voice compression technology, signal processing technology, modulation technology and smart antenna technology, the cost per unit of voice will continue to decrease exponentially. And new data and multimedia services will create a more brilliant personal mobile world for us.
3. Evolution to the next generation Internet based on IPv6
The Internet currently widely used around the world is based on the IPv4 protocol, which theoretically has 4 billion Addresses. In fact, only half of the addresses are available after taking various factors into account. It is possible that all global Internet public addresses will be exhausted around 2008. In addition, the inherent flaws of IPv4 in terms of application restrictions, service quality, management flexibility, and security are increasingly unable to meet the needs of future development. It is almost inevitable that the Internet will gradually shift to the next generation Internet based on IPv6.
The most basic reason for adopting IPv6 is that it fundamentally solves the problems of address restrictions and huge routing tables in IPv4 and provides more effective support for mobile IP.
The technical standards for IPv6 have basically taken shape, but the actual network advancement is very slow.
The main reason is that IPv4 can still meet the address demand within 5 years through the use of network address translation (NAT) and other measures. On the other hand, the IP address method is closely related to the upper layer protocol and the operation mode of the network. Implementing IPv6 not only requires upgrading the network layer protocol, but also requires upgrading the application software or changing the user's communication program, changing the packet forwarding module of the router, which involves almost everything on the Internet. Equipment is not only time-consuming and labor-intensive, but there are currently very few IPv6 application tools and application software, and users lack the motivation to apply IPv6.
In general, the evolution to the next generation Internet based on IPv6 has begun, but a lot of network and terminal work needs to keep up, especially how to implement a smooth transition of this major transformation. The strategy still needs to be carefully studied and solved, and there is no generally accepted comprehensive solution. China Telecom has already carried out some preliminary research and test work, and will soon carry out field tests to explore and accumulate experience under actual network conditions and explore transition strategies.
4. Evolution to a diversified broadband access network
Faced with the rapid growth of core network and user-side bandwidth, the intermediate access network still remains narrowband and analog. level, and still supports circuit switching as a basic feature, which is very inconsistent with the development trend of the core network side and user side. Obviously, the access network has become the final bottleneck for the broadbandization of the entire network. The broadbandization of the access network will become the main trend in the development of the access network and will also become the ultimate solution for the fixed network. Therefore, in recent years, the development of broadband access networks at home and abroad has Construction and development are rapid.
However, access networks are very sensitive to costs, regulations, services, and technology. So far, there is no recognized absolutely dominant broadband access technology. From a global perspective, ADSL, HFC and Ethernet will form a tripartite trend in the near future, and they are still being improved. However, various new technologies are still emerging, and for a long time the access network field will present a basic trend of coexistence, complementarity, and competitive development of multiple technologies.
Telecom networks urgently need to transform into next-generation networks. The two-way transformation of cable TV networks cannot violate the laws of technological development. In the two-way transformation of the network, next-generation network technology or technology close to the next-generation network should be used to lay a good foundation for the transition to the next-generation network.
5. Evolution to the next generation transmission network based on optical networking
Due to major technological breakthroughs and market drivers, WDM systems have developed rapidly in recent years. At present, 1.6Tbit/s WDM systems have been commercially used in large quantities. Although WDM technology has basically achieved a breakthrough in transmission link capacity, ordinary point-to-point WDM systems only provide original transmission bandwidth and require flexible nodes to achieve efficient and flexible networking capabilities. The existing electrical DXC system is very complex, and its node capacity doubles approximately every 2 to 3 years, which cannot adapt to the growth rate of network transmission link capacity. Therefore, the hope for further expansion turns to optical nodes, namely optical add-drop multiplexers (OADM) and optical cross-connectors (OXC).
As network traffic continues to converge towards dynamic IP traffic, a flexible and dynamic optical network infrastructure is indispensable. Its latest development trend is to introduce automatic wavelength configuration function, namely automatic switching optical network (ASON), so that optical networking will move from static optical networking to automatic switching optical network. The main benefits brought by ASON are: allowing network resources to be dynamically allocated to routes, shortening the time for business layer upgrades and expansions; rapid service provision and expansion; reducing maintenance and management operating costs; fast service recovery capabilities at the optical layer; reducing The need for operation support system software for new technology configuration management reduces the chance of manual errors; new wavelength services can be introduced, such as on-demand bandwidth services, wavelength leasing, hierarchical bandwidth services, dynamic wavelength allocation leasing services, and optical layer virtualization Private network (OVPN), etc.
Of course, realizing optical networking still requires solving a series of hardware, software and standardization issues, but its development prospects are bright? Intelligent optical networks will become an important direction and market opportunity for the development of optical communications in the next few years.
3. Overview of the development of mobile IP technology
Mobile IP technology is the core technology for realizing next-generation network applications in traditional networks. It mainly supports network mobility and bidirectional access. , supports the real-time nature of multimedia services, etc.
Mobile IP technology is a new field of IP technology development. It is the most successful integration of wireless communication technology and IP, the two most successful information technologies. Its development requires the following aspects:
(1) Trend requirements for network IPization
Since 1994, the emergence and development of Internet technology have enabled various networks to use TCP/IP technology regardless of their respective hardware and low-level protocols. Transparently connected together, it completely realizes Internet communication and information sharing, and truly promotes the arrival of the Internet era. The Internet can provide real-time voice, conference video, VOD and other services. With the trend of integration of telecommunications, television and computers, the demand for multimedia services is getting louder and louder. The Internet will likely become the basis of broadband networks and will replace existing telephone networks and cable television networks. It can be seen that the future network will be based on IP packet switching technology.
(2) The TCP/IP protocol does not support mobility
The Internet protocol stack TCP/IP was designed assuming that the terminal system is static. In a dynamic network task, if one end of the communication moves away, the communication is interrupted. Network services above the TCP/IP level are naturally interrupted. The TCP/IP protocol does not support mobility.
(3) Requirements for seamless roaming between different networks
As the highest level of personal communication, that is, anyone, any place, any time, any way, any business Ideal communication model. In order to realize the above dream, domestic and foreign research institutions have begun research on satellite Internet, cellular mobile network and mobile Internet (or mobile computing network). The central issue is to solve the problem of global mobility support. In terms of mobility or roaming support, there are three different concepts depending on the level of mobility processing: ①Mobility at the application level; ②Mobility at the physical network layer; ③Mobility at the IP layer. The first type of movement mainly refers to the movement of users or applications. Examples of the second type of mobility are DHCP or dial-up network access using digital mobile phones. In this case, users and their portable terminal devices can roam within the coverage of the physical network. The third type of mobility means that users and their portable terminal devices can move between IP networks, that is, they can seamlessly roam among a variety of mobile physical networks (such as wireless LANs and digital mobile phone networks). At present, the wireless network field is composed of various types of access, such as TDMA, CDMA, GSM, etc., and core network technologies, such as IS-41, MAP, etc. Their heterogeneity limits the scope of mobility between them. With the development of heterogeneous network technology and mobile communication technology, it is required that their mobility management should be able to ensure seamless handover between heterogeneous networks. Mobile IP is expected to integrate cellular systems and Internet mobility. The advantage of producing a public mobility solution is that it is independent of the specific access network technology and can be applied to both wired and wireless networks.
(4) Requirements of many network applications
The configuration database of many applications is based on IP addresses rather than host names. If the IP address is changed frequently, these applications will break; in the future, it is possible that the server will also need mobile capabilities, not just the client. In this case, the client who only knows the server's IP address will not be able to find the server unless the server has Mobile functions provided by mobile IP; some application providers provide network registration systems, which only allow users with IP addresses within a certain range to access. Without mobile IP, a roaming node that switches links may change its IP address, making it impossible for it to register with these applications; some security mechanisms determine its access rights based on the node's IP address, and mobile IP makes it possible to Provide node mobility capabilities while still leveraging these security mechanisms.
Therefore, mobile IP will be widely used in all TCP/IP network environments, and at the same time, it will also maximize people's needs for mobile or roaming everywhere. The trend of network IP, the TCP/IP protocol does not support mobility, and users' requirements for seamless roaming between different networks, make mobile IP a new direction for the development of IP technology. It is the two information technologies of wireless communication and IP. fusion. At the same time, from the perspective of humanistic concepts, it more vividly reflects people's pursuit of personalization and promotes a more humane application of the Internet. As a result, the Internet has truly "moved".
Mobile IP is a solution that provides mobile functionality on the global Internet. It provides a special IP routing mechanism that allows mobile nodes to connect to any link with a permanent IP address. In fact, Mobile IP can be viewed as a routing protocol, except that compared to other Internet routing protocols, it can route packets to mobile nodes that may be changing locations rapidly. Simply explained, Mobile IP is a computer network communication protocol that ensures that the existing network IP address will not be changed, ongoing network communications will not be interrupted, and ongoing network applications will not be interrupted when the computer is moving. to achieve uninterrupted access to the network.