Introduction to ADSL and UADSL in Broadband Access Network Technology

With the development of China's access network industry, it also promotes the wide application of broadband access network technology. Here we mainly analyze the introduction of ADSL and UADSL systems in the broadband access network technology. For a long time, access networks have been the oldest and difficult fields in the telecom network field with the largest cost, the slowest technological change, the most cost-sensitive, the most influential regulation, and the worst operating environment. When the core network field (the user's resident network field) is changing and applying various modern new technologies more and more frequently, the access network field still basically maintains the original simulation technology. It is increasingly becoming a drag on the further development of the entire network.

However, in recent years, the new technological revolution represented by the Internet is profoundly changing the traditional telecom concept and architecture. At present, the business volume on the North America backbone network has doubled in about 6-9 months. Traditional telephone networks will inevitably transition to the next-generation telecommunication network centered on data services, especially IP services. The basic features of this next-generation telecommunication network will be broadband and IP. At present, the core network is rapidly evolving towards the internet. On the other hand, the speed of the User-side terminal is also growing by leaps and bounds. The low-cost Gigabit Ethernet network will increase the speed of the LAN by an order of magnitude, and 10 Gbit/s Ethernet will also be available. This trend of broadband and IP access for users is also reflected in the user groups of ordinary residents. The Internet business is becoming an increasingly important access service for ordinary residents, from email to Web browsing and even video services, bandwidth requirements are growing at several times or dozens of times. However, in the face of the rapid growth of the core network and user-side bandwidth, the access network in the middle remains at the level of narrowband and analog, and is still mainly characterized by supporting circuit switching, it is not in coordination with the development trends on the core network side and the user side. Obviously, the broadband access network technology has become the final bottleneck of the whole network bandwidth, and the Broadband Access Network Technology and IP technology will become the main trend of access network development at the beginning of this century. In order to adapt to this new situation, the access network is showing a new development trend. Next we will focus on introducing and discussing the Current Situation and Development of several broadband access network technologies with better development momentum.

Broadband digital user Line System on twisted pair wires

So far, the world's twisted pair wires still occupy more than 90% of all user lines. How can we make full use of this part of valuable resources, developing new broadband services is an important task for telecom companies to develop broadband access network technology in the near future. The digital user Line System (xDSL) is an effective broadband access technology. XDSL has more than a dozen patterns, and the following are the most vital.

ADSL and UADSL Systems

Asymmetric Digital user Line System (ADSL) is a digital user line system that uses DMT line codes. The downlink ticket channel speed can be as high as 8.192 Mb/s. The actual rate depends on the line diameter and transmission distance. The main services supported by ADSL are Internet and telephone. Its biggest feature is that it can provide broadband services without modifying the existing copper network facilities. In the past five years, due to the gradual maturity of technology and the sharp increase in production, the market price of ADSL has dropped by more than 80%. In addition, along with the pressure of rapid development of cable modem, ADSL has entered a stage of development.

However, the traditional full-speed rate ADSL system is costly, and the user line that can actually activate 1.5 Mbit/s or above is usually only about 35%; the user-side equipment CPE installation needs to be sent to install, therefore, it is not only costly to install and activate, but also time-consuming and time-consuming. It is not suitable for large-scale business promotion and development. A lightweight and non-sharded ADSL standard G.992.2 was launched quickly, which is called UADSL. There are two basic ideas: first, the downlink speed is reduced to about 1.5 Mb/s, and second, the user does not need to use telephone segmentation. The former makes the UADSL band only half of the ADSL band, in this way, the complexity and power consumption are only half the same, and the downlink transmission distance of 1.5 Mb/s can reach 5.4 km. The latter can avoid the trouble of sending people to the user for CPE installation and testing and the additional high cost, which is suitable for large-scale application promotion. One of the biggest advantages of this UADSL system is its high degree of standardization, which facilitates compatibility between CPEs of local and user-side equipment of different manufacturers and facilitates large-scale promotion. At present, the interoperability test of the world's major uadsl cpe products has entered the final stage. It is expected that the interoperability between any CPE and any local terminal will be achieved soon, which not only greatly increases the scope of user selection, in addition, it can greatly promote the decline in UADSL prices and large-scale business expansion. The user-side modem will become a computer plug-in card like the analog modem today, and the performance and price are better, the line conditions are not high, it may become one of the leading broadband access network technologies in the next five years.

On the other hand, the ADSL technology is still being improved and developed, especially the no-shard ADSL technology. In this way, you only need to install a small micro-filter in front of each phone. At this time, no-splitter ADSL also has the important advantages of UADSL without requiring someone to install CPE, however, it has all the advantages of the original full-speed rate ADSL, such as high speed, network upgrading, support for future image and interactive online games, and other new businesses as well as VoDSL applications, however, whether it has no effect on all other services remains to be further verified. Another Latest Trend of ADSL development is Voice over ADSL (VoDSL). The basic idea is to provide 4-4 more services without changing the original analog speech service ~ 20 digital voice channels can also provide Ethernet interfaces and even set-top box interfaces. The emergence of this technology greatly increases the user line bandwidth utilization and business income, and strengthens the performance-to-price advantage of ADSL for small and medium-sized enterprises. For ADSL, in order to reduce the laying cost and facilitate large-scale promotion, in addition to improving the equipment technology, you must pay close attention to reducing the costs related to installation and activation operations.

In general, ADSL has entered a stage of development. If there are any obstacles, it is the consideration of the telecom operator's own business strategy, that is, coordination with the 2 Mbit/s leased line and the ISDN service will be a painful but unavoidable choice. In addition, it is also related to the control policy to a large extent. The open market, especially the opening of user lines (non-binding of user rings) will undoubtedly greatly accelerate the development of ADSL. According to reports, in the next few years, several local telephone companies in North America have planned to build a 30 million-line system. The number of non-bound user rings has exceeded 5%, the UK and Germany plan to lay 6 million and 1.5 million lines respectively, while South Korea has laid 2.2 million lines, making it the fastest growing country in the world. China has started trial commercial use of tens of thousands of lines in various regions. The initial response is good. This year, we plan to develop 0.9 million lines of users. The main disadvantage of ADSL is that the strict requirements on the line affect the transmission rate or transmission distance, and the combination with the fiber-optic DLC will be a good measure to foster strengths and circumvent weaknesses. According to SBC analysis, in the above-mentioned DLC environment, at least 80% of users can provide 1.5 Mb/s DSL services online, and 60% of users can provide at least 6 Mb/s services, the service scope of DSL is greatly expanded. In addition, the prices of devices and services are still high, which is not conducive to large-scale promotion. I believe that with the advancement of technology, the development of IP services, and the implementation of a series of non-binding policies on the user ring, ADSL may become one of China's leading broadband access network technologies in the next few years.