Development Trends of mainstream VDSL and ADSL Technologies

Studies have shown that the development of ADSL and VDSL technology will go through the following development processes in the direction of complementary advantages:

ADSL Based on ATM technology first appeared and matured after large-scale application. In fact, ADSL was born in Bell Laboratory as early as 1989. At that time, ADSL was intended to serve as a solution for ATM to users. Therefore, the ADSL Link Layer adopted the Encapsulation Format of ATM cells. However, with the development of networks, IP addresses have almost fully occupied all fields, from the core, edge, access, desktop to flexible and diverse services of man, the adoption of ADSL technology requires an expensive cost to solve the problem of the conversion and efficiency between the ATM and IP addresses, at the same time, the ADSL technology also has the inherent disadvantages of asymmetric rate, small bandwidth, and low outbound rate.

To meet the development needs of network and business IP and Ethernet, and solve the problems existing in ADSL technology, VDSL Based on Ethernet kernel technology emerged. VDSL is short for high-speed digital user line. It is a new DSL technology, known as xDSL's End-level technology. The maximum downlink rate of VDSL in a short distance can reach 55 Mbit/s, and the uplink rate can reach 19.2 Mbit/s. Because it directly uses the Ethernet frame format at the link layer, VDSL and Ethernet provide completely consistent support for IP services and are currently the most ideal xDSL technology for carrying IP addresses and Ethernet networks, it is also the best method to replace FTTH. VDSL not only does not have the problem of converting between ATM and IP, but also overcomes the problem of low transmission bandwidth and low outbound rate. However, VDSL has a short coverage distance from ADSL.

In fact, each access technology has its applicability. Therefore, how to flexibly use these two access technologies based on factors such as network status, line resources, and user distribution to achieve the complementary advantages of ADSL and VDSL has become a common concern of operators and equipment vendors. In the current situation, using the ADSL and VDSL hybrid plug-in technology, the integration of the two mainstream access methods on the device is undoubtedly the best way to combine ADSL and VDSL. This construction mode not only has the advantages of integrated network management of ADSL and VDSL, unified operation and management, unified sharing of uplink ports, and simplified network structure, in addition, the ADSL and VDSL access technologies can be flexibly selected based on user distribution, bandwidth requirements, transmission distance, line quality conditions, and many other objective factors to achieve cross-coverage for different users. This is a market-driven, not a technology-driven construction model that meets the development requirements of broadband network construction. In fact, the ADSL and VDSL hybrid insertion technologies in the industry are already very mature. The hammerw.ip access switch of the Beijing Port and Bay network adopts the pure Ethernet kernel technology, the ADSL and VDSL business boards are completely shared with the same backboard and exchange control network to implement the same-frame hybrid insertion function of VDSL and ADSL. Currently, this device has been commercially available in the market.

Research shows that a more advanced xDSL integration technology is under development, and the ADSL and VDSL technologies will be more integrated in the future. In the near future, VDSL or ADSL can be flexibly accessed based on the same twisted pair Cable without any changes to the network device and user side.