What Is an Asymmetric Digital Subscriber Line?

Asymmetrical Digital Subscriber Line (ADSL) is a type of DSL technology. ADSL technology provides asymmetric upstream and downstream bandwidth, so it is called asymmetric digital subscriber line.

ADSL (Asymmetrical Digital Subscriber Loop) is a new type applied on telephone lines

ADSL access technology can show many advantages in the application process. It does not need to lay another cable, it directly uses the user's telephone line, and it does not interfere with the transmission of data and voice information. It can access the Internet and make calls at the same time. ADSL technology can also ensure fixed and exclusive high-bandwidth for users, suitable for high-speed Internet and other data access. Specifically, it has the following characteristics:

ADSL is a high-speed communication and mutual video function provided by ordinary telephones. It is not only the best way for home users to access at high speed, but also shows its huge potential in the area of network LAN. ADSL uses two methods: dedicated line mode and virtual dialing mode. The former is manifested in the fact that network users can be online 24 hours a day, have a static IP address, and can access the Internet as long as the user is turned on. Most of these are small and medium-sized enterprises. The virtual dial-up method can only be online for a short time, and the amount of data transmitted cannot be too large. It does not have a real dialed phone number, but authenticates to the network according to the user password. The cost has nothing to do with the telephone service. In real life, there are several common ways to apply ADSL:

ADSL has its unique technical principle and modulation method, and cannot be used interchangeably with ordinary dial-up modems and cable modems with cable access.

ADSL compared to ordinary dial-up modems and ISDN

ADSL has obvious advantages in speed, and its transmission rate is 150 times that of ordinary dial-up modems. ADSL carries data and speech signals on the same copper wire. Data transmission and voice signals do not interfere with each other, and data signals are not transmitted through the telephone exchange, which reduces the load on the telephone exchange. At the same time, ADSL dials the IP address of the virtual private network access, not the phone number of the ISP provider. Therefore, you don't need to pay extra phone charges for surfing the Internet with ADSL. You only need to pay for the Internet access. Therefore, with the widespread use of ADSL, Ordinary dial-up modems and ISDN will gradually be phased out.

ADSL and DDN

When network users use the World Wide Web to download information, sending information to the World Wide Web requires a small amount of bandwidth. However, compared to DDN, the asymmetric access method of ADSL is more flexible, more in line with the characteristics of modern networks, and more efficient High, the cost is also lower than DDN.

ADSL and Cable Modem

Cable Modem is a relatively common access method currently used, because the cable television cable it lays is a high-speed broadband, so as long as the line is simply modified, you can reach 8M uplink and 30M downlink access rates. In the United States, more than 50% of users have adopted this Cable Modem access method. However, its shortcomings also gradually show up with the growth of users, because the more users access, the personal access speed will be reduced, and security will be affected. Compared with the Cable Modem, ADSL technology has very great advantages. First, ADSL uses a star topology, and each network user enjoys a fixed and exclusive broadband. This can ensure that the user can send information and data. And security; while Cable Modem uses a bus type in the choice of network topology, although its speed can reach 10 M or even 30 M, but in most cases, it is only theoretically implemented because its width is multiple For network users, the average rate shared by each user will be low. The more users, the lower the personal access speed. Secondly, under the existing technical conditions, HFC must take into account cable TV programs, and therefore occupy some of the width. In fact, only a part of the width is available for sharing. Therefore, ADSL and Cable Modem have great advantages in data transmission and security.

In today's increasing market demand, ADSL urgently needs to solve the following problems. ^[2]

ADSL can provide services on existing lines and make full use of existing line resources. It can provide high-speed Internet access and adapt to high-speed Internet access. It has certain development space and potential. It is currently a telecommunication operator's broadband access The main countermeasures taken in the market competition. With the rapid development of network technology, Modem and ISDN access technologies will be gradually replaced by ADSL broadband access methods, and finally optical fiber access will be realized.