At present, ADSL is sweeping around the world, with PC industry leaders such as MIC (Microsoft, Intel, Compaq) and the world's major network companies such as Nokia, 3COM, CISCO, Siemens, Alcatel, Paradyne, etc., launching ADSL products one after the other and devoting themselves to the development of ADSL; many of the world's major network companies have launched ADSL products and are committed to the development of ADSL; many of the world's major network companies have launched ADSL products and are committed to the development of ADSL. ADSL development; many telecommunications companies around the world, ISPs have to promote their ADSL services, North America, Singapore and other first officially put into business, Japan, South Korea and other countries have entered the experimental stage, China Telecom in Beijing, Shanghai, Guangdong, Fujian and other places have been related to the network test and began to promote experimental, Zhanjiang has entered the use of the stage.
The main characteristics of ADSL and access
DSL (Digital Subscriber Line) is a combination of transmission technologies using copper telephone lines as the transmission medium, which includes HDSL, SDSL, VDSL, ADSL and RADSL, etc., and is generally referred to as xDSL.The main difference is in the speed and distance of signal transmission. The main difference between them is the difference in signaling speed and distance as well as the difference in symmetry between uplink rate and downlink rate.
HDSL and SDSL support symmetrical T1/E1 (1.544Mbps/2.048Mbps) transmission. HDSL has an effective transmission distance of 3-4 kilometers and requires two to four pairs of copper twisted-pair telephone wires; SDSL has a maximum effective transmission distance of 3 kilometers and requires only one pair of copper wires. In comparison, symmetric DSL is more suitable for enterprise point-to-point connectivity applications, such as file transfers, video conferencing, and other tasks where the amount of data sent and received is roughly proportional. The market for symmetric DSL is much smaller compared to asymmetric DSL.
VDSL, ADSL and RADSL are asymmetric transmissions. Among them, VDSL technology is one of the fastest xDSL technology, in a pair of copper twisted-pair telephone line, the uplink data rate of 13 to 52 Mbps, downlink data rate of 1.5 to 2.3 Mbps, but the transmission distance of the VDSL is only within a few hundred meters, VDSL can be a cost-effective alternative to fiber-to-the-home, and at present, Shenzhen's VOD (Video on demand) is using this kind of access to the home. Video on demand) is realized by this access technology; ADSL supports uplink rate of 640Kbps to 1Mbps and downlink rate of 1Mbps to 8Mbps on a pair of copper wires, with an effective transmission distance of 3-5 kilometers; RADSL can provide the same speed range as ADSL, but it can be used according to the quality of twisted copper wires. RADSL can provide the same speed range as ADSL, but it can dynamically adjust the user's access speed according to the quality of the twisted-pair copper wire and the distance of transmission. It is these features that make RADSL the ideal technology for high-speed surfing on the Internet, video-on-demand (IAV), and remote local area network (LAN) access, where users often download more information than they upload (send commands).
The ability of ADSL access services to achieve a high performance-to-price ratio at this point is inseparable from the fact that ADSL access technology has its own unique technical advantages over other access technologies. Here's how ADSL compares to other access services:
Comparison of ADSL and Cable Modem
Compared to Cable Mode, ADSL technology has considerable advantages. However, the technology itself is a rougher bus-type network, which means that users have to share a limited amount of bandwidth with neighboring users, and when there is a surge of users on a line, its speed will be slowed down. In addition, the information shows that, in most cases, the HFC program must take into account the existing cable television programs, and take up part of the bandwidth, only a part of the remaining for the transmission of other data signals, so the theoretical transmission rate of Cable Modem can only reach a small half. Overseas company experiments show that its rate is reduced to 1M-2Mbps, more common is 400K-500Kbps. comprehensive view, even in the ideal state, HFC is only equivalent to a 10Mbps **** enjoy the type of bus-type Ethernet, while the ADSL access program in the network topology is more advanced, because each user has a separate line connected with the ADSL bureau, its structure can be seen as a star-type. Its structure can be seen as a star structure, and its data transmission bandwidth is exclusively shared by each user.
Comparison of ADSL with ordinary dial-up Modem and N-ISDN
A) The rate advantage of ADSL over ordinary dial-up Modem with a maximum rate of 56K and N-ISDN with a rate of 128K is self-evident.
B) What makes ADSL more attractive than regular dial-up Modem or ISDN is that it transmits data and voice signals separately on the same copper line, and the data signals do not pass through the telephone exchange equipment, reducing the load on the telephone exchange. This means that you don't need to pay a separate phone bill to use ADSL to access the Internet.
Types of ADSL access
Dedicated line access: users have a fixed static IP address and are online 24 hours a day.
Virtual dial-up access: It is not a real telephone dial-up, but the user enters the account number and password, and gets a dynamic IP address through the identity verification, which can control the initiative of accessing the Internet.
Installation of ADSL equipment
The installation of ADSL includes the adjustment of the line at the bureau end and the installation of equipment at the user end. On the local side, by the service provider will be the user's original telephone line in the string access to the ADSL local equipment, only 2, 3 minutes; the user side of the ADSL installation is also very easy and convenient, as long as the telephone line connected to the filter, filter and ADSL MODEM with a two-core telephone line connected to the ADSL MODEM and the computer's network card between the use of a cross-over cable connected to the hardware can be completed! The installation is completed by setting the IP, DNS and gateway parameters in the TCP/IP protocol.
The installation of ADSL for LAN users is not very different from that of standalone users, and all that is needed is to add another hub and connect the hub to the ADSL modem with a direct cable.
The application and prospect of ADSL
The application of ADSL
Because of ADSL in the early stage of development, it is specially designed for the video program on demand, with asymmetry and high-speed downstream channel, with the rapid development of Internet, ADSL as a kind of high-speed access to the Internet technology is more viable, which makes it possible to provide multimedia services on the existing Internet network. It makes it possible to provide multimedia services on the existing Internet network.
At present, Zhanjiang ADSL mainly provides high-speed broadband access to the Internet, and users can enjoy a variety of broadband multimedia services free of charge as long as they have access to the corresponding sites through ADSL.
With the further popularization and application of ADSL technology, ADSL access will also be able to provide point-to-point telemedicine, distance learning, remote visual conferencing and other services.
The future of ADSL
Many experts in the industry firmly believe that ADSL-based xDSL technology will eventually become the winner of the copper twisted-pair line, the current use of ordinary dial-up Modem and N-ISDN technology to access the user will be gradually transitioned to ADSL and other broadband access, and ultimately realize the optical fiber access.