Comparison between ADSL Access Technology and other access technologies

What is the difference between broadband and ADSL? With the explosive development of the Internet, commercial applications and multimedia services on the Internet have also been rapidly promoted. To enjoy various services on the Internet, users must access the network in some way. In order to achieve digital and broadband access for users and improve the speed for users to access the Internet, FTTH is an inevitable direction for the development of the user's network. However, due to the high cost of the fiber-optic user network, in the next decade or even decades, most user networks will continue to use existing copper wires. As a result, many transitional broadband access network technologies have been proposed in recent years, including N-ISDN, Cable Modem, And ADSL, among which ADSL (Asymmetric Digital user loop) is the most promising and competitive, it will be dominant in the next decade or even decades.

At present, the popularity of ADSL swept across the world, PC industry leader MIC (Microsoft, Intel, Compaq) and other major network companies around the world, such as Nokia, 3COM, CISCO, Siemens, Alcatel, Paradyne, have successively launched ADSL products and are committed to the development of ADSL; many telecom companies and ISPs around the world have also promoted their respective ADSL Services. North America and Singapore are the first to officially open their business. Japan, South Korea, and other countries have entered the trial phase, china Telecom has carried out relevant network tests in Beijing, Shanghai, Guangdong, Fujian and other places and started trial promotion. Zhanjiang has also entered the use stage.

Main features and access methods of ADSL

DSL (Digital Subscriber Line) is a combination of transmission technologies using copper telephone lines as transmission media. It includes HDSL, SDSL, VDSL, ADSL, and RADSL, which are generally called xDSL. The main difference between them is the differences in signal transmission speed and distance, and the differences in Uplink speed and downlink speed symmetry.

HDSL and SDSL support symmetric T1/E1 (1.544 Mbps/2.048 Mbps) transmission. The valid transmission distance of HDSL is 3-4 kilometers, and two to four pairs of copper twisted pair telephone lines are required. The maximum valid transmission distance of SDSL is 3 kilometers, and only one pair of copper wire is required. In comparison, symmetric DSL is more suitable for enterprise point-to-point connection applications, such as file transmission, video conferencing, and other processes that send and receive data volumes. Compared with asymmetric DSL, the market for symmetric DSL is much smaller.

VDSL, ADSL, and RADSL are asymmetric transmission. Among them, VDSL is the fastest xDSL technology. On a copper pair of twisted pair telephone lines, the uplink data speed is 13 to 52 Mbps, And the downlink data speed is 1.5 to 2.3 Mbps, however, the transmission distance of VDSL is only several hundred meters. VDSL can be a cost-effective alternative to fiber-to-home. Currently, VOD (Video on demand) in Shenzhen) this access technology is used. ADSL supports the uplink speed of 640Kbps to 1 Mbps on a copper line, and the downlink speed is 1 Mbps to 8 Mbps. The valid transmission distance is within 3-5 kilometers; the speed range provided by RADSL is basically the same as that provided by ADSL, but it can dynamically adjust the user access speed based on the quality of twisted pair copper wires and the distance between transmission. These characteristics make RADSL an ideal technology for high-speed surfing, on-demand video streaming (IAV), and remote LAN access, in these applications, the user downloads much more information than the uploaded information (sending instructions.

The price-performance ratio of the ADSL Access Service is high, which is inseparable from the technical advantages of the ADSL Access Technology over other access technologies. Let's take a look at the comparison between ADSL and other access services:

Comparison between ADSL and Cable Modem

Compared with Cable Mode, ADSL technology has considerable advantages. Cable Modem uses a hierarchical tree structure to connect to the HFCs. The advantage is that the bandwidth is relatively high (10 M). However, this technology is a rough bus network, this means that users need to share limited bandwidth with neighboring users. When users on a line surge, the speed will slow down. In addition, the relevant information indicates that, in most cases, the HPC solution must take into account the existing cable TV programs, while occupying part of the bandwidth, only part of the remaining part can be used to transmit other data signals, therefore, the theoretical transmission rate of the Cable Modem can only reach half of that. Foreign Companies' experiments show that the speed is reduced to 1 Mbit/s, and the more common is 400K-500Kbps. In general, even in an ideal situation, HFC is only equivalent to a 10 Mbps shared-bus Ethernet, while the ADSL Access solution is more advanced in terms of network topology, because each user has a separate line connected to the ADSL local terminal, its structure can be viewed as a star structure, and its data transmission bandwidth is exclusive to each user.

Comparison of ADSL, common dial Modem and N-ISDN

A) compared with the ordinary dial Modem up to 56 K rate, and N-ISDN K rate, ADSL speed advantage is self-evident.

B) What makes ADSL more attractive compared with common dial-up Modem or ISDN is that it transmits data and voice signals separately on the same copper line, and the data signals are not transmitted through the telephone switch equipment, reduces the load on telephone switches. This means that you do not have to pay additional phone fees when using ADSL to access the Internet.

ADSL access type

Leased line access mode: You have a fixed static IP address, which is online 24 hours a day.

Virtual dial-in access mode: it is not a real dialing method, but a user enters an account, password, and identity verification to obtain a dynamic IP address, which can grasp the initiative of the Internet.

Install the ADSL Device

ADSL installation includes local line adjustment and client device installation. On the local terminal side, the service provider connects the user's original telephone line to the ADSL local device, which takes 2 or 3 minutes. The user's ADSL installation is also very simple and convenient, as long as the telephone line is connected to the filter, A two-core telephone line is used between the filter and adsl modem, And the adsl modem and the computer NIC are connected by a cross network cable to complete hardware installation, then, set the IP, DNS, and gateway parameters in the TCP/IP protocol to complete the installation.

The ADSL installation of LAN users is no different from that of single-host users. You only need to add a hub and connect the hub to the adsl modem with a direct network cable.

Application and Prospect of ADSL

Application of ADSL

In the early stages of development, ADSL was designed for on-demand video programs and has asymmetric and high-speed downstream channels. With the rapid development of Internet, as a high-speed Internet access technology, ADSL is more active, making it possible to provide multimedia services on the existing Internet.

Currently, ADSL in Zhanjiang provides high-speed broadband access over the Internet. Users can enjoy various broadband multimedia services free of charge when accessing sites through ADSL.

With the further promotion and application of ADSL technology, ADSL access will also provide point-to-point remote medicine, remote teaching, remote visual conference and other services.

Prospect of ADSL

Many experts in the industry believe that ADSL-based xDSL technology will eventually become the winner of Copper Twisted Pair wires, at present, users using ordinary dial Modem and N-ISDN technology access will gradually transition to ADSL and other broadband access methods, and ultimately achieve optical fiber access.