ADSL technology

Features

ADSL technology The main feature of ADSL technology is to make full use of existing copper networks (telephone line networks), add ADSL devices at both ends of the line to provide high broadband service. Another advantage of ADSL is that it can be co-contained on a telephone line with a normal phone, answering the ADSL transmission while making a telephone on a normal telephone line and does not affect each other. The user accesss the broadband multimedia information network through ADSL, and can watch the film and television program, hold a video conference, can also download data files at a high rate, this is not all, you can also use the phone online. It does not affect other activities mentioned above. Installing ADSL is also extremely convenient and fast. Install ADSL on the existing telephone line, in addition to the User-end installed ADSL communication terminal, no change in existing lines without any changes to existing lines. Using ADSL (Asymmetric Digital Subscriber Line, asymmetric digital subscriber line) technology, through a telephone line, you can browse the Internet, browse the Internet, learn, entertainment, shopping, and enjoy advanced data services such as video conferencing. , Video on demand, online music, online TV, online MTV fun, has become a reality.

DSL family

XDSL always said

xDSL (Digital User Line, DigitalSubscriberline) is a transfer technology combination with copper line lines for transmission media, including HDSL, SDSL, VDSL, ADSL, and RADSL, etc., generally referred to as XDSL. Their main difference is to reflect the difference between signal transmission speed and distance and the upstream rate and downstream rate symmetry.

HDSL and SDSL

HDSL support symmetrical T1 / E1 (1.544 Mbps / 2.048Mbps) transmission of SDSL. The effective transmission distance of HDSL is 3-4 kilometers, and two to four pairs of copper twin-shaped telephone lines; the maximum effective transmission distance of SDSL is 3 km and only one pair of copper wires. Comparison, symmetrical DSL is more suitable for enterprise-point-to-point connection applications, such as file transfer, video conferencing, etc. Regulation, which is approximately corresponding. Symmetrical DSL's market is much less compared to non-symmetrical DSL.

VDSL, ADSL, and RADSL

VDSL, ADSL, and RADSL belong to asymmetric transmission. The VDSL technology is the fastest in XDSL technology. On a pair of copper twin-concatenated telephone lines, the downlink data is 13 to 52Mbps, and the speed of uplink data is 1.6 to 2.3Mbps, but the transmission distance of VDSL is only in Within a few hundred meters, VDSL can become a cost-effective alternative to fiber-to-family. At present, Shenzhen's VOD (Video On Demand) is implemented in such access technology; ADSL supports uplift speed 640kbps on a pair of copper wires 1Mbps, downstream rate 1Mbps to 8Mbps, the effective transmission distance is within 3-5 kilometers; the speed range that RADSL can provide is basically the same as ADSL, but it can be dynamically adjusted according to the strength of the two-stranded wire quality and transmission distance. Users' access speed. It is this characteristic of RADSL to make RADSL an ideal technology for online high-speed surfing, video on demand (IAV), remote local area network (LAN), because users downloaded in these applications tend to be uploaded (send instructions) More much more.

ADSL status

my country's current fast-selling network access method

According to CNNIC (China National Network Information Center), as of 1997 10 On the 31st, the Internet users have reached 620,000, of which 49.1% of users think that the most disappointing place for Internet is too slow, 36.2% of users think is too expensive for Internet charging; as of June 1998 Day, in less than a year, the above three statistics are nearly reached, respectively: 11.75 million, 88.9%, 61.2%. It can be seen that with the speed expansion of the number of Internet users in China Internet, the online speed is too slow and the charge is too expensive to become two major obstacles to China's Internet development.

ADSL and other access methods

ADSL access service can achieve higher performance price than this, other access to ADSL access technology Technology has its unique technical advantage to not open. Let's take a look at the comparison of ADSL and other access services:

ADSL and CABLEMODEM comparison:

Compared to CableMode, ADSL technology Has a considerable advantage. The HFC access scheme of CABLEMODEM uses a layered tree structure. The advantage is that the bandwidth is relatively high (10m), but this technology itself is a rough bus type network, which is a limited bandwidth that the user wants to share with the neighboring user When the user has surge on a line, its speed will slow down. Furthermore, the relevant information indicates that in most cases, the HFC program must take into account existing cable TV programs, and occupy some bandwidth, only a part of the remaining part can be transmitted, so the theoretical transmission rate of CableModem can only reach one. Half half. Foreign company experiments show that its rate is reduced to 1M-2Mbps, more common is 400k-500kbps. In whole, even in the ideal state, the HFC is only equivalent to a 10Mbps shared bus type Ethernet, and the ADSL access scheme is more advanced on the network topology, because each user has a separate line and ADSL Bureau. The end is connected, and its structure can be regarded as a star structure, and its data transmission bandwidth is exclusive by each user.

ADSL and normal dial modem and N-ISDN comparison:

a) Compared to ordinary dial MODEM, the highest 56k rate, and N-ISDN128K The rate, the rate advantage of ADSL is self-evident.

b) Compared to ordinary dial modem or ISDN, ADSL is more attractive, it is: it transmits data and speech signals on the same copper wire, and the data signal does not pass the telephone switch device, alleviate The load of the telephone switch is not needed, and it is always online, which is a special online network. This means that the use of ADSL Internet access does not need to pay additional telephone bills.

ADSL Technology Advantage

Asymmetric Digital User Line (ADSL)

ADSL can provide users with 6Mbps or more data transmission bandwidth, this condition is already enough Implement Internet Access, video on demand, and access to the LAN. In interactive mode ADSL can reach the bidirectional transmission rate of 640 kbps. ADSL technology increases the data transmission bandwidth of existing public telephone networks by 50 times.

ADSL technology

ADSL speeds of transmitting data by ordinary telephone lines are almost 200 times faster than today's modem, 90 times faster than ISDN. Early tests and experiments worldwide show that ADSL is a highly desirable access technology.

ADSL drop processing method

ADSL drop involving multifaceted issues, including line failure (line interference), ADSL MODEM fault (fever, quality, compatibility), network card The fault (slow speed, old driver), etc. Operators and users should do the following regular inspections: whether the ADSL phone line connector is safe and reliable: Whether to stay away from power cord and high-power electronic equipment; whether the ADSL portal line and separator are installed with a telephone extension, a fax machine, a billing device and other equipment : Whether to install the separator correctly; eliminate vintage ISA network cards, replace it with 10 / 100m PCI network card and the latest driver; whether ADSL Modem is well cleaned; the ADSL MODEM indicator status is normal. The causes and processing methods for the ADSL drop line are as follows: (1) Grounding line quality problem. PC grounding performance must be better. Otherwise static electricity will affect the transmission rate of ADSL or even cause a drop. Generally, the PC grounding resistance should be less than 10 Ω. In addition, since the power supply is unregulated during construction, there is no grounding line, or the ground line quality is unqualified, and it will affect the normal use of network equipment, and even turn off the line, it should be replaced in time. (2) The line has a strong source of interference. Strong signal interference sources such as radio emission tower, electric welding machine, tram or high voltage power transformer within 100M of the user cable line, using the user's lower line receives the clutter (the copper package steel wire shields weak. "Has strong receiving signal capabilities), causing the user Strong interference. The interferenced signal is often entered from the unshielded lower line portion, because the relay cable has a shielding layer, the interference has little, and if there are some shielded underscore, the rate caused by interference will reduce the rate due to interference. Unstable or dropped. In addition, the power cord cannot be parallel with the ADSL line to prevent crosstalk results in an ADSL failure. (3) NIC quality is unstable. The fault phenomenon is that the network is only disconnected, and it will not even connect. User MODEM's DSL lamp is often on, basically excluded line failures, and most of the problem is on the NIC. If the network cable, microcomputer, slot is excluded, the network card is generally unstable, and the NIC should be replaced in time. (4) The user line distance is far. The irregular turn-off line is caused by line quality or distance far, which can be used to test signal attenuation and strength of the ADSL tester, and find a better line replacement. General user relay lines should not exceed 5km, and the telephone from the split box enters the user room should not exceed 100m. (5) Can be online, but the phone is dropped. The reason is that the passage terminal board is broken, and the data sensing can pass due to the disconnector head and the terminal board distance, and the data can pass, and the voice is not going; if the user is very close, the indoor wire mix line can also cause the above fault. (6) Internet access, call the call. Generally, the outer line is insulated or the joint contact is poor. The user's external line is insulated. When the user is online, the phone handle will make a warning the alarm, the WAN lamp is off, and the fault is released immediately after the outsideline. (7) Can call, but go online. The case where the general user gets the wrong line is to connect the MODEM's line on the phone, and the phone can be used, while the Internet is turned off. At this time, the ADSL MODEM status light LINE light is not lit. When checking the fault, you should carefully check the device to use the wiring position, usually change as little as possible to avoid the error line. (8) Error series phone extension. Because the telephone extension is not correct, it causes crosstalk to cause internet data distortion. If you have to use a telephone extension, you should contact a separator.