How to debug adsl

the following reprint

ADSL as a frequency division technology in the application of traditional telephone twisted pair, so that the theoretical downlink rate of twisted pair with only 64K transmission rate can reach 8Mbps, and the uplink rate can also be between 16Kbps——8Kbps. So how does ADSL plug the old and slow traditional telephone line with wings?

for a long time, the telephones of communication users have been connected to the local exchange through twisted-pair copper wires, entered the public switched communication network (PSTN), and connected to the telephones of the other users, so that both parties can talk to each other. The twisted-pair copper wire provides a frequency band of 3~34 Hz for the traditional analog telephone. Adding a modem to this communication network can make the Internet access rate reach 56 Kbps.

why can twisted-pair copper wire only transmit data with a limit of 56Kbps? It should be said that this is not a problem with the transmission capacity of twisted copper wire, but the switch in the communication network is limited, which only allocates one voice band to telephone communication. Although the user's data information passes through the voice modem, the switch does not think it is a data signal from the voice modem, but only treats it as an ordinary voice signal. However, the twisted copper wire itself does not limit the transmission of data signals, so users can send broadband data signals into the communication network as long as they avoid narrow-band switches. Therefore, if the subscriber line avoids the narrowband voice switch, it can become a digital subscriber line. ADSL is realized by a spectrum splitter, which divides the spectrum above the telephone line into: below 4KHZ, it is sent to an ordinary switch to transmit telephone calls, and the higher spectrum is used to transmit data.

ADSL technology supports symmetric and asymmetric transmission modes on the subscriber lines of traditional telephone networks, which solves the transmission bottleneck problem called "the last kilometer" between network service providers and end users. Because the telephone subscriber loop has been laid in a large number, how to make full use of the existing copper cable resources and realize high-speed access through copper twisted pair has become the research focus of the industry, so DSL technology has quickly gained attention and been widely used in some countries and regions.

the most important feature of ADSL system is that it does not need large-scale infrastructure construction, and it can use the original copper wire facilities to quickly provide broadband services required by users. If users no longer need this service or are replaced by other broadband access facilities, network providers can dismantle and install ADSL equipment to other places where broadband services are needed. ADSL is especially suitable for sporadic users at the beginning of broadband service, because it can avoid large-scale investment in building other broadband access facilities, such as HFC and optical access network, and get economic benefits as quickly as possible. There is no contradiction between the use of the original infrastructure and the extension of optical fiber to users. The closer the optical fiber extends to users, the wider the bandwidth of ADSL, and ADSL is still an ideal means to access users' homes.

In summary, ADSL has the following advantages:

1. High speed and low price

2. It is always online without dialing, and can even be used as a dedicated line without a telephone number.

3. Voice and data communication can be realized at the same time

4. Access to the Internet through ADSL is not required to pay telephone charges

5. The telephone network will not be blocked

6. There is no need to carry out a large number of modifications to the existing telecommunications facilities

7. Broadband multimedia services such as video on demand (interactive TV), karaoke, online games, interactive TV and online shopping

ADSL. We know that the traditional Modem also uses telephone lines to transmit, but it only uses the low frequency band of ~ 4 kHz, while the telephone copper wire theoretically has a bandwidth close to 2MHz. ADSL only uses the high frequency band after 26KHz to provide such a high speed. The specific workflow is: the signal encoded by ADSL Modem is transmitted to the telephone office through telephone line and then through a separator. If it is a voice signal, it is transmitted to the telephone exchange. If it is a digital signal, it is connected to the Internet.

The existing copper twisted-pair ordinary telephone line provides a high-speed download rate as high as 8Mb/s and an uplink rate of 1Mb/s, but the existing line of users with a transmission distance of 3km to 5km does not need to be changed, and the changes only need to be made in the exchange room of the telecommunications bureau. However, users still need to buy an ADSL user terminal. At the same time, because the existing interface can't meet the high-speed operation of ADSL, users also need to buy an ordinary 1-megabit Ethernet card, and its market price is about 1 yuan. In this way, with a 586-level computer, you can use ADSL to surf the Internet.

how to install, debug and use ADSL

1. what are the requirements for users when applying for ADSL?

(1) computer: 586 Pentium and above IBM compatible computers.

(2)ADSL terminal equipment: ADSL Modem (provided by telecommunication bureau) and built-in Ethernet card (the market price of ordinary 1-megabit Ethernet card is about 2 yuan).

2. when installing ADSL, do users need to apply for a dedicated telephone line?

by installing ADSL, users can either rebuild the existing telephone line or apply for a second telephone line dedicated to surfing the Internet. There is no difference in installation and use. If you use the existing telephone line, the previous telephone number will remain unchanged.

3. Do I need to dial if I use ADSL?

ADSL can surf the internet and make phone calls at the same time. Making a phone call is the same as a traditional phone call, and you don't need to dial the other party's number when surfing the Internet. Users only need to connect the ADSL power supply and turn on the computer to surf the Internet.

4. when browsing the internet with ADSL, do you need to charge for the phone?

there is no telephone charge. Because we use ADSL to browse the internet, we don't have to pay the phone bill without going through the telephone exchange.

5. Is it troublesome to install ADSL? How long can't I make a phone call?

ADSL installation does not need to change the user's telephone line, just need to make a simple jumper in the telephone exchange room for a few minutes, and the user will not notice it.

6. I want to install ADSL, but I'm worried that the quality of telephone service will decline. In addition, will making phone calls lead to a decrease in Internet access rate?

ADSL equipment has been designed with this in mind. It uses frequency division multiplexing technology to separate telephone tones from data streams without interfering with each other. In the test of the actual line, there is no difference between the telephone with ADSL and the ordinary telephone. When transmitting data information, the transmission rate remains unchanged when you lift the phone, hang up the phone and talk at will

7. Why is ADSL sometimes not much faster than ordinary dial-up Modem?

The reasons for slow ADSL access are as follows:

(1) If you visit a foreign site, the access will be affected by export bandwidth and the configuration of the other site. However, compared with other access methods, ADSL can still reflect the higher speed advantage;

(2) ADSL technology requires high quality of telephone lines. If the telephone lines between the telephone building and users are disturbed by external factors for a certain period of time, ADSL will dynamically adjust the access speed of users according to the line quality and the transmission distance.

8. why is the actual rate of ADSL not as fast as the theoretical value?

this is not the problem of ADSL itself, but the narrow export bandwidth of the Internet at present.

9. I am an ADSL user, but sometimes I can't surf the Internet normally. What is the reason?

ADSL is a technology based on twisted-pair transmission. Twisted-pair is to wrap two insulated copper wires around each other in a certain law, which can effectively resist external electromagnetic interference. However, most telephone lines in the market are parallel lines, and many lines from the junction box of the telephone company to the user's telephone are used in parallel lines, which is very unfavorable to ADSL transmission. Too long non-twisted pair transmission will cause unstable connection and flashing DSL lights, which will affect Internet access. Because ADSL is to superimpose high-frequency digital signals on the bottom-frequency voice of ordinary telephone lines, the addition of any equipment in the connection from the telephone company to the ADSL filter will endanger the normal transmission of data, so don't connect the telephone, telephone anti-theft device and other equipment before the filter.

1. can ADSL provide LAN access?

Yes, there are three methods:

1) Set the host that directly connects to the Internet through ADSL as a proxy server, and then the clients on the local LAN access external information resources through this proxy server. The advantage of this method is that you need to apply for an account or an IP address, and the local clients can use the reserved IP address;

2) Apply for an IP address from the telephone office for each computer on the local area network by using a private line. The advantage of this method is that there is no need to set up a special proxy service gateway. The disadvantage is that the telephone office can only provide up to 16 IP addresses to the local area network due to the limitations of the current technology.

3) Connect a router behind ADSL, apply to the telephone office for an additional IP address to the LAN machine, and access the Internet after the telephone office sets the route for this address. The advantage of this method is that the number of computers in the LAN is not limited, but an extra router is needed.