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ADSL maintenance manual
Guizhou province telecom company network yunxing maintenance department
May 2004
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In recent years, ADSL technology has developed rapidly, showing a good development momentum and becoming the mainstream broadband access technology. With the rapid development of ADSL business, the maintenance of ADSL business is becoming increasingly prominent. In order to make the staff of each department judge the fault type quickly and accurately in the maintenance work, reduce the business interruption time and improve the maintenance level, we have collected and compiled some materials and compiled them into manuals for the reference of the maintenance personnel.
In the process of compiling the manual, Guiyang Operation Center and Qiannan Telecom Branch Data Center provided us with a lot of information, and we would like to express our gratitude.
Due to the rush of time and lack of experience, omissions and mistakes are inevitable. I hope that all local networks will reflect their opinions to us in time during the use process so as to modify them later.
compilers
catalogue
Chapter 1 Introduction to ADSL basics ... 1
Chapter II ADSL Installation ... 3
Chapter III ADSL Maintenance ... 18
Appendix 1 Handling of ADSL Simple Obstacles in the UPTELL Authentication System
Appendix 2 ADSL disconnection phenomenon analysis
Chapter 1 Introduction to ADSL Basic Knowledge
The principle of 1.ADSL
1, basic concept
ADSL (Asymmetric Digital Subscriber Line) is the abbreviation of asymmetric digital line, which is a technology to provide broadband data transmission service for families and offices through existing ordinary telephone lines. ADSL is an asymmetric digital signal transmission, which can provide high-speed downlink rate up to 8Mbit/s on the existing copper twisted pair, that is, ordinary telephone lines. The uplink rate is 2Mbit/s and the transmission distance is 3 km-5 km. ADSL can make full use of the existing telephone network and provide users with high-bandwidth services by installing ADSL equipment at both ends of the line. ADSL can be stored on the same telephone line as ordinary telephone, and high-speed digital signal transmission can be carried out while answering and making calls on the ordinary telephone line, which does not affect each other.
2. Working principle
1) line spectrum
ADSL makes full use of the spectrum of twisted-pair copper wire. The whole spectrum is divided into three parts: (1) traditional voice service frequency band, which is about 4kHz bandwidth; (2)ADSL uplink duplex low-speed channel, located on the voice spectrum; (3)ADSL downlink simplex high-speed channel, located in the high-frequency part.
In the echo cancellation ADSL system, the downlink channel overlaps with the uplink channel (mainly by using the characteristic of small signal attenuation in the low frequency part). Compared with frequency division multiplexing technology, echo cancellation technology eliminates the interference (such as near-end crosstalk) caused by frequency superposition, so it can greatly improve the performance index of ADSL system. But relatively speaking, echo cancellation technology is more difficult and requires higher hardware integration.
2) Line coding
There are three transmission technologies for ADSL lines: quadrature amplitude modulation (QAM), carrier-free amplitude-phase modulation (CAP) and discrete multi-tone (DMT). Compared with QAM and CAP technology, DMT technology has many advantages, and it is easier to realize the transmission rate above 6 MB/s. According to ANSIT 1.4 13 standard, DMT technology is the first choice.
DMT is a multi-carrier modulation technology, which divides the whole frequency band into 256 sub-channels. A training sequence is sent in advance to measure the characteristics (signal-to-noise ratio) of each subchannel, and a1~1bit signal is allocated to each subchannel according to the data transmission capability of the subchannel, and the subchannel that cannot transmit data is closed. For those loops that are interfered by crosstalk and RF carrier, good performance can be obtained, and the whole system can distribute data adaptively.
DMT system can be regarded as a set of continuous and parallel QAM systems, and each QAM carrier frequency corresponds to a DMT subchannel frequency. Multicarrier modulation (demodulation) requires orthogonal modulation between different sub-channels and is realized by fast Fourier transform (FFT). Because the cable characteristics of each subchannel are almost linear, the impact of impulse noise is minimal. The energy of impulse noise will affect the received characters, but FFT will disperse them into many sub-channels within the FFT window, so the possibility of error code is very small.
2. The main features and typical applications of 2.ADSL
1 and the main technical features of ADSL
ADSL technology adopts asymmetric transmission structure suitable for users' data access services, which can provide users with high-speed transmission channels.
ADSL access system adopts advanced line coding and modulation technology, which has good adaptability to subscriber lines.
ADSL access system can support voice and data services at the same time, and realize the separation of data and voice services in the access section of network structure.
ADSL access system can make full use of a large number of copper cable resources in the existing local telephone network, and can develop in harmony with the optical cable laying plan in the optical fiber access network, thus providing users with high-quality data access services.
2. Typical application of 2.ADSL
Internet high-speed access service
Various broadband multimedia services, such as video-on-demand VOD, online concert hall, online theater, online games, online TV, etc.
VPN service based on ATM or IP
Provide peer-to-peer remote video conferencing, telemedicine, distance education and other services.
Chapter II ADSL Installation
1.ADSL installation process
Business acceptance-wiring billing-pre-opening of computer room-external receipt.
2.ADSL hardware installation
1 and ADSL access mode
The access model of ADSL is mainly composed of central exchange office module and remote module. The central exchange module includes ADSL modem and access multiplexing system in the central location. The ADSL modem in the central position is called ATU-C (ADSL Transmission Unit-Central). The modems in the center of an access multiplexing system are usually combined into an access node, which is also called "DSL access multiplexer". As shown in the figure below:
2. Basic information of main components of 2.ADSL
1) call
Every ADSL line must be connected to an ordinary telephone line, which is called a carrier telephone.
2) network card (NIC)
A network interface card is a device that connects computers to a network and communicates with other computers in the network.
3) ADSL modem
Modem is also called modem, and its function is to realize the conversion between analog signals and digital signals. All signals transmitted on ordinary telephone lines are analog signals. Modem converts the analog signal transmitted on the telephone line into a digital signal that can be recognized by the computer, and at the same time converts the digital signal sent by the computer into an analog signal and sends it through the telephone line.
4) separator
The function of the separator is to separate the high-frequency signal used by ADSL from the low-frequency signal used by ordinary local calls. Users with extensions should connect the telephone lines in parallel after passing through the separator.
5) Cable
Twisted pair: Two insulated copper wires are wound together according to certain rules, which can effectively resist the interference of external electromagnetic fields.
Parallel lines: The relative positions of the two lines are unchanged, and the anti-interference ability is poor. Users with more than 20 meters of parallel lines at home should first change the parallel lines into twisted pairs.
Network cable: It consists of four twisted pairs and two RJ45 connectors.
3, the correct connection
Do not connect the extension and alarm in front of the separator. If there is an extension, it should be followed by a separator. The picture shows the correct connection method of modem and splitter.
Frequently asked questions about the entrance line:
A and B wires are not wrapped with insulating tape, and occasionally short-circuited when touched by external force.
The insulation resistance of line A and line B is too low, because the socket is wet, or one of line A and line B touches the ground.
The length of subscriber line is more than 2.5km, and the length of iron core or aluminum core line for home parallel connection is more than 20 m. The external port of separator is connected with telephone extension, fax machine, audio modem, voice station dial limiter, IP dialer, etc.
The line plug and socket are in poor contact.
The external port of the separator is connected in series with an audio modem, a voice dial limiter, an IP dialer, a telephone burglar alarm, etc.
4. Correct installation method of ADSL telephone accessories.
1) Simple installation
segregator
telephone wire
modulator/demodulator
telephone
Advantages: simple circuit, no interaction between using the telephone and surfing the Internet, few faults and easy maintenance.
Disadvantages: the mobile phone is not convenient to use nearby, and there is no auxiliary machine. (You can use a cordless phone)
2) Add separator and telephone accessories.
segregator
telephone wire
modulator/demodulator
Telephone host
Installing separator
Telephone auxiliary machine
Advantages: the number of auxiliary machines can be increased as required, and it is convenient to use. Surfing the internet and making phone calls do not affect each other.
Disadvantages:
With the addition of telephone accessory lines and separators, the lines tend to be complicated, which increases the hidden trouble of faults and is not conducive to fault investigation.
The equipment cost increases.
Note: When using multiple separators, only one low-impedance separator can be used at most, and other high-impedance separators can be used, otherwise it is easy to generate telephone echo due to line impedance mismatch.
3) After passing through the separator, install the telephone accessories.
segregator
telephone wire
modulator/demodulator
Telephone host
Telephone auxiliary machine
Advantages:
The telephone loop and ADSL loop are separated at the separator, which does not affect each other and is convenient to use and maintain.
No separator is needed, which is economical and practical.
If it is a newly renovated house, all lines can be laid with concealed pipes, which is beautiful, with low failure rate and long service life.
Disadvantages: if it is laid with open wires, there are many wires, which is not beautiful.
3.ADSL software installation
At present, there are two kinds of ADSL access modes: dedicated line access mode and virtual dial-up access mode. Private line access mode (that is, static IP mode) means that the telecommunications company assigns a fixed static IP address to users, which is relatively simple to access the Internet; Virtual dial-up access mode (PPPOE dial-up mode) is not to dial the telephone number, and the cost has nothing to do with the telephone service. Instead, the user enters the account number and password and obtains a dynamic IP address through authentication. Users need to install PPPOE dial-up client software in their computers.
The software setup of ADSL Internet access can be divided into the following steps.
1. Installation and setup of network card
Because the ADSL modem is connected to the computer through a network card, it is necessary to install the network card before installing the ADSL modem. The network card can be 10M network card or 10/ 100M adaptive network card. The installation steps are as follows (take 3COM EtherLink III PCMCIA network card installed under WIN98 as an example):
1) Insert the network card and restart the system. After starting the screen, WINDOWS will automatically search for the network card.
2) Select the network card type in the device list, and insert the drive disk or CD according to the system prompt.
3) After the installation, the 3COM Etherlink III network card appears in the system properties of the control panel.
4) Click Properties to confirm that the network card works normally in the general options and does not conflict with other hardware.
For users who use private line to access the network, IP address, subnet mask, gateway and DNS server address need to be set in TCP/IP properties; For virtual dial-up users, the default setting is enough.
2. Install virtual dialing software
There are many kinds of PPPOE dial-up software, and the following three are common:
Enternet300 (enternet100 enternet500): a PPPoE software developed by American Efficient Network Company, which provides the PPPoE protocol of ADSL and completes virtual dial-up Internet access. It is suitable for win98, win2000 and winNT/4.0.
WinPoET: PPPoE software developed by WindRiver Company in the United States, which provides PPPoE protocols for ADSL and virtual dial-up Internet access. It is suitable for winme, win98 and win2000.
RasPPPoE: PPPoE software developed by German netizens, which provides the PPPoE protocol of ADSL and completes virtual dial-up Internet access. Applicable to winme, win98 and win2000.
The following describes the installation method of Enternet 300.
1) is installed under Windows 95/98/ME.
(1) Enter the installation software directory and double-click the program file "setup.exe".
(2) The installation program starts.
(3) Select the quick installation (accept the default settings) option, click the Next button, and wait for the computer to automatically install PPPOE software and drivers.
(4) When the following window appears, select the Yes option and click the Finish button.
(5) Restart the computer according to the prompt of the computer to complete the software installation of PPPOE.
(6) After the computer restarts, select and double-click the EnterNet 300 icon on the desktop.
(7) Select the Create New Profile icon in the new window and double-click.
(8) Enter the connection name of ADSL dialing mode, such as ADSL, and then click Next.
(9) Enter the correct user name and password in the next window. The password needs to be entered twice.
(10) Continue to press the Next button to enter the next window.
(1 1) Click the Finish button in the Finish Connection window to enter the next window.
(12) A new icon ADSL appears in the Profile-EnterNet 300 window. Select and double-click this icon to open the ADSL connection.
(13) Click the Connect button in the dialing window to establish an ADSL PPPOE call.
(14) In the message status bar of the EnterNet 300 window that pops up, "Start negotiation" is displayed, indicating that you are trying to establish a connection with the server.
(15) Then the message status bar shows "Verifying", which means that the server is verifying.
(16) Then the status bar of "Message" shows "Receiving network parameters", indicating that parameters such as IP are being obtained.
(17) Finally, the whole EnterNet 300 window disappears, and the icon of two computers connecting appears on the Windows status bar in the lower right corner of the computer screen, indicating that the connection has been successfully established.
(18) At this point, users can surf the Internet.
(19) When users want to disconnect from the network, they can double-click the icon above, and then click the "Disconnect" button in the window that appears.
2) Install under Windows 2000.
Open Network Neighborhood, connect the network card with ADSL equipment and select Local Area Connection, right-click into the property panel, select Install, then select Protocol, select Install from Disk, and then locate the path directory where the PPPOE software is located. Finally, it is determined that WIN2000 system will prompt "No digital signature" many times during the installation process, which can be ignored. After the installation is completed, it will be restarted on WIN98.
3) Install under Windows XP
Windows XP is the latest Windows operating system introduced by Microsoft. Windows XP integrates PPPOE protocol. ADSL users can use the Connection Wizard of Windows XP to establish their own ADSL virtual dial-up connection directly without installing any other PPPOE dial-up software.
(1) After installing the network card driver, select (Start->; Program-> Attachment-> Communication-> New Connection Wizard).
(2) The "Welcome to the New Connection Wizard" screen appears, and click "Next" directly.
(3) Then select "Connect to the Internet" by default and click "Next".
(4) Select "Set my connection manually" here, and then click "Next".
(5) Select "Connect a broadband connection that requires a username and password" and click "Next".
(6) You will be prompted to enter "ISP name", which is just the name of the connection. You can just type in, such as "ADSL", and then click "Next".
(7) Here, you can choose whether this connection is for any user or for your own use only, and click "Next" directly.
(8) Then enter your ADSL account (user name) and password (be sure to pay attention to the format of user name and password and the case of letters), make some other security settings for this Internet connection according to the tips of the wizard, and then click "Next".
(9) At this point, the PPPOE dialing setting of Windows XP is completed.
(10) After clicking Finish, you will see a connection icon named ADSL on the desktop.
(1 1) If the user name and password are correct, directly click "Connect" to dial up the Internet.
(12) After the connection is successful, you will see the icon of two computers connected in the lower right corner of the screen.
4. Client network debugging
Hardware requirements of the client:
Computer: INTEL Pentium III or above, the same level of CPU microcomputer.
An ADSL terminal equipment (modem)
10m or 10/ 100m adapter network card (usb port modem is free).
One RJ45 network cable (usb port modem is free)
RJ 1 1 telephone line.
Customer's software requirements:
It is recommended to use WIN98 and above operating systems.
The browser suggests using IE4.0 or above, or Netscape4.0 or above.
Network debugging of static IP users
The modem adopts the factory default mode.
In the computer control panel->; In the network-> Set IP address, subnet mask, gateway and DNS in TCP/IP (Binding Network Card) protocol.
Network debugging of PPPOE users
The modem adopts the factory default mode. The values of vpi and vci of the client should be 0 and 35. If the default values of the modem are not 0 and 35, you must log in to the modem to modify it. The method is as follows: 1) Set the IP address item in the TCP/IP protocol of ADSL network card to "192.168.1.x" subnet mask. 2) Enter "Options", select "Connect" in the address bar of IE browser, and check "Never dial-up connection". Select Local Settings and uncheck Automatic Detection and Use Proxy Server. Press OK to enter Advanced, press Restore Default Settings, and then press OK. Open the webpage and try it.
3.ADSL line test scheme
Because the access mode of ADSL users is carried on the local telephone copper twisted pair for high-speed data transmission, each user has different computer terminals, user modems, local telephone cables, DSLAM data ports and so on. And finally access the network server through the transmission link. Therefore, when measuring an ADSL line, it will be tested simultaneously by layered measurement and segmented measurement to evaluate the location and transmission performance of the fault segment.
1) layered measurement
Hierarchical measurement is mainly divided into data link layer, protocol layer and physical layer measurement. The data link layer mainly carries out Modem simulation test and links with local DSLAM to check whether the parameters on the data link layer are normal and meet the requirements of ADSL link transmission; Ping test is mainly carried out at the protocol layer to verify whether the user account password is valid and whether the data in the computer room is correct; Physical layer measurement is physical line testing, testing and evaluating cable quality and physical performance. In the physical layer test, location is mainly carried out by subsection measurement.
2) Sectional measurement
The main purpose of subsection measurement is to locate the fault line and find the occurrence section or point of the problem. In subsection measurement, the whole link is generally divided into local end segment, user segment and user segment. The local part mainly includes computer room DSLAM port equipment, computer room data management, switching equipment, access equipment and so on. The subscriber line is mainly composed of 1 12 machine room wiring, protector unit, main cable, distribution cable, indoor line, splitter and subscriber modem. ; The user part includes user computer and local area network.
Because the quality of various cables involved in subscriber line segments is quite different, and the transmission performance of ADSL is mainly affected by the length and quality of cables, the problem of subscriber line segments has become the main problem affecting the transmission performance of ADSL.
3) ADSL line test parameters and standards
(1) ATU-R subscriber modem simulation test indicators and standards
Link simulation test
name
Target value
Measured value
Fast channel rate
Uplink (kbps)
User application value
Downlink (kbps)
User application value
Interlaced channel rate international
Uplink (kbps)
User application value
Downlink (kbps)