Access below 56Kbps is called "narrowband", and access above 56 kbps is classified as "broadband". At present, there is no accepted definition of broadband. Generally speaking, it can meet the bandwidth that people need to feel the transmission of various media on the network, so it is also a dynamic and developing concept. At present, broadband means that the transmission rate of home users is above 1M, which can meet the demand of massive information transmission such as voice and image.
Including: optical fiber, xDSL(ADSl, HDSL) and ISDN (broadband in a non-strict sense).
DSL:
Digital users
Line Digital Subscriber Loop (LINE) technology is a broadband access technology based on ordinary telephone lines. It transmits data and voice signals respectively on the same copper wire, and the data signals do not pass through the telephone exchange equipment, thus reducing the load of the telephone exchange. And you don't have to dial, always online. It's a private internet mode. DSL includes ADSL, RADSL, HDSL, VDSL, etc.
VDSL:
VDSL (very high bit rate digital user
Loop) is a high-speed digital subscriber loop. Simply put, VDSL is a fast version of ADSL. Using VDSL, the maximum download rate can reach 55Mbps in a short distance, and the upload rate can reach 19.2Mbps, or even higher.
cable modem
ChinaCablemodem cable modem, also known as cable modem, commonly known as cable cat, English name cable.
Modem is developed with the expansion of network application in recent years, which is mainly used for data transmission in cable TV network.
Cable TV companies usually separate 6MHZ channels from TV channels between 42 MHz and 750 MHz for downlink transmission of data. Usually downlink data is modulated by 64QAM (quadrature amplitude modulation), and the highest rate can reach 27Mbps. If 256QAM is used, the highest rate can reach 36Mbps. Uplink data is generally transmitted through the frequency spectrum between 5 and 5~42MHZ. In order to effectively suppress the accumulation of uplink noise, QPSK modulation is usually used. QPSK is more suitable for noisy environment than 64QAM, but the rate is lower. The maximum uplink rate can reach 10Mbps.
Currently, cable modems
The development of access technology in the world, especially in North America, is very strong, and the number of users increases by more than 100% every year. Cable Modem have been opened in China, Guangdong, Shenzhen, Nanjing and other provinces and cities.
Visit. It is the biggest competitor of telecom company xDSL technology. In the future, the radio and television system will vigorously promote the traditional telephone network developed by the telecom company camp and Cable xDSL access technology promoted by cable TV manufacturers.
modem
Technology will compete fiercely in the access network market (especially in the high-speed Internet access market). In China, the broadband access technology developed by radio and television departments on cable TV network has matured and entered the market. Cable TV network has a wide coverage and many users (according to statistics, the number of cable TV users in China has exceeded 100 million in June 5438+0999+ 10); The network has a wide spectrum range and a high starting point. Most newly-built cable TV networks adopt hybrid fiber coaxial network (HFC network) and use adjacent frequency transmission system with bandwidth above 550MHZ, which is very suitable for providing broadband functional services. Cable modem (cable
Modem technology is a network access technology based on HFC network.
CableModem completely solves the congestion caused by voice and image transmission, and its rate reaches more than 10Mbps, and the downlink rate is higher. Although the traditional modem has developed a product with a speed of 56Kbps, its theoretical transmission limit is 64Kbps, and it is impossible to improve it any more.
CableModem is also the key equipment for building MAN. Hybrid optical fiber coaxial network (HFC) backbone uses optical fiber, and branch bus coaxial cable network is used to connect users in the optical node community. Its transmission frequency can be as high as 550/750MHz. CableModem is needed to transmit data in HFC network.
We can see that CableModem is a necessary thing for future network development, but it is still the international standard of CableModem at present, and the transmission rate of products from different manufacturers is different. Therefore, the establishment of broadband access network in high-speed metropolitan area network has yet to be promulgated by CableModem standard.
[Edit this paragraph] Optical fiber access network:
Optical fiber access network (OAN) is an access network using optical fiber transmission technology, that is, a communication system in which local exchanges and users use optical fiber transmission in whole or in part. Optical fiber has the advantages of broadband, long-distance transmission ability, good confidentiality and strong anti-interference ability, and is the main implementation technology of future access networks. FTTH mode refers to the direct access of optical fiber to users' homes, generally only one or two subscriber lines are needed, which is not economical in the short term, but it is the long-term development direction and the ultimate access network solution.
[Edit this paragraph ]FTTX+ LAN access mode:
This is a scheme that uses optical fiber and five types of network cables to realize broadband access and gigabit optical fiber to the central exchange of a community (building). The central exchange and the corridor exchange are connected by 100-megabit optical fiber or five-class network cable, and the corridor adopts integrated wiring, so that the user's internet access rate can reach 10 Mbps, and the network scalability is strong and the investment scale is small. In addition, there are various access modes such as fiber to the office, fiber to the home, and fiber to the desktop to meet the needs of different users. FTTX+LAN adopts star network topology, and users * * * enjoy bandwidth.
[Edit this paragraph ]ISDN:
ISDN integrated services digital network is a digital telephone network composed of digital transmission and digital exchange, which is abbreviated as ISDN in English. It can realize users' digital signal access to the network and provide end-to-end digital connection, so that the same network can carry all kinds of voice and non-voice services. ISDN basic rate interface includes two 64Kb channels and one 16Kb D channel, which can work independently. Select ISDN.
The Internet access speed of a B channel through 2B+D port can reach 64Kb/s, which is 2.2 times faster than that of ordinary telephone dialing (if the transmission rate of modem is 28.8Kb/s). If two B channels are used together by software, the communication rate can reach128kb/s/s. ..
Bandwidth represents a comprehensive indicator of the display capability of the display, which refers to the number of pixels scanned per second, that is, the sum of frequency points displayed on all scanning lines in unit time, in MHz. The greater the bandwidth, the stronger the display control ability and the better the display effect.
The detailed calculation formula of bandwidth is as follows: theoretically, bandwidth b = r (x) × r (y) × v.
R(x) represents the number of pixels on each horizontal scanning line.
R(y) represents the number of horizontal scanning lines per frame.
V represents the picture refresh rate (i.e. field frequency) per second.
What is ADSL?
Asymmetric digital user
Loop) technology is an asymmetric digital subscriber loop technology, which uses frequency division technology to separate low-frequency signals and high-frequency signals transmitted by ordinary telephone lines. The low-frequency part below 3400Hz is for telephone use; The high-frequency part above 3400Hz is used for surfing the Internet, that is, data and voice signals are transmitted simultaneously on the same telephone line, and the data signals directly enter the Internet without telephone switching equipment. Therefore, ADSL service can not only transmit data at high speed, but also surf the Internet without affecting the normal use of the telephone, which also means that there is no need to pay extra telephone charges when using ADSL to surf the Internet.
(B) ADSL business characteristics
High-speed rate: the transmission rate can reach up to 640Kpbs for uplink and 8Mbps for downlink, which is much higher than dial-up Internet access.
Low rate: only network usage fee, no network call fee.
Excellent function: provide telephone and internet services on one telephone line at the same time, and the telephone and internet services do not affect each other, so that the telephone and internet services are truly correct.
Simple installation: In the case of the existing telephone line, as long as an ADSL modem and a voice separator are added, ADSL can easily get home without making any changes to the line.
(Types of ADSL services
ADSL service can be divided into PPPOE (Virtual Dialing) mode and fixed IP mode according to access mode, and their respective characteristics are as follows:
PPPOE mode:
Every time you surf the Internet, you need to use PPPOE dial-up software to verify the user's account name and password, similar to narrowband registered dial-up service. The rate of PPPOE mode is lower than that of fixed IP mode, which is more suitable for individual users.
Fixed IP mode:
Your computer is always on. Just turn on the computer and ADSL.
The modem can surf the Internet without entering a user name and password for verification. Fixed IP mode is suitable for small businesses and Internet cafe users.
(4) Description of business application
1. Users only need to carry the ID card and photocopy of the owner of the collection phone, and the ID card and photocopy of the handler when going through the formalities of accessing the network or changing.
2. When filling in the business application form, please fill in the user application form in standard font, with neat font and clear handwriting.
3. In order to ensure timely installation for you, it is suggested that you fill in the contact number when handling business, and leave more than two contact information where you can be found at any time, so that we can install the machine at home in the shortest time.
Our company will open ADSL service for you within 2 working days after your business application formalities are completed.
5. If it is not installed within one month from the date of filling in the application form, it will be deemed as automatic disassembly. If necessary, please go to the business window again.
6. If the terminal equipment is rented by the communication company for free, the property right of the equipment still belongs to the communication company, and the user needs to return the terminal intact after disassembling it.
(5) Preparation before installation
Personal and office users (independent Internet users)
1. Prepare a microcomputer with a Pentium 586 or above Microsoft operating system and ensure its normal operation.
2. WIND0WS98, WINDOWS2000 and WINDOWS XP produced by Microsoft are recommended for the operating system.
3. Prepare an adaptive network card of 10M/ 100M, install it by yourself and work normally.
4. If ADSL access is through telephone line, please make sure that the telephone line is connected to your microcomputer before installation.
Internet cafes, corporate users (multi-computer users)
Internet cafes, companies and other local area network users need to configure and install proxy servers or routers themselves.
(6) User Guide
Schematic diagram of ADSL client connection:
The setting and use of ADSL dialing software;
Windows XP
The PC graphics operating system introduced by Microsoft is more powerful and integrated with PPPoE protocol support. Our broadband users do not need to install any other PPPoE software and use Windows XP directly.
You can easily create your own broadband virtual dial-up internet file by using the connection wizard, and the actual use effect is exactly the same as that of Windows.
Like PPPoE under 9x/Me/NT/2K, it is more convenient to use because it is more closely integrated with the operating system.
Installation step
Step 1: After installing the hardware, we choose to run the Windows XP Connection Wizard from the Start menu.
(Start-> Program-> Attachment-> Communication-> New connection wizard), because Windows
Compared with the original Windows system series, XP start menu has intelligent adjustment function, which automatically puts common programs in the previous menu, so the order may be different from ours. Windows.
XP will also run the Connection Wizard during installation, and you can also set it during installation.
Step 2: After running the connection wizard, the "Welcome to the New Connection Wizard" screen appears, as shown in the figure below, and click "Next" directly.
Step 3: Then we choose the default option "Connect to the Internet" and click "Next".
Step 4: Select "Set my connection manually" here, and then click "Next".
Step 5: Select "Use a broadband connection that requires a username and password" and click "Next".
Step 6: You will be prompted to enter the ISP name. This is just the name of the connection. You can just type in, such as "zjjs", and then click "Next".
Step 7: Here you can choose whether this connection is for any user or just for yourself, and click "Next" directly.
Step 8: Then enter your user name (((******@zjjs.net) and password (be sure to pay attention to the format of user name and password and the case of letters), and follow the instructions of the wizard to execute Windows on this Internet connection.
Other security settings for XP, and then click Next.
Step 9: At this point, our virtual dialing setup is completed.
Step 10: After clicking finish, you will see a connection icon named "zjjs" on the desktop.
Step 11: If the user name and password are correct, directly click "Connect" to dial up the Internet.
After the connection is successful, an icon connecting two computers will appear in the lower right corner of the screen, as shown in the figure below, and you can surf the Internet!
Remarks: Due to various irresistible factors, every netizen may have encountered the problem of system crash and had to choose to reinstall your operating system. After reinstalling the system, please reinstall the dial-up software and establish a dial-up connection according to the above tips.
(7) Business changes
When you open, pause, reopen, disassemble and move the machine, please call customer service: 10060.
Introduction of ADSL fault self-check
(A) simple fault judgment
Modem signal light: (Take Alcatel as an example)
ADSL- used to display the synchronization of Modem, and the green light is always on, indicating that the Modem and the same terminal can synchronize normally; A red light means there is no synchronization; A flashing green light indicates that synchronization is being established.
10Baset- Used to show whether the connection between modem and network card or hub is normal. If this light doesn't work, the modem and computer must be disconnected. When there is data transmission in the network cable, this light will blink slightly.
ATM25- displays the status of atm25 ports that are not normally used.
Maint- related to remote management, usually always on.
Power supply-power supply display
(2) Hardware failure
1. The connector is loose, the network cable is broken, the hub is damaged, and the computer system is faulty-the above faults can be located by observing the indicator light of the modem, hub or computer. Perform replacement experiments on suspicious equipment.
2. The modem should be kept dry and ventilated; Avoid showering with water; Keep it clean. During a thunderstorm, please unplug the modem power supply and all wires to avoid lightning damage.
3. If the indicator light is off, or only one light is on, or the 10BaseT light is still off after replacing the network cable and network card, it means that the modem is damaged, please contact the equipment provider.
4. Line quality-the distance is too long; Poor line quality; The connection is unreasonable. It is characterized by frequent loss of synchronization, difficulty in synchronization, or slow inertia speed.
5. Connect the devices that need to be connected in parallel, such as telephone extensions, fax machines, ordinary modems, etc. , behind the telephone port of ADSL voice separator; Check whether all connectors are in good contact, and the household wires with poor quality should be modified or replaced.
(3) Other issues
1. Do I need to buy new parts for my computer to apply for ADSL service?
Because of the high speed of ADSL, the serial port used by traditional Modem can not support it. So to use USB interface or users need to plug in a network card (ordinary 10 megabit Ethernet card, the market price ranges from dozens to 200 yuan), and ADSL needs to be installed on the computer at present.
There are more modems.
2. Is there a telephone charge for surfing the Internet with ADSL?
There is no telephone charge. One advantage of using ADSL is that browsing information on the Internet does not go through the telephone exchange, and there is no need to pay telephone charges.
3. When installing ADSL, do users need to apply for a dedicated telephone line? What are the requirements for users' computers?
By installing ADSL, users can modify the existing telephone line or apply for a second telephone line dedicated to surfing the Internet. There is no difference between installation and use. If you use an existing telephone line, the previous telephone number will remain unchanged. A general 586-level computer will do, and there are no special requirements. Users can use a simple method to judge whether their computers are suitable or not: they can use ordinary modems to surf the Internet, and all computers with acceptable results can use ADSL to surf the Internet (but no ordinary modems are needed).
4. Does the distance affect the network speed?
Because of its own technical characteristics, broadband internet access has certain requirements for distance. ADSL transmission distance is best not to exceed 3 kilometers; The transmission distance of local area network should not exceed 100 meters. (The above distance refers to the distance from the user end to the switch. )
5. Is it troublesome to install ADSL? How long can't you call?
Installing ADSL does not need to change the user's telephone line. It only takes a few minutes to make a simple jumper in the telephone exchange room, and users can make normal calls.
6. I want to install ADSL, but I am worried about the decline of telephone service quality. In addition, will making phone calls reduce the internet access rate?
The design of ADSL equipment takes this into account, and uses frequency division multiplexing technology to separate telephone tones from data streams (
ADSL does not occupy the low-end frequency band used for making phone calls) and does not interfere with each other. In the test of the actual line, there is no difference between the voice of the telephone with ADSL and that of the ordinary telephone: while transmitting data information, the transmission rate remains unchanged when lifting the phone, hanging up the phone and talking casually.
7. Why sometimes ADSL access speed is not much faster than ordinary dial-up modems?
The reasons for slow ADSL access are: 1) If you visit a foreign site, the access will be affected by the export bandwidth and the configuration of the other site; 2) Because ADSL technology requires high quality of telephone lines, if the telephone lines between the telephone office building and users are disturbed by external factors within a certain period of time,
ADSL modem will dynamically adjust the user's access speed according to the line quality and transmission distance. The above two phenomena are similar to the traditional dial-up modem.
8. 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 together according to certain rules, which can effectively resist external electromagnetic interference. However, most telephone lines in the market are parallel lines, from the junction box of the telephone company to the telephone of the user, many lines are parallel lines, which is very unfavorable to ADSL transmission. Non-twisted pair transmission is too long, which will cause unstable connection, DSL light flashing, and affect Internet access. Because ADSL superimposes high-frequency digital signals on the low-frequency voice of ordinary telephone lines, adding any equipment to the connection from the telephone company to the ADSL voice separator will endanger the normal transmission of data, so don't merge the telephone, telephone burglar alarm and other equipment before the ADSL voice separator.
9. Why did my user account password fail to be verified?
First of all, make sure that the password of the user account is entered correctly, pay attention to distinguish the case of the account and password, and log in again. Because you have not used it for a long time, you have forgotten or misremembered the password. Please go to the Netcom business hall to initialize the password, that is, reuse it.