Access to the internet

There are many ways to access the Internet, and there are usually the following access methods.
1. Use public telephone network access to
use a telephone line that can connect to ISP, an account and modem dial-in access. The advantages are simple and low cost; the disadvantages are slow transmission speed and poor line reliability, which affects telephone communication.
2. Integrated Service Digital Network (Integrated Service Digital Network, ISDN)
Narrowband ISDN (N-ISDN) is based on the public telephone network and uses synchronous time division multiplexing technology. It evolved from the Integrated Digital Network (Phone Integrated Digital Network) to provide users with end-to-end connections and support all voice, digital, image, fax and other services. At present, it is widely used. Although the telephone line is used as the communication medium, it does not affect normal telephone communication. Broadband ISDN (B-ISDN) uses optical fiber trunks as the transmission medium and uses asynchronous transmission communication mode ATM technology.
3. Asymmetric Digital Subscriber Line (Asymmetric Digital Subscriber Line, ADSL)
ADSL uses ordinary telephone lines as the transmission medium, and achieves transmission speeds of up to 640 Kbps in the upstream and 8 Mbps in the downstream. You only need to install ADSL equipment at both ends of the line to get the broadband service provided by ADSL. When using ADSL to access the Internet, ADSL Modem generates three information channels, namely a standard telephone channel; a 640 Kbps ~ 1 Mbps uplink channel: a high-speed downlink channel of 1 Mbps ~ 8 Mbps. Telephone communication uses a low frequency band of 4 to 4 kHz (actual phones can have a bandwidth of 2 M). ADSL adopts discrete multi-tone multiplexing technology in the modulation method. It transmits telephone audio from 0 to 4 kHz on a pair of copper wires, and transmits data from 26 kHz to 1.1 MHz, and divides it into 25 uplinks with a width of 4 kHz. Sub-channels and 249 downlink sub-channels. After the input data is encoded and modulated, it is sent to the sub-channel. After being transmitted to the data room, the voice signal is sent to the program-controlled room after passing through the splitter. The data signal is left on the data equipment, and then it is connected to the Internet.
4. Cable Modem
Cable TV network is suitable for all over the country. Cable Modem provides Internet access in many places, and the rate can reach 10 Mbps or more. However, Cable Modem is a shared bandwidth, and the rate will drop during a certain period (busy time).
5. Optical fiber access (FDDI) is
a high-speed metropolitan area network built with optical fiber cables. The backbone network speed can be as high as ten Gbps, and broadband access is introduced. The optical fiber can be laid on the roadside or in front of the user, and can be accessed at a rate of more than 100 Mbps (the optical fiber does not enter the home). In theory, the direct access rate can reach 100 Mbps (access to large enterprises and institutions or the entire region), but access users can reach about 10 Mbps. The actual downlink rate in China is usually 1 to 3 Mpbs.
In recent years, wireless access has been rapidly promoted, especially bringing great convenience to users who carry laptop computers. The user is connected to the ISP through a high-frequency antenna. The general distance is about 10 km. The rate can reach 2 to 11 Mbps under the 3G standard. The current downlink rate is about 30 Kbps. The price is very high and it is very popular. But limited by terrain and distance.
6. Satellite access
Some ISP service providers provide satellite access to Internet services, suitable for users in remote areas that require higher bandwidth. A small-diameter terminal (VSAT) needs to be installed, including antennas and receiving equipment. The transmission rate of downlink data is generally about 1 Mbps, and the upstream access to ISP through ISDN.