Internet access

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).