What Is a VDSL Modem?
A VDSL Modem is a type of communication format that converts analog signals from the telephone line and digital signals from the Web into each other.
The word “modem” means “modulation and demodulation device”, and this device enables Internet communications over telephone lines. VDSL is an abbreviation for “Very high bitrate Digital Subscriber Line” and is the fastest communication method among the existing methods using telephone lines (xDSL).
VDSL is mainly used for internet connections to condominiums, apartments, and other residential complexes.
Usage of VDSL Modem
VDSL Modem is used for VDSL Internet connection. As mentioned above, a VDSL Modem is necessary for communication via telephone lines when using VDSL Internet in a housing complex, etc. By installing a VDSL Modem in the house, it is possible to send and receive analog and digital signals.
Although VDSL communication is faster than other xDSL communication methods, it is slower than fiber-optic communication, at about one-tenth the speed of fiber-optic communication.
Principle of VDSL Modem
In the VDSL system, an optical fiber is connected to the main distribution panel called “MDF room” in a condominium complex, and from there it is connected to each residence via telephone lines. The VDSL system uses a telephone line to connect to the main wiring board in the housing complex.
Since a telephone line is used, a modem is required to access the Internet even with the VDSL system, and a “VDSL Modem” is used for this purpose. In the optical wiring system, which is similar to the VDSL system, optical lines are extended from an electric wire to each residence. Therefore, unlike VDSL, all communication lines are optical lines.
This difference in maximum speed between VDSL and optical wiring systems is due to the difference in whether the communication line is via a telephone line or an all-optical line.
Types of VDSL Modem
1. Asynchronous Modem
This is the most commonly used type. Asynchronous modems communicate with bit synchronization, flag synchronization such as High-Level Data Link Control (HLDC), and block synchronization with character synchronization using the data signal itself. It is less fast and reliable, but less expensive.
2. Synchronous Modem
This type of modem is used in some business applications. Data and synchronization signals are sent from the terminal device on separate signal lines and then transmitted on a single transmission line. At the receiving end, the data and synchronous signals are separated and received by the terminal device on separate signal lines.
Compared to asynchronous modems, VDSL modems provide more reliable and faster communication, but are more expensive.
Other Information on VDSL Modem
1. Communication Method of VDSL Modem
A modem is a device that has the ability to convert between analog signals used in telephone lines and digital signals used in personal computers. Traditionally, dial-up connections using telephone lines were the standard way to connect to the internet, and modems that convert between analog and digital signals were indispensable.
When digital signals are transmitted over telephone lines that carry voice, the digital signals that are processed by the computer cannot be sent directly. A modem is used to convert the digital signal once into an analog signal.
In modulation, a digital signal is put on an analog signal by changing the amplitude and phase of the signal based on a reference signal called a carrier (carrier wave).
2. Start-Stop Synchronous Communication
Asynchronous communication is a communication method in which data transmission start bit (start bit) and data transmission end bit (end bit) are added at the beginning and end of data transmission, respectively, each time one character of information is sent in serial communication.
Although asynchronous communication is less efficient than synchronous communication, it does not require a signal line for synchronization and allows data transmission at any timing.