Data transmission mode and encoding technology

Data transmission mode and encoding technology

The main advantage of analog transmission is that the channel utilization rate is high, but the signal in the transmission process degrades and is subject to noise interference, and the noise is also amplified when the signal is amplified.

The main advantage of digital transmission is that the digital signal only obtains discrete values, the signal transmission is not distorted, and the error rate is low. However, digital signal transmission requires a wider bandwidth than analog signal transmission. Therefore, the channel utilization for digital transmission is low? Measure the test taker's knowledge about different coding technologies, including analog signal coding of digital data, digital signal coding of digital data, and digital signal coding of analog data.

Analog Signal Encoding of digital data. This encoding method is to convert digital data into analog signals for transmission. Generally, the carrier characteristics (amplitude, frequency, and phase) of three analog signals are used) one to represent the modulated digital data, and thus produce three basic modulation methods: one shift keying method (ASK) 2 shift keying method (PSK) 3 phase shift keying method (PSK)

Digital signal coding of digital data. Common digital signal codes include non-zero NRZ (non return to zero) codes, differential codes do not return to dnrz codes, and Manchester (Manchester) codes) and differential Manchester (differentialmanchester) codes.

The digital signal encoding of analog data. The commonly used encoding technology here is the pulse code modulation technology.

Master the types of channel multiplexing technology (three types: frequency, time, and optical );

There are three main Multiplexing technologies: 1. Division Multiplexing; 2. Division Multiplexing; 3. division multiplexing.

The frequency-division multiplexing technology is divided by frequency. Multiple signals can exist and be transmitted at the same time. The frequency bands of each signal are different. The time-division multiplexing technology is divided by time, only one channel of signal exists in each time gap, and multiple signals are transmitted in the channel in time-based rotation. The optical fiber division multiplexing technology is divided by wavelength, and multiple signals can exist and be transmitted at the same time, the wavelength of each signal is different, and the essence is the multiplexing of frequency and division.

Master common error control methods (2 methods ).

Common Error Control Methods Adopt the automatic resend request (ARQ) technology and forward Correction Technology (FEC );

1. Automatic resend request (ARQ) Technology

ARQ is one of the Error Correction protocols for the data link layer in the OSI model.

It includes stopping the Waiting For ARQ protocol and the continuous ARQ protocol, error detection, positive confirmation, re-transmission during failover, and negative validation followed by re-transmission.

2. Forward Correction Technology (FEC)

FEC (Forward errorcorrection) is a data encoding technology. Errors in transmission are verified by the receiver. In FEC mode, the receiver can not only detect errors, in addition, the location of the binary code element error can be determined and corrected. The error code must be used in FEC mode. If an error is found, you do not need to notify the sender to resend it.

 

Data transmission mode and encoding technology