Digital Transmission in the physical layer in DCN

 Digital Transmission in the physical layer

Digital transmission converts digital data into signals suitable for transmission over a physical medium.

 

Key aspects of digital transmission:

 

1. Digital Signals:

   - In digital transmission, data is represented as discrete, binary signals.

These signals can take on two voltage levels, often referred to as 0 and 1.

 

Common encoding schemes for digital signals include Non-Return-to-Zero (NRZ), Return-to-Zero (RZ), and Manchester encoding.

These signals are:

Electrical pulses: 

Light pulses: 

Radio waves: 

 

 

2. Modulation: A process of encoding digital data onto analog signals for transmission

Various modulation techniques are used, such as Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), and Phase Shift Keying (PSK).

 

3. Encoding: Digital data is encoded into specific voltage or frequency levels for transmission.

Line coding uses common techniques including Unipolar, Polar, and Bipolar encoding.

 

4. Multiplexing: A technique of combining multiple signals onto a single transmission medium.

Time-division multiplexing (TDM) and frequency-division multiplexing (FDM) are multiplexing methods.

 

5. Error Detection and Correction: A correction mechanism to ensure data integrity.

Techniques such as cyclic redundancy check (CRC) and Forward Error Correction (FEC) help identify and correct errors that may occur during transmission.

 

6. Synchronization: ensure that the receiver correctly interprets the transmitted bits.

 

7. Data Rate and Baud Rate:

   - The data rate refers to the number of bits transmitted per second, while the baud rate represents the number of signal changes (symbols) per second.

 

8. Digital Transmission Media:

   - Digital signals can be transmitted over various physical media, including copper cables, Fiber  optics, and wireless channels.

 

9. Digital Transmission Standards:

   - Standards and protocols at the Physical Layer, such as Ethernet, USB, and HDMI, define the rules for digital transmission.

 

10. Bit Error Rate (BER): Representing the ratio of incorrectly received bits to the total number of transmitted bits.

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