Computer Network (Basic)-Physical Layer

Physical layer

effect

• Connect different physical signals
• Transport bit stream

Channel

basic concepts

• Channel is the medium through which Wang transmits information in one direction
• A communication circuit contains a receiving channel and a transmitting channel

classification

• Simplex communication channel
  • Can only communicate in one direction, there is no channel for feedback in the opposite direction
  • Cable TV, radio, etc.
• Half-duplex communication channel
  • Both parties can send and receive information
  • Both parties cannot send or receive at the same time
• All-duplex communication Shindo
  • Both parties can send and receive information at the same time

Demultiplexing technology

• Multiple computers are connected to multiplexers and multiple computers are connected to demultiplexers, and multiple computers share a communication line
  

• effect

  • Improve channel utilization efficiency

• Reuse technology

  • Frequency division multiplexing
  • Time division multiplexing
  • Wavelength division multiplexing
  • Code division multiplexing

Question: Will sending and receiving conflict? What to do if there is a conflict?

• Solved by demultiplexing technology