Data Transmission Techniques and Communication Channels
Modes of Transmission
Simplex Mode
The transmitter only sends information to the receiver.
Half-Duplex Mode
Protocols manage the transmission turn of each machine.
Full-Duplex Mode
Communication occurs simultaneously in both directions.
Communication Channels
A signal travels through designated “rails”.
Signals require specific bandwidth (range of frequencies for undistorted transmission).
The number of channels depends on the transmission medium.
Channel changes on a transmission medium involve modulation, switching, and multiplexing.
Modulation
Modulation inserts information into a transmission medium.
- FM: Frequency Modulation
- AM: Amplitude Modulation
Purposes:
- Facilitate and spread radiation during transmission.
- Reduce noise and signal disturbance.
- Sort and divide transmission media and communication channels.
Switching
Switching interconnects transmission channels or circuits for signal transmission.
Communication Circuits
- Request Circuit
- Confirmation of the Circuit
- Transmission of Information
- Disconnecting the Circuit
Message Switching
A message travels through an intelligent network (node), releasing each section for other messages and waiting for the next section to become available.
Packet Switching
The network fragments a message into smaller packets. If a packet has an error, only the damaged packet is retransmitted.
Multiplexing
Multiplexing transmits multiple messages simultaneously in a single channel.
A demultiplexer at the destination separates the original signals.
Time Division Multiplexing (TDM)
Each channel receives the total bandwidth for a specific time interval.
Frequency Division Multiplexing (FDM)
The total bandwidth is divided into portions, each assigned to a channel.