Multiplexing - secuguru/security-terms GitHub Wiki

Multiplexing is a technique used in telecommunications and computer networks to combine multiple signals or data streams into a single transmission medium or channel. By using multiplexing, multiple users or data streams can share the same physical medium (e.g., a cable or a frequency band), improving the efficiency and capacity of communication systems.

Types of Multiplexing

  1. Time-Division Multiplexing (TDM):
  • In TDM, multiple signals share the same channel, but each signal is assigned a different time slot. Only one signal transmits at a time, but they alternate so quickly that it appears they are transmitting simultaneously.
  • Example: In telephone networks, multiple phone calls can share a single line by being transmitted in alternating time slots.
  1. Frequency-Division Multiplexing (FDM):
  • In FDM, different signals are transmitted simultaneously over the same channel by using different frequency ranges. Each signal occupies a unique frequency band within the overall channel.
  • Example: Radio broadcasting uses FDM, where different radio stations transmit on different frequencies but share the same airwaves.
  1. Wavelength-Division Multiplexing (WDM):
  • WDM is a type of FDM used in fiber optic communication, where multiple light signals of different wavelengths (colors) are transmitted simultaneously through a single optical fiber.
  • Example: Fiber optic networks use WDM to transmit multiple data streams (e.g., internet, TV, and phone) through the same fiber cable.
  1. Code-Division Multiplexing (CDM):
  • In CDM, multiple signals are transmitted simultaneously over the same frequency band, but each signal is encoded with a unique code. Receivers decode the signals using the corresponding code to separate them.
  • Example: CDM is used in cellular networks (such as 3G) to allow multiple users to share the same frequency without interference.

Advantages of Multiplexing:

  • Efficient Resource Usage: It allows the efficient use of a limited communication medium (e.g., bandwidth, fiber optic cables).
  • Cost-Effective: Sharing a single medium among multiple signals reduces the need for additional infrastructure.
  • Scalability: Allows for more devices or users to be connected over the same medium without significant upgrades.

Real-World Examples:

  • Internet Connections: DSL and cable modems use multiplexing to send and receive multiple streams of data over the same line.
  • TV Broadcasting: Cable TV uses FDM to send multiple channels over a single cable.
  • Mobile Communication: Cellular networks use CDM to allow multiple users to share the same frequencies.

In summary, multiplexing enables the efficient use of communication channels by allowing multiple signals to share the same medium, which increases capacity and reduces infrastructure costs.