Data Transmissions

Data Transmissions

Data Transmission Methods

Serial Transmission

  • Data is transmitted one bit at a time, in a single line.
  • Simpler and cheaper to install than parallel transmission.
  • Useful for long distance transmission, but slower than parallel transmission.

Parallel Transmission

  • Transmits multiple bits at a time in parallel channels (typically eight).
  • Faster than serial transmission for short distances.
  • More expensive and complex due to multiple lines.

Simplex Transmission

  • One-directional data transmission.
  • Examples include radio and television broadcasts.

Half-Duplex Transmission

  • Two-way data transmission, but only one way at a time.
  • Examples include walkie-talkies.

Full-Duplex Transmission

  • Allows data flow in both directions simultaneously.
  • Examples include telephone systems.

Transmission Modes

Asynchronous Transmission (Start/Stop Mode)

  • Transmission includes start and stop bits for each byte, indicating when data starts and ends.
  • The sender and receiver do not need to be synchronised.
  • Suitable for low speed data transmission.

Synchronous Transmission

  • Large amounts of data can be sent without start and stop bits, making it faster.
  • Sender and receiver must be synchronised.

Isochronous Transmission

  • Data is transmitted at regular intervals, commonly used in multimedia applications.
  • Ensures a constant delay and avoids issues with synchronisation.

Data Transmission Errors

Single Bit Error

  • Only one bit is changed due to error.

Burst Error

  • Multiple bits in a row have changed due to error.

Methods of Error Detection

Parity Check

  • Extra bit (the parity bit) is added to ensure total number of 1’s is even (even parity) or odd (odd parity).

Checksum

  • Blocks of data are added up, and the total checked against a value transmitted with the data.

Cyclic Redundancy Check (CRC)

  • Data is divided by a specific divisor, and the remainder is sent with the data. Receiver repeats the calculation to check for errors.

Remember, understanding how data transmissions works is important, as it forms the basis of data exchange and communication in computer systems.