Communication Basics

Communication Basics

Data Transmission

  • Simplex transmission allows data to flow only in one direction, such as in a television or radio broadcast.
  • Half-duplex transmission allows data to flow in both directions, but not simultaneously.
  • Full-duplex transmission is when data can flow in both directions at the same time, such as in a telephone conversation.

Types of Data

  • Analog data is continuous and varies over a range of values, like sound waves.
  • Digital data is discrete and has specific values, represented by binary digits (0s and 1s).

Data Conversion

  • ADC (Analog to Digital Converter) transforms analog signals to digital so that a computer can process it.
  • DAC (Digital to Analog Converter) transforms digital signals to analog for output devices such as speakers.

Signal Transmission Methods

  • Serial transmission sends data one bit at a time in a sequence, suitable for long distance transmission like in networking.
  • Parallel transmission sends data several bits at a time over separate channels, suitable for short distance transmission like between computer internal components.

Synchronous and Asynchronous Transmission

  • Synchronous transmission operates with two devices synchronised with each other. Blocks of data are sent at once, increasing speed but requiring more complex hardware.
  • Asynchronous transmission does not require sender and receiver to be synchronised. Data is sent one byte at a time with start and stop bits, suitable for less reliable transmission but can be slower.

Error Detection and Correction

  • Parity check is an error detection method where an additional bit is added to ensure the number of 1s is always even (even parity) or odd (odd parity).
  • Checksum adds all the bytes together in a block of data and takes the complement of the last byte for error detection.
  • Cyclic redundancy check (CRC) uses binary division to create a checksum which is more reliable than basic checksum method.

Modem and its Function

  • Modem (Modulator-Demodulator) used to modulate digital signals into analog for transmission, and demodulate received analog signals into digital. Essential for internet connection over telephone lines.

Different Data Rates

  • Baud rate measures the number of signal changes per second.
  • Bit rate measures the number of bits transmitted per second.
  • Generally, the higher these rates, the faster the data transmission. However, higher rates might require better hardware and can be more prone to errors.