Digital Signals, Communication Media, and Computer Networks

Posted on Mar 20, 2025 in Computer Engineering

Digital Signals

Analog Vs. Digital: The world primarily uses analog signals, while machines use digital signals. We can convert analog signals into digital ones through sampling and quantification. Bit depth determines how much information can be stored for every sample. The more bits used for each sample, the more faithful the digital signal will be to the original.

Communication Media

Between 1835 and 1900, the first 60 years of modern telecommunications, two main types of communication media emerged:

  • Cables: Connect one point to another.
  • Air: Utilize electromagnetic waves.

Types of Cables

Twisted Pair:

  • The most basic and familiar type of cable.
  • Used for basic telephone connections and low-bandwidth applications.
  • Easy installation and low cost.
  • Limited bandwidth, susceptible to electrical noise.

Coaxial:

  • Used to transport high-frequency electrical signals.
  • Contains an insulator.
  • Offers more bandwidth than a basic twisted pair, suitable for cable TV and broadband internet.
  • High bandwidth, minimal interference.
  • More expensive than twisted pair.

UTP (Unshielded Twisted Pair):

  • Braiding eliminates electrical noise from adjacent pairs and other sources.
  • Commonly used in computer networks and Ethernet connections.
  • Low cost, low susceptibility to interference.
  • Limited distance without signal boosters.

Optic Fiber:

  • Uses a fine thread of transparent material.
  • The light source can be a laser or LED.
  • Used in telecommunications, high-speed data transmission, and local networks.
  • High bandwidth, immunity to interference, low losses, and stable.
  • Very delicate and expensive to install and maintain.

Electromagnetic Waves

A wave is a propagation of a disturbance in an environment. This phenomenon involves the transmission of energy without the transport of material. Humans use sound waves (mechanical) and light waves (electromagnetic).

Electromagnetic waves have two perpendicular components: an electric field (E) and a magnetic field (B). These waves propagate through a vacuum, such as air or water, and are governed by Maxwell’s equations.

Mobile Wireless Networks

Mobile wireless networks use coverage areas organized into cells. The terminals connect to a base station, and communication is transmitted through wiring.

Computer Networks

A computer network is a group of interconnected devices (such as computers, servers, printers, and routers) that can communicate with each other and share resources, data, and information. The network can be formed by physical cables, wireless connections, or a combination of both.

Network Classification

  1. PAN (Personal Area Network):
    • Connects devices within a single person’s workspace.
    • Range: Up to 10 meters.
    • Typical Devices: Personal devices (e.g., laptops, smartphones, tablets).
    • Topology: Point-to-point or star.
    • Technologies: Bluetooth and Zigbee.
  2. LAN (Local Area Network):
    • Connects devices within a small geographic area, such as an office building or campus.
    • Range: Up to a few kilometers.
    • Typical Devices: Switches, routers, servers, desktops, laptops, printers, and other peripherals.
    • Topology: Bus, star, ring, mesh, or hybrid.
    • Technologies: Ethernet, Wi-Fi.
  3. MAN (Metropolitan Area Network):
    • Connects devices within a city or metropolitan area.
    • Range: Up to tens of kilometers.
    • Typical Devices: Bridges, routers, switches, servers, and other networking equipment.
    • Infrastructure: Fiber to the node, cabinet, building, or home.
    • Examples: Cable TV network, WiMAX.
  4. WAN (Wide Area Network):
    • Connects devices over a large geographic area, such as a country or even the world.
    • Range: Up to thousands of kilometers.
    • Typical Devices: Routers, switches, modems, and other networking equipment.
    • Topology: Mesh or hybrid.
    • Examples: The Internet, MPLS.
    • Related Terms: WMAN or WiMAX.

LAN Components

  • Router: Connects multiple networks and directs traffic between them. It uses routing tables to determine the best path for data.
  • Access Point: Acts as a bridge between the wired network and wireless devices, such as laptops, smartphones, and tablets.
  • Repeater: Receives a weak signal and amplifies it, extending the range of a wireless network.
  • Power Lines: Cables that carry electrical power; can also be used to transmit data by modulating the electrical signals.
  • Nodes: Individual devices on a network that can send, receive, or relay data (e.g., computers, printers, routers).
  • Hosts: Any device on a network that can be addressed by a network protocol (e.g., computers, servers, printers).
  • Network Devices: Devices used to connect computers, printers, and other devices to a network (e.g., routers, switches, hubs, repeaters, access points).
  • Switch: Connects devices on a LAN, using Media Access Control (MAC) addresses to direct data, improving network speed and efficiency.

Communication Protocols

TCP/IP is a framework used to standardize communication between two hosts over the internet. It specifies how data should be packetized, addressed, transmitted, routed, and received. Every layer uses the services of the layer below it.