Hardware and Collisions

• WNIC – Wireless network interface cards/controllers
  • Used to connect devices to the internet or other networks
  • Uses an antenna to communicate with networks via microwaves
  • Normally plug into USB port
• WAP – Wireless access point
  • Connected into the wired network at fixed locations
  • Receives and transmits data between the WLAN and the wired network
• Cables
  • Carry data
  • Types:
    • Twisted pair cables
    • Coaxial cables
    • Fibre optic cables

Router §

• A router takes a packet of data, looks at its IP address and then redirects it, or routes it to the correct desination on a network
• The network might be a LAN or a WAN, such as the internet
• A router could be compared to a post office that knows all the addresses of any equipment on the network, whether it is a computer or a printer or a scanner, for example
  • Every time the post office receives some information from inside or outside the network, it knows exactly where to redirect it to

Bridges §

• Bridges - are the devices that connect one Lan to another using the same protocol. They are used to connect different parts of a LAN so that they can function as a single LAN
• Repeaters are devices that boost signal for transmissions systems over long distances. Analogue and digital.

Switches §

• Switches are similar to hubs, but they distribute the data packets more efficiently. As with hubs, they connect a number of devices or computers together to form a LAN. However, unlike a hub, the switch checks the data packet received and works out its destination address (or addresses) and sends the data to the appropriate computer(s) only. This makes using a switch a more secure and efficient way of distributing data

NIC §

A network interface card (NIC) is needed to allow a device to connect to a network (such as the internet). It is usually part of the device hardware and frequently contains the MAC address generated at the manufacturing stage.

• Satellites
  • 3 types
    • GEO (Geostationary Earth-orbit) – long distance communication (telephone and computer network) – 3 GEO for full global coverage – orbital period: 24 hours
    • MEO (Medium Earth-orbit) – closer to Earth (GPS) – 10 MEO – orbital period: 2 to 12 hours
    • LEO (Low Earth-orbit) – work in ‘constellations’, to supplement the mobile phone networks – 50 LEO – orbital period: 80 mins to 2 hours
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Cables §

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• More stable and reliable (wireless often subject to interference)

• Data rates are generally higher than wireless

• Can be cheaper despite the material costs

• Devices are not mobile and need to reach cables

• Cables can look untidy and restrict flexibility

• Wireless

  • Electromagnetic radiation - radio, microwave, infrared – each type has a different frequency of the waves.
  • 
  • Easier to expand network
  • Increased mobility of devices, provided within range of wireless access point (WAP)
  • Less secure as easier to intercept data transmissions (need for encryption such as WPA2)
  • Signals can be stopped by thick walls with varying signal strength
  • Can have dead spots
  • Wireless access points often need to be cabled