An ad hoc network is one that is spontaneously formed when devices connect and communicate with each other. The term ad hoc is a Latin word that literally means “for this,” implying improvised or impromptu. Ad hoc networks are mostly wireless local area networks (LANs).

Outline

  1. What is an ad hoc network?
  2. Challenges facing ad hoc networks.
  3. General Concepts

Types of wireless networks: Infrastructure vs ad hoc networks

Infrastructure Networks


• Fixed, wired backbone
• Mobile communicates directly with access points
• Suitable for locations where access points can be placed
• Cellular networks

Why Ad Hoc Networks ?

❒ Ease of deployment
❒ Speed of deployment
❒ Decreased dependence on infrastructure

What is an Ad hoc Network?

  1. A network without any base stations “infrastructure-less” or multi-hop
  2. A collection of two or more devices equipped with wireless communications and networking capability.
  3. Supports anytime and anywhere computing
  4. Two topologies:

Mobile Ad Hoc Networks?

Mobile Ad Hoc Networks?

  • Mobility causes route changes

What is an Ad hoc Network?

❒ Self-organizing and adaptive – Allows spontaneous formation and deformation of mobile networks
❒ Each mobile host acts as a router
❒ Supports peer-to-peer communications
❒ Supports peer-to-remote communications
❒ Reduced administrative cost
❒ Ease of deployment

Ad Hoc Networks – Operating Principle

Example of an Ad Hoc Network

❒ Fig. depicts a peer-to-peer multi hop ad hoc network
❒ Mobile node A communicates directly with B (single hop) when a channel is available
❒ If Channel is not available, then multi-hop communication is necessary e.g. A->D->B
❒ For multi-hop communication to work, the intermediate nodes should route the packet i.e. they should act as a router
❒ Example: For communication between A-C, B, or D & E, should act as routers.\

Bringing up an Ad hoc Network

  • Ad hoc network begins with at least two nodes broadcasting their presence (beaconing) with their respective address information.
  • They may also include their location info if GPS equipped.
  • Beaconing messages are control messages. If node A is able to establish a direct communication with node B verified by appropriate control messages between them, they both update their routing tables.

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