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
- What is an ad hoc network?
- Challenges facing ad hoc networks.
- 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?
- A network without any base stations “infrastructure-less” or multi-hop
- A collection of two or more devices equipped with wireless communications and networking capability.
- Supports anytime and anywhere computing
- 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
❒ 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.