12-06-2013, 04:51 PM
MANET, WMN and WSN
MANET, WMN.ppt (Size: 2.45 MB / Downloads: 19)
Mobile Ad Hoc Networks
Formed by wireless hosts which may be mobile
Without (necessarily) using a pre-existing infrastructure
Routes between nodes may potentially contain multiple hops
Many Applications
Personal area networking
cell phone, laptop, ear phone, wrist watch
Military environments
soldiers, tanks, planes
Civilian environments
taxi cab network
meeting rooms
sports stadiums
boats, small aircraft
Emergency operations
search-and-rescue
policing and fire fighting
Many Variations
Fully Symmetric Environment
all nodes have identical capabilities and responsibilities
Asymmetric Capabilities
transmission ranges and radios may differ
battery life at different nodes may differ
processing capacity may be different at different nodes
speed of movement
Asymmetric Responsibilities
only some nodes may route packets
some nodes may act as leaders of nearby nodes (e.g., cluster head)
Challenges
Limited wireless transmission range
Broadcast nature of the wireless medium
Hidden terminal problem
Packet losses due to transmission errors
Mobility-induced route changes
Mobility-induced packet losses
Battery constraints
Potentially frequent network partitions
Need to scale to large networks
Ease of snooping on wireless transmissions (security hazard)
Unicast Routing Protocols
Many protocols have been proposed
Some have been invented specifically for MANET
Others are adapted from previously proposed protocols for wired networks
No single protocol works well in all environments
some attempts made to develop adaptive protocols
Routing Protocols
Proactive protocols (Maintain updated routes )
Determine routes independent of traffic pattern
Traditional link-state and distance-vector routing protocols are proactive
e.g.,variations of Dist. Vector (Destination Sequence Distance Vector, DSDV) and Link state (Optimized Link State Routing, OLSR)
Reactive protocols (discover routes on-demand)
Maintain routes only if needed
e.g., Source Routing (Dynamic Source Routing, DSR), Table driven (AODV, ABR, TORA etc.)
Hybrid protocols
Combination of reactive and proactive routing
e.g., ZRP
Location-aware Routing Protocols
Location information helps in optimizing routing
e.g., LAR
Flooding for Data Delivery
Sender S broadcasts data packet P to all its neighbors
Each node receiving P forwards P to its neighbors
Sequence numbers used to avoid the possibility of forwarding the same packet more than once
Packet P reaches destination D provided that D is reachable from sender S
Node D does not forward the packet
DSDV
DSDV (Destination Sequenced Distance Vector)
Each node sends and responds to routing control message the same way
No hierarchical structure
Avoids the resource costs involved in maintaining high-level structure
Scalability may become an issue in larger networks
Hybrid WMNs:
This architecture is the combination of infrastructure and client meshing.
Mesh clients can access the network through mesh routers as well as directly meshing with other mesh clients.
While the infrastructure provides connectivity to other networks such as the Internet, Wi-Fi, WiMAX, cellular, and sensor networks, the routing capabilities of clients provide improved connectivity and coverage inside WMNs.