Wireless networks - Lecture 28: Mobile Ad-hoc network

Wireless networks - Lecture 28: Mobile Ad-hoc network. The main topics covered in this chapter include: introduction to mobile Ad-hoc network; routing protocol; expected properties of Ad-hoc routing protocols; a taxonomy for routing protocols in Mobile ad; some common protocols (DSDV, AODV, DSR, ZRP, TORA);...

Wireless Networks

Lecture 28Mobile Ad hoc Network

Dr Ghalib A Shah

► Expected Properties of Ad-hoc Routing Protocols

► A taxonomy for routing protocols in Mobile ad

► Some common protocols (DSDV, AODV, DSR, ZRP,

TORA)

Last Lecture Review

What is Ad hoc

► For a specific purpose of occasion

► For this case alone

► a network composed solely of stations within mutual

communication range of each other via the wireless media.

► an independent basic service set

 Mobile distributed multi-hop wireless network

(manet)

► a group of mobile, wireless nodes which

cooperatively and spontaneously form a network independent of any fixed infrastructure or centralized administration

► A node communicates

• directly with nodes within wireless range

• indirectly with all other destinations using a dynamically determined multi-hop route though other nodes in the manet

The characteristic of ad hoc networks

► one hop(uplink or downlink)

► PCF(pointed coordination function)

Expected Properties of Routing

 Ideally an ad hoc network routing protocol

should

► be distributed in order to increase reliability

► assume routes as unidirectional links

► Multi-channel: Channel assignment using low-layer info

► Single channel model

► Are all nodes treated uniformly?

► How are distinguished nodes selected (neighbors or

 is based on the idea of Ballman-Ford routing algorithm

 Every mobile station maintains a routing table that lists

► all available destinations

► the number of hops to reach the destination

► the sequence number assigned by the destination node

 A station transmits its routing table

 Put figure with same illustration of DSR

 It borrows

► the basic on-demand mechanism of route discovery

and route maintenance from DSR

► the use of hop-by-hop routing, sequence numbers,

and periodic beacons from DSDV

 A node periodic broadcasts hello information to

maintain the local connectivity

 It only supports the use of symmetric links

 is based on the concept of link reversal

 finds multiple routes from a source node to a

destination node

 the control messages are localized to a very

small set of nodes near the occurrence of a topological change

 A node maintains route caches containing the source routes that it

is aware of

 The node updates entries in the route cache as and when it learns 

about new routes

 route discovery

► route request packet contains

► route reply is generated by

 OLSR uses multipoint relays to reduce

superfluous broadcast packet retransmission and also the size of the LS packets

 OLSR thus leads to efficient flooding of control

messages in the network

OLSR (cont’d)

 Only the multipoint relays nodes (MPRs) need

to forward LS updates

 OLSR is particularly suited for dense networks

 In sparse networks, every neighbor becomes a

multipoint relay, then OLSR reduces to pure LS protocol

 A hybrid routing protocol that combines both

proactive and on-demand routing strategies

 Each node has a predefined zone

 Inside zones: proactive routing

 Outside zones: on-demand routing

 ZRP provides more flexibility

► Expected Properties of Ad-hoc Routing Protocols

► A taxonomy for routing protocols in Mobile ad

► Some common protocols (DSDV, AODV, DSR, ZRP,