Routing in wireless networks - cpham.perso.univ-pau.fr

Routing Routing in in wireless wireless networksnetworks

C. PhamUniversité de Pau et des Pays de l’AdourDépartement Informatiquehttp://www.univ-pau.fr/[email protected]

Routage 2Cours de C. Pham, Université de Pau et des Pays de l’Adour

Routing Routing in in wireless wireless networksnetworks

What’s a wireless network ?– Wireless terminals– Embedded– Mobility– With or without a fixed infrastructure– With or Without a centralized administration– Connected to the Internet or autonomous

Exemples– GSM– WiFi, WiMax– Bluetooth– Ad-Hoc, Manet– Wireless Sensor Networks– Vehicle network– …


Ad-hoc Ad-hoc networksnetworks

Infrastructure-less networks MANET (Mobile Adhoc NETworks)


Design Design choices choices (1)(1)

Single-hop or multi-hop ?

Single-path or multi-path?



Proactive?– Maintain & update routing table independently of communication

needs– Periodical updates– Same philosophy than in wired-networks (RIP, OSPF)– Low latency– « Waste » bandwidth and energy

Reactive, on-demand?– On-the-fly discovery of routes, when communication needs appear– Save bandwidth and energy– Higher latency– Generally efficient at low load

Hybrid?– Proactive or reactive depending on the distance



Flat routing?– Simple– Not scalable!

Hierarchical routing?– More efficient– « leaders » election overhead– Mobility cost– Multiple hierarchy levels are possible

Geographical routing?– GPS-aided for instance– Efficient routing towards the destinations– Geographical information are

propagated using flooding


Structuration of Structuration of the the networknetwork

Desired properties– Hide topology changes (stability)– Structure the network (hierarchy)– Optimize information diffusion– Take into account the heterogeneity of nodes– Distributed

« backbone » approaches « clustering » approaches


ClassificationClassification


ExampleExample: AODV: AODV

Initiated when a communication need arises: reactive Source node initiates path discovery by broadcasting a

route request (RREQ) packet to its neighbors A neighbor either broadcasts the RREQ to its neighbors or

satisfies the RREQ by sending a RREP back to the source– Later copies of the same RREQ request are discarded

Node records the address of the sender of RREQ (indicatedin the RREQ)– Reverse path are automatically set-up– Entries are discarded after a time-out period

Eventually, a RREQ arrives at a node that possesses thecurrent route for the destination (Comparison of sequencenumbers)

The RREP travels along the path established in the reversepath set-up

Each node along the RREP journey sets up a forwardpointer, updates time-out entries, records the destinationsequence number of requested destination

AODV (Example)AODV (Example)

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RREQ


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ReversePath Setup


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ForwardPath Setup


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ExampleExample: OLSR: OLSR

Proactive protocol, similar to Link State with HELLOpackets

Uses « multipoint relay » to reduce informationdiffusion costs– « multipoint relay » of node A are nodes N such that all 2-hop

neighbors of A are 1-hop neighbors of N.– Ex: C & E are multipoint relay of A

A

B F

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Node with information from A


OLSR (OLSR (concon’’tt))

Nodes C & E send information from A Nodes E & K are multipoint relays of H Node K send information from H

A

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Node with information from A


Other protocolsOther protocols

Homework for next week– Find another proactive or reactive protocol (Internet search)– Understand it, explain it in front of class– Compare it to AODV and/or OLSR

Routing in wireless networks - cpham.perso.univ-pau.fr

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