Routing in Mobile Ad-hoc Networks 6 April 2019 Routing in Mobile Ad-hoc Networks EECS 4215

Mobile Ad hoc Networks (MANETs) No infrastructure (no base stations or access points) Mobile nodes Form a network in an ad-hoc manner Act both as hosts and routers Communicate using single or multi-hop wireless links Topology, locations, connectivity, transmission quality are variable.

MANETs: Operations X D D Y X Z S S

MANETs vs. WMNs Supporting end-user applications One type of radio on devices Supporting end-user applications

MANETs vs. WMNs (2) MANETs: end-user devices also perform routing and configuration functionalities for all other nodes. WMNs: mesh routers perform these tasks. Mesh routers vs. mobile devices: power and resource constraints mobility MANETs: usually only one radio. WMNs: can have multiple channels, multiple radios.

MANETs: Applications Civil Military Disaster recovery Taxi cabs Communications over water using floats Vehicular ad-hoc network Military Battlefield communications Monitoring and planning

MANETs: Challenges Wireless channels: error-prone media Low bandwidth channels Security Unpredictable mobility Devices: low power, limited resources Maintaining connectivity, states

Routing: Wired vs. Wireless Ad-hoc networks have dynamic time-dependent topology Links (edges) added/deleted Nodes (vertices) added/deleted Bi-directional or uni-directional links Wireless medium Inherently a broadcast medium Fading, shadowing cause burst errors and/or intermittent connectivity Network topology changes frequently Low bandwidth: routing protocols must minimize the amount of control traffic generated.

Routing Approaches On-demand (reactive) Proactive (table-driven) acquiring & maintaining routes on demand DSR (Dynamic Source Routing), AODV (Ad-hoc On-demand Distance Vector) Proactive (table-driven) All nodes maintain routes to all destinations in the network at all times. OLSR (Optimized Link State Routing) Hybrid: combines reactive and proactive Zone Routing Protocol (ZPR) Zone-based Hierarchical Link Sate (ZHLS)

Unicast Routing Protocol for MANETs (topology-based) Table-Driven/ Proactive Hybrid On-Demand/ Reactive Clusterbased/ Hierarchical Distance- Vector Link- State ZRP DSR AODV TORA LANMAR CEDAR DSDV OLSR TBRPF FSR STAR

AODV Notes AODV uses a mechanism similar to distance vector routing  routing loops (e.g., due to “counting to infinity” problem). AODV uses destination sequence numbers to ensure loop- freedom at all times. AODV maintains (caches) forward and reverse routes (and sub-routes) as DSR. Difference from DSR: routing entries are associated with DSNs (“side effect” of DSNs: help avoid obsolete routes) Route caching speeds up route discovery, minimize control traffic overhead, minimize delay. Reverse routes can be used for future data packets going in that direction (if the routes are still valid).