Lecture 28 Mobile Ad hoc Network Dr. Ghalib A. Shah Wireless Networks Lecture 28 Mobile Ad hoc Network Dr. Ghalib A. Shah

Outlines Introduction Routing Protocol What is Ad hoc networks? Characteristic Ad hoc vs. cellular networks Application Challenges 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)

Last Lecture Review Problems with DCF Virtual Carrier Sensing RTC/CTS Protocol Interframe Spacing PCF Fragmentation / Reassembly MAC Frame Format Frame Types Physical Media in Original IEEE 802.11

What is Ad hoc Ad hoc IEEE802.11 For a specific purpose of occasion For this case alone IEEE802.11 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 Heterogeneous nodes Self-creating not rely on a pre-existing fixed infrastructure Self-organizing no predetermined topology Self-administering no central control creating a network “on the fly”

Ad hoc networks Cellular networks infrastructureless multiple hop Radio power limitation, channel utilization, and power-saving concerns DCF(distributed coordination function) Cellular networks infrastructure-based one hop(uplink or downlink) PCF(pointed coordination function)

Challenges Spectrum allocation Self-configuration Medium access control (MAC) Energy efficiency TCP Performance Mobility management Security & privacy Routing protocols Multicasting QoS Service Location, Provision, Access

Routing Protocols Expected Properties of Ad-hoc Routing Protocols A taxonomy for routing protocols in Mobile ad hoc networks Reactive or On-demand routing protocols Proactive or Table-driven Hybrid Hierarchical Geographical

Expected Properties of Routing Ideally an ad hoc network routing protocol should be distributed in order to increase reliability assume routes as unidirectional links be power efficient. consider its security be hybrid protocols be aware of Quality of Service

Taxonomy Communication model Structure State information Scheduling Multi-channel: Channel assignment using low-layer info Single channel model Structure Are all nodes treated uniformly? How are distinguished nodes selected (neighbors or cluster-based)? State information Is network-scale topology obtained at each node? Scheduling Is route information continually maintained for each destination (proactive or reactive)?

DSDV 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 periodically if a significant change has occurred in its table from the last update sent The routing table updates can be sent in two ways full dump incremental update

Put figure with same illustration of DSR

AODV 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

TORA 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

DSR 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 the address of the source the destination a unique identification number route reply is generated by an intermediate node with current information about the destination route maintenance Route error packets are generated at a node when the data link layer encounters a fatal transmission problem Acknowledgements, including passive acknowledgments

OLSR 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

ZRP 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

Outlines Introduction Routing Protocol What is Ad hoc networks? Characteristic Ad hoc vs. cellular networks Application Challenges 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)