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

2. 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)

3. 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

4. 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

5. 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

6. 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”

7. 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)

8. 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

9. 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

10. 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

11. 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)?

13. 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

14. Put figure with same illustration of DSR

15. 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

17. 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

19. 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

21. 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

23. 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

24. 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

25. 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)