1. 1 Mobile ad hoc networking: imperatives and challenges Imrich Chlamtac, Marco Conti, Jennifer J.N. Liu 2005. 10. 10. MMLAB, Seongil Han sihan@mmlab.snu.ac.kr

2. -2- Contents Introduction Mobile ad hoc network research Medium Access Control Networking issues Applications and middleware Cross layers’ research issues Discussion and conclusions

3. -3- Introduction Mobile Ad hoc Network (MANET) Sensor network An important part of the 4G architecture Non infrastructure based Spontaneous networking Can be connected to a backbone network Attractive technology

4. -4- MANET issues Traditional problems of wireless network Channel characteristics Hidden and exposed terminal MANET specifics Autonomous and infrastructure-less Multi-hop routing Dynamically changing network topology Variation in link and node capabilities Energy constrained operation Network scalability

5. -5- Research area 3 layers and cross layers issues

6. -6- Medium Access Control Bluetooth De-facto standard For low-cost, short-range radio links Contention-free token-based multi-access Masters and slaves Many applications is developed and being developed. Mobile phone, headset, etc. The scatternet Multi-hop Bluetooth networks, interconnecting several piconets Various formation algorithm

7. -7- Medium Access Control (cont.) IEEE 802.11 Infrastructure-based and infrastructure-less Little or no attention was given to Ad hoc mode With TCP, problems get large HiperLAN ETSI has promoted “High Performance Radio Local Area Network” HiperLAN/2 is noticeable

8. -8- MAC research issues Random access Used by most proposal Collision avoidance and utilization maximization Hidden-terminal and exposed-terminal problem Controlled access More suitable for QoS Handling dynamic change of topology TDMA Time Spread Multiple Access (TSMA)

9. -9- Networking Considerations Self-organizing, dynamic, energy-constrained Location service Reactive and proactive Routing and forwarding algorithms Unicast, geocast, multicast, broadcast Redesign of Transport layer mechanisms Mainly TCP issues

10. -10- Routing Unicast Proactive routing protocols Table-driven, periodic and event-driven updates DSDV, CGSR, WRP, OLSR, TBRPF, FSR Reactive routing protocols On demand, route discovery DSR, AODV, TORA, ABR, SSR, ZRP Multicast Tree based : AMRoute, MAODV, AMRIS Mesh based : CAMP, ODMRP

11. -11- Routing (cont.) Location aware routing Greedy forwarding, directed flooding, hierarchical routing Clustering Clusterhead Inter-cluster, intra-cluster communication Cluster bottleneck problem

12. -12- TCP issues Impact of mobility Route failure Packet loss and increased delay Exacerbate unfairness Nodes’ interaction at MAC Impact of TCP congestion window size Small congestion windows is good New mechanisms Explicit Link Failure Notification (ELFN) Ad hoc TCP (ATCP) Link RED

13. -13- Applications and middleware Applications Tactical, sensor, emergency service, commercial environment, home and enterprie networking, educational application, entertainment, location aware services Middleware Provide service abstraction Efficiency is open issue Service discovery and location QoS-Aware resource discovery

14. -14- Cross layers’ research issues Energy conservation Local strategy : power saving mode Global strategy : maximize the network lifetime Security Attacks and protections Cooperation Simulation and performance evaluation Quality of Service

15. -15- Security Attacks Passive attacks Eavesdropping Active attacks Impersonation, Denial of Service, Disclosure attack Security mechanism Preventive and detective Key-based, Intrusion detection Wired Equivalent Privacy Secure routing Wormhole attack

16. -16- Discussion and conclusions The center of evolution Toward 4G wireless technology Flexibility, easy maintenance, infrastructure-less, auto-configuration, self-administration capability, cost advantage IETF MANET WG “killer application(s)” has yet emerged. Many open research issues