Mobile Ad Hoc Networks

1. Mobile Ad Hoc Networks Myungchul Kim mckim@icu.ac.kr

2. From Handbook of Wireless Networks and Mobile Computing, edited by Ivan Stojmenovic. 2002 John Wiley & Sons. • Introduction • Ad hoc networks : no infrastructure = without any central control • Applications: • The multihop nature and the lack of fixed infrastructure -> new research problems such as configuration advertising, discovery, maintenance, addressing and self-routing. • The characteristics of mobile ad hoc networks • The topology is highly dynamic • Lower capacity due to wireless links • Physical security • Higher loss rate, delay and jitter • Energy saving

3. Layered architecture of mobile ad hoc networks • Cellular systems: single-hop wireless systems • Radio spectrum • Power consumption: circuit, architecture and software • MAC layer of IEEE 802.11: all the nodes must use the same channel • The existing standard of IEEE 802.11 does not support multihop systems. • MANET in IETF: routing in ad hoc networks scaling up to hundreds of routers • Location management • Zeroconf working group • Security • QoS for multimedia data • Location-area application • Sensor networks

4. MAC layer • Wireless personal area networks (WPAN): a radius of 10 meters • Multiple access networks • Random access: IEEE 802.11 • Demand assignment: Bluetooth, QoS • IEEE 802.11 • Physical and MAC layer • Physical layers: infrared, frequency hopping and direct sequence spread spectrum • CSMA/CA • Neighboring cells can use different frequencies to avoid interference and increase the cell’s capacity • 802.11 ad hoc link • Power saving policy

5. Bluetooth • The physical layer utilizes frequency hopping spread spectrum • 1Mb/s • Contention-free, token-based multiple access network • A master and slaves • Synchronous connection-oriented (SCO) link and asynchronous connectionless (ACL) link • Piconet: two or more devices sharing the same frequency • Scatternet: piconets overlap • Can support one asyn. Data link between two devices, up to three simultaneous syn. voice links. • A max asym data rate of 723.2kb/s (and up to 57.6 kb/s in the return direction) or a sym data rate of 433.9 kb/s

6. Mobile ad hoc networks and the internet • Mobile ad hoc network’s characteristics • Dynamic topologies • Bandwidth-constrained and variable capacity links • Energy-constrained operation • Limited physical security • Desirable qualitative properties of mobile ad hoc network routing protocols • Distributed operation • Loop-freedom • Demand-based operation • Proactive operation • Security • “sleep” period operation • Unidirectional link support

7. Quantitative metrics • End-to-end data throughput and delay • Route acquisition time • Percentage out-of-order delivery • Efficiency • Proactive protocols ( table-driven protocols) • Control overhead in terms of both traffic and power consumption • Reactive protocols • Latency period due to the route discovery procedure • The on-demand design is based (1) on the observation that in a dynamic topology routes expire frequently and (2) on the assumption that not all the routes are used at the same time. • New addressing approach • The existing location-based routing protocols propose to use location information for reducing the propagation of control messages.

8. Scalability: clustering with clusterheads and border nodes • Multicast routing: allow optimization of resource usage • Mobile ad hoc networks do not provide QoS by design • QoS provisioning • Routing in self-organized networks • Large mobile ad hoc networks (larger than a thousand nodes and/or constituting a wide or geographical network with limited resources): business model of citizen band, amateur radio and walkie-talkie systems, in which multihop wireless comm allow voice and data messaging among all users. • These networks are likely to be very large and not Internet-based. • Self-organization • Nonauthority-based networks • Very large and not regularly distributed • Highly cooperative

9. Six degrees of separation: Entire human population has a diameter of six or less edges. • Routing solution design • Scalability • Dynamic changing network connectivity • High collaboration among nodes • For a potentially large network, both traditional proactive and reactive approaches are not feasible. • People-based networks • PDA • Mobile ad hoc network with no central administration • Self-organizing and fairly robust • The users have, simultaneously, their traditional role and “network” role. • User/application-oriented approach

10. Minimize the inexpert user’s exposure to the administrative infrastructure and make necessary activities as intuitive as possible