Ad Hoc Networks: Overview

1. Ad Hoc Networks: Overview

2. Textbook • C. Siva Ram Murthy and B. S. Manoj, Ad Hoc Wireless Networks: Architectures and Protocols, Prentice Hall PTR, 2004. • References • Carlos de Morais Cordeiro and Dharma Prakash Agrawal, Ad Hoc & Sensor Networks: Theory and Applications, World Scientific Publishing Co., 2006. • Feng Zhao and Leonidas Guibas, Wireless Sensor Networks: An Information Processing Approach, Elsevier, 2004. • Edgar H. Callaway, Jr., Wireless Sensor Netwoks: Architectures and Protocols, Auerbach, 2004.

3. Related Sites • Advanced Network Technologies Division, NIST, • Wireless Ad Hoc Networks, http://w3.antd.nist.gov/wahn_home.shtml • Autonomous Networks Research Group, USC • WSN bibliography, http://ceng.usc.edu/~anrg/SensorNetBib.html • IETF MANET WG • http://www.ietf.org/html.charters/manet-charter.html • IEEE 802 WG • http://grouper.ieee.org/groups/802/dots.html • Zigbee • http://www.zigbee.org • TinyOS • http://www.tinyos.net/

4. Wireless Network Technology

5. Internet WLAN Cellular [Mobile/Wireless] Ad Hoc Networks Wireless Networks • Wireless Networks • Infrastructured Network • Cellular Network (3GPP or 3GPP2) • Wireless LAN (IEEE 802.11) • Infrastructureless Network • Ad Hoc Network

6. Ad Hoc Networks vs. … • Ad hoc networks vs. Wireless mobile networks • Infrastructureless vs. Infrastructured Network • All devices of an ad hoc network are likely to have similar constraints • Ad hoc networks vs. Peer-to-peer networks • P2P devices use existing networked structures such as Internet • All P2P networks are not ad hoc network • Because NOT all ad hoc network utilize an existing structure for the communication among devices • Ad hoc computing vs. Pervasive computing • The devices for pervasive computing are usually very small and can be embedded in any type of objects • Users are sometimes not even aware of the existence of the embedded electronic chips

7. Ad hoc networks (1) • Temporary network composed of mobile nodes without preexisting communication infrastructure, such as Access Point (AP) and Base Station (BS). • Each node plays the role of router for multi-hop routing. • Self-organizing network without infrastructure networks • Started from DARPA PRNet in 1970 • Cooperative nodes (wireless) • Each node decode-and-forward packets for other nodes • Multi-hop packet forwarding through wireless links • Proactive/reactive/hybrid routing protocols • Most works based on CSMA/CA to solve the interference problem • IEEE 802.11 MAC

8. A F C D B E Ad hoc networks (2) • But, there is no links • Nodes simply radiate energy • Nodes can be cooperative in many other ways (complex) • Amplify and forward • interference cancellation to increase SINR • There may be many things out there that we can take advantage of across layers for improvement!

9. Ad Hoc Network (3) •  The application areas, the security requirements and the • constraints of the single devices differ …

10. Cellular Net vs. Ad Hoc Net (1)

11. Cellular Net vs. Ad Hoc Net (2)

12. Major Applications Demands for group communications • Military • Emergency Service • Collaborative and Distributed Computing • Wireless Mesh Network • Wireless Sensor Network • Telematics • Wireless Personal Area Network • Home Network • Ad Hoc Relay for Cellular Network • Networks for ubiquitous computing

13. Military

14. Emergency Service

15. MANET No infrastructure Self organizing networks Communications via mobile nodes Dynamic topology Heterogeneity bandwidth-constrained variable-capacity links Limited physical security Nodes with limited battery life and storage capabilities Issues in MANET Ad Hoc Unicast Routing Ad Hoc Multicast/Broadcast Routing Power Saving Global Connectivity for MANET Addressing & DNS Service Automatic Support of Networking in MANET MANET Autoconfiguration MANET – Research Target

16. Wireless Mesh Networks • Mesh network implemented over WLAN • Industrial standards Activities • IEEE 802.11, IEEE 802.15, IEEE 801.16 have established sub-working groups to focus on new standards for WMNs

17. WMN Architecture • WMNs (Wireless Mesh Networks) consist of: mesh routers and mesh clients • Mesh routers • Conventional wireless AP (Access Point) functions • Additional mesh routing functions to support multi-hop communications • Usually multiple wireless interfaces built on either the same or different radio technologies • Mesh clients • Can also work as a router for client WMN • Usually one wireless interface • Classification of WMN architecture • Infrastructure/Backbone WMNs • Client WMNs • Hybrid WMNs

18. Infrastructure/backbone WMNs

19. Client WMNs

20. Hybrid WMNs

21. Sink Sink Sensor Network Model Stimulus Source

22. Ad Hoc Net Wireless Sensor Network Wireless Sensor Networks • A sort of ad-hoc networks • A network of low cost,densely deployed,untethered sensor nodes • Application areas:heath, military, and home • Placed in inaccessible terrains or disaster areas • It may be impossible to recharge batteries • Different Node Characteristics from Traditional nodes • # of nodes in a sensor network can be several orders of magnitude higher than the nodes in an Ad Hoc network (100s to 1000s nodes) • Densely deployed (20 nodes/m3) • Prone to failures • Topology changes very frequently • Mainly use a broadcast communication, whereas most Ad Hoc networks are based on point-to-point • Limited in power, computing capacities, and memory • May not have global ID because of the large amount of overhead and large number of sensors

23. Existing Wireless Net vs. Sensor Net

24. Sensor Networks Architecture • Sensor node • Made up of four basic components • Sensing unit, Processing unit, Transceiver unit, and Power unit • Additional application-dependent components • Location finding system, power generator, and mobilizer • Scattered in a sensor field • Collect data and route data back to the sink • Sink • Communicate with the task manager node (user) via Internet or satellite

25. Challenges in Ad Hoc Networks • Limited wireless transmission range • Broadcast nature of the wireless medium • Packet losses due to transmission errors • Mobility-induced route changes • Mobility-induced packet losses • Battery constraints • Potentially frequent network partitions • Ease of snooping on wireless transmissions (security hazard)

26. Issues in Ad Hoc Networks • Medium access scheme • Routing • Multicasting • Transport layer protocol • Pricing shceme • QoS provisioning • Security • Energy management • Addressing and service discovery • Scalability • Deployment considerations

27. Medium Access Scheme • Distributed operation • Synchronization • Hidden terminal problem • Exposed terminal problem • Throughput • Access delay • Fairness: especially for relaying nodes • Real-time traffic support • Resource reservation • Ability to measure resource availability • Capability for power control • Adaptive rate control • Use of directional antennas

28. Routing (1) • Challenges • Mobility • results in path breaks, packet collisions, transient loops, stale routing information, and difficulty in resource reservation • BW constraints • Error-prone and shred channel • BER: 10-5 ~ 10-3 wireless vs. 10-12 ~ 10-9 wired • Location-dependent contention • Distribute load uniformly

29. Routing (2) • Requirements • Minimum route acquisition delay • Quick route reconfiguration • Loop-free routing • Distributed routing approach • Minimum control overhead • Scalability • QoS provisioning • Support for time-sensitive traffic • Security and privacy

30. Multicasting • Robusteness • recover and reconfigure quickly from potential mobility-induced link breaks • Efficiency • Min control overhead • QoS support • Efficient group management • Scalability • security

31. Transport Layer Protocols • UDP • No congestion control  congestion  increase contention  degrade throughput • TCP: major performance degradation due to • Frequent path break •  route reconfiguration  RTO  ReTx/CC  low throughput • Stale routing information • Increase out-of-order packets  dup ACKs  CC • High channel error rate • Loss of data/ACK  ACK is delayed  RTO  CC • Frequent network partition • All the packets dropped  RTO/multiple ReTx  increase RTO/CC

32. Security • DoS attack • Resource consumption • Energy depletion • Buffer overflow • Host impersonation • Information disclosure • Interference

33. Energy Management • Tx power mgmt • MAC: sleep mode • Routing: consider battery life time: load balancing • Transport: reduce ReTx • App • Battery energy mgmt • Extend battery life by taking adv of chemical properties, discharge patterns, and by the selection of a battery from a set of batteries • Processor power mgmt • Device power mgmt

34. Deployment Consideration (1) • Adv. in ad hoc net • Low cont of deployment • Incremental deplyment • Short deplyment time • Reconfigurablity • Scenario of deployment • Military deployment: data-centric or user-centric • Emergency operation deployment: hend-held, voice/data, < 100 nodes • Commercial wide-area deployment: e.g. WMN • Home network deplyment

35. Deployment Consideration (2) • Required longevity of network • Area of coverage • Service availability: redundancy • Operational integration with other infrastructure • Satellite network, UAV(unmanned aerial vehicles), GPS • Cellular network • Choice of protocols • TDMA or CSMA-based MAC? • Geographical routing (using GPS) • Power-saving routing ? • TCP extension ?