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Research Topics Mirela Damian

Research Topics Mirela Damian. Wireless Networks. How do they work?. Access Points (APs) are connected to a wired network. Access Points enable wireless networking. Hybrid Networks. Include Ad-Hoc Networks. Mobile Ad-Hoc Networks (MANET). Characteristics Limited transmission range

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Research Topics Mirela Damian

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  1. Research TopicsMirela Damian Mirela Damian 1

  2. Wireless Networks Mirela Damian 2

  3. How do they work? • Access Points (APs) are connected to a wired network. • Access Points enable wireless networking. Mirela Damian 3

  4. Hybrid Networks • Include Ad-Hoc Networks Mirela Damian 4

  5. Mobile Ad-Hoc Networks (MANET) • Characteristics • Limited transmission range • Operate on battery • Limited memory • Zero configuration • No fixed infrastructure • Easy to construct • Frequent changes in topology Transmission Range Mirela Damian 5

  6. Ad-Hoc Networks • Challenges • Broadcast nature of the wireless medium. • Packet losses due to transmission errors. • Mobility-induced route changes. • Mobility-induced packet losses. • Battery constraints. Mirela Damian 6

  7. Research Area: Topology Control Mirela Damian 7

  8. Example of Topology Control Topology Control Topology Control: minimizing the overall power consumption while maintaining network connectivity. Mirela Damian 8

  9. Topology Control Problem • Given • A collection of nodes on the plane • A collection of transmission links • Determine a topology that is: • Connected • Low-degree • reduced battery consumption at each node • Lightweight • it has energy-efficient paths • A spanner: • p(u→v) in the topology close to p(u→v) in the transmission graph • Adaptable: • maintain the above properties efficiently when nodes move Mirela Damian 9

  10. Approach 1: RNG • Relative Neighborhood Graph • Edge (u, v) exists if the intersection of the disks centered at u and v is free of other nodes. Mirela Damian 10

  11. Relative Neighborhood Graph u u v v u v v u Mirela Damian 11

  12. Relative Neighborhood Graph u v • Properties • Planar • Long paths • Stretch factor Θ(n) Mirela Damian 12

  13. Approach 2: GG • Gabriel Graph • Edge (u,v) exists iff disk(u,v) is free of other nodes Mirela Damian 13

  14. Gabriel Graph Mirela Damian 14

  15. Gabriel Graph Mirela Damian 15

  16. Gabriel Graph Gabriel Relative Neighborhood Mirela Damian 16

  17. Gabriel Graph Gabriel Relative Neighborhood u u v v Planar Long paths Mirela Damian 17

  18. Approach 3: Delaunay Triangulation • Triangle Duvw exists iff disk(u,v,w) is empty. Mirela Damian 18

  19. Approach 3: Delaunay Triangulation Mirela Damian 19

  20. Approach 3: Delaunay Triangulation Mirela Damian 20

  21. Approach 3: Delaunay Triangulation Mirela Damian 21

  22. Approach 3: Delaunay Triangulation Mirela Damian 22

  23. Approach 3: Delaunay Triangulation Delete edges longer than the transmission range. Mirela Damian 23

  24. Approach 3: Delaunay Triangulation • Spanner • Planar Mirela Damian 24

  25. Approach 3: YG • Yao Graph [Yao 82] • Divide the plane around u into sectors of angle q ≤ p / 3 • Connect u to the nearest neighbor in each sector u Mirela Damian 25

  26. Yao Graph u Mirela Damian 26

  27. Yao Graph • Properties • High degree u Mirela Damian 27

  28. Approach 4: Greedy Order edges. Add (u, v) if no short path from u to v exists. Mirela Damian 28

  29. Greedy Graph • Spanner • Constant degree at each node • Lightweight Mirela Damian 29

  30. Dynamic Topologies Mirela Damian 30

  31. Challenges • Self-construction • Self-maintenance • Scalability • Reliability • Resource efficiency – energy, storage • Fault-/disaster-tolerance • Tolerate simultaneous node/link failures • Fast reconfiguration on detection of faults Mirela Damian 31

  32. Topic Ideas • Topology Control Approaches: • Relative Neighborhood Graph (RNG) • Gabriel Graph (GG) • Delaunay Triangulation (DT) DT > GG > RNG • Yao-Graph • Greedy • Beta-Skeleton • Cone-Based Graph (dynamic version of Yao graph) • XTC: Lightweight Topology Control Mirela Damian 32

  33. Research Area: Wireless Routing Mirela Damian 33

  34. What is Routing? • Finding a best path from source to target. Mirela Damian 34

  35. Routing in MANET Ad hoc Routing Protocol On-Demand / Reactive Hybrid Table-Driven / Proactive ZRP ABRTORAAODVDSRCBRDRDMAR DSDVCGSRWRDSTAR Mirela Damian 35

  36. Topic Ideas • Routing Strategies: • Static vs. Mobile • Flooding-based routing • Reactive vs. Proactive • Source routing vs. Table-driven routing • Flat vs. Hierarchical routing • Non-location based vs. Location based routing • Routing Vulnerabilities Mirela Damian 36

  37. Research Area: Wireless Security Mirela Damian 37

  38. Wired vs. Wireless • Wired networks offer more and better security options than wireless • More thoroughly established standards with wired networks • Easier to implement security policies on wired networks • Wired networks less susceptible to hackers/crackers. • Hacking • Gaining unauthorized access to networks/devices • Cracking • Extending the use of devices past original intentions Mirela Damian 38

  39. Security in MANET • Goals: • Availability -defend against DoS attacks • Confidentiality –block access to private info. • Integrity –keep on-route messages uncorrupted • Authentication -ensure the identity of the peer • Non-repudiation –ensure that the sender cannot deny having sent the message Mirela Damian 39

  40. Topic Ideas (1) • Survey of Wireless Attacks: • Packet sniffingor eavesdropping • Resource stealing –using a valid user’s MAC addr. • Traffic redirection –modifying ARP tables • Denial of service • Man in the middle • Weak key attacks(WEP broken in less than 2 hrs.) • Dictionary attacks • Birtday attacks • Realtime decryption? Mirela Damian 40

  41. Topic Ideas (2) • Security Solutions: • Use of inherent redundancies in ad-hoc networks (multiple, possibly disjoint, routes between nodes) • Diversity coding(transmit redundant information through additional routes for error detection and correction) • Public Key Infrastructure (PKI) • Temporal Key Integrity Protocol(TKIP) Mirela Damian 41

  42. Topic Ideas (3) • Security Solutions: • Strong Encryption(SHA-1) • Cryptographic schemes (digital signatures) • WEP Security (or lack of security) • The 802.11i IEEE security standard Mirela Damian 42

  43. Research Area:Channel Assignment Mirela Damian 43

  44. What is interference? • If two or more neighbors of a node b transmit at the same time (RTS, for instance), b will be unable to receive any of those messages; we say that b experiences collision; interference occurs at b. • Solution: Have a and c use different frequency channels (different colors). Mirela Damian 44

  45. Interference I • Where does interference occur? • What messages should be retransmitted? Mirela Damian 45

  46. Interference II • Where does interference occur? • What message(s) must be retransmitted? Mirela Damian 46

  47. Interference III • Where does interference occur? • What message(s) must be retransmitted? Mirela Damian 47

  48. Topic Ideas • Survey existing interference measures and their shortcomings. • Approaches to reducing interference: • Channel assignment. • Topology control with power adjustment. Mirela Damian 48

  49. Research Area:Folding and Unfolding Mirela Damian 49

  50. Unfolding Polyhedra Mirela Damian 50

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