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Computer Networks: Wireless Networks

Computer Networks: Wireless Networks. Ivan Marsic Rutgers University. Chapter 6 – Wireless Networks. Wireless Networks. Chapter 6. Topic : Mobile Ad-hoc Networks (MANETs).  Ad-hoc Network Definition Routing Protocols Dynamic Source Routing (DSR) Ad Hoc On-Demand Distance-Vector (AODV).

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Computer Networks: Wireless Networks

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  1. Computer Networks:Wireless Networks Ivan Marsic Rutgers University Chapter 6 – Wireless Networks

  2. Wireless Networks Chapter 6

  3. Topic:Mobile Ad-hoc Networks (MANETs)  Ad-hoc Network Definition Routing Protocols Dynamic Source Routing (DSR) Ad Hoc On-Demand Distance-Vector (AODV)

  4. Ad-hoc Networks Each mobile device (node) can act as a router Links form and break based on mobility and environmental factors Connectivity (e.g., high probability of instantaneous end-to-end paths existing) is assumed

  5. Mobile Ad-hoc Networks (MANETs) Physical wireless links Network topology

  6. Network Layer Notation vs.Link Layer Transmissions (1)

  7. Network Layer Notation vs.Link Layer Transmissions (2)

  8. Multihop Throughput Challenge: more hops, less throughput Links in route share radio spectrum Extra hops reduce throughput Throughput = 1 Throughput = 1/2 Throughput = 1/3

  9. Ad-hoc Networks S D • Goal: Nodes within the network can send data between themselves. • Challenges: • No centralized coordinator to help routing • No “default route” for nodes within the network • Fast topology changes • Limited bandwidth – can’t have too much overhead

  10. Ad-hoc Networks S D Control Plane Data Plane • Nodes that want to route messages must: • Find out about the topology of the network • Use that topology to do something with the message

  11. Routing Protocol Categories Control Plane • Proactive: • Nodes actively maintain and share topology information, regardless of if there is data to send • Generally timer- or event-based • Reactive (On-demand): • “Lazy” approach: Don’t do more work then you have to • Only discover topology/routes when there is data to send

  12. Routing Protocol Categories Data Plane S A B D A B D • Local next-hop forwarding: • Consult forwarding table for a next hop • Completely local decision • Source routing: • Source node places complete path in packet header • Intermediate nodes don’t have to consult their forwarding tables

  13. Reactive Protocols Dynamic Source Routing (DSR) MANET Source Routing Ad-hoc On-demand Distance Vector (AODV) Reactive Next-hop Forwarding MANET Distance Vector Names are useful hints at understanding the protocol properties:

  14. Dynamic Source Routing (DSR) When node S wants to send a packet to node D, but does not know a route to D, node S initiates a route discovery. Source node S floods the network with route request (RREQ) packets (also called query packets). Each node appends its own address in the packet header when forwarding RREQ. 14

  15. Route Discovery in DSR (1)

  16. Route Discovery in DSR (2) Broadcast RREQ[C] Represents a node that has received RREQ for H from C

  17. Route Discovery in DSR (3)

  18. Route Discovery in DSR (4)

  19. Route Discovery in DSR (5) Unicast RREP[C, E, G, H]

  20. Route Discovery in DSR

  21. Route Discovery in AODV (1)

  22. Route Discovery in AODV

  23. Topic:IEEE 802.11n (MIMO Wi-Fi)  Physical (PHY) Layer Enhancements MAC Layer Enhancements: Frame Aggregation Block Acknowledgement Reverse Direction (RD) Protocol  Backward Compatibility

  24. IEEE 802.11n - MIMO

  25. 802.11n Channel Bonding and20/40 MHz Operation

  26. 802.11n PHY-layer Frame Format

  27. IEEE 802.11 Terminology

  28. 802.11n MAC-layer Frame Format

  29. Packet Aggregation

  30. 802.11n Frame Aggregation E{b0}=16 slots

  31. Frame Aggregation:A-MSDU and A-MPDU

  32. Block Acknowledgement Session

  33. Block Acknowledgement Frame

  34. Block ACK Frame Subfields

  35. Block ACK Example

  36. Reverse Direction (RD) Protocol Unidirectional vs. Bidirectional RTS/CTS Access Scheme

  37. 802.11n Backwards Compatibility Modes: CTS-to-Self

  38. Dual-CTS protection (CTS-to-self)

  39. Example of L-SIG Duration Setting

  40. 802.11n Phased Coexistence Operation (PCO)

  41. Topic:RFID: Radio-Frequency Identification  Query Slot Protocol (ALOHA) for Tag Interrogation

  42. Visit http://www.gs1.org/epcglobal/standards for RFID Protocols Class-1 Generation-2 RFID - Query Slot Protocol

  43. Classification of QoS Techniques in 802.11

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