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 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 S D

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

11. Routing Protocol Categories 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 Control Plane

12. Routing Protocol Categories 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 Data Plane S S A A B B D D ABD

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

14. 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.

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 and 20/40 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{b 0 }=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. RFID - Query Slot Protocol Visit http://www.gs1.org/epcglobal/standards for RFID Protocols Class-1 Generation-2http://www.gs1.org/epcglobal/standards

44. Classification of QoS Techniques in 802.11