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Mobile Computing CS4830

Mobile Computing CS4830

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Mobile Computing CS4830

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  1. Mobile Computing CS4830 Emerging Wireless Networks Mr. Abdul Haseeb Khan

  2. Outlines • Power line Networks • UWB • WSN • Flash OFDM • MANETS • Ad hoc vs. cellular networks • MANETS Applications • MANETS Challenges • Routing Protocol • Expected Properties of Ad-hoc Routing Protocols • A taxonomy for routing protocols in Mobile ad • common protocols(DSDV, AODV, DSR, ZRP, TORA)

  3. Powerline Communication Networks

  4. UWB

  5. UWB

  6. Comparison of UWB with other WLANs

  7. Wireless Sensor Networks (Overview) • WSNs) typically consist of small, low-powered devices (sensors) • Sensors can be developed to measure temperature, humidity, motion, color changes in a painting, or any other measurable thing. • Most WSNs consist of millions of tiny processors communicating over slow wireless networks, • WSNs may consist of devices with a wide range of computation, communication, and sensing capabilities. • The WSNs may use Bluetooth or IEEE 802.11 networks

  8. Sensor Node (Mote)

  9. WSN Hierarchy

  10. WSN Design

  11. WSN Protocol Stack

  12. Flash OFDM Orthogonal frequency-division multiplexing • An all-IP Celular Network • Uses Mobile IP for handoffs • High data rates

  13. Flash OFDM Architecture Mobile Node A NSP POP Home Network for A 3 Foreign Agent NSP POP Foreign Network for A 4 2 Home Agent Managed IP Network 5 1 Media Gateway PSTN Cell 1 IP Router Cell 2 Radio Router Radio Router

  14. B A A B Mobile Ad Hoc Networks • Host movement frequent • Topology change frequent • No cellular infrastructure. Multi-hop wireless links. • Data must be routed via intermediate nodes. • May need to traverse multiple links to reach destination Source: Vaidya

  15. Mobile distributed multi-hop wireless network (MANET) • A group of mobile, wireless nodes which cooperatively and spontaneously form a network independent of any fixed infrastructure or centralized administration • A node communicates • directly with nodes within wireless range • indirectly with all other destinations using a dynamically determined multi-hop route though other nodes in the MANET.

  16. MANET PSTN Access Point Cellular Network MANET Connection

  17. MANETs PC H G PC F I Piconet2 (Cubicle2) PC printer Ear Phone C Cellular Phone PC E D printer Piconet1 (Cubicle 1) A B PC Piconet3 (Cubicle3)

  18. MANET Configuration B A Router C D E Internet

  19. MANETs characteristics • Heterogeneous nodes • Do not need backbone infrastructure support • Self-creating • not rely on a pre-existing fixed infrastructure • Self-organizing • no predetermined topology • Self-administering • no central control • creating a network “on the fly” • Are easy to deploy • Useful when infrastructure is absent, destroyed or impractical • Infrastructure may not be present in a disaster area or war zone • because there is no dependence on infrastructure, the network is robust and low-cost. • Finally, MANETs form the basis of all pervasive and ubiquitous computing.

  20. MANETs Applications • Military environments • Soldiers, tanks, planes • Emergency operations • Search-and-rescue • Policing and fire fighting • Civilian environments • Taxi cab network • Meeting rooms • Sports stadiums

  21. Ad hoc networks & Cellular networks • Ad hoc networks • Infrastructure less • Multiple hop • Radio power limitation, channel utilization, and power-saving concerns • DCF(distributed coordination function) • Cellular networks • Infrastructure-based • one hop(uplink or downlink) • PCF(pointed coordination function)

  22. MANETs Challenges • Spectrum allocation • Self-configuration • Medium access control (MAC) • Energy efficiency • TCP Performance • Mobility management • Security & privacy • Routing protocols • Multicasting • QoS • Service Location, Provision, Access

  23. Routing in MANET • In general, MANET routing protocols are expected to satisfy the following essential principles: • Tolerance of unexpected network faults (e.g. device and link failures) • Flexibility to increasing traffic loads • Minimal energy consumption (especially for smaller clients) • Mobile IP needs infrastructure • Home Agent/Foreign Agent in the fixed network • DNS, routing etc. are not designed for mobility • MANET • No default router available • “every” node also needs to be a router

  24. Properties of good routing protocol in MANET • Must be distributed • Adaptive to frequent topology changes • Must be localized, since global state maintenance involves a huge state propagation control overhead • Loop free and free from stale routes • Convergence should be quick

  25. Issues in Routing in MANET • Mobility • Topology highly dynamic due to movement of nodes • Ongoing sessions suffer frequent path breaks • Even though wired network protocol find alternate paths when a path breaks, the convergence is slow • Bandwidth constraint • Limited bandwidth imposes constraint on routing protocols to maintain topological information • Due to frequent changes in topology the control overhead of keeping the topology current could be very high

  26. MANET routing protocols • Proactive or Table-driven protocols • Traditional distributed shortest-path protocols • Example: DSDV (destination sequenced distance vector) • Reactive or On-demand routing protocols • Determine route if and when needed • Example: DSR (dynamic source routing) • Hybrid protocols • Adaptive; Combination of proactive and reactive • Example : ZRP (zone routing protocol) • Hierarchical • Geographical

  27. Expected Properties of Routing • Ideally an ad hoc network routing protocol should • be distributed in order to increase reliability • assume routes as unidirectional links • be power efficient. • consider its security • be hybrid protocols • be aware of Quality of Service

  28. Proactive routing protocols-DSDV • Is based on the idea of Bellman-Ford routing algorithm • Every mobile station maintains a routing table that lists • all available destinations • the number of hops to reach the destination • the sequence number assigned by the destination node • A station transmits its routing table • periodically • if a significant change has occurred in its table from the last update sent • The routing table updates can be sent in two ways • full dump • incremental update

  29. Example DSDV MH3 MH5 MH4 MH8 MH2 MH6 MH7 MH1 MH1

  30. Example DSDV Routing table at MH4

  31. Example DSDV Advertisement from MH4

  32. Example DSDV Routing table at MH4 (after MH1 moves)

  33. Example DSDV Advertisement from MH4 (after MH1 moves)

  34. DSDV: Advantages & Disadvantages • Advantages • Routes available to all destinations • Less latency in route set up • Disadvantages • Updates are propagated throughout the network • Updates due to broken link (due to mobility) can lead to heavy control traffic • Even a small network with high mobility or large network with low mobility can choke the network • In order to get information about a particular destination node, a node has to wait for a table update message initiated by the same destination node • This delay would result in stale routing information

  35. Reactive routing protocols- DSR • Reactive routing protocols are intended to maintain routing information about ‘active’ routes only. Routes are created when desired by the source node. Hence, the protocols are known as on-demand routing protocols. • However, no periodic routing advertisement messages are sent, thereby reducing network bandwidth overhead, particularly during periods when little or no significant host movement is taking place.

  36. DSR • A node maintains route caches containing the source routes that it is aware of • The node updates entries in the route cache as and when it learns about new routes • route discovery • route request packet contains • the address of the source • the destination • a unique identification number • route reply is generated by • the destination • an intermediate node with current information about the destination • route maintenance • Route error packets are generated at a node when the data link layer encounters a fatal transmission problem • Acknowledgements, including passive acknowledgments

  37. Dynamic Source Routing (DSR) • Source S initiates a route discovery by flooding Route Request (RREQ) • Each node appends its own identifier when forwarding RREQ • Destination D on receiving the first RREQ, sends a Route Reply (RREP) • RREP sent on route obtained by reversing the route appended in RREQ • RREPincludes the route from S to D, on which RREQ was received by D • S routes data using “source route” mechanism

  38. Dynamic Source Routing (DSR) • Routing Discovery Example: A H I B C J Destination G Source D E F K

  39. Dynamic Source Routing (DSR)

  40. Route Discovery in DSR Y Z S E F B C M L J A G H D K I N Represents a node that has received RREQ for D from S Source: Vaidya

  41. Route Discovery in DSR Y Broadcast transmission Z [S] S E F B C M L J A G H D K I N Represents transmission of RREQ [X,Y] Represents list of identifiers appended to RREQ

  42. Route Discovery in DSR Y Z S [S,E] E F B C M L J A G [S,C] H D K I N • Node H receives packet RREQ from two neighbors: • potential for collision

  43. Route Discovery in DSR Y Z S E F [S,E,F] B C M L J A G H D K [S,C,G] I N • Node C receives RREQ from G and H, but does not forward • it again, because node C has already forwarded RREQ once

  44. Route Discovery in DSR Y Z S E F [S,E,F,J] B C M L J A G H D K I N [S,C,G,K] • Nodes J and K both broadcast RREQ to node D • Since nodes J and K are hidden from each other, their • transmissions may collide

  45. Route Discovery in DSR Y Z S E [S,E,F,J,M] F B C M L J A G H D K I N • Node D does not forward RREQ, because node D • is the intended targetof the route discovery

  46. Route Reply in DSR Y Z S RREP [S,E,F,J,D] E F B C M L J A G H D K I N Represents RREP control message

  47. Data Delivery in DSR Y Z DATA [S,E,F,J,D] S E F B C M L J A G H D K I N Packet header size grows with route length

  48. Route Error (RERR) Y Z RERR [J-D] S E F B C M L J A G H D K I N J sends a route error to S along route J-F-E-S when its attempt to forward the data packet S (with route SEFJD) on J-D fails (an ACK mechanism has to be there in packet forwarding)

  49. Route caching • Uses: • Finding alternate routes in case original route breaks • Route reply from intermediate nodes • Problems: • Cached routes may become invalid over time and due to host mobility • Stale caches can adversely affect performance

  50. DSR: Route caching • Each node caches a new route it learns by any means • When node S finds route [S,E,F,J,D] to node D, node S also learns route [S,E,F] to node F • When node K receives Route Request [S,C,G] destined for node, node K learns route [K,G,C,S] to node S