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Ad Hoc Wireless Networks: MANET

Ad Hoc Wireless Networks: MANET. Instructor: CUI Yong. Outline. Introduction Routing Protocol Overview Routing Protocol Design Reactive protocols DSR and Optimization AODV Proactive protocols OLSR DSDV Hybrid protocols ZRP, LANMAR Conclusion. Introduction to Ad hoc.

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Ad Hoc Wireless Networks: MANET

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  1. Ad Hoc Wireless Networks: MANET Instructor: CUI Yong CUI Yong

  2. Outline • Introduction • Routing Protocol Overview • Routing Protocol Design • Reactive protocols • DSR and Optimization • AODV • Proactive protocols • OLSR • DSDV • Hybrid protocols • ZRP, LANMAR • Conclusion CUI Yong

  3. Introduction to Ad hoc • Infrastructure-basedNetworks • PSTN • GSM • WLAN with AP • Infrastructureless Networks • Ad Hoc CUI Yong

  4. The differences Base-station example Ad Hoc example • A,C have a session • B retransmit • Protocol needed • MN only • Host and router • Multi-hop • BS+MN • Wireless between BS and MN • Wired between BS； CUI Yong

  5. Applications • Disaster recovery • Battlefield • Smart office • Gaps in cellular infrastructure • Etc. CUI Yong

  6. More Features • Wireless and mobile • Self-organizing • Dynamic topology • Resource limited • Fully distributed • Host and router • … CUI Yong

  7. Classes of Wireless Ad Hoc Networks • Three distinct classes • Mobile Ad Hoc Networks (MANET) • possibly highly mobile nodes • power constrained • Wireless Ad Hoc Sensor/Device Networks • relatively immobile • severely power constrained nodes • large scale • Wireless Ad Hoc Backbone Networks • rapidly deployable wireless infrastructure • largely immobile nodes • Common attributes • Ad hoc deployment, no infrastructure • Routes between S-D nodes may contain multiple hops CUI Yong

  8. Ad Hoc research • Application Layer • New applications • Transport Layer • congestion and flow control • Network Layer • Addressing and routing • Link Layer • Media access • Physical Layer • Bit error and interface CUI Yong

  9. Outline • Introduction • MANET Routing Overview and Background • MANET Routing Protocol Design • Reactive protocols • DSR and Optimization • AODV • Proactive protocols • OLSR • DSDV • Hybrid protocols • ZRP, LANMAR • Conclusion CUI Yong

  10. MANET Overview • Traverse multiple links to reach a destination CUI Yong

  11. MANET • Mobility causes route changes CUI Yong

  12. Unicast Routing in MANET • Host mobility • link failure/repair due to mobility may have different characteristics than those due to other causes • Instability • Rate of link failure/repair may be high when nodes move fast • New performance criteria needed • route stability despite mobility • energy consumption • Proposed protocols • Some have been invented specifically for MANET • Others are adapted from older protocols for wired networks • No single protocol works well • some attempts made to develop adaptive protocols CUI Yong

  13. Types of Protocols Advantage & Disadvantage? Internet router? • On-demand/reactive • the routes are determined when they are required by the source using a route discovery process; • Global/proactive • determine routes to all the destinations at the start up • maintain by using periodic route update process; • Hybrid • combine the basic properties of the first two classes of protocols into one. CUI Yong

  14. Trade-off • Latency of route discovery • Proactive protocols may have lower latency since routes are maintained at all times • Reactive protocols may have higher latency because a route from X to Y will be found only when X attempts to send to Y • Overhead of route discovery/maintenance • Reactive protocols may have lower overhead since routes are determined only if needed • Proactive protocols can (but not necessarily) result in higher overhead due to continuous route updating • Depend on the traffic and mobility patterns CUI Yong

  15. How to send msg to destination • Routing • Reactive • Proactive • No routing in advance? • Any simple solutions? CUI Yong

  16. Flooding for Data Delivery Y Sending a packet from S to D Z S E F B C M L J A G H D K I N Represents a node that has received packet P Represents that connected nodes are within each other’s transmission range CUI Yong

  17. Flooding for Data Delivery Y Broadcast transmission Z S E F B C M L J A G H D K I N Represents a node that receives packet P for the first time Represents transmission of packet P CUI Yong

  18. Flooding for Data Delivery Y Z S E F B C M L J A G H D K I N • Node H receives packet P from two neighbors: • potential for collision CUI Yong

  19. Flooding for Data Delivery Y Z S E F B C M L J A G H D K I N • Node C receives packet P from G and H, but does not forward • it again, because node C has already forwarded packet P once CUI Yong

  20. Flooding for Data Delivery Y Z S E F B C M L J A G H D K I N • Nodes J and K both broadcast packet P to node D • Since nodes J and K are hidden from each other, their • transmissions may collide • =>Packet P may not be delivered to node D at all, • despite the use of flooding CUI Yong

  21. Flooding for Data Delivery Y Z S E F B C M L J A G H D K I N • Node D does not forward packet P, because node D • is the intended destination of packet P CUI Yong

  22. Flooding for Data Delivery Y Z S E F B C M L J A G H D K I N • Flooding completed • Nodes unreachable from S do not receive packet P (e.g., node Z) • Nodes for which all paths from S go through the destination D • also do not receive packet P (example: node N) CUI Yong

  23. Flooding for Data Delivery Y Z S E F B C M L J A G H D K I N • Flooding may deliver packets to too many nodes • (in the worst case, all nodes reachable from sender • may receive the packet) CUI Yong

  24. Flooding for Data Delivery: Advantages/ Disadvantages • Simplicity • Higher reliability of data delivery • Because packets may be delivered to the destination on multiple paths • Potentially lower reliability of data delivery • Reliable broadcast (collision)? • Flooding uses broadcasting -- hard to implement reliable broadcast delivery without significantly increasing overhead CUI Yong

  25. Flooding for Data Delivery: Disadvantages • High overhead • Data packets may be delivered to too many nodes who do not need to receive them • Being efficient when … • Rate of information transmission is low enough • the overhead of explicit route discovery/maintenance is relatively higher • Example • nodes transmit small data packetsinfrequently • topology changesfrequently CUI Yong

  26. Outline • Introduction • Routing Protocol Overview • Routing Protocol Design • Reactive protocols • DSR and Optimization • AODV • Proactive protocols • OLSR • DSDV • Hybrid protocols • ZRP, LANMAR • Conclusion CUI Yong

  27. Flooding for Data Delivery • If we have continuous data to send, How to extend flooding to routing? • Append Node ID when flooding msg, Node D has path information, useful? Y • Who should store the path? • Find a path and store the path at source S, useful? • Store the path on the path or packet Z S E F B C M L J A G H D K I N CUI Yong

  28. Outline • Introduction • Routing Protocol Overview • Routing Protocol Design • Reactive protocols • DSR and Optimization • AODV • Proactive protocols • OLSR • DSDV • Hybrid protocols • ZRP, LANMAR • Conclusion CUI Yong

  29. Dynamic Source Routing (DSR) [Johnson96]@Mobile Computing • Three steps in DSR • Route Discovery • Data Delivery • Route maintenance • Route Discovery • 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 Route Request (RREQ) • Each node appends own identifier when forwarding RREQ CUI Yong

  30. 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 CUI Yong

  31. 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 CUI Yong

  32. 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 CUI Yong

  33. 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 CUI Yong

  34. 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 CUI Yong

  35. 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 CUI Yong

  36. Route Discovery in DSR • Route Reply • Destination D on receiving the first RREQ, sends a Route Reply (RREP) • RREP is sent on a route obtained by reversing the route appended to received RREQ • RREP includes the route from S to D on which RREQ was received by node D CUI Yong

  37. 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 How to do on unidirectional (asymmetric) links? Represents RREP control message CUI Yong

  38. Dynamic Source Routing (DSR) • Three steps in DSR • Route Discovery • Data Delivery • Route maintenance • Data delivery • Node S on receiving RREP, caches the route included in the RREP • When node S sends a data packet to D, the entire route is included in the packet header • hence the name source routing • Intermediate nodes use the source route included in a packet to determine to whom a packet should be forwarded CUI Yong

  39. Data Delivery in DSR Y • Any problem? • Packet header size grows with route length • Route failure may occur • Who should recover the failure? Z DATA [S,E,F,J,D] S E F B C M L J A G H D K I N CUI Yong

  40. Route Maintenance Y Route Error (RERR) 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 CUI Yong

  41. DSR Optimization: Route Caching Y • What can cache? • When should cache? Z DATA [S,E,F,J,D] S E F B C M L J A G H D K I N CUI Yong

  42. DSR Optimization: Route Caching • Each node caches a new route it learns by any means • When? • 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 • When node F forwards Route Reply RREP[S,E,F,J,D], node F learns route [F,J,D] to node D • When node E forwards Data [S,E,F,J,D] it learns route [E,F,J,D] to node D • A node may also learn a route when it overhears Data packets CUI Yong

  43. Use of Route Caching [S,E,F,J,D] [E,F,J,D] S E [F,J,D],[F,E,S] F B [J,F,E,S] C M L J A G [C,S] H D K [G,C,S] I N Z [X,X,X] Represents cached route at a node (DSR maintains the cached routes in a tree format) CUI Yong

  44. Use of Route Caching:Can Speed up Route Discovery [S,E,F,J,D] [E,F,J,D] S E [F,J,D],[F,E,S] F B [J,F,E,S] C M L [G,C,S] J A G [C,S] H D K [K,G,C,S] I N RREP RREQ Z When node Z sends a route request for node C, node K sends back a route reply [Z,K,G,C] to node Z using a locally cached route CUI Yong

  45. Use of Route Caching:Can Reduce Propagation of Route Requests Y [S,E,F,J,D] [E,F,J,D] Caching problem? Staleness! S E [F,J,D],[F,E,S] F B [J,F,E,S] C M L [G,C,S] J A G [C,S] H D K [K,G,C,S] I N RREP RREQ Z Assume that there is no link between D and Z. Route Reply (RREP) from node K limits flooding of RREQ. In general, the reduction may be less dramatic. CUI Yong

  46. Dynamic Source Routing • Advantages • Low overhead • Reliable • Disadvantage • Large Packet header size • Stale cached • Collisions may occur • Storm problem CUI Yong

  47. Optimization of DSR • Problems in further step on flooding request • Receiving useless packet • Receiving same packet more than once • Collision of flooding request • Two classes ? • How to reduce the scope of the route request flooding? • LAR [Ko98] @ Mobicom • Query localization [Castaneda99] @ Mobicom • How to reduce The Broadcast Storm Problem ? • [Ni99] @ Mobicom CUI Yong

  48. Optimization 1:Location-Aided Routing (LAR) • Location information is used • Exploits location information to limit scope of route request flood • Location information may be obtained using GPS • Expected Zone • determined as a region that is expected to hold the current location of the destination • Expected region determined based on potentially old location information, and knowledge of the destination’s speed • Request Zone • Route requests limited to a that contains the Expected Zone and location of the sender node CUI Yong

  49. Expected Zone in LAR X = last known location of node D, at time t0 Y = location of node D at current time t1, unknown to node S r = (t1 - t0) * estimate of D’s speed X r Y Expected Zone CUI Yong

  50. Request Zone in LAR Network Space • Request zone explicitly specified in the route request • Node A does not forward RREQ, but node B does • Each node must know its physical location to determine whether it is within the request zone Request Zone X r B A Y S CUI Yong

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