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Mobile Ad-hoc Networks -- Overview and a case study

Mobile Ad-hoc Networks -- Overview and a case study. Yinzhe Yu Oct. 8, 2003. Contents . Introduction on MANET Recent research topics Case study: Dynamic Source Routing. What is a MANET ? Mobile nodes, wireless links Infrastructure-less: by the nodes,…

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Mobile Ad-hoc Networks -- Overview and a case study

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  1. Mobile Ad-hoc Networks-- Overview and a case study Yinzhe Yu Oct. 8, 2003

  2. Contents • Introduction on MANET • Recent research topics • Case study: Dynamic Source Routing

  3. What is a MANET ? • Mobile nodes, wireless links • Infrastructure-less: by the nodes,… • Multi-hop routing: …,and for the nodes • Minimal administration: no hassles

  4. Application Example – The Simpson's Be home early, Homer. Hmm, A MANET makes sense. Yes. What are you doing, Nelson? Dad, you can use Nelson if I am too fast. Hi, Marge. I miss you. I can hear u, Lisa. Can u hear me?

  5. Why a MANET? • Fast deployment of ad-hoc networks Special events/conference, military combat/emergency rescue • What about also cheaper ? sensor dust, home networking

  6. What’s unique about a MANET ? • Moving nodes  ever changing topology • Wireless links  various and volatile link quality • Pervasive (cheap) devices  Power constraints • Security • Confidentiality, other attacks

  7. MANET Protocol Zoo • Topology based routing • Proactive approach, e.g., DSDV. • Reactive approach, e.g., DSR, AODV, TORA. • Hybrid approach, e.g., Cluster, ZRP. • Position based routing • Location Services: DREAM, Quorum-based, GLS, Home zone etc. • Forwarding Strategy: Greedy, GPSR, RDF, Hierarchical, etc.

  8. Recent Research Topics • Routing Better metric, higher throughput A high-throughput path metric for multi-hop wireless routing. MobiCom 03. • Transport Layer TCP performance: throughput, fairness, etc. Enhancing TCP fairness in ad-hoc networks using neighborhood RED. MobiCom 03. Improving fairness among TCP flows crossing wireless ad-hoc and wired networks. MobiHoc 03. • MAC Layer MAC protocol for directional antennas A MAC protocol for full exploitation of directional antennas in ad-hoc wireless networks. MobiHoc 03.

  9. Recent Research Topics (cont.) • Security Reliable routing against malicious nodes Ariadne: A secure on-demand routing protocol for ad-hoc networks. MobiCom 2002. • Power Management Power saving and power control Asynchronous wakeup for ad hoc networks. MobiHoc 2003. A power control MAC protocol for ad hoc network. MobiCom 2002.

  10. A Case study: Dynamic Source Routing • On-demand • Source Routing • Route Discovery • Route Request • Route Reply • Route Maintenance

  11. Assumption: • Cooperative nodes • Relatively small network diameter (5-10 hops) • Detectable packet error • Unidirectional or bidirectional link • Promiscuous mode (optional)

  12. A-B-D-G A-B-D-G A-B-D-G A-B A A-B-D A-C-E A A-C-E A-C-E A-C Route Discovery RREQ FORMAT B Initiator ID G Initiator seq# Target ID D Partial route A H E A-B-C Route Request (RREQ) C A-B-C F Route Reply (RREP) Route Discovery is issued with exponential back-off intervals.

  13. Lookup Cache for route A to G Route found? Start Route Discovery Protocol no Buffer packet yes Continue normal processing yes Write route in packet header Packet in buffer? Route Discovery finished Send packet to next-hop no done Route Discovery: at source A A need to send to G wait

  14. Accept route request packet Discard route request yes no Host’s address already in patrial route Discard route request yes Append myAddr to partial route no no myAddr=target Store <src,id> in list Send route reply packet Broadcast packet done Route Discovery: At an intermediate node <src,id> in recently seen requests list? yes

  15. RERR RERR Route Maintenance B G D G A Route Cache (A)G: A, B, D, G G: A, C, E, H, GF: B, C, F H E C F

  16. V W X Y Z Additional feature #1: Caching Overheard Routes Node C CacheE: C, D, E E: C, D, E A: C, B, A E: C, D, E A: C, B, A Z: C, X, Y, Z V: C, X, W, V Node A CacheE: A, B, C, D, E A B C D E

  17. RERR RERR RREQ (! D-G) RREQ RREQ RREQ (! D-G) RREQ (! D-G) G:A,C,E,H,G RREP Additional feature #2: RREP with Cached Routes B D G A Route Cache (A)G: A, B, D, G F: B, C, F H E C F Route Cache (C)G: C, E, H, G Route Cache (C)G: C, E, D, G

  18. RERR RERR Additional feature #3: Packet Salvage B G D G Route Cache (D)G: D, E, H, G A H E C F Caution: No double salvage allowed !!!

  19. A Summary of DSR • Entirely on-demand, potentially zero control message overhead • Trivially loop-free with source routing • Conceptually supports unidirectional links as well as bidirectional links • High packet delays/jitters associated with on-demand routing • Space overhead in packets and route caches • Promiscuous mode operations consume excessive amount of power

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