Routing and Broadcast in a Mobile Ad Hoc Network

1. Routing and Broadcast in a Mobile Ad Hoc Network Professor Yu-Chee Tseng Dept. of Computer Science and information Engineering National Central University (曾煜棋 中央大學 資訊工程系)

2. Outline • Introduction to Wireless Networks • Mobile Ad Hoc Network (MANET) • Routing in a Mobile Ad Hoc Network • Review • Fully Location-Aware Routing • Broadcast Storm Problem in MANET • MAC Introduction (IEEE 802.11 Background)

3. Introduction to Wireless Networks

4. When You Are Mobile Today • Desperately looking for a computer to check your e-mails • Need to access Internet, WWW Info, etc. • Need cellular phone, airphone, pager, FAX, etc. • Using a laptop to do work while traveling • People of the late 20th century: Keeping “connected” any time, any where!!

5. Applications of Wireless Communications • Mobile Office/Meeting Room: • with multitude of notebooks, palmtop, PDA, etc. • One who needs to work with customers face-to-face • doctor/nurse • clerk/salespersons • adv.: paperless, less error-prone • Hospitality: 服務業, 餐廳入座, 代客泊車 • Utility: 水公司, 電力公司 • Kansas City: wireless metering system. • Field work, Field services: always on the road • Warehousing/Supermarket: • pricing, order, bar-code input, etc.

6. Wireless LAN: infrastructured Wireless LAN: ad hoc Wireless Network Models

7. Cellular: Diffused: (Infrared) Wireless Network Models (cont.)

8. Wireless MAN: Wireless WAN: Wireless Network Models (cont.)

9. MANET:Mobile Ad Hoc Network

10. MANET • MANET = Mobile Ad Hoc Networks • a set of mobile hosts, each with a transceiver • no base stations; no fixed network infrastructure • multi-hop communication • needs a routing protocol which can handle changing topology

11. Applications of MANET • battlefields (戰場) • nature disaster areas (緊急救難) • fleet in oceans • historical cites (古蹟) • festival ground (集會)

12. Related Information • IEEE 802.11 for Wireless LANs • MAC • PHY • IETF manet group • to stimulate research in this area • RFC 2503 • Routing Protocols: • unicast – AODV, DSR, ZRP, TORA, CBRP, CEDAR • multicast – AMRoute, ODMRP, AMRIS

13. Research Issues GPS應用 Application Layer WWW 行動教室 TCP/UDP Multicast GeoCasst IP Layer LA Routing MAC Layer Power Ctl Channel Assignment PHY Layer multi-code CDMA

14. Routing in a Mobile Ad Hoc Network (Part I: Review) Ant’s Food Search Reviews (DSR, ABR, SSR, LAR, TORA)

15. Ants Searching for Food ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

17. Three Main Issues in Ants’ Search • Route Discovery: • searching for the places with food • Packet Forwarding: • delivering foods back home • Route Maintenance: • when foods move to new place

18. Protocol 1:DRS (Dynamic Source Routing) • on-demand • Source Routing: • routes are denoted with complete information (each hop is registered) • Two major parts: • route discovery • route maintenance

19. Route Discovery of DSR • When a host has a packet to send, it first consults its route cache. • If there is an unexpired route, then it will use it. • Otherwise, a route discovery will be performed. • Route Discovery: • A ROUTE_REQUEST packet is sent by flooding. • There is a “route record” field in the packet. • Each node will append its address to the record.

20. Route Request Route Reply

21. Route Reply of DSR • A ROUTE_REPLY packet is generated when • the route request packet reaches the destination • an intermediate host has an “unexpired” route to the destination • A route is then generated in two manner: • from destination: • the route traversed by the ROUTE_REQUEST packet • from intermediate host: • the route traversed by the ROUTE_REQUEST packet concatenated with the route in the intermediate host’s route cache

22. Path of ROUTE_REPLY • Which way should be taken by the ROUTE_REPLY? • Two possibilities: • symmetric path: • follow the same route in the reverse order to reach the source • asymmetric path: • need to discover a new route to the source by initiating a ROUTE_REQUEST to the source • piggyback the discovered route to the ROUTE_REQUEST packet S D

23. Route Maintenance of DSR • When the data link layer encounters a link breakage, a ROUTE_ERROR packet will be initiated. • The packet will traverse in the backward direction to the source. • The source will then initiate another ROUTE_REQUEST. • Maintenance of route cache: • All routes which contain the breakage hop have to be removed from the route cache. S D

24. How to Detect a Link Breakage • Active Acknowledge: • The receiver of a packet actively sends an ACK to the sender. • Passive Acknowledge: • The sender passively listen to the receiver’s sending. S R S R V data packets active/passive ACK

25. Protocol 2: ZRP • ZRP = Zone Routing Protocol • A hierarchical approach: • zone = the area that a node knows the complete routing information • so routing goes in a zone-to-zone basis

26. Protocol 3: ABR(Associativity-Based Routing) • ABR considers the stability of a link. • Basic Idea: • Each node periodically generates a beacon to signify its existence. • On receipt of the beacon, a node increases the “tick” of the sender by 1. • A higher degree means more stability. • A lower degree means less reliable. • When a link becomes broken, the node will set the tick of the other node to 0.

27. ABR Outline • Route Discovery: • (similar to DSR) • On needing a route, a host will broadcast a ROUTE_REQUEST packet. • Each receiving host will append its address to the packet. • The “ticks” will be appended in the ROUTE_REQUEST packet. • The destination node will select the route with the highest tick. 7 5 8 source destination 10 4

28. Route Ｍaintenance: • On route error, a node will perform a local route search. • in hope of rebuild the path locally. • If the local search fails, a ROUTE_ERROR will be reported to the source. source local searched zone destination

29. Protocol 4: SSR(Signal Stability Routing) • Observation: • The ABR only considers the stability to nodes. • Two more metrics: • signal strength: • the strength of a signal • provided by link layer • location stability • how fast a host moves • could be measure by: • the change of signal strength over a period of time • location devices (such as GPS)

30. Protocol 5: Location-Aided Routing (LAR) • to limit the area to search for the route • I will forward the ROUTE_REQ; • J will not forward the ROUTE_REQ. A B D J I Expected zone of D S C Route search zone

31. Assumption of LAR • Location Device is available. • outdoor positioning device: • GPS: global positioning system • accuracy: in about 20 to 50 meters • indoor positioning device: • Infrared • short-distance radio, bluetooth, etc.

32. Protocol 6: TORA (Temporally Ordered Routing Algorithm) • source-initiated protocol • provide multiple paths for any source-destination pair • Like water flowing, it goes from upstream to downstream. • for highly dynamic mobile networks

33. Main Idea • Regard the network as a directed graph. • For each destination, a DAG (directed acyclic graph) will be maintained. • Note: There are n copies of DAG’s, each associated with one destination, where n is the number of hosts. • In the following discussion, we only discuss one DAG associated with a destination. • The DAG is accomplished by assigning each node i a height metric hi. • A link from i to j means hi > hj.

34. Full Reversal Method • A node will update its height to adapt to the change of network topology. • Height hi = (valuei, IDi) • a node will change its value to change the direction of a link • Relation: hi > hj if the following is true: • valuei > valuej • (valuei = valuej) and (Di > Dj) • Ex: (5, 4) > (4, 6) • Ex: (5, 4) > (5, 2) • Property: Given any to heights, there must exist a “>” relation between them.

35. Rule: • Each node other than the destination that has no outgoing links reverses the direction of all its incoming links. • This means that the node’s height is a local minimum. • This is done by getting a larger height such that the node becomes a local maximum. • MAX{all neighbors’ heights} + 1 a, 5 b, 6 e, 3 d, 4 f, 1 c, 3 dest, 8 g, 2

36. a, 7 b, 6 e, 6 original a, 5 d, 9 f, 7 c, 9 b, 6 e, 3 dest, 8 g, 5 d, 4 f, 1 c, 3 a, 5 dest, 8 g, 2 b, 6 e, 6 d, 4 f, 4 c, 9 a, 5 b, 6 e, 3 dest, 8 g, 5 d, 4 f, 4 c, 9 dest, 8 g, 2

37. a, 7 b, 10 e, 10 d, 9 f, 7 c, 9 dest, 8 g, 10 a, 11 b, 10 e, 10 d, 9 f, 11 c, 9 dest, 8 g, 10 Eventually, the DAG will stablize.

38. TORA Summary • There will exist multiple paths leading to a destination. • Note: • The above DAG is associated with node dest. • Associated with each node, there is a DAG. • The above scheme is called Full Reversal. • In TORA, more complicated rules are used. • Partial reversal • Temporally-ordered routing • Height metric

39. Routing in a Mobile Ad Hoc Network(Part II: Fully Location-Aware Routing) “GRID: A Fully Location-Aware Routing Protocol for Mobile Ad Hoc Networks”, Telecommunication Systems (to appear)

40. Basic Idea • Adopt Positioning Systems • such as GPS receivers • President Clinton ordered to discontinue SA (selective availability) in May 2000 • will increase the accuracy by an order • Fully utilize location information: • route discovery • data forwarding • route maintenance • We propose a new protocol called GRID.

41. Observation 1 • Determine route quality based on location information: • passing B is better than passing A

42. Observation 2 • Improving the vulnerability and quality of a route based on location information: • When B moves away, E can work on behalf of B. • When F roams in, using F is more reliable.

43. Comparison of Using Location Information

44. The GRID Routing Protocol • Partition the physical area into d x d squares called grid.

45. Protocol Overview • In each grid, a leader will be elected, called gateway. • Routing is performed in a grid-by-grid manner. • Responsibility of gateway: • forward route discovery packets • propagate data packets to neighbor grids • maintain routes which passes the grid

46. Route Search • We can adopt any existing route discovery protocol. • Major features/differences: • limit the search range by the locations of source and destination • only gateway will help with the discovery process • The more crowded the area is, the more saving. • routing table is indicated by grid ID (instead of host address)

47. Route Search Example route search route reply

48. Route Search Range Options

49. Routing Table Format • Next-hop routing: • the next hop is identified by grid ID

50. Route Maintenance • Two issues: • how to maintain a gateway in each grid • how to maintain a grid-by-grid route • Special Feature: • longer route lifetime: • as long as there is a host in each gateway, a route will be alive • more robust • In existing protocols, once a node in the route roams away, the route will be broken.