1. Wireless, Mobile, Ad-Hoc Network Routing Mario Gerla, UCLA CSD FOCUS 99

2. Outline: –What is an Ad-Hoc Wireless Network –The wireless routing challenge –Review of proposed solutions (Distance Vector, Link State, On- Demand, Location Based) –Simulation test bed –Performance results

3. Cellular vs Multihop Standard Base-Station Cellular Networks Instant Infrastructure, Multihop wireless Networks

4. Ad-Hoc Network Characteristics Instantly deployable, reconfigurable infrastructure Node mobility Heterogeneous nodes (big/small; fast/slow etc) Heterogeneous traffic (voice, image, video, data) Limited battery power Multihopping ( to save power, overcome obstacles, enhance spatial spectrum reuse, etc.)

5. Ad-Hoc Network Applications Disaster Recovery (flood, fire, earthquakes etc) Law enforcement (crowd control, border patrol etc) Search and rescue in remote areas Sport events, festivals Ad hoc nomadic, collaborative computing Indoor network appliances Sensor networks Battlefield

6. Wireless multihop routing challenges mobility need to scale to large numbers (1000's) unreliable radio channel (fading etc) limited bandwidth limited power need to support multimedia (QoS)

7. Proposed Routing Approaches Conventional wired-type schemes (global routing, proactive): –Distance Vector; Link State Hierarchical (global routing) schemes: –Fisheye, Hierarchical State Routing On - Demand, reactive routing: –Source routing; backward learning Location Assisted routing (Geo-routing): –DREAM, LAR etc

8. Conventional wired routing limitations Distance Vector (eg, Bellman-Ford): –routing control O/H linarly increasing with net size –convergence problems (count to infinity); potential loops Link State (eg, OSPF): –link update flooding O/H caused by frequent topology changes CONVENTIONAL ROUTING DOES NOT SCALE TO SIZE AND MOBILITY

9. Distance Vector 0 5 1 2 4 3 Routing table at node 5 :

10. Link State Routing At node 5, based on the link state packet, topology table is constructed: Dijkstra’s Algorithm can then be used for the shortest path 0 5 1 2 4 3 {1} {0,2,3} {1,4} {2,4} {2,3,5} {1,4,5}

11. REMEDY #1: use hierarchical routing to reduce table size and table update overhead Proposed hierarchical schemes: –Fisheye (implicit hierarchy induced by "scope") –Hierarchical State Routing –Zone routing (hybrid scheme)

12. Fisheye State Routing Topology based routing –similar to link state (e.g., OSPF) Routing information is periodically exchanged with neighbors only –similar to distance vector Routing update frequency decreases with distance to destination –Higher frequency updates within a close zone and lower frequency updates to a remote zone –Highly accurate routing information about the immediate neighborhood of a node; progressively less detail for areas further away from the node

13. Scope of Fisheye

14. Message Reduction in FSR 0 5 1 2 4 3 0:{1} 1:{0,2,3} 2:{5,1,4} 3:{1,4} 4:{5,2,3} 5:{2,4} 101122101122 LSTHOP 0:{1} 1:{0,2,3} 2:{5,1,4} 3:{1,4} 4:{5,2,3} 5:{2,4} 212012212012 LSTHOP 0:{1} 1:{0,2,3} 2:{5,1,4} 3:{1,4} 4:{5,2,3} 5:{2,4} 221101221101 LSTHOP

15. Hierarchical State Routing (HSR) Main challenge: maintain/update the hierarchical partitions in the face of mobility Solution: distinguish between “physical” partitions and “logical” grouping –physical partitions are based on geographical proximity –logical grouping is based on functional affinity between nodes (e.g., tanks of same battalion, students of same class) Physical partitions enable reduction of routing overhead Logical groupings enable efficient location management strategies using Home Agent concepts

16. HSR - physical multilevel partitions Level = 0 5 1 7 6 11 4 2 3 10 9 8 1 2 3 4 Level = 1 1 3 Level = 2 DestID 1 6 7 Path 5-1 5-1-6 5-7 5-1-6 5-7 HSR table at node 5: HID(5): HID(6): (MAC addresses) Hierarchical addresses

17. HSR - logical partitions and location management Logical (IP like) type address –Each subnet corresponds to a particular user group (e.g., tank battalion in the battlefield, search team in a search and rescue operation, etc) –logical subnet spans several physical clusters –Nodes in same subnet tend to have common mobility characteristic (i.e., locality) –logical address is totally distinct from MAC address

18. HSR - logical partitions and location management (cont’d) Each subnetwork has at least one Home Agent to manage membership Each member of the subnet registers its own hierarchical address with Home Agent –periodically/event driven registration; stale addresses are timed out by Home Agent Home Agent hierarchical addresses propagated via routing tables; or queried at a Name Server

19. On-Demand Routing Protocols Routes are established “on demand” as requested by the source Only the active routes are maintained by each node Channel/Memory overhead is minimized Two leading methods for route discovery: source routing and backward learning (similar to LAN interconnection routing)

20. Existing On-Demand Protocols Dynamic Source Routing (DSR) Associativity-Based Routing (ABR) Ad-hoc On-demand Distance Vector (AODV) Temporarily Ordered Routing Algorithm (TORA) Zone Routing Protocol (ZRP) Signal Stability Based Adaptive Routing (SSA)

21. Dynamic Source Routing (DSR) Uses source routing instead of hop-by-hop routing No periodic routing update message is sent Nodes ignore topology changes not affecting active routes with packets in the pipe The first path discovered is selected as the route Two main phases –Route Discovery –Route Maintenance

22. DSR - Route Discovery Route RequestTo establish a route, the source floods a Route Request message with a unique request ID Route ReplyRoute Reply message containing path information is sent back to the source either by –the destination, or –intermediate nodes that have a route to the destination Route CacheEach node maintains a Route Cache which records routes it has learned and overheard over time

23. Performance Evaluation Enviroment PARSEC simulation enviroment –100 nodes –1000mx1000m square area –transmission range: 100m –channel data rate: 2 Mbps –random mobility model –UDP traffic between randomly selected node pairs –cluster-token MAC layer protocol HSR –2 level physical partition –1 level logical groupings, number of logical subnets varies with network size FSR –2 level fisheye scoping –fisheye radius is 2 hops

24. DSR - Route Maintenance Route maintenance performed only while route is in use Monitors the validity of existing routes by passively listening to acknowledgments of data packets transmitted to neighboring nodes Route ErrorWhen problem detected, send Route Error packet to original sender to perform new route discovery

25. Location-Aided Routing Ko and Vaidya (Texas A & M) Location assisted (requires GPS) On-demand No periodic messages Route RequestsWorks similar to DSR except LAR limits the flooded area of Route Requests using location information

26. LAR (cont’d) Scheme 1 –The source specifies a request zone which includes the source and the area where the destination may reside Route Requests – Nodes within the request zone propagate Route Requests Scheme 2 –The source specifies the distance between itself and the destination Route Requests –Nodes forward Route Requests if their distances to the destination is less than or equal to the distance indicated by the packet

27. DREAM Basagni, et al. (U of Texas, Dallas) Location assisted (requires GPS) Coordinates of each node are recorded in the route table instead of route vectors Distance EffectDistance Effect: Send location updates to nearby nodes more frequently Location update frequencies are adjusted to mobility rate

28. DREAM (cont’d) The source partially floods data to nodes that are in the direction of the destination The source specifies possible next hops in the data header using location information Next hop nodes select their own list of next hops and include the list into data header If the source finds no neighbors in the direction of the destination or has no fresh location information of the destination, data is flooded to the entire network

29. GloMoSim Simulation Layers Application Processing Propagation Model Mobility Frame Processing Radio Status/Setup CS/Radio SetupRTS/CTSFrame Wrapper Ack/Flow Control Clustering Packet Store/Forward VC Handle Flow Control Routing IP Wrapper IP/Mobile IP RSVP Transport Wrapper TCP/UDP Control Channel Radio MAC Layer Network IP Transport Application RTP WrapperRCTP Packet Store/Forward Clustering Routing Link Layer Application Setup Data Plane Control Plane

30. Control O/H vs. number of nodes

31. Control O/H vs. Traffic Pairs

32. Control O/H vs. Mobility (100 pairs)

33. Average Delay (ms)

34. Location Based Routing Simulation (LAR and DREAM) 50 nodes; 750m X 750 m space Free space channel propagation model Radio with capture ability MAC: IEEE 802.11 DCF 10 UDP data sessions with constant bit rate

35. Simulation Results Number of data packets transmitted per data packet delivered

36. Simulation Results (cont’d) Number of control bytes transmitted per data byte delivered

37. Simulation Results (cont’d) Packet delivery ratio

38. Conclusions Conventional (wired net) routing schemes suffer of O/H, mobility and scalability limitations Hierarchical routing reduces O/H and improves scalability (at the expense of accuracy). On Demand routing eliminates background routing control O/H. It introduces latency; it does not support QoS routing

39. Conclusions (cont’d) Location assisted routing can enhance performance in both on demand (LAR) and table driven (DREAM) settings; GPS required. No routing scheme works best in all situations; selection must be guided by application scenario Open problem: efficient location management and resource discovery in highly mobile environment