Efficient Geographic Routing for Mobile Ad-hoc Networks (Joint work with Xiaojing Xiang and Zehua Zhou) Xin Wang Assistant Professor Director, Wireless and Networking Systems Lab (WINS) SUNY, Buffalo http: //www. cse. buffalo. edu/~xwang 8
Future Common Network, Common Applications 3 G Cellular Networks • Outdoor Areas • High Mobility Radio Controller Aggregation Router Access Router Urban Networks • Broadband Distribution Presence Enterprise Networks Location Networks • High Speed Access Pico Cells Router • 802. 11++ Core Internet • Broadband • Local Mobility Backbone Aggregation Wireless • Packet Voice Aggregation Router • High Data Rates Authentication Router Home 4 G Air Networks Interface Access • DSL/Cable Router Ad Hoc 4 G • Allow Peer-to-Peer • Community 4 G Networks Radios wireless Communications Radios networks • Self Configuring
Talk Overview q Background and motivation q Part I: Self-adaptive geographic unicast routing q Part II: Scalable geographic multicast routing q On-going and future work
Background q Mobile Ad Hoc Networks (MANET) q Routing: find a packet delivery path – Unicast: one-to-one – Multicast: one-to-many or many–to-many
Challenges of MANET Routing q Host mobility leads to dynamic topology q Rate of link failure/repair increases with moving speed q Topology and routing path maintenance become more difficult with the increase of path length and node density q Mobile devices have very limited energy, and small devices such as sensors have very limited per-node resources
Existing Unicast Routing Protocols q Proactive protocols (DSDV, OLSR) – Maintain routes continuously, large overhead when there is no traffic – Actively track network topology changes, not suitable for high mobility q Reactive protocols (DSR, AODV, TORA, FLR) – Maintain routes only if needed – May need network-wide flooding to discover routes, larger delay due to searching for path before sending packet q Hybrid protocols (ZRP, SHARP) – Combine the proactive and reactive approaches q Geographic routing protocols (GPSR, GFG) – Make use of location information to reduce routing overhead – Only need to be aware of local topology
Information Required for Geographic Routing q A node’s own position: obtained through positioning service such as GPS q The position of the destination: determined through location service q The positions of all neighbors: learned through periodic beacons sent by neighbors
Forwarding Formats q Greedy forwarding – Make local optimal forwarding decision D x q Perimeter forwarding (GPSR) – Calculate a planar sub-graph (no crossed-edges) from the local topology – Route around the perimeter of void area until greedy forwarding can be resumed D x
Problems with Classical Geographic Routing q Proactive fixed-interval beaconing for positions – Generate unnecessary overhead and consume energy – Create collisions with normal data transmissions q Beaconing interval affects accuracy of the local topology and routing performance – Outdated topology => non-optimal routing, transmission failures => more network resource consumption q Continuous retransmissions due to inaccurate position – Reduce link throughput and fairness, and increase collisions => further delay and energy consumption
Possible Performance Improvement q Change Beacon Sending Interval – Send out beacons only after moving a certain distance – Send beacons more frequently, e. g. piggyback position with packets (Are the sending nodes the best next hop? ) Does not consider traffic conditions. May generate unnecessary beacons. q Do not use Beacons (CBF’ 03, BLR’ 04) – Focus only on finding the next hop for greedy forwarding, and there is no recovery strategy – Do not have a good strategy to use the path detected or perform any route optimization.
Talk Overview q Background and motivation q Part I: Self-adaptive geographic unicast routing q Part II: Scalable geographic multicast routing q On-going and future work
Our Contributions q Propose two self-adaptive routing protocols BIGR: Beaconless Interactive Geographic Routing BTGR: Beacon-on-Trigger Geographic Routing – On demand: alleviate unnecessary overhead due to proactive beacons – More flexible position distribution: more updated topology, more efficient routing and less failure – Self adaptive: adaptive to traffic pattern and robust to topology changes
Importance of updated positions: some analysis q Positions obtained may become outdated – A mobile may move out of transmission range before the position is timed out and removed. q Analysis – assumptions – Node B sends beacons periodically to refresh its position at A – Neighbor area of A: centered at A, within transmission range R – Moving area of B: centered at B, within r Neighbor time-out interval B’s speed relative to A Current distance between A, B Maximum distance traveled by B after t t R z r A B
Different Scenarios z r A B R r z R B A Same as this case A R A z zr R B r A R R A z r B
Probability of Moving Out of Range Case 1: Case 2: Case 3:
Probability of the mobile moving out-of-range (expressed in percentages) 4 s 6 s 8 s 10 s 12 s 14 s 10 m/s 3. 57 5. 49 7. 51 9. 64 11. 88 14. 27 20 m/s 7. 51 11. 88 16. 80 22. 43 29. 19 38. 26 30 m/s 11. 88 19. 51 29. 19 42. 94 55. 38 65. 24 40 m/s 16. 80 29. 14 47. 37 62. 22 72. 89 80. 07 50 m/s 22. 43 42. 94 62. 22 75. 00 82. 64 87. 24 Timeout Vmax
Proposed Geographic Routing Protocols q BIGR: Beaconless Interactive Geographic Routing q BTGR: Beacon-on-Trigger Geographic Routing
Beaconless Interactive Geographic Routing (BIGR) q There is no beacon, routing path is built on-demand q Route searching phase – Forwarding decision made through the cooperation of forwarding node and its neighbors How to find next hop without positions of neighbors? q Route optimization phase – Forwarding path optimized jointly by sending node and its neighbors
Proposed Geographic Routing Protocols q BIGR: Beaconless Interactive Geographic Routing – Route searching – Route optimization q BTGR: Beacon-on-Trigger Geographic Routing
Route Searching q After a route searching, a node keeps a record for next hop F Dest’s position, time (x_F, y_F), t Next. Hop C New position, time (x_new, y_new), t_new Old position, time (x_old, y_old), t_old Transmission mode greedy or recovery A Next hop table for node B B Next-hop position Destination F C
How to find next hop? q When a node (C) does not have next hop information, broadcast REQ S B A E F C H M J G I L D K N Within neighborhood A node that receives a packet for the first time REQ message with Dest. Pos Send. Pos Hop D XD, YD Xc, Yc 1
Forwarding Node Selection q Reply sending: nodes closer to destination respond after a competition delay, which is smaller for a node closer to destination q Reply suppression: a node cancels its reply if it overhears packet forwarding, or overhears reply sent by node closer to destination q Multiple replies: select the node closer to the destination as next hop S E F B M L C J A G H D I K N REPLY message Dest Sender Send. Pos Hop D G XG, YG 1
Packet Sending q C’s next hop table Destination D Dest’s position, time (x_D, y_D), t Next. Hop G New position, time (x_new, y_new), t_new Old position, time (x_old, y_old), t_old Transmission mode greedy S B A E F C H M J G I K L D N
Recovery from Local Void q Without local topology, cannot use perimeter forwarding. How to recover? q Broadcast REQ to N-hop neighbors E S B F C L J A H I M D G K N Dest. Pos Send. Pos Hop REQ message with D XD, YD Xc, Yc 2
Finding Path in Recovery Mode q Reply sending: – If one-hop neighbor is nearer to destination, it replies with Hop = 1; Otherwise continues broadcasting REQ – A two-hop neighbor nearer to destination replies (reverse path), Hop = 2; q Reply suppression: drop the REPLY if having forwarded/overhead one from the node closer to destination q Multiple replies: select the node closer to destination E S B H F C I Dest L G M J K D Sender Send. Pos Hop D G 2 XG, YG Reply message
Proposed Geographic Routing Protocols q BIGR: Beaconless Interactive Geographic Routing – Route searching – Route optimization q BTGR: Beacon-on-Trigger Geographic Routing
Position Update and Route Optimization q Update next hop position when overhearing packet forwarding by next hop (carrying sending node position) q Validate next hop – Estimate next hop Ø If both old and new positions are fresh Ø If only new position is available, it will be used as the estimated position – Search for new route Ø If both old and new positions are outdated Ø If estimated position is out of transmission range or no longer closer to destination than current forwarding node q Optimize routing path: three cases
Case 1: A is the destination A Move A CORRECT B C q As A is the destination, B should send packet directly to A, so A sends CORRECT to B q B sets its next hop to A Old position Old path Current position New path
Case 2: Greedy Mode Forwarding A F Move q If A is closer to F than C is to F, A sends CORRECT to B A CORRECT B Greedy C q B compares A’s and C’s positions to F, and sets its next hop to A if it is closer to F Old position Current position Old path New path
Case 3: Recovery Forwarding F Move D A q If A is closer to F than that from B and C, A sends CORRECT to B A CORRECT C Recovery mode B Greedy Old position Current position Old path New path q B compares A and C’s positions relative to F, if A is closer to F, B sets its next hop to A q If B is the first hop of recovery, change mode to greedy
Proposed Geographic Routing Protocols q BIGR: Beaconless Interactive Geographic Routing q BTGR: Beacon-on-Trigger Geographic Routing
Position Distribution and Path Finding q Position distribution: through beacons q Packet forwarding: greedy, parameter q Beacon generation: triggered by data traffic and route optimization q Topology maintenance: positions of neighbors
Route Optimization q Route validation – Delete invalid neighbors – Update the positions of other members based on estimation q Route optimization: also three cases – The first two cases are similar to those of BIGR – Case 3: When A overhears forwarding from B to C using perimeter mode Ø If A is closer to the destination that of the node position where the perimeter mode started, B should resume greedy forwarding earlier Ø A broadcasts a beacon to refresh its position, B will send future packets to A
Performance: Impact of Mobility Delivery ratio Control overhead BIGR and BTGR delivery ratios are not impacted by speed BIGR more actively updates the position as speed increases
Performance: Impact of Mobility (cont) Total transmissions Average end-to-end delay Our protocols have significantly lower transmission redundancy and end-to-end delay than GPSR due to more updated topology.
Summary of Unicast q Propose two self-adaptive on-demand geographic routing protocols – Alleviate unnecessary overhead due to proactive beacons – More efficient position distribution and very robust to topology change: packet transmission delay is reduced more than three times compared to GPSR – Outperform existing geographic protocols in all test scenarios, including mobility, node density and traffic load
Talk Overview q Background and motivation q Part I: Self-adaptive geographic unicast routing q Part II: Scalable geographic multicast routing q On-going and future work
Existing Multicast Routing Protocols q Tree-based (AMRIS, MAODV, LAM) – Utilize network resources efficiently q Mesh-based (FGMP, CAMP, ODMRP) – Robust Difficult to scale due to overhead for route searching, group membership management, and tree/mesh maintenance over dynamic topology q Geographic multicast (LGT, DSM, PBM) – Only consider packet forwarding scheme – Reduce topology maintenance overhead, but not scalable
Why Is Geographic Multicast Difficult to Scale? q Putting the information of all group members into packet header creates excessive overhead for large group q Relying on location service to obtain positions for all group members adds more overhead
Our Contributions q Design an efficient on-demand hierarchical group membership management scheme q Use geographic forwarding to avoid building and maintaining tree/mesh structure q Introduce the home zone to avoid periodical network-range flooding of source information q Combine group membership management with location service to avoid location searches for group members
Terms Used in SGMP Source Member Zone Group member Zone leader Home zone Track the addresses and Zone IDs of sources
High Level Picture RFRESH (Join) REPORT (Join) DATA
Source Announcements q At session initiation time: floods an ANNOUNCE, with address, position, and group ID q During packet transmissions: piggybacks its position with the multicast packets
Home Zone Management q Home zone information update – A source sends its zone ID to home zone when moving to new zone – The first home zone node floods source info to whole zone q Home zone searching – Other nodes: search home zone with ring of increasing size. – Source: announces its current zone as home zone, and sets sequence number to 0; sequence number increases by one each time home zone changes. q Home zone election – Will be triggered when a node receives a message addressed to home zone with ID different from record (due to zone update or zone announcement from a new source)
Membership Management within Zone q A member – Sends REFRESH to leader (periodically, join, leave), carrying its membership and position q A leader – Floods LEADER periodically within the zone, carrying its own position and the positions and group IDs of the multicast members
Membership Management at Upper Tier Source: records the member zones Membership report Leader knows source location SOURCE message Home Zone Leader does not know source location or Source information is outdated
Moving between Zones q When a node moves into a new zone – Clears old zone’s information q If the node is a group member – Will continue receiving packets forwarded by old zone – Sends next REFRESH to new zone leader q When a leader is moving out of a zone – Hands leadership to other nodes
Empty Zone Problem 20 40 60 80 100 m 74. 885 56. 282 44. 864 36. 865 30. 853 200 m 36. 857 19. 208 10. 985 6. 5467 3. 9951 400 m 6. 4964 0. 9643 0. 1605 0. 0281 0. 0051 600 m 0. 5930 0. 0112 0. 0002 5. 4 E-06 1. 2 E-07
Empty Zone Handling q Member zone – The departing leader notifies the source q Home zone – The last node: 1) Announces the new zone it is moving to as the home zone; 2) Floods source information within new home zone; 3) Sends ANNOUNCE to network with sequence number of home zone increased by one
Multicast Packet Delivery q Source – Sends packets to all member zones and members in its zone – Sends one copy if several members share next hop q Intermediate nodes – Take similar action – If the message includes their current zone, replace zone ID in the message with the information of the members in the zone. Source Zone leader Group member Other nodes
Performance: Impact of mobility Delivery ratio Control overhead SGMP has up to 35% higher delivery ratio and 20 % lower overhead at high mobility
Performance: Scalability Group size Network size SGMP has higher delivery ratio under all group sizes, and has more than 2. 5 times higher delivery ratio for large network sizes.
Summary of Multicast q Design a scalable geographic multicast routing scheme – Scalable group membership management and robust packet forwarding – Avoid the need to build and maintain the tree/mesh structure over dynamic topology – Avoid network-range flooding of source information and location searches for the group members – Performance: scalable in terms of group size, network range and mobility
On-going and Future Work q Cross-Layer Optimization and Design of Mobile and Wireless Systems – Create infrastructure and algorithms to enable more optimal performance of the wireless system, by adopting an integrated, multi-layer approach – On-going projects Ø Power control and energy efficient transmissions in mobile Ad Hoc networks Ø Architecture design and cooperative resource management for IP-based radio access network
On-going and Future Work (cont) q Next Generation Mobile Infrastructure and Service Wireless Network – Development of network infrastructure and services over emerging radio and computing technologies. – On-going projects Ø Sensor Network Applications and Services Ø Programmable Wireless Networking and Service Infrastructure Design Ø Scalable and Resilient Wireless Mesh Network Design Ø Context-aware Mobile Computing and Wireless Services q Architecture and Design for Heterogeneous Networks
Q & A
Performance Studies q Setup: – Tool: Glomo. Sim – Network size: 3000 m x 1000 m, 300 nodes – Traffic: 30 CBR with rate 8 kbps each – Mobility model: Random Waypoint q Measures: – Packet delivery ratio Ø The ratio of packets delivered to those originated by the source – Control overhead Ø The number of control messages over the number of packets received – Average number of data packet transmissions Ø The total number of packet transmissions accumulated from each hop over the total number of packets received – Average end-to-end delay Ø Average time interval for packets to traverse from source to destination
SGMP: Basic Principles Join (RERESH) Member (REPORT) Zone Leader Data Member Zone Source Data Source Packet sending: geographic unicasting, and the packet for a zone is sent towards the zone center.
Performance: Number of groups q Delivery ratio Overhead
Home Zone Election q When a node receives a message carrying home zone ID different from that in its record – If the message has larger sequence number, update its home zone info; otherwise, forward the message to recorded home zone Home Zone SEQ = 0 Forward to home zone with larger SEQ Membership report SOURCE message Home Zone SEQ = 1
Impact of node density
Impact of node density (cont)
Impact of traffic load
Impact of traffic load (cont)
Performance: Impact of node density
Performance: Impact of node density
Overhead Group size Network size
Impact of the number of groups Delivery ratio Overhead
… Tomorrow – Common Net, Common Apps 3 G Cellular Networks • Outdoor Areas • High Mobility Radio Controller Aggregation Router Access Router Presence Enterprise Location Networks Access Router • 802. 11++ Core Internet • Local Mobility Backbone • Packet Voice Aggregation • High Data Rates Authentication Router 4 G Air Interface 4 G 4 G Radios Access Router Ad Hoc Networks Urban Networks • Broadband Distribution Networks • High Speed Pico Cells Aggregation Router Home Networks • DSL/Cable • Allow Peer-to-Peer • High Speed Internet Access Communications • Self Configuring è Unifies access technologies (wireless and wireline) èEnd-to-end Internet Service – common mobility management and control – common transport infrastructure – common services infrastructure
q Architecture and Design for Heterogeneous Networks – Enable end-to-end communications over heterogeneous networks: WPAN, WLAN, WMAN, W-WAN, and Internet. q Secure and Cooperative Routing over Ad Hoc Networks – Provide security and incentive to enable the relay-based hop-by-hop transmissions.
Beacon Triggering by Data Traffic q Three types of beacons (for position information) – BEACON message – REQ (Carrying position) – Data packets (Carrying position) q Beacon request – Receiving REQ – Overhearing data transmission q Beacon sending – Only if the request interval is smaller than threshold q For packet sending – Use local topology information forwarding if request sent interval is smaller than threshold – Otherwise, send REQ to neighbor
Route Searching q How to find a path without beacon? – Depend on forwarding states: greedy or recovery q Greedy forwarding – Find a neighbor closest to the destination q Recovery forwarding – How to forward when there is no neighbor closer to the destination?
Membership Management in Local Zone q Membership reporting by mobiles nodes q Leader election q Moving between different zones
Membership Reporting in Local Zone q A group member sends REFRESH to leader to report its membership – If leader is known, unicast – If leader is not known, elect leader q Leader election (on demand) – Flood the REFRESH, indicating leader information is requested Ø A leader will send back a LEADER message Ø If no LEADER is received, the member announces itself as the leader and floods a LEADER message within the zone Zone leader Group member Other nodes
Membership Management at Upper Tier q A source needs to record the member zones q Source announcement q Home zone election q Zone membership reporting
Protocol Overview q Group membership management – At local zone tier, a leader will collect the positions and membership of the member nodes in the zone. – At upper tier, the leader will represent the member zone to join a multicast tree. Location of group members is combined with group membership management q Packet forwarding – At upper tier, the source sends a packet to member zones; At lower tier, the first node in the zone that receives the data packet forwards it to the group members. – Both data and control packets are generally transmitted through geographic unicasting; Packets for a zone are sent towards the zone center
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