Reliable Mobicast via Face- Aware Routing Qingfeng Huang,Chenyang Lu and Gruia-Catalin Roman Department of Computer Science and Engineering Washington University INFOCOM 2004

Outline Introduction Previous Work Face-Aware Routing For Mobicast Simulation Conclusion

Introduction Many sensor network applications have spatiotemporal constraints Tracking Electronic directed siren Information scouting

Previous Work(cont.) Example(hole) Drawbacks  Not scalable  High overhead A B d

The Planar Spatial Neighborhood Face The subdivision of maximal connected subset of the plane Spatial Neighborhood A node in a planar graph to be the set of nodes in all faces adjacent to that node except the node itself

The Planar Spatial Neighborhood Face and Spatial Neighborhood Example(Face) A ： 6 faces G ： 3 faces Example(Spatial Neighborhood) A ： 6 spatial neighbors G ： 11 spatial neighbors

Face-Aware Routing The essence of the algorithm Every node that has at least one spatial neighbor that is a delivery-zone node will forward(locally broadcast) the mobicast message Face-aware algorithm Greedy forwarding Timed forwarding

Greedy Forwarding All nodes that are currently(previously) covered by the delivery zone,or have at least one spatial neighbor that is currently(or previously) covered by the delivery zone In such cases,a node forwards a new packet in an “ as soon as possible ” fashion

Greedy Forwarding(cont.) A,J,C,B,D,K apply the greedy forwarding Because P,G,L,M,N,E,F have no spatial neighbors in the delivery zone,they use timed forwarding G L M E F I H P C B A J D N K P G L M E N F AA J C B D K

Timed Forwarding The timed forwarding category A node that has no spatial neighbor in the current delivery zone but either itself will soon be in the delivery zone or has at least one spatial neighbor that will be in the delivery zone If a node X receives a new mobicast packet at time t and finds itself in the timed forwarding category, it makes a forwarding decision based on the relative times the delivery zone reaches its delivery zone neighbors and the expected latency

Timed Forwarding(cont.) X ： the node will be in the delivery zone  t i ： the delivery zone to reach node i(one of spatial neighbors of X) h i ： the hop distance from X to I T 1 ： the expected 1-hop network latency

Timed Forwarding(cont.) B,L,M will be in the delivery zone(packet information) H,G,L,M,E,F,I will apply the timed forwarding and make the forwarding decision G L M E F I H P C B A J D N K P G L M E N F AA J C B D K Node L The first time receiving mobicast message The second time receiving mobicast message tLtL A B L M K J P N G H E F I Ta=  t L -h L T1 H G L M F I E

Protocol Termination A mobicast termination method based on the packet lifetime value in the packet header A expired packet is dropped only in the timed forwarding mode The expired packet will still be forwarded in the greedy forwarding Tolerate some level of timing uncertainty

Protocol Termination(cont.)

Drawback

Planar Graphs Planar graphs Gabriel Graph(GG) Relative Neighborhood Graph(RNG)

Topology Discovery The protocol creates a discovery message flow in each face As a discovery message traverses a face,the coordinates of the nodes it has traversed are added to the message After a discovery message finishing traversing a face,all nodes’ location on the face are collected And a message traverses the same face another time to inform everyone on the face

Topology Discovery

Simulation Over 8 random unit disk graphs 1000x1000 area 1600 nodes A communication range ： 50 units

Face size Faces Size Distribution in Gabriel Spanner of Random Unit Disk Graphs

Spatial Neighborhood Size Spatial Neighborhood Size Distribution in Gabriel Spanner of Random Unit Disk Graphs

Node degree Node Degree Distribution in Gabriel Spanner of Random Unit Disk Graphs

Node density Spatial Neighborhood Size and Network Neighbor Size

Overhead FAR Protocol Per node Communication Overhead

Conclusion The face-aware routing protocol Reliable spatial delivery Minimums broadcast cost Achieves good mobicast temporal characteristics Just-in-time etc.