Virtual Domain and Coordinate Routing in Wireless Sensor Networks Chien-Chun Hung CMLab, CSIE, NTU, Taiwan

Outline Introduction and Related Work VDCR Assignment Protocol VDCR Routing Protocol Performance Evaluation Future Work and Conclusion

Introduction and Related Work The effectiveness of the routing scheme directly affect resource usage. Data centric storage, Database-like query, Data transfer

Introduction and Related Work The design goals for sensor networks: Small hop stretch The ratio of the hop distance of the selected route to the hop distance of the shortest path. Light overhead Preprocess overhead Path lookup overhead Delivery-guarantee

Introduction and Related Work Existing studies for end-to-end routing: On-demand routing No preprocess overhead Delivery-guaranteed The smallest hop stretch Significant path lookup overhead Ex: AODV, DSR

Introduction and Related Work 2. Geographic location-based routing Use physical location as network address Relay packet to the neighbor which is closer to the destination Might fail at dead end Might have larger hop stretch in sparse network Difficult to get location information Ex: GPSR, GFG

Introduction and Related Work 3. Location-free routing Operate without location information while improving the hop stretch with reasonable overhead. None of the previous works achieve all of the design goals simultaneously. Ex: Vcap, ABVCap, GEM

Introduction and Related Work The goal of our work: A location-free point-to-point routing scheme Achieve smaller hop stretch Exploit low overhead Delivery-guaranteed

Outline Introduction and Related Work VDCR Assignment Protocol VDCR Routing Protocol Performance Evaluation Future Work and Conclusion

Why designing domain? Anchor nodes Domain neighbors Anchor trees: shortest path Domain neighbors All the ancestor and descendent nodes in all anchor tress Exploit domains to locate any node belonging to the destination’s domain neighbors

VDCR Assignment Protocol Virtual coordinate Assist the relay node greedily select the neighbor closer to the destination. Virtual domain Verify whether there exists an established shortest path to the destination.

VDCR Assignment Protocol Select k nodes as anchor nodes Each node has a k - tuple domain and a k – tuple coordinate. The assignment procedure can be divided into 3 phases: CoorAssign phase SizeCollect Phase DomainAssign phase

VDCR Assignment Protocol CoorAssign phase Anchor i assigns the coordinates by flooding an i_COOR message to all nodes in the tree. SizeCelloct phase Collect the size of leaf node of each sub-tree DomainAssign phase Assign the domain to each of its child a subset of its domain

Outline Introduction and Related Work VDCR Assignment Protocol VDCR Routing Protocol Performance Evaluation Future Work and Conclusion

VDCR Routing Protocol We assume that: Each sensor node is aware of virtual domains and virtual coordinates of its one hop neighbors The source node can get the address of the destination by location service The source issues a path-discovery packet to discover routing path to the destination. Domain mode Coordinate mode Angle-based landmark mode

VDCR Routing Protocol Domain mode If the relay node’s domain is within the destination’s domain, the next hop is its parent. Otherwise, the next hop is its child whose domain contains the destination’s domain.

VDCR Routing Protocol Coordinate mode: Greedily select the neighbor that is closest to the destination. The distance function is defined as:

VDCR Routing Protocol Angle-based landmark mode: Proposed to solve the dead-end problem. Pick an anchor as the landmark Angle-based instead of distance-based The Cosine Formula:

VDCR Routing Protocol

Outline Introduction and Related Work VDCR Assignment Protocol VDCR Routing Protocol Performance Evaluation Future Work and Conclusion

Performance Evaluation 20 connected network topologies are randomly generated. 1000 source-destination pairs are selected for each topology. The obstacles are circles of radius 40m.

Performance Evaluation Comparison schemes: ABVCap GEM GPSR VDCR (k=3) VDCR (k=4)

Impact of Number of Anchor Nodes

Impact of Network Density The improvement of VDCR to ABVCap and GEM are 50% ~ 62% and 81% ~ 87%

Scalability of Large Topologies The average path length grows as the network gets larger.

Impact of Obstacles For GPSR, physical position cannot reflect the situation of obstacles. The higher probability it suffers from dead-end. The longer path is required to bypass the obstacles.

Outline Introduction and Related Work VDCR Assignment Protocol VDCR Routing Protocol Performance Evaluation Future Work and Conclusion

Conclusion A location-free point-to-point routing protocol: VDCR Assignment protocol in preprocess stage Routing protocol in routing stage Delivery-guaranteed Minimize hop stretch With low preprocess overhead Compared with ABVCap and GEM, the improvement by VDCR is obtained by 75% ~ 84%, and 62% ~ 70%, respectively.

Future Work How to balance loads among sensor nodes? How to prolong a network lifetime? How to support disconnected or mobile networks due to switch-of or mobility?

VDCR Assignment Protocol The first anchor node is the sink node Select the next anchor node which is likely to be at the boarder of the sensor network. Increase the number of each node’s domain neighbor Increase the probability of meeting destination’s domain neighbors