Virtual Domain and Coordinate Routing in Wireless Sensor Networks

Chien-Chun HungCMLab, 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.o Data centric storage,o Database-like query, o Data transfer

Introduction and Related Work

• The design goals for sensor networks:1.Small hop stretch

1.The ratio of the hop distance of the selected route to the hop distance of the shortest path.

2.Light overhead Preprocess overhead Path lookup overhead

• Delivery-guarantee

Introduction and Related Work

• Existing studies for end-to-end routing:1.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 routingo Use physical location as network addresso Relay packet to the neighbor which is closer to the

destinationo Might fail at dead endo Might have larger hop stretch in sparse networko Difficult to get location informationo Ex: GPSR, GFG

Introduction and Related Work

3. Location-free routingo Operate without location information while improving

the hop stretch with reasonable overhead.o None of the previous works achieve all of the design

goals simultaneously.o Ex: Vcap, ABVCap, GEM

Introduction and Related Work

• The goal of our work:o A location-free point-to-point routing schemeo Achieve smaller hop stretch o Exploit low overhead o Delivery-guaranteed

Outline

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

Why designing domain?

• Anchor nodeso Anchor trees: shortest path

• Domain neighborso 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 coordinateo Assist the relay node greedily select the

neighbor closer to the destination.• Virtual domain

o Verify whether there exists an established shortest path to the destination.

VDCR Assignment Protocol

• Select k nodes as anchor nodeso Each node has a k - tuple domain and a k –

tuple coordinate.• The assignment procedure can be divided

into 3 phases:1.CoorAssign phase• SizeCollect Phase• DomainAssign phase

VDCR Assignment Protocol

• CoorAssign phaseo Anchor i assigns the coordinates by flooding an

i_COOR message to all nodes in the tree.• SizeCelloct phase

o Collect the size of leaf node of each sub-tree• DomainAssign phase

o 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:o Each sensor node is aware of virtual domains and

virtual coordinates of its one hop neighborso 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.o Domain modeo Coordinate modeo Angle-based landmark mode

VDCR Routing Protocol

• Domain modeo If the relay node’s domain is within the

destination’s domain, the next hop is its parent.o Otherwise, the next hop is its child whose

domain contains the destination’s domain.

VDCR Routing Protocol

• Coordinate mode:o Greedily select the neighbor that is closest to

the destination.o The distance function is defined as:

VDCR Routing Protocol

• Angle-based landmark mode:o Proposed to solve the dead-end problem.o Pick an anchor as the landmarko 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:1.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.o The higher probability it suffers from dead-end.o 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: VDCRo Assignment protocol in preprocess stageo Routing protocol in routing stageo Delivery-guaranteedo Minimize hop stretcho 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.o Increase the number of each node’s domain neighboro Increase the probability of meeting destination’s

domain neighbors