TreeCast: A Stateless Addressing and Routing Architecture for Sensor Networks Santashil PalChaudhuri, Shu Du, Ami K. Saha, and David B. Johnson Department of Computer Science, Rice University IEEE IPDPS 2004 Speaker: Hao-Chun Sun

Outline  Introduction  TreeCast Architecture  Stateless Scoped Addressing  Evaluation  Conclusion

Introduction -background-  Sensor Networks Sinks, sensor nodes  Small, inexpensive  Low power  Sensing and report sensory data to sink Dense deployment  Tolerating the low quality of sensor nodes

Introduction -motivation-  State in the sensors Robustness of the network  Node failure  Temporary wireless failures  Communication pattern Sink floods a query to sensor network and sensor node reply with relative data. A sensor node sends data to sink after sensing without an explicit query.

Introduction -related work-  Data centric routing Directed Diffusion Mechanism  Using the interests  gradients  routing info. interests sink

Introduction -related work-  Data centric routing SPIN Mechanism  Sensors flood short description and wait for request from sinks. Short description sink

TreeCast Architecture  Overview Address Allocation  Address assignment  Tree Construction Tree Maintenance  Parent failure  Node Addition Routing Messages

TreeCast Architecture  Address Allocation basic idea Node address has some correlation with  the distance of the node from the sink and  the subtree it belongs to. Node address form  ((0 | 1) b ) k k: level  b: neighbor number 2 b >> N (N: maximum neighbor number) s abc de k: 0 k: 1 k: 2 b=2

TreeCast Mechanism  Address assignment algorithm

TreeCast Mechanism  Address assignment algorithm Choose Parent— a Level M Level (M+1) Level (M+2) CONFIRM 1.Source address 2.b value 1.Source address 2.b value 1.k x T wait 1.Strongest signal 2.Random selection 1.k x T wait 1.Strongest signal 2.Random selection

TreeCast Mechanism  Address assignment algorithm Do Allocation— a Level M Level (M+1) Level (M+2) CONFIRM 1.Source address 2.b = 2 1.Source address 2.b = 2 1.random b-bit number 2.concatenate with parent address 1.random b-bit number 2.concatenate with parent address (10) (01) (11) (1110) PROBE 1.Source address 2.Random tag 1.Source address 2.Random tag COMPLAINT APPROVE

TreeCast Mechanism  Address assignment algorithm Hear Allocation— a Level M Level (M+1) Level (M+2) CONFIRM 1.Source address 2.b = 2 1.Source address 2.b = 2 Check address (10) (01) (11) (1110) PROBE 1.Source address 2.Random tag 1.Source address 2.Random tag COMPLAINT APPROVE

TreeCast Mechanism  Tree Construction Property: 1.A node know own level 2.A node know its parent’s address Property: 1.A node know own level 2.A node know its parent’s address

TreeCast Mechanism  Tree Maintenance Parent failure New nodes b a s e f g h d k j i l m n c Do Allocation CONFIRM PROBE COMPLAINT APPROVE Orphan node

TreeCast Mechanism  Routing Messages Sink floods a query to sensor network.  Broadcast Tree Orphan: forward all unique query packets. Sensor node sends sensory data to sink.  Every node sends to its parent and parent forwards the packets. K level Orphan:  (K-1) level any parent (ANY PARENT flag)  K level any other node (LATERAL flag)

Stateless Scoped Addressing  A subset sensors query A particular geographical area A particular attribute  Reinforcement Learning First time—  Sink sends a query with flooding.  Sensor node response relative data and its own address. Once the sink knows the relevant sensors, it can direct the query to only the nodes.

Stateless Scoped Addressing  Address Aggregation Set Approximation

Stateless Scoped Addressing  Address Aggregation Set Approximation—Threshold based  (n / N)  n: Number of nodes in subtree rooted in children nodes which did not respond to this query  N: Number of nodes in the subtree rooted at this node 45/60

Stateless Scoped Addressing  Address Aggregation Address Coalescence  Basic delta compression technique ( ) ( ) ( ) ( ), (5,6.7.8), (4,5.6.7)

Stateless Scoped Addressing  Address Aggregation Address Coalescence  Basic delta compression technique ( ) ( )( ) [( ), (5,6.7.8), (4,5.6.7)] [( ), (6,4)] E ( ) ( )

Stateless Scoped Addressing  Query Optimization ( ) ( ) [( ),(3,2.4.5)],[…………],….., [( ), (5,6.7.8), (4,5.6.7)] (1.2.3)[( ), (5,6.7.8), (4,5.6.7)] ( )( ) [( ), (5,6.7.8)][( )]

Evaluation  Ns-2 simulator  Network size:1000m x 1000m  Nodes number: 200  Nodes deployment: uniform random distribution  Radio transmission range: 125m (avg. density: 10 nodes per transmission area)

Evaluation  Simulation Parameters Parameter NameParameter Value Number of runs10 Timeout to wait for probable parents 12s Bits per level8 (2 8 address per level)

Evaluation  Scenario 200 nodes, 1000m x 1000m

Evaluation  Generated Tree

Evaluation  Levels assigned to nodes with increasing distance from sink

Evaluation  Reachability of sensor nodes under node failures

Conclusion  It has been presented a novel way to auto-configure a deployment of sensor network.  Unique address allocation lets routing messages becomes stateless and trivial.  It has been presented a stateless addressing scheme for addressing a specific group of sensors using reinforcement learning, thus decreasing message overhead.