# A Distributed Algorithm for the Dead End Problem of Location Based Routing in Sensor Networks Le Zou, Mi Lu, Zixiang Xiong, Department of Electrical Engineering,

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A Distributed Algorithm for the Dead End Problem of Location Based Routing in Sensor Networks Le Zou, Mi Lu, Zixiang Xiong, Department of Electrical Engineering, Texas A&M University IEEE Transactions,Vehicular Technology 2005

Outline Introduction Network Model The PAGER (partial-partition avoiding geographic routing) Algorithm Simulation Conclusions

Introduction Base Station Sensor nodes Sensor nodes forward data packets to BS in a multihop manner

Introduction Base Station The dead end problem x y Greedy forwarding z g Concave Node: distance(x,BS) < distance(y,BS ) ∀ y ∈ N(x),

Introduction Sink Destination GPSR (RHR)

Introduction st Face Routing

Network Model A number of sensor nodes randomly deployed on an unobstructed two-dimensional sensing field with a BS. All sensor nodes within communication range r The BS is located either adjacent to the sensing field or inside it Each node knows the location information of the BS.

The PAGER Algorithm The Shadow Spread Phase Divides a connected graph into subgraphs originated from concave nodes The Cost Spread Phase Establishes paths on a given subgraph obtained in the first phase

The Shadow Spread Phase Base Station A B C D E F concave node

The Cost Spread Phase 5 12 7 16 20 Base Station 18 8 15 16 20 19 23 A B C D E F Euclidian distance to the BS 19+∆ ∆ should be set to the average Euclidean distance between neighboring sensor nodes ∆ is set to 3 in this example 22

The Cost Spread Phase 5 12 7 16 20 Base Station 18 8 15 16 20 19 23 A B C D E F 22+∆ 22 25

The Cost Spread Phase 5 12 7 16 20 Base Station 18 8 15 16 20 19 23 A B C D E F 23+∆ 22 25 26

The Cost Spread Phase 5 12 7 16 20 Base Station 18 8 15 16 20 19 23 A B C D E F 26+∆ 26 25 22 29

The Cost Spread Phase Once the status of a sensor node turns from bright to shadow, the cost spread phase can be triggered on that node immediately The convergence length of the cost spread algorithm in the whole sensor network is only associated with the maximum size of these shadow areas

Multiple BS BS 1BS 2

PAGER-M A changes its status to “bright”, then sends out beacon message

Path Redundancy We use path redundancy to reduce forwarding failure Choosing the neighbor with closest arrival time among available forwarding candidates

Simulation ~PAGER-S

Simulation ~PAGER-M

Conclusions PAGER has the loop free guarantee delivery property The mobility adaptability of PAGE make it suitable for use in mobile sensor networks with frequent topology changes

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