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Congestion Performance Improvement in Wireless Sensor Networks (WSN)

Junjie Xiong, Michael Lyu, Kam-Wing Ng

The Chinese University of Hong Kong

March 7, 2012

2012 IEEE Aerospace ConferenceBigsky, Montana

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Outline

MotivationLIFO Queueing Mechanisms for Congested WSNsMulti-queue Mechanisms for Congested WSNsPerformance EvaluationConclusion

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Outline

MotivationLIFO Queueing Mechanisms for Congested WSNsMulti-queue Mechanisms for Congested WSNsPerformance EvaluationConclusion

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WSN Introduction

Application-orientedSurveillance, e.g., space explorationTarget tracking

Resource-constrained E.g. Energy supply: 2 AA batteriesE.g. RAM: 10k bytes

Subject to dynamic traffic changes

RegionRegion

Base station (BS)Base station (BS)

Sensor nodes

Sensor nodes

InternetInternet

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Motivation

Serious problems happen in congested WSNs. Delay degradation: Base station (BS) cannot receive data from the

sensor nodes in time Fairness degradation: BS fails to receive data from far-away nodes

Current congestion-related methods Congestion avoidance method Congestion recovery method

No method considers improving the congestion performance in the aspect of the queueing mechanism We are the first to suggest using LIFO (Last-In, First-Out) to replace

FIFO (First-In, First-Out) in congested WSNs We also employ multi-queue mechanism

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Outline

MotivationLIFO Queueing Mechanisms for Congested WSNsMulti-queue Mechanisms for Congested WSNsPerformance EvaluationConclusion

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LIFO Queueing Mechanisms for Congested WSNs

Delay performance comparison of LIFO and FIFO.

According to the well-established theory on a congested M/M/1 queue: LIFO achieves better delay performance than that of FIFO

LIFO also achieves better delay performance than FIFO in congested WSNs.

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Fairness Definition

In a time interval T, suppose the BS receives xi packets from the i-th node, and N is the total number of nodes in the WSN. Then the fairness index the WSN is defined as:

If xi is equal to each other, then f(x) =1 (fairest).

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Fairness Performance Comparison of LIFO and FIFO (1)

Setting: Mean service time: Ts = 3s

Mean arrival time: Ti = 1s

Deadline of data freshness: Td = 30s.

The WSN is overloaded: Ts/Ti > 1

Fairness: LIFO is better.For FIFO, the nodes far away from the BS may never have

data received by the BS.For LIFO, the nodes far away from the BS will have data

received by the BS.

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Fairness Performance Comparison of LIFO and FIFO (2)

Ts = 3s, Ti = 1s , Td = 30s.

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Fairness Performance Comparison of LIFO and FIFO (3)

Ts = 3s, Ti = 1s , Td = 30s.

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Outline

MotivationLIFO Queueing Mechanisms for Congested WSNsMulti-queue Mechanisms for Congested WSNsPerformance EvaluationConclusion

Size of trees: Tree BS:10 Tree 7: 3 Tree 8: 6 Tree 9:1 Tree 14: 3

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Multi-queue Mechanisms for Congested WSNs (1)

V

V/3V/3 V/3

V/9

V/9

V/12 V/12V/12

V/36 V/36

No logical multi-queue at each

node

Multi-queue mechanism is adopted to improve fairness: Each node maintains a queue for itself, and a queue for each of its

child nodes. Each node gives higher service capacity to packets from queues

with larger length.

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Multi-queue Mechanisms for Congested WSNs (2)

V3V/10

6V/10 V/10

V/10

V/10

V/10 V/103V/10

V/10 V/10

Maintain a logical multi-queue at each

node

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Outline

MotivationLIFO Queueing Mechanisms for Congested WSNsMulti-queue Mechanisms for Congested WSNsPerformance EvaluationConclusion

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Performance Evaluation – Delay (1)

196-node networkQueue size: 30, data generation interval Ti = 200s

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Performance Evaluation – Delay (2)

Queue size: 30, deadline Td = 400s

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Performance Evaluation – Fairness (1)

Queue size: 30, data generation interval Ti = 200s

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Performance Evaluation – Fairness (2)

Queue size: 30, deadline Td = 400s

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Outline

MotivationLIFO Queueing Mechanisms for Congested WSNsMulti-queue Mechanisms for Congested WSNsPerformance EvaluationConclusion

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Conclusion

We are the first to improve the delay and fairness performance of congested WSNs with queueing mechanisms:

First, we employ LIFO instead of FIFO to improve both the delay and fairness performance.

Second, we implement a logical multi-queue mechanism.

Finally, our experiments show that the multi-queue-LIFO mechanism achieves better delay and fairness performance than the traditional FIFO.

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Q & A Thank you!