An Integrated Approach to Sensor Role Selection

by Mark Perillo and Wendi Heinzelman

Outline Motivation

Background

Modeling

Solution (DAPR)

Analysis

Comparison

Conclusion

1. MOTIVATION (WSN Energy Efficiency) Limited energy supply VS long network lifetimes

Hardware, Operating System, Low-level protocol design

Balance/reduce energy consumption

Reduce redundancy but ensure QoS requirement dynamic sensor selection, in-network aggregation, distributed source coding

BACKGROUND Abundant data

Filter sensors

Multi-hopping

Design routing

Diverse importance

Assign duties

Relevant Work -- Sensor Selection( Ｉ )

Principle : desired coverage

•PEAS activeness probing/querying;

•Gur game paradigmstate switching according to base station

•Sensing coverage protocolsleep/wake time scheduling according to neighbors’ with

differentiated surveillanceneighbor redundancy, coverage redundancy

•CCPcoverage and connectivity

Relevant Work -- Sensor Selection( ＩＩ )

Principle: Considering routing

less sensors + some routings + short path = desired coverage

Relevant Work – Routing Protocols( Ｉ )

Principle: Shortest path•Table-driven routing protocol•destination-sequenced distance vector routing•clusterhead gateway switch routing•the wireless routing protocol

•Source-initiated on-demand routing•ad hoc on-demand distance vector routing•dynamic source routing•temporally ordered routing algorithm•associativity-based routing•signal stability routing

Relevant Work – Routing Protocols( ＩＩ )

Principle: considering energy efficiency•Power-aware MAC layer routing•route through nodes with sufficient remaining power•route through lightly-loaded nodes

• Maximizing the network lifetime•minimize the energy consumed every packet

PROPOSALSensor selection + Energy conserved routing

PRINCIPLETo use the sensors not as important as data

generators more liberally as routers

Critical Nodes

The sensors in the sparsest regions

MODELING – Assumptions

•Power consumption largely from traffic transmitted and received

•Portion or entirety of an area A needs to be monitored by any one or multiple sensors

•There may be one or several data sink locations

MODELING -- Varianbles

MODELING – Formalization( Ｉ )

Coverage:

Number of nodes:Nt = Ns + Nsink

Data flow:

MODELING – Formalization( ＩＩ )Energy consumption:

Scheduling:

Lifetime:

MODELING – Coverage-Aware Routing CostCommon cost (energy-aware cost):

Total energy in a subset area x:

MODELING – Worst Coverage-Based Cost

Finds out the least-covered subregion

E(Xa) = 2; E(Xb) = 3; E(Xc) = 2; E(Xd) = 1;Cwc(S1) = ½; Cwc(S2) = ½; Cwc(S3) = 1;

MODELING – Comprehensive Coverage-Based Cost

Weighted sum (in terms of area of subregion) of 1/E(x)

It provides a more balanced view of a nodes importance to the sensing task.

E(Xa) = 2; E(Xb) = 3; E(Xc) = 2; E(Xd) = 1;Ccc(S1) = area(A)/2 + area(B)/2Ccc(S2) = area(A)/2 + area(B)/3+are(C)/2Ccc(S3) = area(B)/3 + area(C)/2+are(D)/1

MODELING – Combining Cost Functions

Most effective in extending lifetime with 100 percent coverage:

Effective in providing long network lifetimes with graceful degradation:

SOLUTION – DAPR (Distributed Activation with Predetermined Routers)

The decision made in sensor selection and route discovery are influenced each other.

Procedure:Route Discovery Phase

Sensor Selection Phase

Sensor query

DAPR – Route Discovery Phase( Ｉ )

Assumption:•Nodes have location information of neighbors with redundant coverage regions;•Low power wakeup system

Cost of a link = routing cost nodei x energy for transmission + routing cost nodej x energy for reception

Cost of a route = sum of links in the route

DAPR – Route Discovery Phase( ＩＩ )

Data Sink Node

Initiate query

flood query receive query

Calculate link cost

Update query packet

forward query (delay scheme): proportional to Clink(Si)

Next Node

DAPR – Sensor Selection Phase*

Initial: be inactive to sense and generate data

•Assign activation delay (proportional to the route cost)

•Check received activation beaconcheck if the neighborhood is already covered

•Send activation beaconsend activation beacon to neighbors if possible

•(Send deactivation beacon)send deactivation beacon if in high redundancy and in the highest cost route

* DAPR: A Protocol for Wireless Sensor Networks Utilizing an Application-based Routing Cost

DAPR (Cont’d)•Awareness of neighbors

•Location•Redundant coverage

•Given highest priority•Nodes along highest route•Reserving opt-out/deactivation beacon

•Sending beacon•In single hop (Dtransmission_range >> Dsensing_range)•Forwarding (no guarantee)

SIMULATION&ANALYSIS – Simulation result

SIMULATION&ANALYSIS – Experiment Result

deployment

C(Si) 1 Cea(Si) Cwc(Si) Ccc(Si)

Uniform100% coverage 362 1094 1178 90498% coverage 521 1198 1184 1200

Clustered

100% coverage 62 247 365 376

98% coverage 81 260 377 388

Video100% coverage 381 855 1063 71798% coverage 585 1097 1108 921

SIMULATION&ANALYSIS – Experiment Result for Sensor SelectionConfiguring activation/backoff delay in Worst Coverage-Coverage

Routing Cost

Selection Criteria

Random Individual Cost Cumulative Routing Cost

Uniform 1036 1088 1178

Clustered 364 365 365

Video 818 800 1063

SIMULATION&ANALYSIS – Experiment Result for Combing routing costWorst coverage-based + energy-aware routing cost

β 0 Cwc 0.05 0.25 0.5 1 Cea

Uniform 1178 1192 1224 1093 1094

Clustered 365 365 360 245 247

Video 1062 1082 1106 853 855

U + routers 1368 1572 1635 1549 1402

C + routers 476 567 576 525 403

V + routers 1214 1299 1306 1083 1083

COMPARISON – to Centralized Approach Assuming subject to these conditions:

data flow, energy consumption constraints and scheduling constraints, we try to maximize the operation time of the system

COMPARISON – to Centralized Approach

Uniform scenario: worst coverage + energy-aware cost with DAPR gains 14% over the nonintegrated approach.56% closer to centralized solution.

COMPARISON – to Centralized Approach (Cond’t)

In clustered scenario:Worst coverage routing cost with DAPR improves lifetime by 56%.77% closer to centralized solution,Due to use of the coverage-aware routing cost.

COMPARISON – to Centralized Approach (Cond’t)

In video scenario:DAPR with the combined worst coverage and energy-aware cost makes lifetime gain 50%,Closing gap by 76%,Because the selection of sensors based on the cumulative route cost.

CONCLUSIONContributionIncorporation of coverage information into the routing protocol and the

priority for sensor selection

Worst coverage-based cost – maintaining 100% coverage for the maximum lifetime

Comprehensive coveraged-based cost – giving a more balanced interpretation of a node’s value to the sensing task

Thank You