# Localization and Secure Localization

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24-Feb-2016Category

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Localization and Secure LocalizationLearning ObjectivesUnderstand why WSNs need localization protocolsUnderstand localization protocols in WSNsUnderstand secure localization protocols

PrerequisitesModule 7Basic concepts of network securityBasic concepts of computer networksThe ProblemThe determination of the geographical locations of sensor nodesWhy do we need Localization?Manual configurations of locations is not feasible for large-scale WSNsLocation information is necessary for some applications and services, e.g. geographical routingProviding each sensor with localization hardware (e.g., GPS) is expensive in terms of cost and energy consumptionLocalizationIn some applications, it is essential for each node to know its locationGlobal Positioning System (GPS) is not always possibleGPS cannot work indoorsGPS power consumption is very highSolutionsRange-basedUse exact measurements (point-to-point distance estimate (range) or angle estimates)More expensiveRanging: the process of estimating the distance between the pair of nodesRange-freeOnly need the existences of beacon signalsCost-effective alternative to range-based solutionsLocalization Algorithms in WSNsBeacon Nodes know their locationsRange-based AlgorithmsSensor nodes need to measure physical distance-related propertiesHow to measure distanceRSSI (Received Signal Strength Indication)ToA (Time of Arrival)TDOA (Time Difference of Arrival)How to estimate locationMMSE (Minimum Mean Square Estimation)Range Free AlgorithmsDo Not involve distance estimation

Localization Algorithms in WSNs

Range-based Solutions - MMSEMMSE:Minimum Mean Square Estimation

Range-based Solutions - MMSE

Ideally, ei should be 0Range-based Solutions - MMSERearrange the previous equations, we have

We have N equationsRange-based Solutions - MMSEEliminate , we get the following N-1 equations

Hx = zRange-based Solutions - MMSEH

Range-based Solutions - MMSEz

Range-based Solutions - MMSEx

SolutionRange-free Approach - CentroidRef[Loc_1], Section 2.1

Security Concerns in WSNsSecure Localization Problem

Secure Localization Solutions

Secure LocalizationAttack-resistant Minimum Mean Square EstimationRef[Loc_2]Attack-resistant Minimum Mean Square EstimationMinimum Mean Square Estimation

Ref[Loc_2], Section 2The more inconsistent a set of location references is, the greater the corresponding mean square error should beImpact of Malicious Beacons

Impact of Malicious Beacons

Minimum Mean Square Estimation is important: Depend on many factors

How to Decide the set of Consistent Location References?Given a set L of n location references and a threshold Optimal solutionGreedy solutionHow to decide ?Measurement error modelHow to obtain?Study the distribution of the mean square error when there are no malicious attacks

Voting-based Location Estimation Basic Ideas

Iterative RefinementThe larger the number of cellsMore state variables need to be keptThe smaller each cell will be precisionIterative RefinementInitially, the number of cells is chosen based on memory constraintsAfter the first round, the node may perform the voting process on the smallest rectangle that contains all the cells having the largest vote Assignment1. What is the basic idea of the MMSE-based localization protocols in wireless sensor networks?2. What is the basic idea of the MMSE-based secure localization protocols in wireless sensor networks?3. What are the differences between range-based and range-free localization algorithms?

Beacon Nodes

Sensor Node Which need to estimate its location

d0

d1

d2

(x0, y0)

(x1, y1)

(x2, y2)

Trilateration

Beacon Nodes

Sensor Node Which need to estimate its location

(xN, yN)

dN

d1

d2

How to estimate (x0, y0)?

(x1, y1)

(x2, y2)

Beacon Nodes

Sensor Node Which need to estimate its location

Compromised Beacon Signals

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