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Localization and Secure Localization. Learning Objectives. Understand why WSNs need localization protocols Understand localization protocols in WSNs Understand secure localization protocols. Prerequisites. Module 7 Basic concepts of network security Basic concepts of computer networks.

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## Localization and Secure Localization

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**Learning Objectives**• Understand why WSNs need localization protocols • Understand localization protocols in WSNs • Understand secure localization protocols**Prerequisites**• Module 7 • Basic concepts of network security • Basic concepts of computer networks**The Problem**• The determination of the geographical locations of sensor nodes • Why do we need Localization? • Manual configurations of locations is not feasible for large-scale WSNs • Location information is necessary for some applications and services, e.g. geographical routing • Providing each sensor with localization hardware (e.g., GPS) is expensive in terms of cost and energy consumption**Localization**• In some applications, it is essential for each node to know its location • Global Positioning System (GPS) is not always possible • GPS cannot work indoors • GPS power consumption is very high**Solutions**• Range-based • Use exact measurements (point-to-point distance estimate (range) or angle estimates) • More expensive • Ranging: the process of estimating the distance between the pair of nodes • Range-free • Only need the existences of beacon signals • Cost-effective alternative to range-based solutions**Localization Algorithms in WSNs**• Beacon Nodes know their locations • Range-based Algorithms • Sensor nodes need to measure physical distance-related properties • How to measure distance • RSSI (Received Signal Strength Indication) • ToA (Time of Arrival) • TDOA (Time Difference of Arrival) • How to estimate location • MMSE (Minimum Mean Square Estimation) • Range Free Algorithms • Do Not involve distance estimation**Range-based Solutions - MMSE**• MMSE: • Minimum Mean Square Estimation**Ideally, ei should be 0**Range-based Solutions - MMSE**Range-based Solutions - MMSE**• Rearrange the previous equations, we have • We have N equations**Range-based Solutions - MMSE**• Eliminate , we get the following N-1 equations • Hx = z**Range-based Solutions - MMSE**• x • Solution**Range-free Approach - Centroid**• Ref[Loc_1], Section 2.1**Security Concerns in WSNs**• Secure Localization Problem • Secure Localization Solutions**Secure Localization**• Attack-resistant Minimum Mean Square Estimation • Ref[Loc_2]**Minimum Mean Square Estimation**• The more inconsistent a set of location references is, the greater the corresponding mean square error should be • Ref[Loc_2], Section 2**Minimum Mean Square Estimation**• τis 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 τ • Optimal solution • Greedy solution**How to decide τ?**• Measurement error model • How to obtain? • Study the distribution of the mean square error when there are no malicious attacks**Iterative Refinement**• The larger the number of cells • More state variables need to be kept • The smaller each cell will be – precision • Iterative Refinement • Initially, the number of cells is chosen based on memory constraints • After the first round, the node may perform the voting process on the smallest rectangle that contains all the cells having the largest vote**Assignment**• 1. 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?

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