localization and secure localization
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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. - PowerPoint PPT PresentationTRANSCRIPT
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
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
Localization Algorithms in WSNs
Beacon Nodes
Sensor Node Which need to estimate its location
d0
d1
d2
(x0, y0)
(x1, y1)
(x2, y2)Trilateration
Range-based Solutions - MMSE
• MMSE:– Minimum Mean Square
Estimation
Beacon Nodes
Sensor Node Which need to estimate its location
dN
d1
d2
How to estimate (x0, y0)?
(x1, y1)
(x2, y2)
(xN, yN)
Range-based Solutions - MMSE
• Ideally, ei should be 0
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
• H
Range-based Solutions - MMSE
• z
Range-based Solutions - MMSE
• x
• Solution
Range-free Approach - Centroid
• Ref[Loc_1], Section 2.1
Security Concerns in WSNs
• Secure Localization Problem
Beacon Nodes
Sensor Node Which need to estimate its location
Compromised Beacon Signals
• Secure Localization Solutions
Secure Localization
• Attack-resistant Minimum Mean Square Estimation
• Ref[Loc_2]
Attack-resistant Minimum Mean Square Estimation
Minimum Mean Square Estimation
• Ref[Loc_2], Section 2
• The more inconsistent a set of location references is, the greater the corresponding mean square error should be
Impact of Malicious Beacons
Impact of Malicious Beacons
Minimum Mean Square Estimation
• τ 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 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
Voting-based Location Estimation – Basic Ideas
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?