6.4 Global Positioning of Nodes

Advanced Operating SystemsRuizhe Ma

September 28, 2015

Overview

0. Introduction

1. Fundamentals

2. Current Work

3. Future Work

0. Introduction

For many applications, data without position is useless, so sensor nodes have to clearly state its position to be able to transmit “where the specific even is occuring”.

Moreover, knowing the position information of sensor nodes can also improve router efficiency, provide network namespaces， achieve network load balancing, network topology self configuration, etc..

1.Fundamentals

Global Positioning of Nodes

Example

Node Coordinate

Inconsistancy of Distance Measures

Global Positioning of Nodes

When the number of nodes in a distributed system grows, it becomes increasingly difficult for any node to keep track of the others.

Important for executing distributed algorithms such as routing, multicasting, data placements, searching, etc.

Simple Example

Distance corresponds to internode latency.

Given nodes P and Q, the distance d(P,Q) reflects how long it would take for a message to travel from P to Q.

Node Position ComputationPositioning a node in an m-dimensional geometric space requires m+1 distance measures to nodes with known positions.

Node Coordinate

P can compute its coordinated (Xp,Yp) by solving three equations with the two unknowns Xp and Yp:

d generally corresponds to measuring the latency between P and the node at (Xj, Yj), this value will differ over time. The effect is a different positioning whenever P would want to recompute its position.

P will also affect the accuracy of the positionin of other nodes.

Inconsistancy of Distance Measures

Measured distance by different nodes will generally not be consistant.

This can be solved simply by computing positions in a two-dimensional space.

However, this is not a general solution.

Why Simple Solution Doesn’t Work

Internet latency measurements may violate the triangle of inequality.

It is generally impossible to resolce inconsistencies completely.

2. Current Work

Common Algorithms

Node Position

Distance Estimation

Position Estimation

Common Algorithms

Range basedAHLos

RADAR

Range free Centroid

Distance Vector Hop

APIT

MAP

Amorphous

Ring Overlapping

Node Position

Range based measurement: in a sensor network when some of the position information is known, the position of other sensor nodes can be estimated using measurement and position estimation.

Range free: takes advantage of network connectivity or topology to estimate the distance, and then uses the trilateration or maximum likelihood to estimate the position.

Distance Measurement Methods

TOA (Time of Arrival)

TDOA (Time Differential of Arrival)

AOA (Angle of Arrival)

RSS (Received Sinnal Strength)

Position Estimation Methods

Trilateration

Maximum likelihood

Future Work (Research Areas)

Improved algorithms for efficiency and accuracy for distance measurement and position estimation.

Extend distance measurement model to three-dimensional.

Applying node positioning to real world applications, such as animal tracking and protection.

ReferencesTsui, James Bao-Yen. Fundamentals of global positioning system receivers. Wiley-Interscience, 2000.

Čapkun, Srdjan, Maher Hamdi, and Jean-Pierre Hubaux. "GPS-free positioning in mobile ad hoc networks." Cluster Computing 5.2 (2002): 157-167.

Niculescu, Dragoş, and Badri Nath. "DV based positioning in ad hoc networks."Telecommunication Systems 22.1-4 (2003): 267-280.

Savarese, Chris, Jan M. Rabaey, and Jan Beutel. "Location in distributed ad-hoc wireless sensor networks." Acoustics, Speech, and Signal Processing, 2001. Proceedings.(ICASSP'01). 2001 IEEE International Conference on. Vol. 4. IEEE, 2001.

Thank youQuestions?