Location of mobile devices in the Ad Hoc Network Ben-Gurion University of the Negev Department of Communication Systems Engineering Location of mobile devices in the Ad Hoc Network Supervisor: Dr. Michael Segal Technical adviser: Mr. Michael Rothschild Students: Alexander Gerkules Evgeniy Litver

Contents Motivation Background Project Goal Heuristic algorithm Distance measurements Future work Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Motivation Who need it? Why they need to know location? search & rescue teams military forces medical units fire fighters police Why they need to know location? coordinate activity of teams economize time save the life Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Motivation (cont.) Why GPS is not suitable? GPS signal can be too weak (e.g., indoor) GPS signal can be jammed GPS receiver has to be avoided for integration reasons cost Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Background What is wireless Ad Hoc Network? An autonomous self organizing system of mobile nodes connected by wireless links where nodes not in direct range communicate via intermediate nodes. Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Background (cont.) Advantage of usage mobile Ad Hoc Network works without the assistance of any centralized structures suited for an environment where either the infrastructure is lost where deploy an infrastructure is not very cost effective Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Background (cont.) Distance Geometry Problem (DGP) Complexity of DGP reconstruction location of nodes (graph), based on set of distance between nodes. Complexity of DGP problems with all distances solvable in O(n3) problems with sparse sets of distances: NP-complete Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Project Goal Heuristic algorithm which solve DGP RSSI technology for distance measurements Check performance of distributed algorithm by using clever broadcast, implemented in Maxtech Networks ad hoc devices Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Heuristic algorithm Study of the existing algorithms which offer a solution to the problem Development Implementation Simulations Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Existing algorithms Anchor-based algorithms- rely on anchor nodes assume that a certain minimum number or fraction of the nodes know their position Anchor-free algorithms- use local distance information to attempt to determine node coordinates when no nodes have preconfigured positions Incremental algorithms- start with a core of three or four nodes with assigned coordinates. Then they repeatedly add appropriate nodes to this set by calculating the node’s coordinates using the measured distances to previous nodes with already computed coordinates Concurrent algorithms- all the nodes calculate and refine their coordinate information in parallel Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Development Consider N nodes labeled 1… N, at unknown distinct locations in some physical region Every node have the range matrix D, where dij is a distance from node i to j In case measurement of distance from node i to node j is unsuccessful, dij=x Every node runs the algorithm Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Assumption We are assume, that accuracy of measurements is at least 10-3 m. Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

High Level DGP Solve block 1 . . . n x y z Partial distance matrix (nxn) 1 . n 1 . . . n DGP Solve block x y z 1 … n Coordinates of nodes Coordinates of 4 random nodes x y z 1 2 3 4 Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

DGP Solve block sets_array (array of dgp_set) Build Up general matrix original coordinates Build Up dgp_set[i] sets_array (array of dgp_set) 1 ... n updated dgp_set[i] 1 . n 1 . . . n updated general matrix Find coordinates largest dgp_set Coordinates matrix Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Build Up Nodes: z d1 Initial set y d2 x Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Implementation For implementation of our project we use visual studio C++ environments with additional library LEDA for visual C++. Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Simulation example Run simulation Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Simulation results Number of nodes Dropping probability ( % ) Reconstruction probability ( % ) 50 40 95 55 87 70 75 96 90 78 100 99 91 Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

RSSI Received Signal Strength Indication is a measurement of the received radio signal strength (energy integral, not the quality) Distance Estimation with RSSI in Theory: PR – received strength GR – gain of receiver PS – transmitted strength GS – gain of transmitter λ0 – wave length d - distance Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Problem with RSSI Transceiver sensitivity Signals in real world are strongly influenced Attenuation when passing objects Signal propagation characteristics can change frequently Received Signal Strength depends on battery level Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

RSSI Conclusions Generally, 3-D deployments is Similar distances can produce very different RSSI values Very different distances can produce the same RSSI values Generally, 3-D deployments is extremely difficult if not impossible Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Future work Observe Ultra Wide Band technology for distance measurements Check performance of distributed algorithm by using clever broadcast, implemented in Maxtech Networks ad hoc devices Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Questions ? Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

Thank you Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver