1. 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

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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

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

14. 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) n
updated dgp_set[i] 1 . n n
updated general matrix
Find coordinates
largest dgp_set
Coordinates matrix
Location of mobile devices in the Ad Hoc Network Alexander Gerkules Evgeniy Litver

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

16. 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

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

18. 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

19. 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

20. 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

21. 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

22. 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

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

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