Massively Distributed Data-base Systems

In-Network Query Processing(Ad-Hoc Sensor Network)

Spring 2014Ki-Joune Li

http://isel.cs.pusan.ac.kr/~likPusan National University

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Basic Concepts – in-network query processing

each node has - a local & tiny DB and- sensors

a query "find the nodes where temperature is higher than 35oC"

How to process it?

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Why in-network query processing ?

• scalable• No need to store the entire DB• Interact with neighbor nodes• A node failure is not critical

• Issue• Query processing time determined by # of hops• Energy consumption

• Battery is normally limited• Energy consumption for communication is relatively high

• SQL-like query

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Energy Consumption

in S. Banerjee, A. Misra, http://pages.cs.wisc.edu/~suman/pubs/winet03.pdf

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Energy Consumption

. . .

Prx

Ptx

Ptx

r

N r

𝑃 𝑃𝑟𝑥∝𝑃 𝑡𝑥

𝑟𝛼

What does it imply?

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Multi-hop instead of infrastructure network

• No global network topology like TCP/IP• Network topology with its neighbors

local stateless routing algorithm

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Unit-Disk Graph

• UDG: Graph G(N,E) where N is the set of nodes (sensors) andE is set of edges whose length is less than 1 (unit)

• Types if UDG• RNG• Gabriel Graph• Delaunay Graph

• Each node in V maintains the node IDs connected via edges in E

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Gabriel Graph

• Graph GG(V,E) • V is a set of nodes n (id, p) where p is a point in Euclidean space• E is a set of edge (a, b) that there is no other node within the closed

disk of (a, b)

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RNG – Relatively Neighborhood Graph

• Graph RNG(V,E) • V is a set of nodes n (id, p) where p is a point in Euclidean space• E is a set of edge (a, b) that two points a and b by an edge

whenever there is no third point c that is closer to both a and b than they are to each other (there is no other point within the intersection of the circles centered at a and b with radius the distance d(a, b))

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Delaunay Triangulation Graph

• Graph DTG(V,E) • V is a set of nodes n (id, p) where p is a point in Euclidean space• E is a set of edge e (a, b) where e is a side of triangle constructed by

Delaunay Triangulation.• Delaunay Triangulation: for a set P of points in a plane is a

triangulation DT(P) such that no point in P is inside the circumcircle of any triangle in DT(P)

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Routing - GPSR

• in Brad Karp and H.T. Kung in MobiCom 2000, pp.243-254• GPSR (Greedy Perimeter Stateless Routing)• A node x

• broadcasts a query message with destination point D• the closest node y receives and forwards the message.

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Example

full UDG with 200 nodes GG with 200 nodes(subset of full UDG)

RNG with 200 nodes(subset of GG)

GG with 200 nodes over 2Km X 2Km where radio range is 250 m

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Routing - GPSR

• Problem• both of node x are farther

from the destination D

• Right-Hand Rule: Perimeter

• Combination of UNG and Perimeter routing

circle(xD)