Processing Monitoring Queries on Mobile Objects

1
Processing Monitoring Queries on Mobile Objects
CS461 Lecture Department of Computer
Science Iowa State University
2
What is a mobile database?

• A mobile database is a set of mobile devices
• Centralized there exists a central server with
  which each mobile device can communicate
• Decentralized these devices form a network by
  themselves
• Mobile ad hoc network (MANET)
• Mesh networks

3
Characteristics

• Large number of mobile objects
• Continuous movement of mobile objects
• Limited battery power
• Limited communication bandwidth

4
Processing Range-Monitoring Query

• What is range-monitoring query?
• Retrieve mobile objects in a spatial region, and
• continuously monitor the population in the area

5
Range-Monitoring Queries
Q2
a
d
e
Q1
c
b
f
6
Range-Monitoring Queries
Q2
a
d
Q1
e
b
c
f
7
Some Potential Applications

• Tourist guiding
• Automatic traffic control
• Digital battlefield vehicle tracking
• Wild animal tracking

8
Research Issues

• How to minimize location updates?
• Excessive mobile communication could drain
  battery power quickly
• How to minimize server processing cost?
• Query results keep changing

9
Related Works

• Location Estimation Woflson98, Woflson99, etc.
• Trajectory Indexing Kollios99, Saltenis00, etc.
• Safe Region Approach Prabhakar00, Prabhakar01

10
Safe Regions
Rectangular Safe Region
Q1
Q2
Q5
a
Q3
Q4
Circular Safe Region
11
Problems with Safe Regions

• Computing a safe region takes from O(n) to O(n
  log3 n)
• Adding a new query requires to re-compute safe
  regions for all objects

12
Challenge

• How to provide
• accurate query results, and
• real-time updates?

13
Proposed Monitoring-Query Management
Q1
Q6
Q3
Q2
a
Q5
Q7
Q4
Resident Domain
14
Computing a Resident Domain

• Given an objects position P and its processing
  capability N, its resident domain should

• contain position P, and

• be as large as possible, but

• contain no more than N queries

15
Domain and Query Decomposition
Q2
Q3
R1
R21
R22
Q1
R31
Q4
R42
R41
16
Domain and Query Decomposition
Q2
Q3
R1
R21
R22
Q1
R31
a
Q4
R42
R41
17
Domain and Query Decomposition
Q2
Q3
R1
R21
R22
Q1
R31
a
Q4
R42
R41
18
Domain Tree (D-tree)
D
domain node
D
data node
19
Domain Tree (D-tree)
D
d1
d2
d1
d2
20
Domain Tree (D-tree)
D
d21
d1
d2
d1
d21
d22
d22
21
Mobile Communication Cost
30
25
20
Safe Region
15
Number of messages sent by mobile objects
(millions)
MQM
10
5
0
10
20
30
40
50
60
70
80
90
100
Number of monitoring queries (thousands)
22
Server Processing Cost
1000
100
Safe Region
10
MQM
Number of index nodes accessed (millions)
1
0.1
10
20
30
40
50
60
70
80
90
100
Number of monitoring queries (thousands)
23
Significant and Impact of MQM

• MQM is the first scalable technique, in terms of
  mobile communication and server processing costs,
  for real-time range-monitoring query management

24
Questions

• Any other types of queries?
• Can any type of queries be converted into one or
  a number of range monitoring query?