Research Profile of My Group

1
Research Profile of My Group

• Guoliang Xing
• Department of Computer ScienceCity University of
  Hong Kong

2
Facts of My Group

• Members
• Three PhD students
• CityU, CityU-USTC, CityU-WuhanU
• One Master student
• Two research assistants (joint supervision)
• Part of CityU wireless group
• 6 faculty members
• more than 20 research staff/students
• 3 million HK government funding in 2007-08

3
Research Directions

• Controlled mobility
• Data fusion based target detection
• Power management
• Sensing coverage

4
2007-08 Conference Publications

• Controlled mobility
• Rendezvous Design Algorithms for Wireless Sensor
  Networks with a Mobile Base Station, G. Xing, T.
  Wang, W. Jia, M. Li, MobiHoc 2008, 44/30014.6.
• Rendezvous Planning in Mobility-assisted Wireless
  Sensor Networks, G. Xing, T. Wang, Z. Xie and W.
  Jia RTSS 2007, 44/17125.7.
• Data fusion based target detection
• Mobility-assisted Spatiotemporal Detection in
  Wireless Sensor Networks, G. Xing J. Wang K.
  Shen Q. Huang H. So X. Jia, ICDCS 2008,
  102/63816.
• Collaborative Target Detection in Wireless Sensor
  Networks with Reactive Mobility, R. Tan, G. Xing,
  J. Wang and H. So, IWQoS 2008
• Power management
• Link Layer Support for Unified Radio Power
  Management in Wireless Sensor Networks. K. Klues,
  G. Xing and C. Lu, IPSN 2007 38/17022.3.
• Dynamic Multi-resolution Data Dissemination in
  Storage-centric Wireless Sensor Networks. H. Luo,
  G. Xing, M. Li, and X. Jia, MSWiM 2007,
  41/16124.8.

5
Earlier Work on Sensor Networks

• ACM/IEEE Transactions Papers
• Minimum Power Configuration for Wireless
  Communication in Sensor Networks, G. Xing C. Lu,
  Y. Zhang, Q. Huang, R. Pless, ACM Transactions on
  Sensor Networks, Vol 3(2), 2007, extended MobiHoc
  2005 paper
• Impact of Sensing Coverage on Greedy Geographic
  Routing Algorithms, G. Xing C. Lu R. Pless Q.
  Huang. IEEE Transactions on Parallel and
  Distributed Systems (TPDS),17(4), 2006, extended
  MobiHoc 2004 paper
• Integrated Coverage and Connectivity
  Configuration for Energy Conservation in Sensor
  Networks, G. Xing X. Wang Y. Zhang C. Lu R.
  Pless C. D. Gill, ACM Transactions on Sensor
  Networks, Vol. 1 (1), 2005, extended SenSys 2003
  paper, one of the most widely cited work on the
  coverage problem of sensor networks, total number
  of citations is 358 in Google Scholar.

6
Focus of this Talk

• Controlled mobility
• Rendezvous Planning in Mobility-assisted Wireless
  Sensor Networks, G. Xing, T. Wang, Z. Xie and W.
  Jia RTSS 2007, 44/17125.7.
• Power management
• Link Layer Support for Unified Radio Power
  Management in Wireless Sensor Networks. K. Klues,
  G. Xing and C. Lu, IPSN 2007 38/17022.3.
• Sensing Coverage
• Integrated Coverage and Connectivity
  Configuration for Energy Conservation in Sensor
  Networks, G. Xing X. Wang Y. Zhang C. Lu R.
  Pless C. D. Gill, ACM Transactions on Sensor
  Networks, Vol. 1 (1), 2005, extended SenSys 2003
  paper

7
Motivations

• Sensor nets face the fundamental performance
  bottleneck
• Many applications are data-intensive
• Multi-hop wireless relays are power-consuming
• A tension exists between the sheer amount of data
  generated and limited power supply
• Controlled mobility is a promising solution
• Number of related papers increases significantly
  in last 3 years MobiSys, MobiHoc, MobiCom, IPSN

8
Mobile Sensor Platforms
XYZ _at_ Yale http//www.eng.yale.edu/enalab/XYZ/
Robomote _at_ USC Dantu05robomote
Networked Infomechanical Systems (NIMS) _at_ CENS,
UCLA

• Low movement speed (0.12 m/s)
• Increased latency of data collection
• Reduced network capacity

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Basic idea

• Some nodes serve as rendezvous points (RPs)
• Other nodes send their data to the closest RP
• Mobiles visit RPs and transport data to base
  station
• Advantages
• In-network caching controlled mobility
• Mobiles can collect a large volume of data at a
  time
• Minimize disruptions due to mobility
• Mobiles contact static nodes at RPs at scheduled
  time

10
An Example
mobile node
The field is 500 500 m2 The mobile moves at
0.5 m/s It takes 20 minutes to visit six
randomly distributed RPs It takes gt 4 hours to
visit 200 randomly distributed nodes.
rendezvous point
source node
11
The Rendezvous Planning Problem

• Formulated as graph problem
• An optimal algorithm for limited-mobility without
  data aggregation
• Two approx. algorithms with aggregation

12
Focus of this Talk

• Controlled mobility
• Rendezvous Planning in Mobility-assisted Wireless
  Sensor Networks, G. Xing, T. Wang, Z. Xie and W.
  Jia RTSS 2007, 44/17125.7.
• Power management
• Link Layer Support for Unified Radio Power
  Management in Wireless Sensor Networks. K. Klues,
  G. Xing and C. Lu, IPSN 2007 38/17022.3.
• Sensing Coverage
• Integrated Coverage and Connectivity
  Configuration for Energy Conservation in Sensor
  Networks, G. Xing X. Wang Y. Zhang C. Lu R.
  Pless C. D. Gill, ACM Transactions on Sensor
  Networks, Vol. 1 (1), 2005, extended SenSys 2003
  paper

13
Traditional Core Radio Functionality
Incoming and Outgoing data buffers
State machine
Integrated Radio Power Management
CCA Functionality
Real Implementations do not separate these
functional components so nicely
14
Implementation

• Implemented UPMA in TinyOS 2.0 for both Mica2 and
  Telosb motes
• Developed interfaces with different types of MAC
• CSMA based S-MAC Ye et al. 04, B-MAC Polastre
  et al. 04
• TDMA based TRAMA Rajendran et al. 05
• Hybrid 802.15.4, Z-MAC Rhee et al. 05
• Separated sleep scheduling modules from B-MAC
• Implemented two new sleep schedulers on top of
  B-MAC

15
Focus of this Talk

• Controlled mobility
• Rendezvous Planning in Mobility-assisted Wireless
  Sensor Networks, G. Xing, T. Wang, Z. Xie and W.
  Jia RTSS 2007, 44/17125.7.
• Power management
• Link Layer Support for Unified Radio Power
  Management in Wireless Sensor Networks. K. Klues,
  G. Xing and C. Lu, IPSN 2007 38/17022.3.
• Sensing Coverage
• Integrated Coverage and Connectivity
  Configuration for Energy Conservation in Sensor
  Networks, G. Xing X. Wang Y. Zhang C. Lu R.
  Pless C. D. Gill, ACM Transactions on Sensor
  Networks, Vol. 1 (1), 2005, extended SenSys 2003
  paper

16
An Integrated Model

• Assume a number of active nodes can achieve
• K-coverage every point is monitored by at least
  K active sensors
• N-connectivity network is still connected if N-1
  active nodes fail
• Bounded routing paths hop count between any two
  nodes can be predicted
• Focus on fundamental relations between the
  constraints

Active nodes
Sensing range
Sleeping node
Communicating nodes
A network with 1-coverage and 1-connectivity
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Connectivity vs. Coverage Analytical Results

• Network connectivity does not guarantee coverage
• Connectivity only concerns with node locations
• Coverage concerns with all locations in a region
• If Rc/Rs ? 2
• K-coverage ? K-connectivity
• Implication given requirements of K-coverage and
  N-connectivity, only needs to satisfy max(K,
  N)-coverage
• Solution Coverage Configuration Protocol (CCP)
• If Rc/Rs lt 2
• CCP SPAN chen et al. 01

18
Student Profiles

• Self-motivated
• Ambitious and persistent
• Theory background
• Graph theory, optimization, probabilistic theory,
  computational geometry
• Hands-on experiences
• C/C programming, embedded systems, OS, network
  programming

19
Problem Formulation

• Given a tree T(V,E) rooted at B and sources si,
  find RPs, Ri, and a tour no longer than LvD
  that visits BURi, and
• The problem is NP-hard (reduction from the
  Traveling Salesman Problem)

dT(si,Ri) the on-tree distance between si and Ri
20
Rendezvous Planning under Limited Mobility

• The mobile only moves along routing tree
• Simplifies motion control and improves
  reliability

XYZ _at_ Yale
21
An Optimal Algorithm

• Sort edges in the descending order of the number
  of sources in descendents
• Choose a subset of (partial) edges from the
  sorted list whose length is L/2
• The mobile tour is the pre-order traversal of the
  chosen edges

22
Thanks!
23
Unified Power Management Architecture
interfaces of sleep schedulers
Protocol 2
Protocol 1
Protocol 3
Protocol 0

SyncSleep
AsyncSleep
Other Interface

parameters specified by upper-level protocols
OnTime
Mode
Param 0
OffTime
Preamble
Param 1
DutyCycling Table
LPL Table
Other Table
Power Management Abstraction

• Consistency check
• Aggregation

Power Manager
sleep scheduling protocols

Async Listening
Others
Sync Scheduler
MAC
PreambleLength
ChannelMonitor
On/Off
interfaces with MAC
PHY