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Current projects
Past work
Data dissemination in vehicular ad hoc networks:
Vehicular ad hoc networks (VANET) have been envisioned to be useful in road
safety and many commercial applications.
Although data dissemination techniques have been widely studied in the database
community and the network community,
many unique characteristics of VANET bring out new research challenges.
The specific goal of this project is to provide a unified data
dissemination framework for VANET.
The proposed research addresses four intertwined issues.
First, for infrastructure-assisted data dissemination, we design and
evaluate service scheduling protocols, and protocols to efficiently
utilization the bandwidth. We also propose a data pouring scheme to push
data to the users to reduce the query delay.
Second, for infrastructureless data
dissemination, we design and evaluate vehicle-assisted data delivery
protocols for sparsely connected VANET. Our solution makes use of
the predictable mobility in VANET,
which is limited by the traffic pattern and the road layout.
Third, besides using network support for data dissemination, we also look
into user-centric data dissemination to maximize data accessibility
to individual users.
Finally, we investigate
mobility characterization techniques which enable individual
vehicles to characterize the fine-grained mobility patterns of their
neighbors, which can be used for clustering or finding a stable
multi-hop route.
SELECTED PUBLICATIONS (COMPLETE LIST)
-
J. Zhao and G. Cao, "VADD: Vehicle-Assisted Data Delivery in
Vehicular Ad Hoc Networks," IEEE Transactions on Vehicular
Technology,
Vol. 57, No. 3, May 2008.
[[PDF]]
(Early version appeared in infocom'06).
-
Y. Zhang, J. Zhao, and G. Cao, "On Scheduling Vehicle-Roadside
Data Access," The Fourth ACM International Workshop on
Vehicular Ad Hoc Networks (VANET) , 2007.
[[PDF]]
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J. Zhao, Y. Zhang, and G. Cao, "Data Pouring and Buffering on The Road:
A New Data Dissemination Paradigm for Vehicular Ad Hoc Networks,"
IEEE Transactions on Vehicular Technology , Volume 56, Issue 6, pp.
3266-3277, November, 2007.
[[PDF]]
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J. Zhao, T. Arnold, Y. Zhang and G. Cao, "Extending Drive-Thru Data
Access by Vehicle-to-Vehicle Relay," ACM International Workshop on
Vehicular Ad Hoc Networks (VANET) , 2008.
[[PDF]]
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Y. Zhang, J. Zhao and G. Cao, "Roadcast: A Popularity Aware Content
Sharing Scheme in VANETs", IEEE International Conference on
Distributed Computing Systems (ICDCS), 2009.
[[PDF]]
Supporting multi-missions in wireless sensor networks:
Wireless sensor networks have been adopted to many military and
commercial applications. However, the sensor network envisioned so far
is targeted for a single mission and often designed for some particular
application. As sensors become widely deployed, multiple missions, each
with different requirements, may share common sensors to achieve their
goals. Each mission may have its own requirements for the type of data
being reported, the sampling rate, accuracy, and location of the
sampling. From resource management point of view, it will be cost
effective for the wireless sensor network to support multiple missions
instead of a single mission. The specific goal of this project is to
support multi-missions in wireless sensor networks. The project addresses
four intertwined issues: (i) various mission-driven scheduling protocols
which can optimize the sensor coverage will be designed, implemented, and
evaluated; (ii) novel techniques will be developed to disseminate the
mission switch code/command to the affected sensor nodes quickly and
efficiently; (iii) mission-driven sensor assignment schemes will be
designed to maximize the network utility; (iv) mission-specific network
configurations will be investigated to meet the real-time requirements of
data transfer for dynamic and competing missions.
SELECTED PUBLICATIONS (COMPLETE LIST)
-
C. Liu and G. Cao,
"Minimizing the Cost of Mine Selection Via Sensor Networks,"
IEEE INFOCOM, 2009.
[[PDF]]
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L. Su, C. Liu, H. Song, and G. Cao, "Routing in Intermittently
Connected Sensor Networks," IEEE International Conference on
Network Protocols (ICNP) , 2008
[[PDF]]
Security in cellular networks:
With the introduction of the iPhone, Openmoko and Android smartphones
amongst several others, we see
an increasing trend in the mobile devices domain to keep the user always
connected to the Internet. At the
same time, surveys and research show that there is an increasing number
of mobile phone malware. Besides
viruses, other types of malware like worms, spyware, adware, trojan
horses, backdoors etc. are emerging.
Moreover, these mobile phones can be used to exploit the
vulnerabilities of the cellular network to launch Denial of
Service attacks and battery attacks.
Despite the severity of these threats, research on security in cellular
networks has not received much
attention and many research challenges remain open.
This research will investigate device-side and network-side solutions for
defending against various security attacks in cellular networks.
SELECTED PUBLICATIONS (COMPLETE LIST)
-
Z. Zhu, G. Cao, S. Zhu, S. Ranjan, A. Nucci,
"A Social Network Based Patching Scheme for Worm
Containment in Cellular Networks," IEEE INFOCOM, 2009.
[[PDF]]
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B. Zhao, C. Chi, W. Gao, S. Zhu, G. Cao,
"A Chain Reaction DoS Attack on 3G Networks: Analysis and Defenses,"
IEEE INFOCOM, 2009.
[[PDF]]
Collaborative data access in wireless P2P networks:
Wireless P2P networks such as ad hoc networks, mesh networks and sensor
networks have received considerable attention due to their
potential applications in many civilian and military environments such as
disaster recovery, wireless office, battlefield and outdoor
assemblies. Design of such networks considering performance and power
optimization has become a recent research focus. As nodes in wireless P2P
networks may perform similar tasks using common data sets,
cooperative data access, which allows sharing and coordination of cached or
replicated
data among multiple nodes, can be used to reduce the bandwidth and power
consumption.
The specific goal of this project
is to provide a collaborative data access framework for wireless P2P networks.
The proposed research addresses four intertwined issues.
First, we design and evaluate two cooperative caching schemes, called
CachePath and CacheData. We identify the tradeoffs between these two
schemes, and rely on HybridCache to further improve the system performance.
Second, various cache replacement and
cache admission control algorithms are proposed and evaluated to balance the
tradeoffs between access latency and data accessibility.
Third, to further reduce the access latency and increase the data
accessibility, data replication techniques are designed and evaluated.
Finally, we identify possible security violations
to maintain data consistency and propose
solutions to defend against such attacks.
SELECTED PUBLICATIONS (COMPLETE LIST)
-
G. Cao, L. Yin, and C. Das, "
Cooperative Cache-Based Data Access
in Ad Hoc Networks," IEEE Computer, pp. 32-39, Feb.
2004.
-
L. Yin and G. Cao, "Supporting Cooperative
Caching in Ad Hoc Networks,''
IEEE Transactions on Mobile Computing , Vol. 5, No. 1, pp. 77- 89,
January, 2006.
-
J. Cao, Y. Zhang, G. Cao, and L. Xie ``Data Consistency for Cooperative
Caching
in Mobile Environments," IEEE Computer, pp. 60-66, April 2007.
[[PDF]]
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J. Zhao, P. Zhang and G. Cao, "
On Cooperative Caching in Wireless P2P
Networks," IEEE International Conference on Distributed Computing Systems
(ICDCS), 2008.
An extended version
to appear in IEEE Transactions on Parallel and Distributed Systems.
Secure wireless sensor networks:
It is a big challenge to secure wireless sensor networks because
of the network scale, the highly constrained system resource, and
the fact that sensor networks are often deployed in unattended and
hostile environments. The objective of this project is to develop
a framework for defending against node compromises in unattended
sensor networks. The framework consists of a suite of security
mechanisms spanning three phases: prevention,
detection, and reaction. This research will
provide fundamental security services covering key management,
authentication, compromise detection, and revocation. These
services are essential for the successful deployment of sensor
networks. In addition, most of the proposed solutions are designed
and implemented in a distributed manner, where no central
authority is involved. This distributed property is critical for
unattended sensor networks deployed in adversarial environments
because the central authority is a single point of failure from
security and performance perspectives.
SELECTED PUBLICATIONS (COMPLETE LIST)
-
W. Zhang and G. Cao, "Group Rekeying for Filtering False Data
in Sensor Networks: A Predistribution and Local
Collaboration-Based Approach,"
IEEE INFOCOM, March 2005.
[PDF]
-
W. Zhang, H. Song, S. Zhu, and G. Cao, "Least Privilege and
Privilege Deprivation: Towards Tolerating Mobile Sink
Compromises in Wireless Sensor Networks,"
ACM MOBIHOC, May 2005.
[PDF]
-
Y. Yang, X. Wang, S. Zhu, and G. Cao, "SDAP: A Secure
Hop-by-Hop Data Aggregation Protocol for Sensor Networks,"
ACM MobiHoc, May 2006.
[PDF]
-
M. Shao, S. Zhu, W. Zhang, and G. Cao, "pDCS: Security and
Privacy Support for Data-Centric Sensor Networks," IEEE INFOCOM,
2007.
[[PDF]]
-
M. Shao, Y. Yang, S. Zhu, and G. Cao,
"Towards Statistically Strong Source Anonymity for Sensor Networks,"
IEEE Infocom, 2008.
[[PDF]]
-
Y. Yang, S. Zhu, and G. Cao. "Improving Sensor Network Immunity under
Worm
Attacks: A Software Diversity Approach." ACM Mobihoc 2008.
[[PDF]]
Mobile sensor networks:
Traditional sensor networks have limitations when applied to support
multiple missions or when the network conditions change. Mobile sensors
can be used to address these problems as mobility can significantly
increase the capability of the sensor network by making it resilient to
failures, reactive to events, and be able to support disparate missions
with a common set of sensors. To support mobility in sensor networks, this
project investigates various research issues in mobility assisted sensing,
network monitoring, mobility assisted routing, and integrated mobility
management for sensing and routing. The expected results from this project
are: (i) Significant theoretical and technical advances in supporting
mobility in sensor networks; (ii) Understanding various performance and
power tradeoffs in designing and implementing sensor relocation protocols;
(iii) Development of network monitoring protocols, coverage hole
estimation and failure effect estimation protocols; (iv) Theoretical
advances on mobility assisted routing; and (v) Understanding of how
sensing and routing interact and how to satisfy different mission
requirements and maximize the network capability.
SELECTED PUBLICATIONS (COMPLETE LIST)
-
G. Wang, G. Cao, T. La Porta, and W. Zhang,
"Sensor Relocation in Mobile Sensor Networks,"
IEEE INFOCOM, March 2005.
[PDF]
-
G. Wang, G. Cao, and T. La Porta, ``Movement-Assisted Sensor
Deployment,''
IEEE Transactions on Mobile Computing,
Vol. 5, No. 6, pp. 640 - 652, June 2006.
[PDF]
-
G. Wang, G. Cao, P. Berman, and T. La Porta, "Bidding Protocols for
Deploying Mobile Sensors,"
IEEE Transactions on Mobile Computing, Vol. 6, No. 5, pp. 515-528,
May 2007.
[[PDF]]
Data centric sensor networks:
Sensor nodes are limited in sensing capacity and are prone to
failure, drift and loss of calibration, and hence
we can not rely on a single sensor node to obtain reliable data.
Instead, multiple nodes should be deployed in close proximity with
the target of interest to obtain fine-grained and high-precision
data. The involvement of many senor nodes in a sensing task
and the constrained energy supply of the sensor nodes
pose new challenges for designing scalable, self-organizing, and
energy efficient data collection and dissemination schemes in
sensor networks.
The specific goal of this proposal is to provide
a data-centric framework for mobile target tracking and data dissemination
in sensor networks. The proposed research addresses three intertwined
issues. The first part focuses on building
a dynamic convoy tree-based framework for data collection.
Tree reconfiguration protocols and collaborative failure
detection and recovery schemes will be designed and evaluated considering
the energy efficiency and scalability issues.
The second part proposes an index-based data dissemination framework.
Considering the scalability and reliability issues, an adaptive
ring-based index solution will be designed and evaluated.
The final part attempts to build a heterogeneous storage structure which
allows the collected sensing data to be saved locally. Protocols
will be designed to help sensor nodes find local storage, and
the tradeoffs between data quality and cost will be investigated.
SELECTED PUBLICATIONS (COMPLETE LIST)
-
W. Zhang and G. Cao, ``Optimizing Tree
Reconfiguration for Mobile Target Tracking in Sensor Networks'',
IEEE INFOCOM, March 2004.
-
W. Zhang and G. Cao, "
DCTC: Dynamic Convoy Tree-Based Collaboration for
Target Tracking in Sensor Networks ,"
IEEE Transactions on Wireless Communication, Vol. 3, No. 5, pp.
1689-1701, September, 2004.
-
W. Zhang, G. Cao, and T. La Porta, "Data Dissemination with Ring-Based
Index
for Wireless Sensor Networks," IEEE Transactions on Mobile
Computing, Vol. 6, No. 7, pp. 832-847, July 2007.
[[PDF]]
Cache invalidation and power-aware data access:
Caching is an effective technique to reduce the query latency,
bandwidth and power consumption in mobile environments.
When cache is used, cache consistency issues must be addressed.
One attractive approach is based on invalidation reports (IR), where
the server periodically broadcasts an IR in which the changed data
items are indicated. The IR-based solution is attractive because
it can tolerate client disconnections and it has good scalability.
However, it has some drawbacks such as long query latency and low bandwidth
utilization. To reduce the query latency, we proposed to
replicate the IR several times. Since the IR contains a large amount of update
history information, we proposed an optimization technique which is called
updated invalidation report (UIR), to remove the redundancy [Mobicom00].
With the UIR-based model,
we designed and evaluated stateful and stateless server approaches
to improve the bandwidth
utilization by actively prefetching the right data into the local cache.
In the stateful server approach [Monet02], a counter is used to
identify the most
frequently accessed data. Techniques are also proposed to deal with client and
server failures. In the stateless server approach [TC02],
we proposed novel solutions
to organize the broadcast channel to help clients prefetch the right data.
Since prefetch consumes power, we investigated the tradeoffs between
performance and power [Twireless04], and extended the solution
to achieve a balance between performance and power considering
various factors such as access rate, update rate, and data size.
SELECTED PUBLICATIONS (COMPLETE LIST)
-
[Mobicom00]
G. Cao, "A Scalable Low-Latency
Cache Invalidation Strategy for Mobile Environments,"
IEEE Transactions on Knowledge and Data Engineering,
Vol. 15, No. 5, September/October 2003
( A preliminary version
appeared in MOBICOM'00).
-
[TC02]
G. Cao, "
Proactive Power-Aware Cache Management for Mobile Computing Systems,"
IEEE Transactions on Computers, vol. 51, no. 6, pp. 608-621,
June 2002.
-
[Monet02]
G. Cao, " On Improving the
Performance of Cache Invalidation in Mobile Environments,"
ACM/Kluwer Mobile Networks and Application (MONET),
Vol. 7, no. 4, pp. 291-303, August 2002
-
[Twireless04]
L. Yin and G. Cao, "
Adaptive Power-Aware Prefetch in Wireless Networks ,"
IEEE Transactions on Wireless Communication, Vol. 3, No. 5,
pp. 1648-1658, September, 2004.
Resource management in wireless networks:
Putting the wireless network interface (WNI) into sleep when the WNI is
idle is an effective technique
to save power. To support streaming applications,
existing techniques cannot put the WNI into sleep due to
strict delay requirements. we have
proposed a novel power-aware and QoS-aware service model
[infocom04b],
where mobile nodes use proxies to buffer data so that the WNIs can sleep
for a long time period. To achieve power-aware communication
while satisfying the delay requirement of each flow,
a scheduling scheme is designed to decide which flow
should be served at which time. To deal with channel errors,
a novel adaptive technique is developed to adjust the sleep time of the WNI
according to the channel condition.
We are also investigating techniques to improve
the performance of Wireless LANs through scheduling.
Since wireless LAN supports multiple data rates in response to different
channel conditions, data packets may be delivered faster through a relay
node than through a direct link if the direct link has low quality and low
rate. To enable MAC layer relay, we have designed and evaluated protocols
[infocom05] to help mobile nodes collect
information about the channel conditions, and notify each other which
data rate to use and whether to transmit the data through a relay station.
SELECTED PUBLICATIONS (COMPLETE LIST)
-
[infocom05]
H. Zhu and G. Cao, "rDCF: A Relay-enabled
Medium Access Control Protocol for Wireless Ad Hoc Networks,"
IEEE Transactions on Mobile Computing, Vol. 5, No. 9,
pp. 1201-1204, September, 2006. (A preliminary version appeared in
infocom'05.)
-
[infocom04b]
H. Zhu and G. Cao, ``A Power-Aware and
QoS-Aware Service Model on Wireless Networks,''
IEEE INFOCOM, March 2004.
An extended version appeared in IEEE Transactions on
Mobile Computing, Vol. 4, No. 4, July/August, pp. 391-403, 2005.
Distributed fault-tolerant computing:
Coordinated checkpointing is an attractive approach
for transparently adding fault tolerance to distributed applications.
We have developed a theory of ``z-dependency'' [TPDS98] to
catch the essence of coordinated checkpointing and proved that there
does not exist a non-blocking algorithm, which forces only a minimum number of
processes to take their checkpoints. Based on this impossibility result,
we have proposed a min-process algorithm which relaxes the
non-blocking condition while tries to minimize the blocking time,
and a non-blocking algorithm [TPDS01] which relaxes the
min-process condition while minimizing the number of checkpoints saved
on the stable storage. The proposed non-blocking
algorithm is based on a novel concept called ``mutable checkpoint''
which is neither a tentative checkpoint nor a
permanent checkpoint. Mutable checkpoints can be saved anywhere;
e.g., the main memory or local disk of the mobile nodes.
In this way, taking a mutable checkpoint
avoids the overhead of transferring large amount of data to the stable
storage at the base station over the wireless network.
We have also designed and evaluated techniques to minimize the number
of mutable checkpoints.
SELECTED PUBLICATIONS (COMPLETE LIST)
-
[TPDS01]
G. Cao and M. Singhal, "
Mutable Checkpoints:
A New Checkpointing Approach for Mobile Computing Systems ,"
IEEE Transactions on Parallel and Distributed Systems,
vol. 12, no.2, pp. 157-172, Feb. 2001.
-
[TPDS98]
G. Cao and M. Singhal,
"On Coordinated
Checkpointing in Distributed Systems," IEEE Transactions on Parallel
and Distributed Systems, vol. 9, no.12, pp. 1213-1225, Dec. 1998.
-
G. Cao and M. Singhal, "Distributed
Fault-Tolerant Channel Allocation for Cellular Networks,"
IEEE Journal on Selected Areas in Communications,
Vol. 18, No. 7, pp. 1326-1337, July 2000.
- G. Cao and M. Singhal, "
A Delay-Optimal Quorum-Based Mutual Exclusion Algorithm
for Distributed Systems ,"
IEEE Transactions on Parallel and Distributed Systems,
vol. 12, no. 12, pp. 1256-1268, Dec. 2001.
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