Mission
Research
Publication
People
Funding
RESEARCH
 

Current projects

Past work

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]

  • 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]]

  • W. Zhang, M. Tran, S. Zhu, and G. Cao, "A Random Perturbation-Based Scheme for Pairwise Key Establishment in Sensor Networks" , ACM MobiHoc 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]]

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. To efficiently support these applications, push/pull-based data dissemination techniques can be used. Although push/pull-based 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 data dissemination framework for VANET. The proposed research addresses three intertwined issues. First, we design and evaluate three push-based data dissemination schemes. Based on different application requirements, these schemes can achieve tradeoffs among dissemination capacity, dissemination coverage, access delay, protocol complexity, data consistency, and the capability of dealing with disconnections. Second, we design and evaluate pull-based data dissemination protocols suitable for sparsely connected VANET, and propose solutions to combine push/pull-based techniques to reduce the data access delay and bandwidth consumption. Finally, infrastructure support (e.g., wireless relay, infostations) is used to further improve the system performance.

SELECTED PUBLICATIONS (COMPLETE LIST)

  • Jing Zhao and Guohong Cao, "VADD: Vehicle-Assisted Data Delivery in Vehicular Ad Hoc Networks," IEEE INFOCOM , April 2006. [PDF]

  • 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]]

  • 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]]

  • T. Arnold, W. Lloyd, J. Zhao, and G. Cao, "IP Address Passing for VANETs," IEEE International Conference on Pervasive Computing and Comunications (Percom), 2008 [[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]]
  • J. Zhao, P. Zhang and G. Cao, "On Cooperative Caching in Wireless P2P Networks," IEEE International Conference on Distributed Computing Systems (ICDCS), 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 INFOCOM, March 2004, an extended version to appear in IEEE Transactions on Mobile Computing.

  • J. Teng, T. Bolbrock, G. Cao, and T. La Porta, "Sensor Relocation with Mobile Sensors: Design, Implementation, and Evaluation," IEEE International Conference on Mobile Ad-hoc and Sensor Systems (MASS) , 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)

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)

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)

Coordinated checkpointing in distributed systems: 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 [ICPP98] which relaxes the non-blocking condition while tries to minimize the blocking time, and a non-blocking algorithm [ICDCS98] 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)

 

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