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Wireless Networks and Systems Lab

Research in the Wireless Networks and Systems Lab focuses on wireless networking, systems, and applications, including wireless LANs, cellular networks, wireless sensor networks, and their system prototyping.


Yonghe Liu, Ph.D., Lab Director

Current Students

  • Jing Wang (Ph.D.)
  • Yanliang Liu (Ph.D.)
  • Shanshan Lu (Ph.D.)
  • Sankalp Shere (M.S.)

Current Research


(Supported by the National Science Foundation: CNS-0721951)

Wireless sensor networks have revealed vast potential in providing accurate and cost-effective monitoring for a plethora of applications. In stark contrast with traditional data forwarding networks exemplified by the Internet, wireless sensor networks are uniquely characterized by drastically low data rate, often at several bytes per minute, owing to application specific requirements. Despite numerous groundbreaking work in this field, the underlying communication techniques, particularly at the physical and link layers, are still largely germinating along the Internet root and its wireless extensions. Moreover, energy efficiency has overwhelmingly relied on coordinated sleep/wakeup schemes, where communications are synchronized into a short time window. Inevitably this will augment the collision probability and irrelevant packet listening, the two dominant power consumption components in wireless networks. Motivated by recent advancements in semi-passive RFID technology, this project will develop an innovative asynchronous communication architecture, in which a sensor node is allowed to directly write data into a special, reactive module (RFID tag based) residing on the receiving node while its main platform (the central controller) is asleep. Owing to the low duty cycle of a sensor node, the proposed asynchronous architecture will liberate the network from collisions and idle listening by fully exploiting time as one dimension of resource (no conventional MAC needed) and hence achieve high energy efficiency. Furthermore, with this fundamentally new paradigm for communication in energy-constrained systems, this project will also study the overlaying computation paradigm, including sampling, in-network processing, and routing, in order to accommodate, fully unleash, and demonstrate its enormous impact.

DoC - Distributed Opportunistic Computing

(Supported by the National Science Foundation: CNS-0834493. Prof. Mohan Kumar is leading this project.)

The objective of this project is to carry out preliminary, fundamental research work in the area of opportunistic computing. When pairs of devices come within each others? communication range, opportunistically, short-lived links (or opportunistic links) are created. Opportunistic computing exploits the opportunistic links created by pair-wise contacts, to share information content, resources and services, leading to a wide variety of applications. Groups of computing nodes and their associated pair-wise contacts in an opportunistic network give rise to a distributed opportunistic computing system. Essentially, opportunistic computing can be described as distributed computing with the caveats of intermittent connectivity and delay tolerance. The novelty of the proposed work lies in the exploitation of opportunistic communication contacts to provide collaborative computing services to applications and users. The unique contributions of this project include the development of an adaptive protocol for opportunistic communication in support of computing, a middleware architecture for masking the disruptive nature of the underlying network from applications and users, and a mechanism for delay tolerant, remote execution of tasks.

CoVo: Collaborative Virtual Observation in Dynamic Environments

(Supported by the National Science Foundation: ECCS-0824120. Prof. Mohan Kumar is leading this project.)

The objective of this project is to develop a framework for anytime, anywhere collaborative virtual observation of events occurring in dynamic environments. The approach is to enhance recently developed virtual observation concepts by adapting software service composition mechanisms developed for pervasive computing systems. The observations, made at different points in time and space, are stitched together based on location, query, device, and other variables. Protocols for soft-real time delivery of data packets in heterogeneous networks comprising a combination of continuous and disruption tolerant communication channels are being developed. Middleware tools are being created to perform reactive and proactive query processing, matching, and synthesis of integrative panoramic views. The intellectual merit of the proposed work lies in the launching of the virtual observers, in retrospect, in soft real-time, on any device in a mobile environment and the concatenation of successive virtual observers to create virtual tours. Development of an integrated framework for video acquisition, stream processing, video synthesis, opportunistic networking, and integrated pervasive services in dynamic and heterogeneous environments are contributions of this project.

Defending Against Compromised Nodes in Wireless Sensor Networks: A Multi-Layer Security Framework

(Supported by Texas Advanced Research Program, ARP 2006)

In this project, we propose an integrated framework to dynamically manage deployed WSNs in a predictable, dependable and timely manner, with a goal to defend internal or external attacks in hostile and unattended environments. In particular, we propose to develop powerful and yet tractable design principles for high information assurance based on rich theoretical concepts like secret key sharing, epidemic theory, belief and trust modeling, information theory and game theory. By combining advanced mathematical tools with efficient cryptographic techniques, our framework will not only be capable of defending against simple attacks such as packet dropping, eavesdropping, and replaying, but also be capable of identifying, isolating, revoking entirely compromised nodes and purging corresponding tampered data. Our fundamental research will be augmented with prototype sensor design, manufacturing, and system integration.

Resource Allocation in Delay Tolerant Networks

(Supported by research gift from Cerion Networks)

delay tolerant networks, custody transfer can provide certain degree of reliability as a custodian node cannot discard a message unless its life time expires or the custody is transferred to another node after a commitment. We are investigating resource allocation strategies for a node to decide when a custody should be accepted.

Green Roof Monitoring

We have established a sensor network monitoring the green roof on the UTA campus. The network will allow researchers to measure and study the correlation of the sunlight, soil moisture (rainfall/irrigation) and soil temperature to plant growth.

Selected Publications

  • P. De, Y. Liu, and S. K. Das, "An Epidemic Theoretic Framework for Vulnerability Analysis of Broadcast Protocols in Wireless Sensor Networks," To appear in IEEE Transactions on Mobile Computing. [pdf].
  • P. De, Y. Liu, and S. K. Das, "Deployment aware modeling of node compromise spread in wireless sensor networks using epidemic theory," To appear in ACM Transactions on Sensor Networks. [pdf].
  • H. Luo, Y. Liu, and S. K. Das, "Distributed algorithm for enroute aggregation decision in wireless sensor networks,? to appear in IEEE Transactions on Mobile Computing. [pdf].
  • W. Zhang, Y. Liu, S. K. Das, and P. De, ?Secure data aggregation in wireless sensor networks: A watermark based authentication supportive approach,? to appear in Elsevier Pervasive and Mobile Computing.
  • S. Zhou, Y. Lin, and Y. Liu, ?Ring based optimal-level distributed wavelet transform with arbitrary filter length for wireless sensor networks,? EURASIP Journal on Advances in Signal Processing, Volume 2008.
  • G. Zhang, Y. Wu, and Y. Liu, "Stability and Sensitivity for Congestion Control in Wireless Mesh Networks with Time Varying Link Capacities," Elsevier Ad Hoc Networks, Vol. 5, no. 6, pp. 769-785, Aug. 2007.
  • H. Ma, and Y. Liu, "Some problems in directional sensor networks," International Journal of Sensor Networks, Vol. 2, no.1/2 pp. 44-52, 2007. [pdf]
  • H. Luo, Y. Liu, and S. K. Das, ?Routing correlated data in wireless sensor networks: A survey,? IEEE Network, Nov. 2007.
  • H. Luo, J. Luo, Y. Liu, and S. Das, "Adaptive Data Fusion for Energy Efficient Routing in Wireless Sensor Networks," IEEE Transactions on Computers, vol. 55, no. 10, Oct. 2006. [pdf]
  • H. Luo, Y. Liu, and S. Das, "Routing correlated data with fusion cost in wireless sensor networks," IEEE Transactions on Mobile Computing, vol. 5, no. 11, Nov. 2006. [pdf]
  • Y. Liu and S. Das, "Information Intensive Wireless Sensor Networks: Potential and Challenges," IEEE Communication Magazine, Nov. 2006. [pdf]
  • V. Gambiroza, P. Yuan, L. Balzano, Y. Liu, S. Shaefor, and E. Knightly, "Design, analysis, and implementation of DVSR: An enhanced protocol for packet rings," IEEE/ACM Transactions on Networking , 12(1), Feburary 2004.. [pdf]
  • Y. Liu, S. Gruhl, and E. Knightly, "WCFQ: an opportunistic scheudler with statistical fairness guarantee," IEEE Transactions on Wireless Communications, 2(5), September 2003. [pdf]
  • Y. Liu and B. Huang, "Network architecture for virtual enterprise modeling," in Journal of Tsinghua University, vol. 12, 1999. (in Chinese)

Book Chapters:

  • J. Wang, G. Zhang, and Y. Liu, ?Enabling multimedia wireless sensor networks," Book chapter in Handbook of Research on Mobile Multimedia - 2nd edition, Editted by I. K. Ibrahim, 2008.
  • H. Luo, G. Zhang, Y. Liu, and S. K. Das, "Adaptive Routing in Wireless Sensor Networks," Book chapter in Adaptation and Cross Layer Design in Wireless Networks, Editted by M. Ibnkahla, 2008.
  • W. Zhang, S. Das, and Y. Liu, "Security in wireless sensor networks: A survey," book chapter in "Security in Wireless Sensor Networks," Editor: X. Yang, CRC Press, 2006.


  • J. Wang, Y. Liu, and S. K. Das "Asynchronous sampling benefits wireless sensor networks," in Proceedings of IEEE Infocom 2007 Mini Conference, Phoenix, AZ, April 2008. [pdf]
  • P. De, Y. Liu, and S. K. Das "ReMo : An energy efficient reprogramming protocol for mobile sensor networks," in Proceedings of Percom 2008, Hong Kong, China, Mar. 2008. [pdf]
  • R. Yu, X. Wang, Y. Liu, and S. K. Das "Energy-efficient dominating tree construction in wireless ad hoc and sensor networks," in Proceedings of 9th International Conferences on Distributed Computing and Networking, Kolkata, India, Jan. 2008.
  • P. De, Y. Liu, and S. K. Das, "An epidemic theoretic framework for evaluating broadcast protocols in wireless sensor networks," in Proceedings of MASS 2007, Pisa, Italy, Oct. 2007.
  • Y. Hu, Y. Lin, and Y. Liu, "A simulation system for modeling and analysis of large scale sensor networks," in Proceedings of 6th International Conferences on Information, Communications and Signal Processing, Singapore, Dec. 2007.
  • Y. Hu, Y. Lin, and Y. Liu, "RAS: A robust authentication scheme for filtering false data in wireless sensor networks," in Proceedings of 15th IEEE International Conference on Networks, Adelaide, Australia, Nov. 2007.
  • H. Luo, Z. Zhang, and Y. Liu, "ReCoDa: Reliable forwarding of correlated data in sensor networks with low latency," in Proceedings of ACM IWCMC 2007, Honolulu, HI, Aug. 2007.
  • P. De, Y. Liu, and S. Das, "Evaluating broadcast protocols in sensor networks: An Epidemic Theoretic Framework," in Poster of DCOSS 2007, Santa Fe, NM, June 2007.
  • W. Zhang, Y. Liu and S. Das, "Aggregation Supportive Authentication in Wireless Sensor Networks: A Watermark Based Approach," in Proceedings of IEEE WoWMoM 2007, Helsinki, Finland, June 2007. (as extended paper)
  • L. Wang, Y. Lin, and Y. Liu, "Key Distribution for Group-based Sensor Deployment Using a Novel Interconnection Graph," in Proceedings of IEEE WoWMoM 2007, Helsinki, Finland, June 2007.
  • J. Wang, Y. Liu, and S. Das, "Asynchronous Sampling of Correlated Data in Wireless Sensor Networks," in Proceedings of IEEE WCNC 2007, Hong Kong, China, Mar. 2007.
  • T. Lewis, A. Dogan, J. Tuckery, and Y. Liu, "Target Interception by UAVs in a Sensor Network," in Proceedings of the 45th AIAA conference, Reno, NV, Jan. 2007.
  • J. Choi, Y. Liu, and R. Elmasri, "Relative Clock Drift based Secure Time Synchronization for Wireless Sensor Networks," in Proceedings of CATA 2007 conference, Honolulu, HI, Mar. 2007.
  • W. Zhang, S. Das, and Y. Liu, "A trust based framework for secure data aggregation in wireless sensor networks," in Proceedings of IEEE SECON 2006, Reston, VA, Sept. 2006.
  • S. Zhou, Y. Lin, and Y. Liu, "Ring based wavelet transform with arbitrary supports in wireless sensor networks," in Proceedings of the 14th European Signal Processing Conference, Florence, Italy, Sept. 2006.
  • P. De, Y. Liu, and S. Das, "Modeling node compromise spreading in wireless sensor networks using epidemic theory," in Proceedings of IEEE WoWMoM 2006, Niagara-Falls, NY, June 2006. [pdf]
  • G. Zhang, Y. Wu, and Y. Liu, "Stability and sensitivity for congestion control in wireless networks with time varying link capacities," in Proceedings of IEEE ICNP 2005 Boston, MA, Nov. 2005. [pdf]
  • A. Chadha, Y. Liu. and S. Das, "Group key distribution via local collaboration in wireless sensor networks," in Proceedings of IEEE SECON 2005, Santa Clara, CA, Sept. 2005. [pdf]
  • H. Luo, J. Luo, Y. Liu, and S. Das, "Energy efficient routing with adaptive data fusion in sensor Networks," in Proceedings of the Third ACM/SIGMOBILE Workshop on Foundations of Mobile Computing, Cologne, Germany, Aug. 2005. [pdf]
  • H. Ma and Y. Liu, "Correlation based video processing in video sensor networks," in Proceedings of IEEE WirelessCom?05, Maui, HI, June 2005.
  • H. Ma and Y. Liu, "On Coverage Problems of Directional Sensor Networks," in Proceedings of theInternational Conference on Mobile Ad-hoc and Sensor Networks (MSN), Wuhan, China, Dec. 2005.
  • D. Tao, H. Ma, and Y. Liu, "Energy-efficient, Cooperative Image Processing in Video Sensor Networks," in Proceedings of the Pacific-rim Conference on Multimedia, Jeju, Korea, Nov. 2005.
  • Y. Liu, "Performance of EDCF: Analysis and simulation," in Proceedings of SCI 2004, Orlando, Florida, July 2004 (invited).
  • Y. Liu and E. Knightly, "Opportunistic fair scheduling over multiple wireless channels," in Proceedings of the IEEE Infocom 2003 , San Franscio, CA, April 2003. [pdf]
  • V. Gambiroza, Y. Liu, P. Yuan, and E. Knightly, "High-performance fair bandwidth allocation for resilient packet rings," in Proceedings of the 15th ITC Specialist Seminar on Internet Traffic Engineering and Traffic Management , Wurzburg, Germany, July 2002.
  • L. Balzano, V. Gambiroza, Y. Liu, P. Yuan, E. Knightly, and S. Shaefor, "DVSR: a high-performance metro ring protocol," ACM SIGCOMM Computer Communication Review, 32(3), July 2002..
  • Y. Liu and B. Huang, "Virtual enterprise: An agent based approach for decision and control," in Proceedings of the 1999 IEEE International Conference on Systems, Man and Cybernetics , Tokyo, Japan, October 1999.
  • T. Janowski, B. Huang, and Y. Liu, "Automating partner selection for a virtual enterprise," in Proceedings of the IFIP/PRODNET Working Conference on Infrastructure for Industry Virtual Enterprises, Lisbon, Portugal, October 1999.