"Make everything as simple as possible, but not simpler." - Albert Einstein

Gang Zhou
Assistant Professor of Computer Science

Department of Computer Science
McGlothlin-Street Hall
College of William and Mary
Williamsburg, VA 23187-8795

Email-ID AT cs.wm.edu: gzhou     Phone: 757-221-3458     Fax: 757-221-1717

Publications      Research      Teaching      Services      Short Bio

Recent and Selected Projects

QoS is nothing new in general wireless networks. But when it comes to body sensor networks, new challenges arise: (1) A body sensor network consists of two levels of sensor device: multiple dumb sensor nodes and a powerful aggregator, which requires an asymmetric QoS. (2) Existing medical sensor devices use different radio technologies, which drives the need for a radio-agnostic QoS. (3) When interference happens and the effective bandwidth reduces, the QoS design is expected to grab more resources from low priority streams and give them to higher priority streams. We develop a QoS framework that successfully deals with all the three challenges.

This work has been reported in IPSN'07, INFOCOM'08.

Different from MANET where data packets are 512+ bytes, data packets in sensor networks are usually 30~50 bytes. The small data packet sizes make the RTS/CTS frequency negotiation used in MANET a big overhead when it comes to sensor applications. Also, many multi-frequency MACs in MANET require sophisticated or even multiple radio transceivers, which are not preferred in widely deployed sensor network systems. Instead, the dominant choice is for each node to carry a single half-duplex radio transceiver. To address these new challenges, we develop MMSN, a multi-frequency MAC specially designed for wireless sensor networks.

This work has been reported in INFOCOM'06.

Both radio propagation theory and our system development experience tell us that it is misleading to use radio communication topologies as the basis for collision-free MAC designs, which unfortunately is one of the widely used strategies in wireless networking. So we develop a radio interference detection protocol, RID, which can detect the radio interference relations in running systems. The interference detection results have been used to assist developing better TDMA protocols. Our performance evaluation demonstrates that a RID-based TDMA protocol can greatly reduce radio interference within the same network and improves the MAC throughput.

Radio interference also exists across co-existing networks and devices. We envision that in 5-10 years, the world will be full of low power wireless sensor devices. Due to the independent design and development, together with the unexpected dynamics during deployment of co-existing networks and devices, the limited frequency spectrum will be extremely crowded. Besides, existing electric appliances like microwaves make the congestion even worse. One of our project goals is to develop new suites of WSN protocols that can manage the crowded spectrum.

This work has been reported in INFOCOM'05, EmNets'06.

Radio irregularity is a common phenomenon which arises from multiple factors, such as variance in RF sending power and different path losses depending on the direction of propagation. It is the first headache for most researchers who plan to build a running sensor network system. With empirical data obtained from the Mica2 and MicaZ platforms, we establish a radio model for simulation, called the Radio Irregularity Model (RIM). The RIM model is the first radio energy model that bridges the discrepancy between spherical radio models used by simulators and the physical reality of radio signals.

With the RIM model, we conduct a systematic study of the impact of radio irregularity on protocol and system designs in wireless sensor networks. We also develop a set of solutions that successfully deal with radio irregularity in running systems.

This work has been reported in MobiSys'04, TOSN'06.

This is one of the major efforts in the sensor network community to build an integrated sensor network system for surveillance missions. The focus of this effort is to acquire and verify information about enemy capabilities and positions of hostile targets. Such missions often involve a high element of risk for human personnel and require a high degree of stealthiness. Hence, the ability to deploy unmanned surveillance missions, by using wireless sensor networks, is of great practical importance for the military. In this work, we design and implement a complete running system, called VigilNet, for energy-efficient surveillance. More...

This work has been reported in SenSys'05, INFOCOM'06, TOSN'06, TECS'07