Research Interests

My main research interests are mainly in communication theory, optimization theory, game theory, and learning theory, with applications in wireless network, power transfer networks, and large-scale data networks. Some specific research topics are:

  • Large-scale data networks

  • Green wireless

  • Distributed protocol design

  • Network optimization and resource management

Main Research Projects

Large-scale Data Networks with Scalable Performance

Large-scale systems continue to grow as one of the most important topics in communication, computing, and many interdisciplinary areas. It is important to develop the themes of ‘‘architecture’’ and ‘‘scalability’’ in large-scale distributed data networks:

  • Network Architecture Design: To tackle the largeness and heterogeneity of data networks, we need to build a unified communication architecture. The architecture decides the allocations of the functionalities, i.e., ‘‘who does what’’ and ‘‘how to connect them’’. The network architecture design is more fundamental, more influential, and less quantitatively understood than any specific network algorithm design.

  • Scalable Communication and Control: To tackle the distributed nature of data networks and many emerging wireless communications (e.g., device-to-device communication system), we need to design resource allocation and control schemes that only require loose coordination among communication units, and are able to adapt to the environmental changes with fast and robust convergence.

The aim of this project is to build scalable distributed data networks with throughput efficiency, low energy/power consumption, less message passing, and robust convergence. The tools and techniques from optimization, machine learning, stochastic processes, and control could be potentially useful.

Green Wireless Networks and Power Systems

Energy efficiency is becoming the critical component in both the communication systems and the power systems. With the recent advances in techniques, it is becoming possible for wireless devices to harvest energy from nature and transfer energy wirelessly. Since 2009, I have been working on improving the energy efficiency in both the mulit-cell wireless networks and the MIMO cognitive radio networks. It is promising to integrate the green energy technologies with wireless network technologies. It is important develop the themes of ‘‘dynamic design’’ and ‘‘coordinated operation’’ in green communications:

  • Dynamic Design: Unlike traditional energy sources, green energy sources (e.g., solar energy) may not be stable and are highly dependent on the local environment of the wireless devices. The green energy sources are dynamic in nature. This requires a dynamic network design and operation (e.g., network planning, resource allocation, transmission scheduling, and power control) for the wireless communication networks powered by the green energy so as to ensure the quality of service (QoS) provisioning.

  • Coordinated Operation: With the capability of transfering energy wirelessly, it is more desirable for the wireless devices to perform coordinated and collaborative operations in both information transmission and the energy transmission. The coordination should be effective, self-organized, and with less message passing among the wireless devices.

The design criterion in developing green wireless networks is shifted from energy efficiency to energy sustainability. The goal is to make the wireless networks to be energy self-sufficient, energy self-sustaining, environmentally friendly, and with practical long lifetimes. Developing innovative solutions requires interdisciplinary expertise from communication, networking, and power systems.

Network Optimization and Resource Management of Next Generation Wireless Systems

In recent years, new innovations at the physical layer of the communication systems have emerged and are becoming implementable due to the advances of technology (e.g., physical-layer network coding (PNC), full duplex, etc.). These developments have necessitated a thorough redefinition and design of efficient control and scheduling at the upper layers. For example, interference is treated as a destructive pheomenon so that an efficient MAC protocol tries to avoid. However if PNC is applied at the physical layer, useful information could be extracted from the superimposed electromagnetic waves so that ‘‘interference’’ is turned to good use. The ‘‘interference’’ term should be redefined in a proper way. The core challenge in the network optimization is how to use the scarce resources of‘‘space’’, ‘‘time’’, and ‘‘frequency’’ as efficiently possible. It is important to understand to interactions between layers and a cross-layer design is desirable to maximize the network performance.

We have begun investigating the network throughput performance in the context of CSMA networks with the ability of performing physical-layer network coding. The network throughput could be significantly improved only if the CSMA protocol is properly adjusted. With my prior research experience on cross-layer design, and network utility maximization and decomposition, I am thrilled about the evolution of the wireless networks brought by the advanced physical-layer techniques. The goal is to establish a foundation for the analysis, design, and optimization of wireless communication systems.