Tsinghua Information Forum
(partially sponsored by Nokia China Research Center)
Title: Managing the Complexities of Open Spectrum
Speaker: Prof. Heather (Haitao) Zheng (Computer Science Dept, Univ. of California, Santa Barbara)
Time: 14:30-15:45, 15 August, 2006
Place: Room 1-315, FIT Building, Tsinghua University
Contact: Prof. Zhisheng Niu (62781423)
Abstract:
Cognitive radios can spark a revolution in wireless communications by making all aspects of wireless transmission and reception programmable. These devices can intelligently select the transmission format and media access technology, and modify them dynamically as needed. Specifically, devices equipped with cognitive radios can continually monitor local spectrum, discover its usage, and dynamically reconfigure themselves to transmit in appropriate frequencies.
Existing spectrum licensing policies have resulted in spectrum scarcity, including over-allocation and under-utilization of licensed bands, and an increasingly crowded unlicensed band. By leveraging cognitive radios, open spectrum systems provide opportunistic spectrum access and exploit underutilized allocated spectrum. This addresses spectrum scarcity while creating additional capacity for new wireless devices. After studying open spectrum systems for several years, government, industry and academic groups are now proposing concrete solutions to the complex challenge of spectrum management. Specifically, we are addressing issues such as efficient and fair spectrum allocation, distributed coordination, and power-conservation in spectrum allocation.
While it shows promise, the technology underlying open spectrum systems is still in its infancy. Issues in wireless communications and networking, once addressed in the context of fixed spectrum assignment, offer new research challenges in the realm of open spectrum systems. In this talk, we describe some initial studies on spectrum management of open spectrum systems. We present a set of algorithms that allow fair spectrum access through the usage of network enforced rules. We introduce both a centralized graph coloring approach that optimizes spectrum allocation for a static topology, a distributed approach where devices use local bargaining to adapt spectrum assignment over topology variations, and a light-weight rule based solution that requires minimum coordination. Next, we discuss a proactive spectrum access scheme to adapt to spectrum dynamics. We conclude by summarizing this work in context, and discussing future directions in combining these results with higher layer mechanisms to produce an end-to-end programmable and adaptive network.
Biography：
Heather (Haitao) Zheng received her B.S.degree (with highest honor) from Xian Jiaotong University in July 1995, her M.S.EE and Ph.D degree in Electrical and Computer Engineering from University of Maryland, College Park, in May 1998 and July 1999, respectively. She joined wireless research lab, Bell-Labs, Lucent Technologies as a member of technical staff in August 1999, and moved to Microsoft Research Asia as a project lead and researcher, in March 2004. Since Sept. 2005, she has been an assistant professor in Computer Science Department, Univ. of California, Santa Barbara. Dr. Zheng was recently named as the 2005 MIT Technology Review Top 35 Innovators under the age of 35 for her work on cognitive radios, and was featured in MIT Technology Review’s 10 Emerging Technologies in 2006. She also received 2002 Bell Laboratories President's Gold Award from Lucent Bell-Labs, and 1998-1999 George Harhalakis Outstanding Graduate Student Award from Institute of System Research, University of Maryland, College Park. She has served as guest editors of JSAC and EURASIP special issues and TPC members of many conferences. Dr. Zheng’s research area includes wireless communications and networking and multimedia computing.
清华信息大讲堂第十一讲（1）
Title: Capacity, cooperation, and cross-layer design in MIMO wireless networks
Speaker: Prof. Andrea Goldsmith (Dept. of Electrical Engineering, Stanford University)
Time: 16:00-17:45, 15 August, 2006
Place: Room 1-315, FIT Building, Tsinghua University
Contact: Prof. Zhisheng Niu (62781423)
Abstract:
Wireless systems of the future must support ubiquitous multimedia communications between people as well as devices. There are many research challenges associated with such systems, including limited bandwidth, random variations in the wireless channel, and battery constraints in small radio transceivers. Many of these challenges can be overcome with multiple antennas at the transmitters and receivers of the wireless network, as well as node cooperation in transmission, reception, and routing.
In this talk we will first explore the fundamental capacity limits and capacity achieving strategies of wireless channels with multiple antennas. Of particular interest are asymptotic results on the optimality of beamforming and the impact of quantized feedback for multiuser MIMO. Next we consider fundamental capacity limits in wireless networks where nodes can cooperate in transmission, reception, and routing. We propose novel cooperation techniques that approach the capacity bounds, including virtual MIMO transmission, relaying, and conferencing. The optimal cooperation strategy is cross-layer in nature and depends on the network topology, the channel SNR, and the channel side information available at the nodes. Moreover, when the network is constrained in energy or delay, cross-layer design is critical and leads to surprising forms of cooperation.
Biography：
Andrea Goldsmith is an Associate Professor of Electrical Engineering at Stanford University, and was previously an Assistant Professor of Electrical Engineering at Caltech. She has also held industry positions at Maxim Technologies and AT&T Bell Laboratories. Her research includes work on capacity of wireless channels and networks, energy-constrained wireless communications, wireless.
communications for distributed control, and cross-layer design of wireless networks. She received the B.S., M.S. and Ph.D. degrees in Electrical Engineering from U.C. Berkeley.
Dr. Goldsmith is a Fellow of the IEEE and of Stanford, and currently holds Stanford's Bredt Faculty Development Scholar Chair. She has received several awards for her research, including the National Academy of Engineering Gilbreth Lectureship, the Alfred P. Sloan Fellowship, the Stanford Terman Fellowship, the National Science Foundation CAREER Development Award, and the Office of Naval Research Young Investigator Award. She was also a co-recipient of the 2005 IEEEE Communications Society and Information Theory Society joint paper award. Dr. Goldsmith has been active in committees, conference organization, and editorial boards for the IEEE Information Theory and Communications Societies. She is a member of the Board of Governors for bothsocieties, and is a Distinguished Lecturer for the Communications Society.
