报告题目：Distributed Zero Forcing Beamforming for Distributed MIMO
报告人简介：苏拉·达斯古帕，山东省计算中心特聘研究员，国家“千人计划”专家，美国爱荷华大学电机与计算机工程系教授，IEEE Fellow。曾获得美国总统特聘研究员奖。在高水平杂志期刊发表论文86篇，会议论文177篇，主持美国国家自然基金项目14项。担任IEEE Control Systems Society，IEEE Transactions on Circuits and Systems，IEEE Transactions on Automatic Control等多个国际知名杂志副主编，担任美国国家自然基金多个领域的专家委员。
Introduction: Multi-antenna, or MIMO technology has revolutionized wireless communication in terms of both power and spectral efficiency, and is now a part of commercial wireless standards (e.g., WiFi and cellular). MIMO techniques today, however, are fundamentally constrained by form factor and carrier wavelength, both of which limit the number of antennas that can be accommodated on a transceiver.
In recent years proposals have been made for distributed MIMO where groups of transceivers self-organize into virtual arrays that are indistinguishable in their functionality from a centralized antenna array and scale to an arbitrary number of nodes. Such distributed MIMO(DMIMO) concepts have been analyzed by theorists and dismissed by practitioners because of fundamental synchronization bottlenecks. Unlike centralized antennas, in distributed MIMO each node has its own oscillator. The frequency and phase of these oscillators undergo drift modeled by Brownian motion. Even expensive oscillators starting in perfect synchrony, become virtually incoherent within tens of milliseconds.
This talk will focus on synchronization issues involving two basic building blocks of DMIMO: distributed beamformingand distributed nullforming. In the former N-nodes collaborate to achieve a coherent beam whose power is N2-fold(as opposed to N-fold) higher than that due to a single node. Incoherence only results in an N-fold increase. In nullforming, nodes achieve a null at a prescribed location. It assists in achieving spatial-multiplexing and also secure communication. The key ingredient is scalable feedback by cooperating receivers. Our focus is on getting the transmitters to send a common message to a set of designated receivers, while protecting some other receivers, by directing a null at them.