SpecEES: Collaborative Research: Stochastic Geometry Meets Channel Measurements: Comprehensive Modeling, Analysis,Fundamental Design-tradeoffs in Real-world Massive-MIMO Networks

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

One promising solution to handle the ever-increasing demand for wireless capacity is to deploy significantly higher number of antenna elements at the base station compared to the number of users in the cell. This so called Massive MIMO approach creates extra degrees of freedom that can be used to "shape" beams, thus enhancing both the energy and spectral efficiency of communication links. Massive MIMO can be implemented in a variety of ways. One extreme is the concentrated implementation in which hundreds of antennas are deployed at a single location within a cell. On the other extreme is the fully distributed implementation in which hundreds of single-antenna remote radio heads, distributed throughout the cell, are connected to a common baseband processing unit, thus forming a distributed base station. In between these extremes is the relatively less-investigated case of semi-distributed implementation in which multi-antenna remote radio heads are distributed across the cell. While the massive MIMO idea has been around for several years now, our understanding of the performance of these systems is still limited. This is mainly due to the lack of real-world propagation models (especially for the semi-distributed implementations) as well as mathematical tools that can expose performance trends for different spatial distributions of the users and base stations, both of which are known to significantly impact the performance of these systems. The main goal of this research is to develop a transformative measurements-driven analytical approach to enable the efficient deployment of massive MIMO networks ultimately leading to better customer experience, via improved spectral efficiency, and greener wireless communications, via improved energy efficiency. All the key outcomes of this project will be widely disseminated through publications, tutorials, and industry collaborations. The proposed research will develop a comprehensive measurement-driven approach to the spectral and energy efficiency analyses of massive MIMO systems by blending ideas from multiple disciplines, such as communication theory, stochastic geometry, point process theory, and propagation modeling, yielding the following key innovations: (1) stochastic geometry-aware spectral and energy efficiency metrics to facilitate fundamental analysis and fair comparison across different flavors of massive MIMO, (2) new stochastic geometry approaches to the coverage analysis of concentrated, distributed, and semi-distributed massive MIMO systems, (3) new results on the channel characterization for distributed massive MIMO systems under different classes of propagation models, (4) extensive measurement campaign (tailored to massive MIMO systems) using a one-of-its-kind channel sounder, (5) fundamentally new channel models for semi-deterministic massive MIMO setups that will incorporate correlation of the pathloss and dispersion metrics, in addition to traditionally modeled correlation of the shadowing from user to different RRHs, and (6) new massive-MIMO channel models for the millimeter-wave frequencies. This project will thus combine the powerful spatial modeling tools from stochastic geometry with real-world massive MIMO channel models to compare and contrast the performance of different flavors of massive MIMO under real-world operational constraints, which will directly impact the design, operation, and management of future cellular networks.