This book presents novel RIS-Based Smart Radio techniques, targeting at
achieving high-quality channel links in cellular communications via
design and optimization of the RIS construction. Unlike traditional
antenna arrays, three unique characteristics of the RIS will be revealed
in this book. First, the built-in programmable configuration of the RIS
enables analog beamforming inherently without extra hardware or signal
processing. Second, the incident signals can be controlled to partly
reflect and partly transmit through the RIS simultaneously, adding more
flexibility to signal transmission. Third, the RIS has no digital
processing capability to actively send signals nor any radio frequency
(RF) components. As such, it is necessary to develop novel channel
estimation and communication protocols, design joint digital and
RIS-based analog beamforming schemes and perform interference control
via mixed reflection and transmission. This book also investigates how
to integrate the RIS to legacy communication systems.
RIS techniques are further investigated in this book (benefited from its
ability to actively shape the propagation environment) to achieve two
types of wireless applications, i.e., RF sensing and localization. The
influence of the sensing objectives on the wireless signal propagation
can be potentially recognized by the receivers, which are then utilized
to identify the objectives in RF sensing. Unlike traditional sensing
techniques, RIS-aided sensing can actively customize the wireless
channels and generate a favorable massive number of independent paths
interacting with the sensing objectives. It is desirable to design
RIS-based sensing algorithms, and optimize RIS configurations. For the
second application, i.e., RIS aided localization, an RIS is deployed
between the access point (AP) and users. The AP can then analyze
reflected signals from users via different RIS configurations to obtain
accurate locations of users. However, this is a challenging task due to
the dynamic user topology, as well as the mutual influence between
multiple users and the RIS. Therefore, the operations of the RIS, the
AP, and multiple users need to be carefully coordinated. A new RIS-based
localization protocol for device cooperation and an RIS configuration
optimization algorithm are also required.
This book targets researchers and graduate-level students focusing on
communications and networks. Signal processing engineers, computer and
information scientists, applied mathematicians and statisticians, who
work in RIS research and development will also find this book useful.
