12 research outputs found
Secrecy Throughput Maximization for Full-Duplex Wireless Powered IoT Networks under Fairness Constraints
In this paper, we study the secrecy throughput of a full-duplex wireless
powered communication network (WPCN) for internet of things (IoT). The WPCN
consists of a full-duplex multi-antenna base station (BS) and a number of
sensor nodes. The BS transmits energy all the time, and each node harvests
energy prior to its transmission time slot. The nodes sequentially transmit
their confidential information to the BS, and the other nodes are considered as
potential eavesdroppers. We first formulate the sum secrecy throughput
optimization problem of all the nodes. The optimization variables are the
duration of the time slots and the BS beamforming vectors in different time
slots. The problem is shown to be non-convex. To tackle the problem, we propose
a suboptimal two stage approach, referred to as sum secrecy throughput
maximization (SSTM). In the first stage, the BS focuses its beamforming to
blind the potential eavesdroppers (other nodes) during information transmission
time slots. Then, the optimal beamforming vector in the initial non-information
transmission time slot and the optimal time slots are derived. We then consider
fairness among the nodes and propose max-min fair (MMF) and proportional fair
(PLF) algorithms. The MMF algorithm maximizes the minimum secrecy throughput of
the nodes, while the PLF tries to achieve a good trade-off between the sum
secrecy throughput and fairness among the nodes. Through numerical simulations,
we first demonstrate the superior performance of the SSTM to uniform time
slotting and beamforming in different settings. Then, we show the effectiveness
of the proposed fair algorithms
Secure Massive MIMO Communication with Low-resolution DACs
In this paper, we investigate secure transmission in a massive multiple-input
multiple-output (MIMO) system adopting low-resolution digital-to-analog
converters (DACs). Artificial noise (AN) is deliberately transmitted
simultaneously with the confidential signals to degrade the eavesdropper's
channel quality. By applying the Bussgang theorem, a DAC quantization model is
developed which facilitates the analysis of the asymptotic achievable secrecy
rate. Interestingly, for a fixed power allocation factor , low-resolution
DACs typically result in a secrecy rate loss, but in certain cases they provide
superior performance, e.g., at low signal-to-noise ratio (SNR). Specifically,
we derive a closed-form SNR threshold which determines whether low-resolution
or high-resolution DACs are preferable for improving the secrecy rate.
Furthermore, a closed-form expression for the optimal is derived. With
AN generated in the null-space of the user channel and the optimal ,
low-resolution DACs inevitably cause secrecy rate loss. On the other hand, for
random AN with the optimal , the secrecy rate is hardly affected by the
DAC resolution because the negative impact of the quantization noise can be
compensated for by reducing the AN power. All the derived analytical results
are verified by numerical simulations.Comment: 14 pages, 10 figure
Fundamentals of Wireless Information and Power Transfer: From RF Energy Harvester Models to Signal and System Designs
Radio waves carry both energy and information simultaneously. Nevertheless,
Radio-Frequency (RF) transmission of these quantities have traditionally been
treated separately. Currently, we are experiencing a paradigm shift in wireless
network design, namely unifying wireless transmission of information and power
so as to make the best use of the RF spectrum and radiations as well as the
network infrastructure for the dual purpose of communicating and energizing. In
this paper, we review and discuss recent progress on laying the foundations of
the envisioned dual purpose networks by establishing a signal theory and design
for Wireless Information and Power Transmission (WIPT) and identifying the
fundamental tradeoff between conveying information and power wirelessly. We
start with an overview of WIPT challenges and technologies, namely Simultaneous
Wireless Information and Power Transfer (SWIPT),Wirelessly Powered
Communication Network (WPCN), and Wirelessly Powered Backscatter Communication
(WPBC). We then characterize energy harvesters and show how WIPT signal and
system designs crucially revolve around the underlying energy harvester model.
To that end, we highlight three different energy harvester models, namely one
linear model and two nonlinear models, and show how WIPT designs differ for
each of them in single-user and multi-user deployments. Topics discussed
include rate-energy region characterization, transmitter and receiver
architecture, waveform design, modulation, beamforming and input distribution
optimizations, resource allocation, and RF spectrum use. We discuss and check
the validity of the different energy harvester models and the resulting signal
theory and design based on circuit simulations, prototyping and
experimentation. We also point out numerous directions that are promising for
future research.Comment: guest editor-authored tutorial paper submitted to IEEE JSAC special
issue on wireless transmission of information and powe