946 research outputs found
Relaying Strategies for Wireless-Powered MIMO Relay Networks
This paper investigates relaying schemes in an amplify-and-forward
multiple-input multiple-output relay network, where an energy-constrained relay
harvests wireless power from the source information flow and can be further
aided by an energy flow (EF) in the form of a wireless power transfer at the
destination. However, the joint optimization of the relay matrix and the source
precoder for the energy-flow-assisted (EFA) and the non-EFA (NEFA) schemes is
intractable. The original rate maximization problem is transformed into an
equivalent weighted mean square error minimization problem and optimized
iteratively, where the global optimum of the nonconvex source precoder
subproblem is achieved by semidefinite relaxation and rank reduction. The
iterative algorithm finally converges. Then, the simplified EFA and NEFA
schemes are proposed based on channel diagonalization, such that the matrices
optimizations can be simplified to power optimizations. Closed-form solutions
can be achieved. Simulation results reveal that the EFA schemes can outperform
the NEFA schemes. Additionally, deploying more antennas at the relay increases
the dimension of the signal space at the relay. Exploiting the additional
dimension, the EF leakage in the information detecting block can be nearly
separated from the information signal, such that the EF leakage can be
amplified with a small coefficient.Comment: Submitted for possible journal publicatio
Secure Two-Way Transmission via Wireless-Powered Untrusted Relay and External Jammer
In this paper, we propose a two-way secure communication scheme where two
transceivers exchange confidential messages via a wireless powered untrusted
amplify-and-forward (AF) relay in the presence of an external jammer. We take
into account both friendly jamming (FJ) and Gaussian noise jamming (GNJ)
scenarios. Based on the time switching (TS) architecture at the relay, the data
transmission is done in three phases. In the first phase, both the
energy-starved nodes, the untrustworthy relay and the jammer, are charged by
non-information radio frequency (RF) signals from the sources. In the second
phase, the two sources send their information signals and concurrently, the
jammer transmits artificial noise to confuse the curious relay. Finally, the
third phase is dedicated to forward a scaled version of the received signal
from the relay to the sources. For the proposed secure transmission schemes, we
derive new closed-form lower-bound expressions for the ergodic secrecy sum rate
(ESSR) in the high signal-to-noise ratio (SNR) regime. We further analyze the
asymptotic ESSR to determine the key parameters; the high SNR slope and the
high SNR power offset of the jamming based scenarios. To highlight the
performance advantage of the proposed FJ, we also examine the scenario of
without jamming (WoJ). Finally, numerical examples and discussions are provided
to acquire some engineering insights, and to demonstrate the impacts of
different system parameters on the secrecy performance of the considered
communication scenarios. The numerical results illustrate that the proposed FJ
significantly outperforms the traditional one-way communication and the
Constellation rotation approach, as well as our proposed benchmarks, the
two-way WoJ and GNJ scenarios.Comment: 14 pages, 6 figures, Submitted to IEEE Transactions on Vehicular
Technolog
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