73 research outputs found
Optimal Power Allocation by Imperfect Hardware Analysis in Untrusted Relaying Networks
By taking a variety of realistic hardware imperfections into consideration,
we propose an optimal power allocation (OPA) strategy to maximize the
instantaneous secrecy rate of a cooperative wireless network comprised of a
source, a destination and an untrusted amplify-and-forward (AF) relay. We
assume that either the source or the destination is equipped with a large-scale
multiple antennas (LSMA) system, while the rest are equipped with a single
antenna. To prevent the untrusted relay from intercepting the source message,
the destination sends an intended jamming noise to the relay, which is referred
to as destination-based cooperative jamming (DBCJ). Given this system model,
novel closed-form expressions are presented in the high signal-to-noise ratio
(SNR) regime for the ergodic secrecy rate (ESR) and the secrecy outage
probability (SOP). We further improve the secrecy performance of the system by
optimizing the associated hardware design. The results reveal that by
beneficially distributing the tolerable hardware imperfections across the
transmission and reception radio-frequency (RF) front ends of each node, the
system's secrecy rate may be improved. The engineering insight is that equally
sharing the total imperfections at the relay between the transmitter and the
receiver provides the best secrecy performance. Numerical results illustrate
that the proposed OPA together with the most appropriate hardware design
significantly increases the secrecy rate.Comment: 29 pages, 7 figures, Submitted to IEEE Transactions on Wireless
Communication
Robust Iterative Transceiver Beamforming For Multipair Two-Way Distributed Relay Networks
OAPA In this paper, the transceiver beamforming problem is studied for multipair two-way distributed relay networks, particularly with multi-antenna user nodes and in the presence of channel state errors. With multi-antenna setting on the user nodes, some of the usual signal processing tasks are shifted from the relay nodes to the user nodes with the proposed transceiver beamforming designs. The transmit beamforming vectors, distributed relay coefficients and the receive beamforming vectors are obtained by iteratively solving three sub-problems, each having a closed-form solution. The tasks of maximizing desired signal power, and reducing inter-pair interference (IPI) and noise are thus allocated to different iteration steps. By this arrangement, the transmit and receive beamformers of each user are responsible for improving its own performance and the distributed relay nodes with simple amplify-and-forward protocol aim at creating a comfortable communication environment for all user pairs. With respect to the channel uncertainty, two relay strategies are proposed considering two different requirements from the communication network: sum relay output power and individual relay output power. Our simulation demonstrates that the performance improvement can be very significant through cooperation of the three components, especially when the number of relay nodes is large
Simultaneous Wireless Information and Power Transfer for Decode-and-Forward Multi-Hop Relay Systems in Energy-Constrained IoT Networks
This paper studies a multi-hop decode-and-forward (DF) simultaneous wireless
information and power transfer (SWIPT) system where a source sends data to a
destination with the aid of multi-hop relays which do not depend on an external
energy source. To this end, we apply power splitting (PS) based SWIPT relaying
protocol so that the relays can harvest energy from the received signals from
the previous hop to reliably forward the information of the source to the
destination. We aim to solve two optimization problems relevant to our system
model. First, we minimize the transmit power at the source under the individual
quality-of-service (QoS) threshold constraints of the relays and the
destination nodes by optimizing PS ratios at the relays. The second is to
maximize the minimum system achievable rate by optimizing the PS ratio at each
relay. Based on convex optimization techniques, the globally optimal PS ratio
solution is obtained in closed-form for both problems. By setting the QoS
threshold constraint the same for each node for the source transmit power
problem, we discovered that either the minimum source transmit power or the
maximum system throughput can be found using the same approach. Numerical
results demonstrate the superiority of the proposed optimal SWIPT PS design
over conventional fixed PS ratio schemes.Comment: 14 pages, 14 figures, Accepted for Publication in IEEE Internet of
Things Journa
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