341 research outputs found
Diversity Combining for RF Energy Harvesting
RF energy harvesting (RFEH) is a promising technology for energy requirements
of wireless communication nodes. However, providing sufficient amount of energy
to ensure self-sufficient devices based on RFEH may be challenging. In this
paper, the use of diversity combining in RFEH systems is proposed to increase
the amount of harvested energy. The power consumption of diversity combining
process is also taken into account to analyze the net benefit of diversity
combining. Performances of RFEH systems are investigated for selection
combining (SC), equal gain combining (EGC), and maximal ratio combining (MRC)
techniques. Simulations are conducted to compare the numerical results of SC,
EGC, and MRC, and the results show that although the diversity combining
techniques can improve the energy harvesting performance, the power consumption
parameters have a critical importance while determining the suitable technique
Frequency Switching for Simultaneous Wireless Information and Power Transfer
A new frequency switching receiver structure is proposed for simultaneous
wireless information and power transfer in multi-carrier communication systems.
Each subcarrier is switched to either the energy harvesting unit or the
information decoding unit, according to the optimal subcarrier allocation. To
implement the system, one-bit feedback is required for each subcarrier. Two
optimization problems are defined, converted to binary knapsack problems, and
solved using dynamic programming approaches. Upper bounds are obtained using
continuous relaxations. Power allocation is integrated to further increase the
performance. Numerical studies show that the proposed frequency switching based
model is better than existing models in a wide range of parameters
Mitigation of Misalignment Error Over Inter-Satellite FSO Energy Harvesting
In this paper, the impact of the acquisition, tracking, and pointing (ATP)
module utilization on inter-satellite energy harvesting in low-earth orbit
(LEO) is investigated for various beam divergence angles. Random elevation and
azimuth misalignment error angles at both the transmitter and the receiver are
modeled with Gaussian distribution hence the radial pointing error angle can be
modeled with Rayleigh distribution statistically. Then, the misalignment loss
factors at the transmitter and receiver are obtained independently. The
harvested power as a function of the transmit power and inter-satellite
distance is analyzed along with the maximum achievable range that satisfies the
1U (i.e., 0.10.10.1 m) small satellite power requirement on
space tasks. Our simulation results show that in a free space optics (FSO) link
without the ATP module, a laser with a wider beam divergence angle
puts an effort to compensate for the loss of misalignment and hence provides
higher harvested power than narrow ones. However, when the ATP module is in
use, the laser with narrower outperforms the laser with wider
in harvested power. Furthermore, the utilization of the ATP module leads to a
significant improvement in the maximum achievable range.Comment: 5 pages, 6 figure
Joint Channel Coding and Cooperative Network Coding on PSK Constellations in Wireless Networks
In this paper, we consider the application of Reed- Solomon (RS) channel
coding for joint error correction and cooperative network coding on non-binary
phase shift keying (PSK) modulated signals. The relay first decodes the RS
channel coded messages received each in a time slot from all sources before
applying network coding (NC) by the use of bit-level exclusive OR (XOR)
operation. The network coded resulting message is then channel encoded before
its transmission to the next relay or to the destination according to the
network configuration. This scenario shows superior performance in comparison
with the case where the relay does not perform channel coding/decoding. For
different orders of PSK modulation and different wireless configurations,
simulation results demonstrate the improvements resulting from the use of RS
channel codes in terms of symbol error rate (SER) versus signal-to-noise ratio
(SNR).Comment: 6 pages, 4 figures, conferenc
Effective Capacity Analysis of H-ARQ Assisted Cooperative Communication Systems
In this paper, the effective capacity of cooperative communication (CC)
systems with hybrid Automatic repeat request (HARQ) is derived. The derived
expressions are valid for any channel distribution and with any arbitrary
number of retransmissions by the source and relay for both HARQ-repetition
redundancy (RR) and HARQ-incremental redundancy (IR) over asymmetric channels.
As an example, we use the derived EC expression over Rayleigh fading channels.
Several results are obtained for a low rate and signal-to-noise ratio (SNR). We
can see that the EC attends its maximum value with a small number of
retransmissions. As expected when the relay-destination channel has low SNR, it
is better than the relay does not participate especially when we assign a large
number of transitions at the relay. For high data rates and strict quality of
service (QoS) constraints, it is better to increase the number of relay
transmissions. Finally, when we increase the number of source retransmissions,
the effective capacity improves even for low values.Comment: 30 pages, 6 figure
Securing the Inter-Spacecraft Links: Doppler Frequency Shift based Physical Layer Key Generation
We propose a novel physical layer secret key generation method for the
inter-spacecraft communication links. By exploiting the Doppler frequency
shifts of the reciprocal spacecraft links as a unique secrecy source,
spacecrafts aim to obtain identical secret keys from their individual
observations. We obtain theoretical expressions for the key disagreement rate
(KDR). Using generalized Gauss-Laguerre quadrature, we derive closed form
expressions for the KDR. Through numerical studies, the tightness of the
provided approximations are shown. Both the theoretical and numerical results
demonstrate the validity and the practicality of the presented physical layer
key generation procedure considering the security of the communication links of
spacecrafts
Distributed Massive MIMO for LEO Satellite Networks
The ultra-dense deployment of interconnected satellites will characterize
future low Earth orbit (LEO) mega-constellations. Exploiting this towards a
more efficient satellite network (SatNet), this paper proposes a novel LEO
SatNet architecture based on distributed massive multiple-input multiple-output
(DM-MIMO) technology allowing ground user terminals to be connected to a
cluster of satellites. To this end, we investigate various aspects of
DM-MIMO-based satellite network design, the benefits of using this
architecture, the associated challenges, and the potential solutions. In
addition, we propose a distributed joint power allocation and handover
management (D-JPAHM) technique that jointly optimizes the power allocation and
handover management processes in a cross-layer manner. This framework aims to
maximize the network throughput and minimize the handover rate while
considering the quality-of-service (QoS) demands of user terminals and the
power capabilities of the satellites. Moreover, we devise an artificial
intelligence (AI)-based solution to efficiently implement the proposed D-JPAHM
framework in a manner suitable for real-time operation and the dynamic SatNet
environment. To the best of our knowledge, this is the first work to introduce
and study DM-MIMO technology in LEO SatNets. Extensive simulation results
reveal the superiority of the proposed architecture and solutions compared to
conventional approaches in the literature.Comment: arXiv admin note: text overlap with arXiv:2106.0983
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