51 research outputs found
Low-cost Cognitive Radios against Spectrum Scarcity
The next generation wireless networks are envisioned to deal with the
expected thousand-fold increase in total mobile broadband data and the
hundred-fold increase in connected devices. In order to provide higher data
rates, improved end-to-end performance, low latency, and low energy consumption
at a low cost per transmission, the fifth generation (5G) systems are required
to overcome various handicaps of current cellular networks and wireless links.
One of the key handicaps of 5G systems is the performance degradation of the
communication link, due to the use of low-cost transceiver in high data rate.
Motivated by this in this paper, we discuss the impact of transceiver front-end
hardware imperfections on the spectrum sensing performance of cognitive radios.Comment: 4 pages, 4 figure
Analytical Performance Evaluation of Beamforming Under Transceivers Hardware Imperfections
In this paper, we provide the mathematical framework to evaluate and quantify
the performance of wireless systems, which employ beamforming, in the presence
of hardware imperfections at both the basestation and the user equipment. In
more detail, by taking a macroscopic view of the joint impact of hardware
imperfections, we introduce a general model that accounts for transceiver
impairments in beamforming transmissions. In order to evaluate their impact, we
present novel closed form expressions for the outage probability and upper
bounds for the characterization of the system's capacity. Our analysis reveals
that the level of imperfection can significantly constraint the ergodic
capacity. Therefore, it is important to take them into account when evaluating
and designing beamforming systems.Comment: 7 pages, 5 figures, IEEE WCNC 201
Ergodic capacity analysis of reconfigurable intelligent surface assisted wireless systems
This paper presents the analytic framework for evaluating the ergodic
capacity (EC) of the reconfigurable intelligent surface (RIS) assisted systems.
Moreover, high-signal-to-noise-ratio and high-number of reflection units (RUs)
approximations for the EC are provided. Finally, the special case in which the
RIS is equipped with a single RU is investigated. Our analysis is verified
through respective Monte Carlo simulations, which highlight the accuracy of the
proposed framework.Comment: 6 pages, 3 figures, accepted in IEEE 5G world foru
Error analysis of mixed THz0RF wireless systems
In this letter, we introduce a novel mixed terahertz (THz)-radio frequency
(RF) wireless system architecture, which can be used for backhaul/fronthaul
applications, and we deliver the theoretical framework for its performance
assessment. In more detail, after identifying the main design parameters and
characteristics, we derive novel closed-form expressions for the end-to-end
signal-to-noise ratio cumulative density function, the outage probability, and
the symbol error rate, assuming that the system experiences the joint effect of
fading and stochastic antenna misalignment. The derived analytical framework is
verified through simulations and quantifies the system's effectiveness and
reliability. Finally, our results contribute to the extraction of useful design
guidelines.Comment: 5 pages, 3 figures, accepted in IEEE Communications Letter
Outage Probability Analysis of THz Relaying Systems
This paper focuses on quantifying the outage performance of terahertz (THz)
relaying systems. In this direction, novel closed-form expressions for the
outage probability of a dual-hop relaying system, in which both the
source-relay and relay-destination links suffer from fading and stochastic beam
misalignment, are extracted. Our results reveal the importance of taking into
account the impact of beam misalignment when characterizing the outage
performance of the system as well as when selecting the transmission
frequencies.Comment: 7 pages, 10 figures, conferenc
A cooperative localization-aided tracking algorithm for THz wireless systems
In this paper, a novel cooperation-aided localization and tracking approach,
suitable for terahertz (THz) wireless systems is presented. It combines an
angle of arrival (AoA) tracking algorithm with the two-way time of arrival
method, in order to accurately track the user equipment (UE) position and
reduce the deafness caused by the estimation errors of the tracking algorithms.
This algorithm can be used by one base station (BS) to estimate the UE
position, or by multiple BSs, that cooperate with each other to increase the
accuracy of the estimations, as well as the probability of successful
estimations and guarantee low-estimation overhead. The efficiency of the
algorithm is evaluated in terms of deafness and probability of successful AoA
estimation and is compared with the corresponding performance of the fast
channel tracking algorithm.Comment: 7 pages, 6 figures, IEEE WCNC 2019 (accepted paper
I/Q-Imbalance Self-Interference Coordination
In this paper, we present a novel low-complexity scheme, which improves the
performance of single-antenna multi-carrier communication systems, suffering
from in-phase and quadrature (I/Q)-imbalance (IQI) at the receiver. We refer to
the proposed scheme as I/Q-imbalance self-interference coordination (IQSC).
IQSC does not only mitigate the detrimental effects of IQI, but, through
appropriate signal processing, also coordinates the self-interference terms
produced by IQI in order to achieve second-order frequency diversity. However,
these benefits come at the expense of a reduction in transmission rate. More
specifically, IQSC is a simple transmit diversity scheme that improves the
signal quality at the receiver by elementary signal processing operations
across symmetric (mirror) pairs of subcarriers. Thereby, the proposed
transmission protocol has a similar complexity as Alamouti's space-time block
coding scheme and does not require extra transmit power nor any feedback. To
evaluate the performance of IQSC, we derive closed-form expressions for the
resulting outage probability and symbol error rate. Interestingly, IQSC
outperforms not only existing IQI compensation schemes but also the ideal
system without IQI for the same spectral efficiency and practical target error
rates, while it achieves almost the same performance as ideal (i.e., IQI-free)
equal-rate repetition coding. Our findings reveal that IQSC is a promising
low-complexity technique for significantly increasing the reliability of
low-cost devices that suffer from high levels of IQI.Comment: Published in IEEE Transactions on Wireless Communication
Performance evaluation of THz wireless systems under the joint impact of misalignment fading and phase noise
In this paper, we investigate the joint impact of misalignment fading and
local oscillator (LO) phase noise (PHN) in multi-carrier terahertz (THz)
wireless systems. In more detail, after establishing a suitable system model
that takes into account the particularities of the THz channel, as well as the
transceivers characteristics, we present simulation results that quantify the
joint impact of misalignment fading and PHN in terms of average
signal-to-interference-plus-noise-ratio (SINR) and outage probability (OP).Comment: 2 pages, 4 figures, Presented in EuCNC201
Analytical Performance Evaluation of THz Wireless Fiber Extenders
This paper presents the theoretical framework for the performance evaluation
of terahertz (THz) wireless fiber extender in the presence of misalignment and
multipath fading. In more detail, after providing the appropriate system model
that incorporates the different operation, design, and environmental
parameters, such as the operation frequency, transceivers antenna gains, the
level of misalignment as well as the stochastic behavior of the channel, we
extract novel closed-form expressions for the ergodic capacity. These
expressions are expected to be used as useful tools for the analysis and design
of such systems. Moreover, several insightful scenarios are simulated. Their
results highlight the importance of taking into account the impact of
misalignment fading when analyzing the performance of the THz wireless fiber
extender.Comment: 6 pages, 6 figures, IEEE PIMRC, September 201
Ergodic capacity evaluation of wireless THz fiber extenders
This paper focuses on delivering quantified results for the evaluation of the
aggregated impact of stochastic antenna misalignment, multipath fading and
hardware imperfections on the terahertz (THz) wireless fiber extenders. In this
line, we present the appropriate signal model that accommodates the different
technical and environmental parameters. In particular, it takes into
consideration the antenna gains, the central frequency, the transmission range,
the environmental conditions, i.e. temperature, humidity and pressure, the
spatial jitter between the transmitter and receiver antennas, which results to
antenna misalignment, the intensity of hardware imperfections, and the
stochastic behavior of the wireless channel. Based on this model, we assess the
joint impact of antenna misalignment and multipath fading, by providing Monte
Carlo simulation results for the channels ergodic capacity.Comment: 4 pages, 2 figures, conference paper, Presented in WWRF, WG High
Frequencies (mmWAVE and THz) Radio Communications Technologies, September
201
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