1,380 research outputs found
Energy-Efficient Cooperative Protocols for Full-Duplex Relay Channels
In this work, energy-efficient cooperative protocols are studied for
full-duplex relaying (FDR) with loopback interference. In these protocols,
relay assistance is only sought under certain conditions on the different link
outages to ensure effective cooperation. Recently, an energy-efficient
selective decode-and-forward protocol was proposed for FDR, and was shown to
outperform existing schemes in terms of outage. Here, we propose an incremental
selective decode-and-forward protocol that offers additional power savings,
while keeping the same outage performance. We compare the performance of the
two protocols in terms of the end-to-end signal-to-noise ratio cumulative
distribution function via closed-form expressions. Finally, we corroborate our
theoretical results with simulation, and show the relative relay power savings
in comparison to non-selective cooperation in which the relay cooperates
regardless of channel conditions
Performance assessment of a radio access network augmented with user equipment enabled with relaying capabilities
This Master's Thesis is encompassed in a vision of a Beyond 5G (B5G) scenario, where the User Equipment is exploited not only to satisfy the specific needs of the user, but also to augment the Radio Access Network (RAN) infrastructure. The research work has consisted in studying and analysing the deployment of a network using UEs as relaying devices in order to achieve an augmented RAN that will be able to offer a better performance to the users, including higher spectral efficiency, and lower outage probability. The conducted studies have consisted in performing variations on the configuration parameters of the network, as well as characterising the relay nodes, by means of simulations. The obtained results have then been analysed, evaluating them in terms of spectral efficiency and outage probability, and a specific relay activation strategy has been proposed, which has proven to introduce improvements in the network performance
Double-Directional Information Azimuth Spectrum and Relay Network Tomography for a Decentralized Wireless Relay Network
A novel channel representation for a two-hop decentralized wireless relay
network (DWRN) is proposed, where the relays operate in a completely
distributive fashion. The modeling paradigm applies an analogous approach to
the description method for a double-directional multipath propagation channel,
and takes into account the finite system spatial resolution and the extended
relay listening/transmitting time. Specifically, the double-directional
information azimuth spectrum (IAS) is formulated to provide a compact
representation of information flows in a DWRN. The proposed channel
representation is then analyzed from a geometrically-based statistical modeling
perspective. Finally, we look into the problem of relay network tomography
(RNT), which solves an inverse problem to infer the internal structure of a
DWRN by using the instantaneous doubledirectional IAS recorded at multiple
measuring nodes exterior to the relay region
On the Performance of Millimeter Wave-based RF-FSO Multi-hop and Mesh Networks
This paper studies the performance of multi-hop and mesh networks composed of
millimeter wave (MMW)-based radio frequency (RF) and free-space optical (FSO)
links. The results are obtained in cases with and without hybrid automatic
repeat request (HARQ). Taking the MMW characteristics of the RF links into
account, we derive closed-form expressions for the networks' outage probability
and ergodic achievable rates. We also evaluate the effect of various parameters
such as power amplifiers efficiency, number of antennas as well as different
coherence times of the RF and the FSO links on the system performance. Finally,
we determine the minimum number of the transmit antennas in the RF link such
that the same rate is supported in the RF- and the FSO-based hops. The results
show the efficiency of the RF-FSO setups in different conditions. Moreover,
HARQ can effectively improve the outage probability/energy efficiency, and
compensate for the effect of hardware impairments in RF-FSO networks. For
common parameter settings of the RF-FSO dual-hop networks, outage probability
of 10^{-4} and code rate of 3 nats-per-channel-use, the implementation of HARQ
with a maximum of 2 and 3 retransmissions reduces the required power, compared
to cases with open-loop communication, by 13 and 17 dB, respectively.Comment: Submitted to IEEE Transactions on Wireless Communication
V2V-Assisted V2I MmWave Communication for Cooperative Perception with Information Value-Based Relay
Millimeter-wave (mmWave) vehicular communication is a key technology that enables autonomous vehicles to collaborate in environment perception, thereby improving traffic efficiency and safety to a new level. Many recent works have focused on relay-based solutions to overcome the inherent defects of mmWave, such as the severe path loss and its sensitivity to blockages. However, the selfishness of the vehicles is often ignored. Considering the application-oriented nature of vehicular communication, we propose an information value-based relay strategy for mmWave vehicle-to-infrastructure (V2I) transmission in this paper. Specifically, the vehicles are allowed to make relay decisions based on the evaluation of the value of messages from their own perspectives. To this end, a simple relay probability model based on the required awareness range is introduced. Through the use of stochastic geometry to model the vehicular network, the outage performance is analyzed and the results are validated by simulations. Impacts of both network and application related parameters on the outage performance are investigated. These preliminary results laid the foundation for the further expansion of the information value-based relay strategies to a wider range of network settings
Impact Assessment of Hypothesized Cyberattacks on Interconnected Bulk Power Systems
The first-ever Ukraine cyberattack on power grid has proven its devastation
by hacking into their critical cyber assets. With administrative privileges
accessing substation networks/local control centers, one intelligent way of
coordinated cyberattacks is to execute a series of disruptive switching
executions on multiple substations using compromised supervisory control and
data acquisition (SCADA) systems. These actions can cause significant impacts
to an interconnected power grid. Unlike the previous power blackouts, such
high-impact initiating events can aggravate operating conditions, initiating
instability that may lead to system-wide cascading failure. A systemic
evaluation of "nightmare" scenarios is highly desirable for asset owners to
manage and prioritize the maintenance and investment in protecting their
cyberinfrastructure. This survey paper is a conceptual expansion of real-time
monitoring, anomaly detection, impact analyses, and mitigation (RAIM) framework
that emphasizes on the resulting impacts, both on steady-state and dynamic
aspects of power system stability. Hypothetically, we associate the
combinatorial analyses of steady state on substations/components outages and
dynamics of the sequential switching orders as part of the permutation. The
expanded framework includes (1) critical/noncritical combination verification,
(2) cascade confirmation, and (3) combination re-evaluation. This paper ends
with a discussion of the open issues for metrics and future design pertaining
the impact quantification of cyber-related contingencies
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