23 research outputs found
Relaying in the Internet of Things (IoT): A Survey
The deployment of relays between Internet of Things (IoT) end devices and gateways can improve link quality. In cellular-based IoT, relays have the potential to reduce base station overload. The energy expended in single-hop long-range communication can be reduced if relays listen to transmissions of end devices and forward these observations to gateways. However, incorporating relays into IoT networks faces some challenges. IoT end devices are designed primarily for uplink communication of small-sized observations toward the network; hence, opportunistically using end devices as relays needs a redesign of both the medium access control (MAC) layer protocol of such end devices and possible addition of new communication interfaces. Additionally, the wake-up time of IoT end devices needs to be synchronized with that of the relays. For cellular-based IoT, the possibility of using infrastructure relays exists, and noncellular IoT networks can leverage the presence of mobile devices for relaying, for example, in remote healthcare. However, the latter presents problems of incentivizing relay participation and managing the mobility of relays. Furthermore, although relays can increase the lifetime of IoT networks, deploying relays implies the need for additional batteries to power them. This can erode the energy efficiency gain that relays offer. Therefore, designing relay-assisted IoT networks that provide acceptable trade-offs is key, and this goes beyond adding an extra transmit RF chain to a relay-enabled IoT end device. There has been increasing research interest in IoT relaying, as demonstrated in the available literature. Works that consider these issues are surveyed in this paper to provide insight into the state of the art, provide design insights for network designers and motivate future research directions
A Comprehensive Overview on 5G-and-Beyond Networks with UAVs: From Communications to Sensing and Intelligence
Due to the advancements in cellular technologies and the dense deployment of
cellular infrastructure, integrating unmanned aerial vehicles (UAVs) into the
fifth-generation (5G) and beyond cellular networks is a promising solution to
achieve safe UAV operation as well as enabling diversified applications with
mission-specific payload data delivery. In particular, 5G networks need to
support three typical usage scenarios, namely, enhanced mobile broadband
(eMBB), ultra-reliable low-latency communications (URLLC), and massive
machine-type communications (mMTC). On the one hand, UAVs can be leveraged as
cost-effective aerial platforms to provide ground users with enhanced
communication services by exploiting their high cruising altitude and
controllable maneuverability in three-dimensional (3D) space. On the other
hand, providing such communication services simultaneously for both UAV and
ground users poses new challenges due to the need for ubiquitous 3D signal
coverage as well as the strong air-ground network interference. Besides the
requirement of high-performance wireless communications, the ability to support
effective and efficient sensing as well as network intelligence is also
essential for 5G-and-beyond 3D heterogeneous wireless networks with coexisting
aerial and ground users. In this paper, we provide a comprehensive overview of
the latest research efforts on integrating UAVs into cellular networks, with an
emphasis on how to exploit advanced techniques (e.g., intelligent reflecting
surface, short packet transmission, energy harvesting, joint communication and
radar sensing, and edge intelligence) to meet the diversified service
requirements of next-generation wireless systems. Moreover, we highlight
important directions for further investigation in future work.Comment: Accepted by IEEE JSA
Joint Pilot and Payload Power Allocation for Massive-MIMO-enabled URLLC IIoT Networks
The Fourth Industrial Revolution (Industrial 4.0) is coming, and this
revolution will fundamentally enhance the way the factories manufacture
products. The conventional wired lines connecting central controller to robots
or actuators will be replaced by wireless communication networks due to its low
cost of maintenance and high deployment flexibility. However, some critical
industrial applications require ultra-high reliability and low latency
communication (URLLC). In this paper, we advocate the adoption of massive
multiple-input multiple output (MIMO) to support the wireless transmission for
industrial applications as it can provide deterministic communications similar
as wired lines thanks to its channel hardening effects. To reduce the latency,
the channel blocklength for packet transmission is finite, and suffers from
transmission rate degradation and decoding error probability. Thus,
conventional resource allocation for massive MIMO transmission based on Shannon
capacity assuming the infinite channel blocklength is no longer optimal. We
first derive the closed-form expression of lower bound (LB) of achievable
uplink data rate for massive MIMO system with imperfect channel state
information (CSI) for both maximum-ratio combining (MRC) and zero-forcing (ZF)
receivers. Then, we propose novel low-complexity algorithms to solve the
achievable data rate maximization problems by jointly optimizing the pilot and
payload transmission power for both MRC and ZF. Simulation results confirm the
rapid convergence speed and performance advantage over the existing benchmark
algorithms.Comment: Accepted in IEEE JSAC with special issue on Industry 4.0. Keywords:
URLLC, Industrial 4.0, Industrial Internet-of-Things (IIoT), Massive MIM
Time-Energy-Constrained Closed-Loop FBL Communication for Dependable MEC
The deployment of multi-access edge computing (MEC) is paving the way towards
pervasive intelligence in future 6G networks. This new paradigm also proposes
emerging requirements of dependable communications, which goes beyond the
ultra-reliable low latency communication (URLLC), focusing on the performance
of a closed loop instead of that of an unidirectional link. This work studies
the simple but efficient one-shot transmission scheme, investigating the
closed-loop-reliability-optimal policy of blocklength allocation under
stringent time and energy constraints.Comment: Accepted for publication at CSCN 2021 V1: accepted version V2: minor
correction in the modulation order V3: corrections to resolve chaos caused by
different normalizations of the FBL PER equation, model figure file updated
in H
Unary Coding Design for Simultaneous Wireless Information and Power Transfer with Practical M-QAM
Relying on the propagation of modulated radio-frequency (RF) signals, we can achieve simultaneous wireless information and power transfer (SWIPT) to support low-power communication devices. In this paper, we proposed a unary coding based SWIPT encoder by considering a practical M-QAM. Markov chains are exploited for characterising coherent binary information source and for modelling the generation process of modulated symbols. Therefore, both mutual information and the average energy harvesting performance at the SWIPT receiver are analysed in semi-closed-form. With the aid of the genetic algorithm, the sub-optimal codeword distribution of the coded information source is obtained by maximising the average energy harvesting performance, while satisfying the requirement of the mutual information. Simulation results demonstrate the advantage of the SWIPT encoder. Moreover, a higher-level unary code and a lower-order M-QAM results in higher WPT performance, when the maximum transmit power of the modulated symbol is fixed
Rate-Energy Balanced Precoding Design for SWIPT based Two-Way Relay Systems
Simultaneous wireless information and power transfer (SWIPT) technique is a
popular strategy to convey both information and RF energy for harvesting at
receivers. In this regard, we consider a two-way relay system with multiple
users and a multi-antenna relay employing SWIPT strategy, where splitting the
received signal leads to a rate-energy trade-off. In literature, the works on
transceiver design have been studied using computationally intensive and
suboptimal convex relaxation based schemes. In this paper, we study the
balanced precoder design using chordal distance (CD) decomposition, which
incurs much lower complexity, and is flexible to dynamic energy requirements.
It is analyzed that given a non-negative value of CD, the achieved harvested
energy for the proposed balanced precoder is higher than that for the perfect
interference alignment (IA) precoder. The corresponding loss in sum rates is
also analyzed via an upper bound. Simulation results add that the IA schemes
based on mean-squared error are better suited for the SWIPT maximization than
the subspace alignment-based methods.Comment: arXiv admin note: text overlap with arXiv:2101.1216
On the Study of Sustainability and Outage of SWIPT-Enabled Wireless Communications
Wireless power transfer technologies such as simultaneous wireless information and power transfer (SWIPT) have shown significant potential to revolutionise the design of future wireless communication systems. When the only energy source is from the wireless signals that are mainly intended for information communications, the sustainability and outage performance of SWIPT systems become critical factors in theoretical evaluation and practical applications. This paper firstly models the energy harvesting and energy consumption of the power splitting protocol based SWIPT systems to investigate the general sustainability condition. We further model the power and information transfer outage probabilities using Markov Chains, which are unique for SWIPT systems since they both could cause communication outage. We further demonstrate how to apply the closed-form expression of the outage to optimise the key parameter of splitting ratio for SWIPT systems. Hardware and numerical experiments demonstrate the validity of the proposed model and outage analysis, and confirm the effectiveness of the solution to calculate the optimal splitting ratios under different signal and channel conditions
Fairness for Freshness: Optimal Age of Information Based OFDMA Scheduling with Minimal Knowledge
It is becoming increasingly clear that an important task for wireless
networks is to minimize the age of information (AoI), i.e., the timeliness of
information delivery. While mainstream approaches generally rely on the
real-time observation of user AoI and channel state, there has been little
attention to solve the problem in a complete (or partial) absence of such
knowledge. In this article, we present a novel study to address the optimal
blind radio resource scheduling problem in orthogonal frequency division
multiplexing access (OFDMA) systems towards minimizing long-term average AoI,
which is proven to be the composition of time-domain-fair clustered round-robin
and frequency-domain-fair intra-cluster sub-carrier assignment. Heuristic
solutions that are near-optimal as shown by simulation results are also
proposed to effectively improve the performance upon presence of various
degrees of extra knowledge, e.g., channel state and AoI.Comment: Accepted on 05.06.2021 by the IEEE Transactions on Wireless
Communications for publicatio
Unary Coding Design for Simultaneous Wireless Information and Power Transfer With Practical M-QAM
Relying on the propagation of modulated radio-frequency (RF) signals, we can achieve simultaneous wireless information and power transfer (SWIPT) to support low-power communication devices. In this paper, we proposed a unary coding based SWIPT encoder by considering a practical M-QAM. Markov chains are exploited for characterising coherent binary information source and for modelling the generation process of modulated symbols. Therefore, both mutual information and the average energy harvesting performance at the SWIPT receiver are analysed in semi-closed-form. With the aid of the genetic algorithm, the sub-optimal codeword distribution of the coded information source is obtained by maximising the average energy harvesting performance, while satisfying the requirement of the mutual information. Simulation results demonstrate the advantage of the SWIPT encoder. Moreover, a higher-level unary code and a lower-order M-QAM results in higher WPT performance, when the maximum transmit power of the modulated symbol is fixed
SWIPT aided Cooperative Communications with Energy Harvesting based Selective-Decode-and-Forward Protocol: Benefiting from Channel Aging Effect
Simultaneous wireless information and power transfer (SWIPT) in radio-frequency (RF) bands enables flexible deployment of battery-powered relays for extending communication coverage. Relays receive downlink RF signals emitted by a source for information decoding and energy harvesting, while the harvested energy is consumed for both information decoding and information forwarding to a destination. An energy harvesting based selective-decode-and-forward (EH-SDF) protocol is proposed, where only the relays having information correctly decoded are activated for information forwarding, while others harvest and store energy for the future use. By considering the channel aging effect, we propose a joint relay selection, power allocation, transmit beamforming and signal splitting design in order to maximise the end-to-end (e2e) throughput of this EH-SDF aided cooperative communication system. Two scenarios with/without direct link between the source and the destination are studied, respectively. The original formulated non-convex optimisation problems with coupled variables are decoupled into three subproblems which are solved by an iterative optimisation algorithm. Numerical results demonstrate that our design with the EH-SDF protocol achieves a higher e2e throughput than the traditional decode-and-forward (DF) counterpart. Moreover, the impact of the channel aging effect on the e2e throughput is also evaluated