10,773 research outputs found
Cell-Free IoT Networks with SWIPT: Performance Analysis and Power Control
In this paper, the performance of simultaneous wireless information and power transfer (SWIPT) in downlink (DL) Internet-of-things (IoT) networks relying on cell-free massive multiple-input multiple-output (CF-mMIMO) technique is investigated. In such a network, the access points (APs) beam the radio-frequency (RF) energy toward IoT sensors during the DL wireless power transfer phase. Tight closed-form expressions for DL harvested energy (HE) and achievable rate with conjugate beamforming (CB) and normalized CB (NCB) are respectively derived, which enable us to analyze the behaviors of CB and NCB schemes in terms of both HE and achievable rate. Apart from this, to guarantee sensor fairness with respect to the HE and achievable rate, a max-min power control strategy based on the accelerated projected gradient (APG) method is proposed. Specifically, the proposed APG-based power control is able to determine the optimal solution in closed form and is more memory-efficient than the convex-solver-based counterpart. These analytical results as well as the effectiveness of the proposed power control policy are verified by experimental simulations
Magneto-inductive Passive Relaying in Arbitrarily Arranged Networks
We consider a wireless sensor network that uses inductive near-field coupling
for wireless powering or communication, or for both. The severely limited range
of an inductively coupled source-destination pair can be improved using
resonant relay devices, which are purely passive in nature. Utilization of such
magneto-inductive relays has only been studied for regular network topologies,
allowing simplified assumptions on the mutual antenna couplings. In this work
we present an analysis of magneto-inductive passive relaying in arbitrarily
arranged networks. We find that the resulting channel has characteristics
similar to multipath fading: the channel power gain is governed by a
non-coherent sum of phasors, resulting in increased frequency selectivity. We
propose and study two strategies to increase the channel power gain of random
relay networks: i) deactivation of individual relays by open-circuit switching
and ii) frequency tuning. The presented results show that both methods improve
the utilization of available passive relays, leading to reliable and
significant performance gains.Comment: 6 pages, 9 figures. To be presented at the IEEE International
Conference on Communications (ICC), Paris, France, May 201
Energy harvesting over Rician fading channel: A performance analysis for half-duplex bidirectional sensor networks under hardware impairments
In this paper, a rigorous analysis of the performance of time-switching energy harvesting strategy that is applied for a half-duplex bidirectional wireless sensor network with intermediate relay over a Rician fading channel is presented to provide the exact-form expressions of the outage probability, achievable throughput and the symbol-error-rate (SER) of the system under the hardware impairment condition. Using the proposed probabilistic models for wireless channels between mobile nodes as well as for the hardware noises, we derive the outage probability of the system, and then the throughput and SER can be obtained as a result. Both exact analysis and asymptotic analysis at high signal-power-to-noise-ratio regime are provided. Monte Carlo simulation is also conducted to verify the analysis. This work confirms the effectiveness of energy harvesting applied in wireless sensor networks over a Rician fading channel, and can provide an insightful understanding about the effect of various parameters on the system performance.Web of Science186art. no. 1781
Energy-Efficient NOMA Enabled Heterogeneous Cloud Radio Access Networks
Heterogeneous cloud radio access networks (H-CRANs) are envisioned to be
promising in the fifth generation (5G) wireless networks. H-CRANs enable users
to enjoy diverse services with high energy efficiency, high spectral
efficiency, and low-cost operation, which are achieved by using cloud computing
and virtualization techniques. However, H-CRANs face many technical challenges
due to massive user connectivity, increasingly severe spectrum scarcity and
energy-constrained devices. These challenges may significantly decrease the
quality of service of users if not properly tackled. Non-orthogonal multiple
access (NOMA) schemes exploit non-orthogonal resources to provide services for
multiple users and are receiving increasing attention for their potential of
improving spectral and energy efficiency in 5G networks. In this article a
framework for energy-efficient NOMA H-CRANs is presented. The enabling
technologies for NOMA H-CRANs are surveyed. Challenges to implement these
technologies and open issues are discussed. This article also presents the
performance evaluation on energy efficiency of H-CRANs with NOMA.Comment: This work has been accepted by IEEE Network. Pages 18, Figure
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