6,795 research outputs found
Wireless Powered Dense Cellular Networks: How Many Small Cells Do We Need?
This paper focuses on wireless powered 5G dense cellular networks, where base
station (BS) delivers energy to user equipment (UE) via the microwave radiation
in sub-6 GHz or millimeter wave (mmWave) frequency, and UE uses the harvested
energy for uplink information transmission. By addressing the impacts of
employing different number of antennas and bandwidths at lower and higher
frequencies, we evaluate the amount of harvested energy and throughput in such
networks. Based on the derived results, we obtain the required small cell
density to achieve an expected level of harvested energy or throughput. Also,
we obtain that when the ratio of the number of sub-6 GHz BSs to that of the
mmWave BSs is lower than a given threshold, UE harvests more energy from a
mmWave BS than a sub-6 GHz BS. We find how many mmWave small cells are needed
to perform better than the sub-6 GHz small cells from the perspectives of
harvested energy and throughput. Our results reveal that the amount of
harvested energy from the mmWave tier can be comparable to the sub-6 GHz
counterpart in the dense scenarios. For the same tier scale, mmWave tier can
achieve higher throughput. Furthermore, the throughput gap between different
mmWave frequencies increases with the mmWave BS density.Comment: pages 1-14, accepted by IEEE Journal on Selected Areas in
Communication
Scalability of the channel capacity in graphene-enabled wireless communications to the nanoscale
Graphene is a promising material which has been proposed to build graphene plasmonic miniaturized antennas, or graphennas, which show excellent conditions for the propagation of Surface Plasmon Polariton (SPP) waves in the terahertz band. Due to their small size of just a few micrometers, graphennas allow the implementation of wireless communications among nanosystems, leading to a novel paradigm known as Graphene-enabled Wireless Communications (GWC). In this paper, an analytical framework is developed to evaluate how the channel capacity of a GWC system scales as its dimensions shrink. In particular, we study how the unique propagation of SPP waves in graphennas will impact the channel capacity. Next, we further compare these results with respect to the case when metallic antennas are used, in which these plasmonic effects do not appear. In addition, asymptotic expressions for the channel capacity are derived in the limit when the system dimensions tend to zero. In this scenario, necessary conditions to ensure the feasibility of GWC networks are found. Finally, using these conditions, new guidelines are derived to explore the scalability of various parameters, such as transmission range and transmitted power. These results may be helpful for designers of future GWC systems and networks.Peer ReviewedPostprint (author’s final draft
Studying Light-Harvesting Models with Superconducting Circuits
The process of photosynthesis, the main source of energy in the animate
world, converts sunlight into chemical energy. The surprisingly high efficiency
of this process is believed to be enabled by an intricate interplay between the
quantum nature of molecular structures in photosynthetic complexes and their
interaction with the environment. Investigating these effects in biological
samples is challenging due to their complex and disordered structure. Here we
experimentally demonstrate a new approach for studying photosynthetic models
based on superconducting quantum circuits. In particular, we demonstrate the
unprecedented versatility and control of our method in an engineered three-site
model of a pigment protein complex with realistic parameters scaled down in
energy by a factor of . With this system we show that the excitation
transport between quantum coherent sites disordered in energy can be enabled
through the interaction with environmental noise. We also show that the
efficiency of the process is maximized for structured noise resembling
intramolecular phononic environments found in photosynthetic complexes.Comment: 8+12 pages, 4+12 figure
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