390 research outputs found
Experiments Validating the Effectiveness of Multi-point Wireless Energy Transmission with Carrier Shift Diversity
This paper presents a method to seamlessly extend the coverage of energy
supply field for wireless sensor networks in order to free sensors from wires
and batteries, where the multi-point scheme is employed to overcome path-loss
attenuation, while the carrier shift diversity is introduced to mitigate the
effect of interference between multiple wave sources. As we focus on the energy
transmission part, sensor or communication schemes are out of scope of this
paper. To verify the effectiveness of the proposed wireless energy
transmission, this paper conducts indoor experiments in which we compare the
power distribution and the coverage performance of different energy
transmission schemes including conventional single-point, simple multi-point
and our proposed multi-point scheme. To easily observe the effect of the
standing-wave caused by multipath and interference between multiple wave
sources, 3D measurements are performed in an empty room. The results of our
experiments together with those of a simulation that assumes a similar antenna
setting in free space environment show that the coverage of single-point and
multi-point wireless energy transmission without carrier shift diversity are
limited by path-loss, standing-wave created by multipath and interference
between multiple wave sources. On the other hand, the proposed scheme can
overcome power attenuation due to the path-loss as well as the effect of
standing-wave created by multipath and interference between multiple wave
sources.Comment: This paper is submitted to IEICE IEICE Transactions on
Communications.
A Study of Trade-off between Opportunistic Resource Allocation and Interference Alignment in Femtocell Scenarios
One of the main problems in wireless heterogeneous networks is interference
between macro- and femto-cells. Using Orthogonal Frequency-Division Multiple
Access (OFDMA) to create multiple frequency orthogonal sub-channels, this
interference can be completely avoided if each sub-channel is exclusively used
by either macro- or a femto-cell. However, such an orthogonal allocation may be
inefficient. We consider two alternative strategies for interference
management, opportunistic resource allocation (ORA) and interference alignment
(IA). Both of them utilize the fading fluctuations across frequency channels in
different ways. ORA allows the users to interfere, but selecting the channels
where the interference is faded, while the desired signal has a good channel.
IA uses precoding to create interference-free transmissions; however, such a
precoding changes the diversity picture of the communication resources. In this
letter we investigate the interactions and the trade-offs between these two
strategies.Comment: This paper is submitted to IEEE Wireless Communications Letter
Experiment of Multi-UAV Full-Duplex System Equipped with Directional Antennas
One of the key enablers for the realization of a variety of unmanned aerial
vehicle (UAV)-based systems is the high-performance communication system
linking many UAVs and ground station. We have proposed a spectrum-efficient
full-duplex directional-antennas-equipped multi-UAV communication system with
low hardware complexity to address the issues of low spectrum efficiency caused
by co-channel interference in areal channels. In this paper, by using the
prototype system including UAVs and ground station, field experiments are
carried out to confirm the feasibility and effectiveness of the proposed
system's key feature, i.e., co-channel interference cancellation among UAVs by
directional antennas and UAV relative position control, instead of
energy-consuming dedicated self-interference cancellers on UAVs in traditional
full-duplex systems. Both uplink and downlink performance are tested.
Specially, in downlink experiment, channel power of interference between a pair
of two UAVs is measured when UAVs are in different positional relationships.
The experiment results agree well with the designs and confirm that the
proposed system can greatly improve the system performance.Comment: The paper was accepted by IEEE Consumer Communications & Networking
Conference (CCNC) 202
WiFi Assisted Multi-WiGig AP Coordination for Future Multi-Gbps WLANs
Wireless Gigabit (WiGig) access points (APs) using 60 GHz unlicensed
frequency band are considered as key enablers for future Gbps wireless local
area networks (WLANs). Exhaustive search analog beamforming (BF) is mainly used
with WiGig transmissions to overcome channel propagation loss and accomplish
high rate data transmissions. Due to its short range transmission with high
susceptibility to path blocking, a multiple number of WiGig APs should be
installed to fully cover a typical target environment. Therefore, coordination
among the installed APs is highly needed for enabling WiGig concurrent
transmissions while overcoming packet collisions and reducing interference,
which highly increases the total throughput of WiGig WLANs. In this paper, we
propose a comprehensive architecture for coordinated WiGig WLANs. The proposed
WiGig WLAN is based on a tight coordination between the 5 GHz (WiFi) and the 60
GHz (WiGig) unlicensed frequency bands. By which, the wide coverage WiFi band
is used to do the signaling required for organizing WiGig concurrent data
transmissions using control/user (C/U) plane splitting. To reduce interference
to existing WiGig data links while doing BF, a novel location based BF
mechanism is also proposed based on WiFi fingerprinting. The proposed
coordinated WiGig WLAN highly outperforms conventional un-coordinated one in
terms of total throughput, average packet delay and packet dropping rate.Comment: 6 pages, 8 Figures, IEEE International Symposium on Personal Indoor
and Mobile Radio Communications (PIMRC) 201
Towards a Decentralized Metaverse: Synchronized Orchestration of Digital Twins and Sub-Metaverses
Accommodating digital twins (DTs) in the metaverse is essential to achieving
digital reality. This need for integrating DTs into the metaverse while
operating them at the network edge has increased the demand for a decentralized
edge-enabled metaverse. Hence, to consolidate the fusion between real and
digital entities, it is necessary to harmonize the interoperability between DTs
and the metaverse at the edge. In this paper, a novel decentralized metaverse
framework that incorporates DT operations at the wireless edge is presented. In
particular, a system of autonomous physical twins (PTs) operating in a
massively-sensed zone is replicated as cyber twins (CTs) at the mobile edge
computing (MEC) servers. To render the CTs' digital environment, this zone is
partitioned and teleported as distributed sub-metaverses to the MEC servers. To
guarantee seamless synchronization of the sub-metaverses and their associated
CTs with the dynamics of the real world and PTs, respectively, this joint
synchronization problem is posed as an optimization problem whose goal is to
minimize the average sub-synchronization time between the real and digital
worlds, while meeting the DT synchronization intensity requirements. To solve
this problem, a novel iterative algorithm for joint sub-metaverse and DT
association at the MEC servers is proposed. This algorithm exploits the
rigorous framework of optimal transport theory so as to efficiently distribute
the sub-metaverses and DTs, while considering the computing and communication
resource allocations. Simulation results show that the proposed solution can
orchestrate the interplay between DTs and sub-metaverses to achieve a 25.75 %
reduction in the sub-synchronization time in comparison to the signal-to-noise
ratio-based association scheme
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