13,934 research outputs found
Leveraging Deliberately Generated Interferences for Multi-sensor Wireless RF Power Transmission
Wireless RF power transmission promises battery-less, resilient, and
perpetual wireless sensor networks. Through the action of controllable Energy
Transmitters (ETs) that operate at-a-distance, the sensors can be re-charged by
harvesting the radiated RF energy. However, both the charging rate and
effective charging range of the ETs are limited, and thus multiple ETs are
required to cover large areas. While this action increases the amount of
wireless energy injected into the network, there are certain areas where the RF
energy combines destructively. To address this problem, we propose a
duty-cycled random-phase multiple access (DRAMA). Non-intuitively, our approach
relies on deliberately generating random interferences, both destructive and
constructive, at the destination nodes. We demonstrate that DRAMA optimizes the
power conversion efficiency, and the total amount of energy harvested. Through
real-testbed experiments, we prove that our proposed scheme provides
significant advantages over the current state of the art in our considered
scenario, as it requires up to 70\% less input RF power to recharge the energy
buffer of the sensor in the same time.Comment: IEEE GLOBECOM 201
Prototyping and Experimentation of a Closed-Loop Wireless Power Transmission with Channel Acquisition and Waveform Optimization
A systematic design of adaptive waveform for Wireless Power Transfer (WPT)
has recently been proposed and shown through simulations to lead to significant
performance benefits compared to traditional non-adaptive and heuristic
waveforms. In this study, we design the first prototype of a closed-loop
wireless power transfer system with adaptive waveform optimization based on
Channel State Information acquisition. The prototype consists of three
important blocks, namely the channel estimator, the waveform optimizer, and the
energy harvester. Software Defined Radio (SDR) prototyping tools are used to
implement a wireless power transmitter and a channel estimator, and a voltage
doubler rectenna is designed to work as an energy harvester. A channel adaptive
waveform with 8 sinewaves is shown through experiments to improve the average
harvested DC power at the rectenna output by 9.8% to 36.8% over a non-adaptive
design with the same number of sinewaves.Comment: accepted for publication in IEEE WPTC 201
Experimental Study on Battery-less Sensor Network Activated by Multi-point Wireless Energy Transmission
This paper empirically validates battery-less sensor activation via wireless
energy transmission to release sensors from wires and batteries. To seamlessly
extend the coverage and activate sensor nodes distributed in any indoor
environment, we proposed multi-point wireless energy transmission with carrier
shift diversity. In this scheme, multiple transmitters are employed to
compensate path-loss attenuation and orthogonal frequencies are allocated to
the multiple transmitters to avoid the destructive interference that occurs
when the same frequency is used by all transmitters. In our previous works, the
effectiveness of the proposed scheme was validated theoretically and also
empirically by using just a spectrum analyzer to measure the received power. In
this paper, we develop low-energy battery-less sensor nodes whose consumed
power and required received power for activation are respectively 142 uW and
400 uW. In addition, we conduct indoor experiments in which the received power
and activation of battery-less sensor node are simultaneously observed by using
the developed battery-less sensor node and a spectrum analyzer. The results
show that the coverage of single-point and multi-point wireless energy
transmission without carrier shift diversity are, respectively, 84.4% and
83.7%, while the coverage of the proposed scheme is 100%. It can be concluded
that the effectiveness of the proposed scheme can be verified by our
experiments using real battery-less sensor nodes.Comment: This paper is submitted to IEICE Transactions on Communication
Optical Wireless Communication Systems, A Survey
In the past few years, the demand for high data rate services has increased
dramatically. The congestion in the radio frequency (RF) spectrum (3 kHz ~ 300
GHz) is expected to limit the growth of future wireless systems unless new
parts of the spectrum are opened. Even with the use of advanced engineering,
such as signal processing and advanced modulation schemes, it will be very
challenging to meet the demands of the users in the next decades using the
existing carrier frequencies. On the other hand, there is a potential band of
the spectrum available that can provide tens of Gbps to Tbps for users in the
near future. Optical wireless communication (OWC) systems are among the
promising solutions to the bandwidth limitation problem faced by radio systems.
In this paper, we give a tutorial survey of the most significant issues in OWC
systems that operate at short ranges such as indoor systems. We consider the
challenging issues facing these systems such as (i) link design and system
requirements, (ii) transmitter structures, (iii) receiver structures, (iv)
challenges and possible techniques to mitigate the impairments in these
systems, (v) the main applications and (vi) open research issues. In indoor OWC
systems we describe channel modelling, mobility and dispersion mitigation
techniques. Infrared communication (IRC) and visible light communication (VLC)
are presented as potential implementation approaches for OWC systems and are
comprehensively discussed. Moreover, open research issues in OWC systems are
discussed
A baseband wireless spectrum hypervisor for multiplexing concurrent OFDM signals
The next generation of wireless and mobile networks will have to handle a significant increase in traffic load compared to the current ones. This situation calls for novel ways to increase the spectral efficiency. Therefore, in this paper, we propose a wireless spectrum hypervisor architecture that abstracts a radio frequency (RF) front-end into a configurable number of virtual RF front ends. The proposed architecture has the ability to enable flexible spectrum access in existing wireless and mobile networks, which is a challenging task due to the limited spectrum programmability, i.e., the capability a system has to change the spectral properties of a given signal to fit an arbitrary frequency allocation. The proposed architecture is a non-intrusive and highly optimized wireless hypervisor that multiplexes the signals of several different and concurrent multi-carrier-based radio access technologies with numerologies that are multiple integers of one another, which are also referred in our work as radio access technologies with correlated numerology. For example, the proposed architecture can multiplex the signals of several Wi-Fi access points, several LTE base stations, several WiMAX base stations, etc. As it able to multiplex the signals of radio access technologies with correlated numerology, it can, for instance, multiplex the signals of LTE, 5G-NR and NB-IoT base stations. It abstracts a radio frequency front-end into a configurable number of virtual RF front ends, making it possible for such different technologies to share the same RF front-end and consequently reduce the costs and increasing the spectral efficiency by employing densification, once several networks share the same infrastructure or by dynamically accessing free chunks of spectrum. Therefore, the main goal of the proposed approach is to improve spectral efficiency by efficiently using vacant gaps in congested spectrum bandwidths or adopting network densification through infrastructure sharing. We demonstrate mathematically how our proposed approach works and present several simulation results proving its functionality and efficiency. Additionally, we designed and implemented an open-source and free proof of concept prototype of the proposed architecture, which can be used by researchers and developers to run experiments or extend the concept to other applications. We present several experimental results used to validate the proposed prototype. We demonstrate that the prototype can easily handle up to 12 concurrent physical layers
High-Level System Design of IEEE 802.11b Standard-Compliant Link Layer for MATLAB-Based SDR
Software defined radio (SDR) allows unprecedented levels of flexibility by
transitioning the radio communication system from a rigid hardware platform to
a more user-controlled software paradigm. However, it can still be time
consuming to design and implement such SDRs as they typically require thorough
knowledge of the operating environment and a careful tuning of the program. In
this work, our contribution is the design of a bidirectional transceiver that
runs on the commonly used USRP platform and implemented in MATLAB using
standard tools like MATLAB Coder and MEX to speed up the processing steps. We
outline strategies on how to create a state-action based design, wherein the
same node switches between transmitter and receiver functions. Our design
allows optimal selection of the parameters towards meeting the timing
requirements set forth by various processing blocks associated with a DBPSK
physical layer and CSMA/CA/ACK MAC layer so that all operations remain
functionally compliant with the IEEE 802.11b standard for the 1 Mbps
specification. The code base of the system is enabled through the
Communications System Toolbox and incorporates channel sensing and exponential
random back-off for contention resolution. The current work provides an
experimental testbed that enables creation of new MAC protocols starting from
the fundamental IEEE 802.11b standard. Our design approach guarantees
consistent performance of the bi-directional link, and the three node
experimental results demonstrate the robustness of the system in mitigating
packet collisions and enforcing fairness among nodes, making it a feasible
framework in higher layer protocol design.Comment: 19 pages, in press, IEEE Access Journa
Communicating Using Spatial Mode Multiplexing: Potentials, Challenges and Perspectives
Time, polarization, and wavelength multiplexing schemes have been used to
satisfy the growing need of transmission capacity. Using space as a new
dimension for communication systems has been recently suggested as a versatile
technique to address future bandwidth issues. We review the potentials of
harnessing the space as an additional degree of freedom for communication
applications including free space optics, optical fiber installation,
underwater wireless optical links, on-chip interconnects, data center indoor
connections, radio frequency and acoustic communications. We focus on the
orbital angular momentum (OAM) modes and equally identify the challenges
related to each of the applications of spatial modes and the particular OAM
modes in communication. We further discuss the perspectives of this emerging
technology. Finally, we provide the open research directions and we discuss the
practical deployment of OAM communication links for different applications
Development of Wireless Techniques in Data and Power Transmission - Application for Particle Physics Detectors
Wireless techniques have developed extremely fast over the last decade and
using them for data and power transmission in particle physics detectors is not
science- fiction any more. During the last years several research groups have
independently thought of making it a reality. Wireless techniques became a
mature field for research and new developments might have impact on future
particle physics experiments. The Instrumentation Frontier was set up as a part
of the SnowMass 2013 Community Summer Study [1] to examine the instrumentation
R&D for the particle physics research over the coming decades: {\guillemotleft}
To succeed we need to make technical and scientific innovation a priority in
the field {\guillemotright}. Wireless data transmission was identified as one
of the innovations that could revolutionize the transmission of data out of the
detector. Power delivery was another challenge mentioned in the same report. We
propose a collaboration to identify the specific needs of different projects
that might benefit from wireless techniques. The objective is to provide a
common platform for research and development in order to optimize effectiveness
and cost, with the aim of designing and testing wireless demonstrators for
large instrumentation systems
A Comparative Survey of Optical Wireless Technologies: Architectures and Applications
New high-data-rate multimedia services and applications are evolving
continuously and exponentially increasing the demand for wireless capacity of
fifth-generation (5G) and beyond. The existing radio frequency (RF)
communication spectrum is insufficient to meet the demands of future
high-datarate 5G services. Optical wireless communication (OWC), which uses an
ultra-wide range of unregulated spectrum, has emerged as a promising solution
to overcome the RF spectrum crisis. It has attracted growing research interest
worldwide in the last decade for indoor and outdoor applications. OWC offloads
huge data traffic applications from RF networks. A 100 Gb/s data rate has
already been demonstrated through OWC. It offers services indoors as well as
outdoors, and communication distances range from several nm to more than 10000
km. This paper provides a technology overview and a review on optical wireless
technologies, such as visible light communication, light fidelity, optical
camera communication, free space optical communication, and light detection and
ranging. We survey the key technologies for understanding OWC and present
state-of-the-art criteria in aspects, such as classification, spectrum use,
architecture, and applications. The key contribution of this paper is to
clarify the differences among different promising optical wireless technologies
and between these technologies and their corresponding similar existing RF
technologie
Underwater Optical Wireless Communications, Networking, and Localization: A Survey
Underwater wireless communications can be carried out through acoustic, radio
frequency (RF), and optical waves. Compared to its bandwidth limited acoustic
and RF counterparts, underwater optical wireless communications (UOWCs) can
support higher data rates at low latency levels. However, severe aquatic
channel conditions (e.g., absorption, scattering, turbulence, etc.) pose great
challenges for UOWCs and significantly reduce the attainable communication
ranges, which necessitates efficient networking and localization solutions.
Therefore, we provide a comprehensive survey on the challenges, advances, and
prospects of underwater optical wireless networks (UOWNs) from a layer by layer
perspective which includes: 1) Potential network architectures; 2) Physical
layer issues including propagation characteristics, channel modeling, and
modulation techniques 3) Data link layer problems covering link configurations,
link budgets, performance metrics, and multiple access schemes; 4) Network
layer topics containing relaying techniques and potential routing algorithms;
5) Transport layer subjects such as connectivity, reliability, flow and
congestion control; 6) Application layer goals and state-of-the-art UOWN
applications, and 7) Localization and its impacts on UOWN layers. Finally, we
outline the open research challenges and point out the future directions for
underwater optical wireless communications, networking, and localization
research.Comment: This manuscript is submitted to IEEE Communication Surveys and
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