153 research outputs found
Advanced Radio Frequency Antennas for Modern Communication and Medical Systems
The main objective of this book is to present novel radio frequency (RF) antennas for 5G, IOT, and medical applications. The book is divided into four sections that present the main topics of radio frequency antennas. The rapid growth in development of cellular wireless communication systems over the last twenty years has resulted in most of world population owning smartphones, smart watches, I-pads, and other RF communication devices. Efficient compact wideband antennas are crucial in RF communication devices. This book presents information on planar antennas, cavity antennas, Vivaldi antennas, phased arrays, MIMO antennas, beamforming phased array reconfigurable Pabry-Perot cavity antennas, and time modulated linear array
Study, analysis and application of Optical OFDM, Single Carrier (SC) and MIMO in Intensity Modulation Direct Detection (IM/DD)
With the rapid growth of wireless data demands and saturation of radio frequency (RF) capacity,
visible light communication (VLC) has become a promising candidate to complement
conventional RF communication, especially for indoor short range applications. However the
performance of the system depends on the propagation and type of system used. An optical
Orthogonal Frequency Division Multiplexing (O-OFDM) together with multiple input multiple
output (MIMO) in different scenario and modulation techniques are studied in the thesis.
A novel optical wireless communication (OWC) multi-cell system with narrow field of view
(FOV) is studied. In this system the intensity modulated beam from four light sources are
used for communication. The system allows beams to be concentrated in specific areas of
the room to serve multiple mobile devices with low interference and hence increase system
capacity. The performance of asymmetrically clipped optical orthogonal frequency division
multiplexing (ACO-OFDM), direct current biased optical OFDM (DCO-OFDM) and single
carrier (SC) modulation are then compared in this system considering single user and multiusers
scenarios. The performance of the multi-cell is compared with single cell with wide FOV.
It is shown that the capacity for multi-cell system increases with the number of users to 4 times
the single user capacity. Also the findings show that multi-cell system with narrow beams can
outperform a single wide beam system in terms of coverage area and hence average throughput
of about 2.7 times the single wide beam system capacity.
One of the impairments in line of sight (LOS) OWC systems is coverage which degrades the
performance. A mobile receiver with angular diversity detectors in MIMO channels is studied.
The objective is to improve the rank of the channel matrix and hence system throughput. Repetition
coding (RC), spatial multiplexing (SMP) and spatial modulation (SM) concepts are used
to evaluate throughput across multiple locations in a small room scenario. A novel adaptive
spatial modulation (ASM) which is capable of combating channel rank deficiency is devised.
Since the receiver is mobile, the channel gains are low in some locations of the room due to
the lack of LOS paths between transmitters and receivers. To combat the situation adaptive
modulation and per antenna rate control (PARC) is employed to maximise spectral efficiency.
The throughputs for fixed transmitters and receivers are compared with the oriented/inclined
detectors for different cases. Angular diversity detectors offer a better throughput improvement
than the state of the art vertical detectors, for example in ASM angular diversity receiver gives
throughput of about 1.6 times that of vertical detectors. Also in SMP the angular detectors
offer throughput about 1.4 times that of vertical detectors. SMP gives the best performance
compared to RC, SM and ASM, for example SMP gives throughput about 2.5 times that of RC
in both vertical detectors and angular diversity receivers. Again SMP gives throughput about 6
times that of SM in both vertical detectors and angular diversity receivers. Also SMP provides
throughput about 2 times that of ASM in both vertical detectors and angular diversity receivers.
ASM exhibit improvement in throughput about average factor of 3.5 times SM performance in
both vertical detectors and angular diversity detectors.
As the performance of the system may be jeopardized by obstructions, specular and diffuse
reflection models for indoor OWC systems using a mobile receiver with angular diversity detectors
in MIMO channels are considered. The target is to improve the MIMO throughput
compared to vertically oriented detectors by exploiting reflections from different reflecting surfaces
in the room. The throughput across multiple locations in the small room by using RC,
SMP and SM approaches is again evaluated. The results for LOS only channels against LOS
with specular or diffuse reflection conditions, for both vertical and angular oriented receivers
are then compared. The results show that exploiting specular and diffuse reflections provide
significant improvements in link performance. For example the reflection coefficient (α) of
0.9 and the antenna separation of 0.6 m, RC diffuse model shows throughput improvement of
about 1.8 times that of LOS for both vertical detectors and angular diversity receivers. SM
diffuse model shows throughput improvement of about 3 times that of LOS for both vertical
detectors and angular diversity receivers. ASM diffuse model shows throughput improvement
of about 2 times that of LOS for both vertical detectors and angular diversity receivers. SMP
diffuse model shows throughput improvement of about 1.5 times that of LOS for both vertical
detectors and angular diversity receiver
MAC Protocols for Wireless Mesh Networks with Multi-beam Antennas: A Survey
Multi-beam antenna technologies have provided lots of promising solutions to
many current challenges faced in wireless mesh networks. The antenna can
establish several beamformings simultaneously and initiate concurrent
transmissions or receptions using multiple beams, thereby increasing the
overall throughput of the network transmission. Multi-beam antenna has the
ability to increase the spatial reuse, extend the transmission range, improve
the transmission reliability, as well as save the power consumption.
Traditional Medium Access Control (MAC) protocols for wireless network largely
relied on the IEEE 802.11 Distributed Coordination Function(DCF) mechanism,
however, IEEE 802.11 DCF cannot take the advantages of these unique
capabilities provided by multi-beam antennas. This paper surveys the MAC
protocols for wireless mesh networks with multi-beam antennas. The paper first
discusses some basic information in designing multi-beam antenna system and MAC
protocols, and then presents the main challenges for the MAC protocols in
wireless mesh networks compared with the traditional MAC protocols. A
qualitative comparison of the existing MAC protocols is provided to highlight
their novel features, which provides a reference for designing the new MAC
protocols. To provide some insights on future research, several open issues of
MAC protocols are discussed for wireless mesh networks using multi-beam
antennas.Comment: 22 pages, 6 figures, Future of Information and Communication
Conference (FICC) 2019, https://doi.org/10.1007/978-3-030-12388-8_
Antennas Performance Comparison of Multi-Bands for Optimal Outdoor and Indoor Environments Wireless Coverage
This paper aims to implement a wireless Wi-Fi network (Indoor and Outdoor) in order to cover the environment of the Oxford Institute (to learn languages and computer skills) in the best methods and lowest cost in order to provide Wi-Fi service for faculty members and all members of the administrative board and students. The realistic three-floor indoor and outdoor environments of the Institute were designed with Wireless InSite Package (WIP). In addition, emphasis was focus on the use of two types of transmitting devices (Directional and Omni-Directional). The aim of using these two devices is to determine which device is better to cover the Institute's environment well. In this work, a different frequency bands scenario was used to determine which band is suitable for coverage and stability of the wireless network. These bands are S-Band (2.4GHz), C-Band (5GHz), C-Band (10GHz), Ku-Band (15GHz), Ka-Band (28GHz), and MmWave (39GHz). Moreover, the focus has been on the most important basic parameters to determine the performance level of the two devices (Directional and Omni-Directional) as well as to determine the performance level of the wireless network. The most important of these parameters are Path Losses (LPath), Path Gain (GPath), Received Signal Strength (RSS), Strongest Received Power, Coverage Ratio (CR), and Received Signal Quality Ratio (RSQR). According to the results that emerged, it was observed that Omni-Directional antennas are much better than Directional antennas, especially in NLOS (None-Line-of-Sight) regions. It was also noted that CR, LPath, and RSS at S-Band (2.4GHz) are much better than the rest of the bands, so that the CR and the RSQR at this band reach 83.2184% and 95.7383%, respectively. While at the MmWave-Band (39GHz), it reaches 31.0345% and 70.7937% respectively
Optimization of linear multielement antennas for selection combining by means of a Butler matrix in different MIMO environments
An optimized linear multielement antenna (MEA)
is presented for selection combining schemes that improves the
selection diversity gain and selection diversity capacity in medium
and low multipath environments, with respect to the performance
achieved with a simple uniform linear array (ULA) using omnidirectional
antennas, while it performs equally as well as a
ULA in highly scattered environments. An analytical investigation
based on the analysis of the correlation coefficients, together with
simulations and extensive measurements, have been carried out
for different fading multiple-input multiple-output environments
ranging from line of sight (LOS) to non-LOS. Two MEAs are
compared: a simple ULA with omnidirectional antennas and a
MEA combining a ULA and a Butler matrix. The measurement
results show that the nature of the proposed MEA is such that it
is adaptive to any propagation scenario by simultaneously taking
advantage of beamforming gain and signal diversity gain.Peer Reviewe
Antennas and Propagation Aspects for Emerging Wireless Communication Technologies
The increasing demand for high data rate applications and the delivery of zero-latency multimedia content drives technological evolutions towards the design and implementation of next-generation broadband wireless networks. In this context, various novel technologies have been introduced, such as millimeter wave (mmWave) transmission, massive multiple input multiple output (MIMO) systems, and non-orthogonal multiple access (NOMA) schemes in order to support the vision of fifth generation (5G) wireless cellular networks. The introduction of these technologies, however, is inextricably connected with a holistic redesign of the current transceiver structures, as well as the network architecture reconfiguration. To this end, ultra-dense network deployment along with distributed massive MIMO technologies and intermediate relay nodes have been proposed, among others, in order to ensure an improved quality of services to all mobile users. In the same framework, the design and evaluation of novel antenna configurations able to support wideband applications is of utmost importance for 5G context support. Furthermore, in order to design reliable 5G systems, the channel characterization in these frequencies and in the complex propagation environments cannot be ignored because it plays a significant role. In this Special Issue, fourteen papers are published, covering various aspects of novel antenna designs for broadband applications, propagation models at mmWave bands, the deployment of NOMA techniques, radio network planning for 5G networks, and multi-beam antenna technologies for 5G wireless communications
成層圏飛翔体通信における無線通信路及びその性能に関する研究
制度:新 ; 文部省報告番号:甲2383号 ; 学位の種類:博士(国際情報通信学) ; 授与年月日:2007/3/15 ; 早大学位記番号:新447
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