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Wireless indoor localisation within the 5G internet of radio light
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonNumerous applications can be enhanced by accurate and efficient indoor localisation using wireless
sensor networks, however trade-offs often exist between these two parameters. In this thesis, realworld
and simulation data is used to examine the hybrid millimeter wave and Visible Light
Communications (VLC) architecture of the 5G Internet of Radio Light (IoRL) Horizon 2020 project.
Consequently, relevant localisation challenges within Visible Light Positioning (VLP) and asynchronous
sampling networks are identified, and more accurate and efficient solutions are developed.
Currently, VLP relies strongly on the assumed Lambertian properties of light sources.
However, in practice, not all lights are Lambertian. To support the widespread deployment of VLC
technology in numerous environments, measurements from non-Lambertian sources are analysed to
provide new insights into the limitations of existing VLP techniques. Subsequently, a novel VLP
calibration technique is proposed, and results indicate a 59% accuracy improvement against existing
methods. This solution enables high accuracy centimetre level VLP to be achieved with non-
Lambertian sources.
Asynchronous sampling of range-based measurements is known to impact localisation
performance negatively. Various Asynchronous Sampling Localisation Techniques (ASLT) exist to
mitigate these effects. While effective at improving positioning performance, the exact suitability of
such solutions is not evident due to their additional processes, subsequent complexity, and increased
costs. As such, extensive simulations are conducted to study the effectiveness of ASLT under variable
sampling latencies, sensor measurement noise, and target trajectories. Findings highlight the
computational demand of existing ASLT and motivate the development of a novel solution. The
proposed Kalman Extrapolated Least Squares (KELS) method achieves optimal localisation
performance with a significant energy reduction of over 50% when compared to current leading ASLT.
The work in this thesis demonstrates both the capability for high performance VLP from non-
Lambertian sources as well as the potential for energy efficient localisation for sequentially sampled
range measurements.Horizon 202
A review of gallium nitride LEDs for multi-gigabit-per-second visible light data communications
The field of visible light communications (VLC) has gained significant interest over the last decade, in both fibre and free-space embodiments. In fibre systems, the availability of low cost plastic optical fibre (POF) that is compatible with visible data communications has been a key enabler. In free-space applications, the availability of hundreds of THz of the unregulated spectrum makes VLC attractive for wireless communications. This paper provides an overview of the recent developments in VLC systems based on gallium nitride (GaN) light-emitting diodes (LEDs), covering aspects from sources to systems. The state-of-the-art technology enabling bandwidth of GaN LEDs in the range of >400 MHz is explored. Furthermore, advances in key technologies, including advanced modulation, equalisation, and multiplexing that have enabled free-space VLC data rates beyond 10 Gb/s are also outlined
Physical Layer Security for Visible Light Communication Systems:A Survey
Due to the dramatic increase in high data rate services and in order to meet
the demands of the fifth-generation (5G) networks, researchers from both
academia and industry are exploring advanced transmission techniques, new
network architectures and new frequency spectrum such as the visible light
spectra. Visible light communication (VLC) particularly is an emerging
technology that has been introduced as a promising solution for 5G and beyond.
Although VLC systems are more immune against interference and less susceptible
to security vulnerabilities since light does not penetrate through walls,
security issues arise naturally in VLC channels due to their open and
broadcasting nature, compared to fiber-optic systems. In addition, since VLC is
considered to be an enabling technology for 5G, and security is one of the 5G
fundamental requirements, security issues should be carefully addressed and
resolved in the VLC context. On the other hand, due to the success of physical
layer security (PLS) in improving the security of radio-frequency (RF) wireless
networks, extending such PLS techniques to VLC systems has been of great
interest. Only two survey papers on security in VLC have been published in the
literature. However, a comparative and unified survey on PLS for VLC from
information theoretic and signal processing point of views is still missing.
This paper covers almost all aspects of PLS for VLC, including different
channel models, input distributions, network configurations,
precoding/signaling strategies, and secrecy capacity and information rates.
Furthermore, we propose a number of timely and open research directions for
PLS-VLC systems, including the application of measurement-based indoor and
outdoor channel models, incorporating user mobility and device orientation into
the channel model, and combining VLC and RF systems to realize the potential of
such technologies
Impact of Device Orientation on Error Performance of LiFi Systems
Most studies on optical wireless communications (OWCs) have neglected the
effect of random orientation in their performance analysis due to the lack of a
proper model for the random orientation. Our recent empirical-based research
illustrates that the random orientation follows a Laplace distribution for a
static user equipment (UE). In this paper, we analyze the device orientation
and assess its importance on system performance. The reliability of an OWC
channel highly depends on the availability and alignment of line-of-sight (LOS)
links. In this study, the effect of receiver orientation including both polar
and azimuth angles on the LOS channel gain are analyzed. The probability of
establishing a LOS link is investigated and the probability density function
(PDF) of signal-to-noise ratio (SNR) for a randomly-oriented device is derived.
By means of the PDF of SNR, the bit-error ratio (BER) of DC-biased optical
orthogonal frequency division multiplexing (DCO-OFDM) in additive white
Gaussian noise (AWGN) channels is evaluated. A closed-form approximation for
the BER of UE with random orientation is presented which shows a good match
with Monte-Carlo simulation results. Furthermore, the impact of the UE's random
motion on the BER performance has been assessed. Finally, the effect of random
orientation on the average signal-to-interference-plus-noise ratio (SINR) in a
multiple access points (APs) scenario is investigated.Comment: 10 pages, 11 figures, journa
Measurements-Based Channel Models for Indoor LiFi Systems
Light-fidelity (LiFi) is a fully-networked bidirectional optical wireless
communication (OWC) that is considered a promising solution for high-speed
indoor connectivity. Unlike in conventional radio frequency wireless systems,
the OWC channel is not isotropic, meaning that the device orientation affects
the channel gain significantly. However, due to the lack of proper channel
models for LiFi systems, many studies have assumed that the receiver is
vertically upward and randomly located within the coverage area, which is not a
realistic assumption from a practical point of view. In this paper, novel
realistic and measurement-based channel models for indoor LiFi systems are
proposed. Precisely, the statistics of the channel gain are derived for the
case of randomly oriented stationary and mobile LiFi receivers. For stationary
users, two channel models are proposed, namely, the modified truncated Laplace
(MTL) model and the modified Beta (MB) model. For LiFi users, two channel
models are proposed, namely, the sum of modified truncated Gaussian (SMTG)
model and the sum of modified Beta (SMB) model. Based on the derived models,
the impact of random orientation and spatial distribution of LiFi users is
investigated, where we show that the aforementioned factors can strongly affect
the channel gain and system performance
Performance investigation of spatial modulation systems under realistic channel models
In order to fulfil the explosive demand for convenient wireless data access, novel wireless technologies such as the multiple-input-multiple-output (MIMO) have widely been used to improve the link reliability and capacity of wireless communication systems. In recent years, a new MIMO technology named the spatial modulation (SM) has attracted signi cant research interest due to its reported enhancement on the system performance with the reasonable system complexity. Before a new technology comes into real use, it is necessary to comprehensively evaluate its performance under different scenarios. In this thesis, we investigate the performance of SM systems under some important realistic scenarios for future wireless communications, such as the vehicle-to-vehicle (V2V), the high-speed train (HST), and the massive MIMO scenarios. Firstly, the bit error rate (BER) performance of SM systems under a novel threedimensional (3D) geometry based stochastic model (GBSM) for V2V MIMO channels is investigated by both theoretical analysis and system simulations. The impacts of vehicle tra c density (VTD), Doppler effect, and 3D feature on the BER performance of SM systems are thoroughly studied. In addition, other MIMO technologies, such as the vertical Bell Labs layered space-time (V-BLAST), the Alamouti scheme are compared with SM under different simulation settings. Secondly, the BER performance of SM systems is studied under a non-stationary wideband HST GBSM considering the non-ideal channel estimation case. The timevarying behaviour of the channel and its impact on the performance of SM systems are comprehensively investigated. The accurate theoretical BER expression of SM systems under a non-stationary wideband HST channels with non-ideal channel estimation is derived. A novel statistic property named stationary interval in terms of the space-time correlation function (STCF) is introduced in order to clearly explain all theoretical and simulation results. Thirdly, the performance of SM systems is evaluated under a Kroneck-based massive MIMO channel model. As a massive MIMO system employs large numbers of antennas, antenna elements are distributed over a wide range. Thus, different antenna elements may observe different sets of clusters. How this phenomenon affects the performance of SM systems is investigated by considering a survival probability of clusters, which abstracts the birth-death process of each cluster in the channel model. Moreover, the performance of SM systems is also compared with that of other MIMO technologies under the massive MIMO channel model. In summary, all research works in this thesis have considered realistic MIMO channel models, which are meaningful for the test, performance evaluation, and implementation of SM technology for future advanced wireless communications systems
Drone Networking in 6G Era - A Technology Overview
International audienceSixth generation (6G) wireless communication networks are envisioned to be empowered with novel enabling technologies to guarantee ubiquitous coverage requirements, heterogeneous communication scenarios, improved network intelligence, spectral rates and security. 6G vision is not only limited to terrestrial networks, but also extends to non-terrestrial networks encompassing satellites and aerial networks, thus exploring a full spectra of heterogeneous communication links. In 6G scenarios, the role of Unmanned Aerial Vehicles (UAVs) is of paramount importance, as flying devices are expected to densely populate aerial space, providing an intermediate network layer between ground networks and space ones. As a vision of fully integrated 6G heterogeneous networks, ground, aerial and satellite networks will coexist, thus realizing space-air-ground integrated communication network for 6G scenarios. This work highlights several novel 6G enabling technologies, and presents the detailed study and evaluation of communication technology candidates from the perspective of aerial communication networks, key design considerations and technical challenges
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