266 research outputs found
Physical layer security scheme based on power efficient multi-antenna transmitter
Security is a demanding challenge in wireless systems due to the broadcast nature
of the channel. One the other hand security at physical layer can increase overall system’s
security since it can be combined with other security schemes from higher layers. High throughput
required by modern wireless networks can be assured by MIMO (Multiple-input multiple-output),
but when high spectral efficiencies are needed multilevel modulations with high peak-to-average
power ratios should be used, which may affect efficiency of power amplification. This problem
can be avoided by the MISO (Multi input Single Output) transmitter considered here, where
transmitted multilevel constellations are the result of the combination of several uncorrelated
BPSK (Bi-Phase Shift Keying) components, that are amplified and transmitted independently
by an antenna. The constellation shaping done by this transmitter means directivity in the
transmitted constellation that can be used to assure security at physical layer. Security as
well complexity are assured since any eavesdropper must know the set of coefficients associated
to each BPSK component as well as the antenna array configuration. It is shown that the
inherent security assured by this transmitter allows secrecy at physical layer. Several examples
are analyzed and the corresponding results show the effectiveness of the proposed approach to
implement a security scheme at physical layer level
Simultaneous Wireless Information and Power Transfer in 5G communication
Green communication technology is expected to be widely adopted in future generation
networks to improve energy efficiency and reliability of wireless communication network.
Among the green communication technologies,simultaneous wireless information and
power transfer (SWIPT) is adopted for its flexible energy harvesting technology through
the radio frequency (RF) signa lthati sused for information transmission. Even though
existing SWIPT techniques are flexible and adoptable for the wireless communication
networks, the power and time resources of the signal need to be shared between infor-
mation transmission and RF energy harvesting, and this compromises the quality of the
signal. Therefore,SWIP Ttechniques need to be designed to allow an efficient resource
allocation for communication and energy harvesting.
The goal oft his thesisis to design SWIP Ttechniques that allow efficient,reliable and
secure joint communications and power transference. A problem associated to SWIPT
techniques combined with multi carrier signals is that the increased power requirements
inherent to energy harvesting purposes can exacerbate nonlinear distortion effects at the
transmitter. Therefore, we evaluate nonlinear distortion and present feasible solutions to
mitigate the impact of nonlinear distortion effects on the performance.Another goal of
the thesisis to take advantage of the energy harvesting signals in SWIP Ttechniques for
channel estimation and security purposes.Theperformance of these SWIPT techniques is
evaluated analytically, and those results are validated by simulations. It is shownthatthe
proposed SWIPT schemes can have excellent performance, out performing conventional
SWIPT schemes.Espera-se que aschamadas tecnologiasde green communications sejam amplamente ado-
tadas em futuras redes de comunicação sem fios para melhorar a sua eficiência energética
a fiabilidade.Entre estas,encontram-se as tecnologias SWIPT (Simultaneous Wireless
Information and Power Transference), nas quais um sinal radio é usado para transferir
simultaneamente potência e informações.Embora as técnicas SWIPT existentes sejam fle-
xÃveis e adequadas para as redes de comunicações sem fios, os recursos de energia e tempo
do sinal precisam ser compartilhados entre a transmissão de informações e de energia, o
que pode comprometer a qualidade do sinal. Deste modo,as técnicas SWIPT precisam ser
projetadas para permitir uma alocação eficiente de recursos para comunicação e recolha
de energia.
O objetivo desta tese é desenvolver técnicas SWIPT que permitam transferência de
energia e comunicações eficientes,fiáveis e seguras.Um problema associado às técnicas
SWIPT combinadas com sinais multi-portadora são as dificuldades de amplificação ine-
rentes à combinação de sinais de transmissão de energia com sinais de transferência de
dados, que podem exacerbar os efeitos de distorção não-linear nos sinais transmitidos.
Deste modo, um dos objectivos desta tese é avaliar o impacto da distorção não-linear em
sinais SWIPT, e apresentar soluções viáveis para mitigar os efeitos da distorção não-linear
no desempenho da transmissão de dados.Outro objetivo da tese é aproveitar as vantagens
dos sinais de transferência de energia em técnicas SWIPT para efeitos de estimação de
canal e segurança na comunicação.Os desempenhos dessas técnicas SWIPT são avaliados
analiticamente,sendo os respectivos resultados validados por simulações.É mostrado que
os esquemas SWIPT propostos podem ter excelente desempenho, superando esquemas
SWIPT convencionais
Power allocation and signal labelling on physical layer security
PhD ThesisSecure communications between legitimate users have received considerable
attention recently. Transmission cryptography, which introduces
secrecy on the network layer, is heavily relied on conventionally to secure
communications. However, it is theoretically possible to break the
encryption if unlimited computational resource is provided. As a result,
physical layer security becomes a hot topic as it provides perfect secrecy
from an information theory perspective. The study of physical layer
security on real communication system model is challenging and important,
as the previous researches are mainly focusing on the Gaussian
input model which is not practically implementable.
In this thesis, the physical layer security of wireless networks employing
finite-alphabet input schemes are studied. In particular, firstly, the secrecy
capacity of the single-input single-output (SISO) wiretap channel
model with coded modulation (CM) and bit-interleaved coded modulation
(BICM) is derived in closed-form, while a fast, sub-optimal power
control policy (PCP) is presented to maximize the secrecy capacity performance.
Since finite-alphabet input schemes achieve maximum secrecy
capacity at medium SNR range, the maximum amount of energy that
the destination can harvest from the transmission while satisfying the
secrecy rate constraint is computed. Secondly, the effects of mapping
techniques on secrecy capacity of BICM scheme are investigated, the secrecy
capacity performances of various known mappings are compared on
8PSK, 16QAM and (1,5,10) constellations, showing that Gray mapping
obtains lowest secrecy capacity value at high SNRs. We propose a new
mapping algorithm, called maximum error event (MEE), to optimize the
secrecy capacity over a wide range of SNRs. At low SNR, MEE mapping
achieves a lower secrecy rate than other well-known mappings, but
at medium-to-high SNRs MEE mapping achieves a significantly higher
secrecy rate over a wide range of SNRs. Finally, the secrecy capacity and
power allocation algorithm (PA) of finite-alphabet input wiretap channels
with decode-and-forward (DF) relays are proposed, the simulation
results are compared with the equal power allocation algorithm
Exploiting the reciprocal channel for discrete jamming to secure wireless communications against multiple-antenna eavesdropper
The purpose of this paper is to advance the current state of physical layer security through
the design and analysis of a discrete jamming scheme that exploits the reciprocal characteristic of the
wireless channel with the aim to create equivocation to a passive multiple-antenna eavesdropper. Closed form
solutions of the secrecy capacity for different configurations of the jamming component were obtained and
successfully compare with the simulation results. Furthermore, the secrecy level provided by the developed
scheme is analyzed taking into account the number of bits extracted from the channel. The asymptotic study
of the proposed secrecy technique allowed to conclude that in the high-power regime, full secrecy is obtained
even considering that the eavesdropper is equipped with an unlimited number of antennas.publishe
Interference Exploitation via Symbol-Level Precoding: Overview, State-of-the-Art and Future Directions
Interference is traditionally viewed as a performance limiting factor in wireless communication systems, which is to be minimized or mitigated. Nevertheless, a recent line of work has shown that by manipulating the interfering signals such that they add up constructively at the receiver side, known interference can be made beneficial and further improve the system performance in a variety of wireless scenarios, achieved by symbol-level precoding (SLP). This paper aims to provide a tutorial on interference exploitation techniques from the perspective of precoding design in a multi-antenna wireless communication system, by beginning with the classification of constructive interference (CI) and destructive interference (DI). The definition for CI is presented and the corresponding mathematical characterization is formulated for popular modulation types, based on which optimization-based precoding techniques are discussed. In addition, the extension of CI precoding to other application scenarios as well as for hardware efficiency is also described. Proof-of-concept testbeds are demonstrated for the potential practical implementation of CI precoding, and finally a list of open problems and practical challenges are presented to inspire and motivate further research directions in this area
A Tutorial on Interference Exploitation via Symbol-Level Precoding: Overview, State-of-the-Art and Future Directions
IEEE Interference is traditionally viewed as a performance limiting factor in wireless communication systems, which is to be minimized or mitigated. Nevertheless, a recent line of work has shown that by manipulating the interfering signals such that they add up constructively at the receiver side, known interference can be made beneficial and further improve the system performance in a variety of wireless scenarios, achieved by symbol-level precoding (SLP). This paper aims to provide a tutorial on interference exploitation techniques from the perspective of precoding design in a multi-antenna wireless communication system, by beginning with the classification of constructive interference (CI) and destructive interference (DI). The definition for CI is presented and the corresponding mathematical characterization is formulated for popular modulation types, based on which optimization-based precoding techniques are discussed. In addition, the extension of CI precoding to other application scenarios as well as for hardware efficiency is also described. Proof-of-concept testbeds are demonstrated for the potential practical implementation of CI precoding, and finally a list of open problems and practical challenges are presented to inspire and motivate further research directions in this area
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