339 research outputs found
A Versatile Secure Transmission Strategy in the Presence of Outdated CSI
We study secure transmission considering the practical scenario
where only outdated knowledge of the legitimate receiver’s channel
and statistical knowledge of the eavesdropper’s channel is available at
the transmitter. Conditioned on the limited channel knowledge, we adopt
an on-off secure transmission scheme and propose a versatile strategy to
determine the codeword transmission rate. We first analyze the outage
performance of the system and then provide the design of optimal wiretap
code parameters maximizing the secrecy throughput. Compared with
the existing solution in the literature, the proposed secure transmission
design enlarges the achievable reliability-security region and increases
the maximum secrecy throughput.ARC Discovery Projects Grant DP15010390
Hybrid satellite–terrestrial networks toward 6G : key technologies and open issues
Future wireless networks will be required to provide more wireless services at higher data rates and with global coverage. However, existing homogeneous wireless networks, such as cellular and satellite networks, may not be able to meet such requirements individually, especially in remote terrain, including seas and mountains. One possible solution is to use diversified wireless networks that can exploit the inter-connectivity between satellites, aerial base stations (BSs), and terrestrial BSs over inter-connected space, ground, and aerial networks. Hence, enabling wireless communication in one integrated network has attracted both the industry and the research fraternities. In this work, we provide a comprehensive survey of the most recent work on hybrid satellite–terrestrial networks (HSTNs), focusing on system architecture, performance analysis, design optimization, and secure communication schemes for different cooperative and cognitive HSTN network architectures. Different key technologies are compared. Based on this comparison, several open issues for future research are discussed
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Uplink secrecy performance of RIS-based RF/FSO three-dimension heterogeneous networks
In this paper, a novel reconfigurable intelligent surface (RIS)-assisted HAP-UAV secure multi-user mixed radio frequency (RF)/free space optical (FSO) system is proposed. Specifically, the Gamma-Gamma distribution is utilized to characterize the atmospheric turbulence effect for the FSO link from UAV to HAP, while the Rayleigh and Nakagami- m distribution fading are applied to simulate the legitimate and wiretap RF links, respectively. We present the closed-form expressions for the probability density functions, the cumulative distribution functions, and the secrecy outage probability (SOP) of the end-to-end signal-to-noise ratio (SNR) in terms of Meijer’s G-function. To gain more insight into secrecy performance, we further obtain the closed-form expressions for the asymptotic SOP, the asymptotic probability of positive secrecy capacity (PPSC), the diversity gain, and the coding gain at high SNR regions. We can observe that the secrecy performance depends on the weaker channel between the RF and FSO, and is closely related to the number of RIS elements, the number of terrestrial users, the atmospheric turbulence factor, pointing error parameters, and the fading parameter of Nakagami- m distributed wiretap link. Finally, numerical results validate the derived results and demonstrate that the proposed design achieves superior secrecy performance over the benchmarks
Joint Spatial and Spectrum Cooperation in Wireless Network.
PhDThe sky-rocketing growth of multimedia infotainment applications and broadband-hungry
mobile devices exacerbate the stringent demand for ultra high data rate and more spectrum resources. Along with it, the unbalanced temporal and geographical variations
of spectrum usage further inspires those spectral-efficient networks, namely, cognitive
radio and heterogeneous cellular networks (HCNs). This thesis focuses on the system
design and performance enhancement of cognitive radio (CR) and HCNs. Three different
aspects of performance improvement are considered, including link reliability of cognitive
radio networks (CNs), security enhancement of CNs, and energy efficiency improvement
of CNs and HCNs.
First, generalized selection combining (GSC) is proposed as an effective receiver design
for interference reduction and reliability improvement of CNs with outdated CSI. A uni-
ed way for deriving the distribution of received signal-to-noise ratio (SNR) is developed
in underlay spectrum sharing networks subject to interference from the primary trans-
mitter (PU-Tx) to the secondary receiver (SU-Rx), maximum transmit power constraint
at the secondary transmitter (SU-Tx), and peak interference power constraint at the
PU receiver (PU-Rx), is developed. Second, transmit antenna selection with receive
generalized selection combining (TAS/GSC) in multi-antenna relay-aided communica-
tion is introduced in CNs under Rayleigh fading and Nakagami-m fading. Based on
newly derived complex statistical properties of channel power gain of TAS/GSC, exact
ergodic capacity and high SNR ergodic capacity are derived over Nakagami-m fading.
Third, beamforming and arti cial noise generation (BF&AN) is introduced as a robust
scheme to enhance the secure transmission of large-scale spectrum sharing networks
with multiple randomly located eavesdroppers (Eves) modeled as homogeneous Poisson
Point Process (PPP). Stochastic geometry is applied to model and analyze the impact of
i
BF&AN on this complex network. Optimal power allocation factor for BF&AN which
maximizes the average secrecy rate is further studied under the outage probability con-
straint of primary network. Fourth, a new wireless energy harvesting protocol is proposed
for underlay cognitive relay networks with the energy-constrained SU-Txs. Exact and
asymptotic outage probability, delay-sensitive throughput, and delay-tolerant through-
put are derived to explore the tradeoff between the energy harvested from the PU-Txs
and the interference caused by the PU-Txs. Fifth, a harvest-then-transmit protocol is
proposed in K-tier HCNs with randomly located multiple-antenna base stations (BSs)
and single antenna mobile terminals (MTs) modeled as homogeneous PPP. The average
received power at MT, the uplink (UL) outage probability, and the UL average ergodic
rate are derived to demonstrate the intrinsic relationship between the energy harvested
from BSs in the downlink (DL) and the MT performance in the UL. Throughout the
thesis, it is shown that link reliability, secrecy performance, and energy efficiency of
CNs and HCNs can be signi cantly leveraged by taking advantage of multiple antennas,
relays, and wireless energy harvesting
Advanced interference management techniques for future wireless networks
In this thesis, we design advanced interference management techniques for future wireless
networks under the availability of perfect and imperfect channel state information
(CSI). We do so by considering a generalized imperfect CSI model where the variance of
the channel estimation error depends on the signal-to-noise ratio (SNR).
First, we analyze the performance of standard linear precoders, namely channel inversion
(CI) and regularized CI (RCI), in downlink of cellular networks by deriving the
received signal-to-interference-plus-noise ratio (SINR) of each user subject to both perfect
and imperfect CSI. In this case, novel bounds on the asymptotic performance of linear precoders
are derived, which determine howmuch accurate CSI should be to achieve a certain
quality of service (QoS). By relying on the knowledge of error variance in advance, we
propose an adaptive RCI technique to further improve the performance of standard RCI
subject to CSI mismatch.
We further consider transmit-power efficient design of wireless cellular networks. We
propose two novel linear precoding techniques which can notably decrease the deployed
power at transmit side in order to secure the same average output SINR at each user compared
to standard linear precoders like CI and RCI.
We also address a more sophisticated interference scenario, i.e., wireless interference
networks, wherein each of the K transmitters communicates with its corresponding receiver
while causing interference to the others. The most representative interference
management technique in this case is interference alignment (IA). Unlike standard techniques
like time division multiple access (TDMA) and frequency division multiple access
(FDMA) where the achievable degrees of freedom (DoF) is one, with IA, the achievable
DoF scales up with the number of users. Therefore, in this thesis, we quantify the
asymptotic performance of IA under a generalized CSI mismatch model by deriving novel
bounds on asymptotic mean loss in sum rate and the achievable DoF. We also propose
novel least squares (LS) and minimum mean square error (MMSE) based IA techniques
which are able to outperform standard IA schemes under perfect and imperfect CSI. Furthermore,
we consider the implementation of IA in coordinated networks which enable us
to decrease the number of deployed antennas in order to secure the same achievable DoF
compared to standard IA techniques
Wireless networks physical layer security : modeling and performance characterization
Intrigued by the rapid growth and expand of wireless devices, data security is increasingly playing a significant role in our daily transactions and interactions with different entities. Possible examples, including e-healthcare information and online shopping, are becoming vulnerable due to the intrinsic nature of wireless transmission medium and the widespread open access of wireless links. Traditionally, the communication security is mainly regarded as the tasks at the upper layers of layered protocol stack, security techniques, including personal access control, password protection, and end-to-end encryption, have been widely studied in the open literature. More recently, plenty of research interests have been drawn to the physical layer forms of secrecy. As a new but appealing paradigm at physical layer, physical layer security is based on two pioneering works: (i) Shannon’s information-theoretic formulation and (ii) Wyner’s wiretap formulation.
On account of the fundamental of physical layer security and the different nature of various wireless network, this dissertation is supposed to further fill the lacking of the existing research outcomes. To be specific, the contributions of this dissertation can be summarized as three-fold:(i) exploration of secrecy metrics to more general fading channels; (ii) characterization a new fading channel model and its reliability and security analysis in digital communication systems; and (iii) investigation of physical layer security over the random multiple-input multiple-output (MIMO) α −μ fading channels.
Taking into account the classic Alice-Bob-Eve wiretap model, the first contribution can be divided into four aspects: (i) we have investigated the secrecy performance over single-input single-output (SISO) α −μ fading channels. The probability of non-zero (PNZ) secrecy capacity and the lower bound of secrecy outage probability (SOP) are derived for the special case when the main channel and wiretap channel undergo the same non-linearity fading parameter, i.e., α. Later on, for the purpose of filling the gap of lacking closed-form expression of SOP in the open literature and extending the obtained results in chapter 2 to the single-input multiple-output (SIMO) α − μ wiretap fading channels, utilizing the fact that the received signal-tonoise ratios (SNRs) at the legitimate receiver and eavesdropper can be approximated as new α −μ distributed random variables (RVs), the SOP metric is therefore derived, and given in terms of the bivariate Fox’s H-function; (ii) the secrecy performance over the Fisher-Snedecor F wiretap fading channels is initially considered. The SOP, PNZ, and ASC are finalized in terms of Meijer’s G-function; (iii) in order to generalize the obtained results over α −μ and Fisher-Snedecor F wiretap fading channels, a more flexible and general fading channel, i.e., Fox’s H-function fading model, are taken into consideration. Both the exact and asymptotic analysis of SOP, PNZ, and average secrecy capacity (ASC), are developed with closed-form expressions; and (iv) finally, motivated by the fact that the mixture gamma (MG) distribution is an appealing tool, which can be used to model the received instantaneous SNRs over wireless fading channels, the secrecy metrics over wiretap fading channels are derived based on the MG approach.
Due to the limited transmission power and communication range, cooperative relays or multi-hop wireless networks are usually regarded as two promising means to address these concerns. Inspired by the obtained results in Chapters 2 and 3, the second main contribution is to propose a novel but simple fading channel model, namely, the cascaded α −μ. This new distribution is advantageous since it encompasses the existing cascaded Rayleigh, cascaded Nakagami-m, and cascaded Weibull with ease. Based on this, both the reliability and secrecy performance of a digital system over cascaded α −μ fading channels are further evaluated. Closed-form expressions of reliability metrics (including amount of fading (AF), outage probability, average channel capacity, and average symbol error probability (ABEP).) and secrecy metrics (including SOP, PNZ, and ASC) are respectively provided. Besides, their asymptotic behaviors are also performed and compared with the exact results.
Considering the impacts of users’ densities, spatial distribution, and the path-loss exponent on secrecy issue, the third aspect of this thesis is detailed in Chapter 8 as the secrecy investigation of stochastic MIMO system over α −μ wiretap fading channels. Both the stochastic geometry and conventional space-time transmission (STT) scheme are used in the system configuration. The secrecy issue is mathematically evaluated by three metrics, i.e., connection outage, the probability of non-zero secrecy capacity and the ergodic secrecy capacity. Those three metrics are later on derived regarding two ordering scheme, and further compared with Monte-Carlo simulations
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