Physical layer security in cognitive radio networks using improper gaussian signaling

Orientador: Prof. Dr. Evelio Martin Garcia FernandezCoorientador: Prof. Dr. Samuel Baraldi MafraTese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia Elétrica. Defesa : Curitiba, 25/10/2018Inclui referências: p.55-60Resumo: Em redes de comunicação sem fio que possuem restrições de interferência, a adoção de sinais assimétricos ou impróprios pode atingir taxas de transmissão mais altas do que as obtidas com sinais próprios, devido a maior entropia diferencial destes. Portanto, uma vez que o desempenho de segurança de uma rede está diretamente relacionado a taxa de transmissão de seus usuários, esta tese propõe o emprego de sinais impróprios para melhorar o desempenho do sigilo em redes de Radio Cognitivo. Ate onde sabemos, este e o primeiro trabalho que aborda a Segurança da Camada Física deste tipo de sistema usando sinais assimétricos. Os resultados foram obtidos para dois cenários diferentes em um mesmo modelo de sistema: uma rede cognitiva underlay com uma ligacao direta entre o transmissor secundário e seu receptor, cuja comunicação está sendo espionada. Usuários primários e secundários causam interferência entre si. Em ambos os cenários, apenas a informação estatística do estado do canal foi considerada disponível para os usuários cognitivos. Para o primeiro cenário, em que a localização dos nós do sistema foi definida arbitrariamente, derivamos uma expressao analótica para a Probabilidade de Falha de Sigilo, a principal métrica de desempenho analisada, e foi mostrado que a adoção de sinalização impropria pode ser benéfica tanto para os usuários que causam quanto para os que recebem interferência. Em um segundo cenário, em que a localização dos nos foi distribuída uniformemente sobre uma célula circular, encontramos valores ótimos ou sub-ótimos para a potencia de transmissão e grau de impropriedade dos sinais dos usuários secundários simultaneamente, a fim de otimizar o desempenho de segurança da rede. A otimização foi feita com o auxílio de Algoritmos Genéticos. Em seguida, os benefícios do esquema de transmissão em termos da probabilidade de falha de sigilo e da vazão de dados segura do sistema, bem como o custo de eficiência energética foram avaliados. Os resultados indicam que, para sistemas limitados por interferência, ao buscar por baixas probabilidades de falha de sigilo, e sempre uma estratégia melhor para os usuários secundários adotar algum grau de impropriedade em suas transmissões. Além disso, a adoção de sinais impróprios também pode melhorar as taxas seguras atingíveis no lado dos usuários cognitivos em redes underlay. No entanto, em termos de eficiência energética do sistema, otimizar apenas a potencia de transmissão secundaria e adotar sinais próprios obtém o melhor desempenho. Os resultados apresentados nesta pesquisa são promissores, uma vez que em muitas redes sem fio, inclusive cognitivas, existem restrições de interferência e sinais assimétricos poderiam alcançar um desempenho melhor do que os próprios, o paradigma atual. Palavras-chave: Radio Cognitivo, Segurança na Camada Física, SinaisAbstract: In interference constrained wireless communication networks, adopting asymmetric or improper signals may attain higher transmission rates than those achieved by proper ones, due to the higher differential entropy of the latter. Therefore, since the secrecy performance of a network is directly related to the transmission rate of its users, this thesis proposes employing improper signals in order to enhance the secrecy performance of Cognitive Radio networks. As far as we know, this is the first work that addresses the Physical Layer Security of these type of system by using asymmetric signals. The results were obtained for two different scenarios in the same system model: an underlay cognitive network with a direct link between secondary transmitter and receiver, whose communication is being eavesdropped. Both primary and secondary users cause interference at each other. In both scenarios only Statistical Channel State Information was considered available at the cognitive users. For the first scenario, in which nodes locations were defined arbitrarily, we derived an analytical expression for the Secrecy Outage Probability, the main performance metric analyzed, and it was shown that adopting improper signaling can be beneficial for users either causing or receiving interference. In a second scenario, in which nodes locations were uniformly distributed over a circular cell, we found optimal or suboptimal values of the secondary users transmit power and degree of impropriety, concurrently, in order to optimize the secrecy performance, with the aid of Genetic Algorithms. Then, the benefits of the transmission scheme in terms of the Secrecy Outage Probability and the Secure Throughput of the system, as well as the Secure Energy Efficiency cost were assessed. Results indicate that, for systems with interference constraints, when searching for lower Secrecy Outage Probabilities, it is always a better strategy for the Secondary Users to adopt some degree of impropriety in their transmissions. In addition, adopting improper signals can also improve the achievable secure rates at the cognitive users side in underlay networks. However, in terms of the energy efficiency of the system, optimizing only the secondary transmit power while employing proper signals achieves the best performance. The results presented in this research are promising, since in many wireless channels, including Cognitive Networks, there are interference constraints and asymmetric signals could attain better performance than proper ones, the current paradigm. Keywords: Cognitive Radio Networks, Physical Layer Security, Improper Gaussian Signaling, Secrecy Outage Probability

Interference Alignment for Cognitive Radio Communications and Networks: A Survey

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Interference alignment (IA) is an innovative wireless transmission strategy that has shown to be a promising technique for achieving optimal capacity scaling of a multiuser interference channel at asymptotically high-signal-to-noise ratio (SNR). Transmitters exploit the availability of multiple signaling dimensions in order to align their mutual interference at the receivers. Most of the research has focused on developing algorithms for determining alignment solutions as well as proving interference alignment’s theoretical ability to achieve the maximum degrees of freedom in a wireless network. Cognitive radio, on the other hand, is a technique used to improve the utilization of the radio spectrum by opportunistically sensing and accessing unused licensed frequency spectrum, without causing harmful interference to the licensed users. With the increased deployment of wireless services, the possibility of detecting unused frequency spectrum becomes diminished. Thus, the concept of introducing interference alignment in cognitive radio has become a very attractive proposition. This paper provides a survey of the implementation of IA in cognitive radio under the main research paradigms, along with a summary and analysis of results under each system model.Peer reviewe

Physical and medium access control layer advances in 5G wireless networks

No abstract available

Jointly Optimal RIS Placement and Power Allocation for Underlay D2D Communications: An Outage Probability Minimization Approach

In this paper, we study underlay device-to-device (D2D) communication systems empowered by a reconfigurable intelligent surface (RIS) for cognitive cellular networks. Considering Rayleigh fading channels and the general case where there exist both the direct and RIS-enabled D2D channels, the outage probability (OP) of the D2D communication link is presented in closed-form. Next, for the considered RIS-empowered underlaid D2D system, we frame an OP minimization problem. We target the joint optimization of the transmit power at the D2D source and the RIS placement, under constraints on the transmit power at the D2D source and on the limited interference imposed on the cellular user for two RIS deployment topologies. Due to the coupled optimization variables, the formulated optimization problem is extremely intractable. We propose an equivalent transformation which we are able to solve analytically. In the transformed problem, an expression for the average value of the signal-to-interference-noise ratio (SINR) at the D2D receiver is derived in closed-form. Our theoretical derivations are corroborated through simulation results, and various system design insights are deduced. It is indicatively showcased that the proposed RIS-empowered underlaid D2D system design outperforms the benchmark semi-adaptive optimal power and optimal distance schemes, offering $44\%$ and $20\%$ performance improvement, respectively