Enhancing Physical Layer Security in AF Relay Assisted Multi-Carrier Wireless Transmission

In this paper, we study the physical layer security (PLS) problem in the dual hop orthogonal frequency division multiplexing (OFDM) based wireless communication system. First, we consider a single user single relay system and study a joint power optimization problem at the source and relay subject to individual power constraint at the two nodes. The aim is to maximize the end to end secrecy rate with optimal power allocation over different sub-carriers. Later, we consider a more general multi-user multi-relay scenario. Under high SNR approximation for end to end secrecy rate, an optimization problem is formulated to jointly optimize power allocation at the BS, the relay selection, sub-carrier assignment to users and the power loading at each of the relaying node. The target is to maximize the overall security of the system subject to independent power budget limits at each transmitting node and the OFDMA based exclusive sub-carrier allocation constraints. A joint optimization solution is obtained through duality theory. Dual decomposition allows to exploit convex optimization techniques to find the power loading at the source and relay nodes. Further, an optimization for power loading at relaying nodes along with relay selection and sub carrier assignment for the fixed power allocation at the BS is also studied. Lastly, a sub-optimal scheme that explores joint power allocation at all transmitting nodes for the fixed subcarrier allocation and relay assignment is investigated. Finally, simulation results are presented to validate the performance of the proposed schemes.Comment: 10 pages, 7 figures, accepted in Transactions on Emerging Telecommunications Technologies (ETT), formerly known as European Transactions on Telecommunications (ETT

Secure communication via untrusted switchable decode-and-forward relay

In this paper, a practical power efficient technique is proposed for an untrusted decode-and-forward (DAF) based cooperative communication system to provide secure communication between the source and the destination. More specifically, a DAF relay, called switchable DAF (sDAF), is designed in such a way that it can be switched to amplify-and-forward (AAF) in certain predefined situations. The algorithm is based on destination-assisted jamming and comprised of two phases. The first phase securely shares the random manipulating sequence (RMS) through an untrusted relay, while the second phase uses this RMS for secure communication through untrusted relay. This algorithm not only provides secrecy, but also enhances the power efficiency as compared to other destination-assisted jamming techniques.Institute of Electrical and Electronics EngineersIEEE Spanish SectionPolytechnic University of Valenci

Secure and reliable IoT communications using nonorthogonal signals’ superposition with dual-transmission

Ensuring secure communication for internet of things (IoT) has drawn much attention because of the lim itation in the use of conventional cryptographic techniques owing to the unique features of IoT devices such as low complexity, lightweight computing, and power constraints. Physical layer security (PLS) has the potential to provide security solutions that are suitable for such applications. In this article, an efficient PLS approach is proposed for providing secure communication against external and internal eavesdroppers in a downlink multi-carrier IoT communication system. The system consists of a transmitter with a single active antenna (and a single radio frequency chain) that is trying to communicate with two single antenna IoT devices in the presence of a passive eaves dropper. In the proposed algorithm, frequency selective channel based pre-coder matrices and dual-transmission approach are jointly employed to provide simple and secure communication without complex computational processing at the IoT devices. Simulation results showed that the proposed algorithm can provide security against internal and external eavesdroppers and is suitable for IoT devicesNo sponso

Secure pre-coding and post-coding for OFDM systems along with hardware implementation

An effective and hardware-friendly physical layer security design, composed of a channel-based frequency pre-coder and a post-coder for OFDM-based systems, is proposed. The design is achieved by decomposing the diagonal matrix of the channel frequency amplitude of the legitimate receiver in order to obtain two unitary orthonormal matrices. The first matrix is used as a pre-coder just before the IFFT process at the transmitter, while the second matrix is used as a post-coder just after the FFT process at the receiver. Besides security, the presented design is interestingly found out to work as a shuffler or inter-leaver, which does not only provide secrecy, but also enhances the performance against burst errors. Moreover, a new channel calibration technique is developed to overcome the effect of channel reciprocity mismatch on the proposed scheme. The provided simulations and USRP hardware testbed implementation results validate the effectiveness of the proposed design in achieving practical and reliable secrecy with just minor modifications on the OFDM structure.Institute of Electrical and Electronics Engineers (IEEE)IEEE Spanish SectionPolytechnic University of Valenci

Physical layer security for NOMA: requirements, merits, challenges, and recommendations

Non-orthogonal multiple access (NOMA) has been recognized as one of the most significant enabling technologies for future wireless systems due to its eminent spectral efficiency, its ability to provide an additional degree of freedom for ultra reliable low latency communications (URLLC), and grant free random access. Meanwhile, physical layer security (PLS) has got much attention for future wireless communication systems due to its capability to efficiently complement the cryptography-based algorithms for enhancing overall security of the communication system. In this article, security design requirements for downlink power domain NOMA and solutions provided by PLS to fulfil these requirements are discussed. The merits and challenges which were encountered while employing PLS to NOMA are identified. Finally, future recommendations and prospective so lutions are also presented.No sponso

Enhancing physical layer security of OFDM systems using channel shortening

This work presents a simple, spectral and power efficient scheme for providing secure OFDM communication system using channel shortening. The basic concept is to utilize a channel shortening technique, whose design is based on the channel of the legitimate user (Bob), in such a way that the length of the effective channel is made equal to or less than the cyclic prefix (CP) at Bob only, while the length of the effective channel at the illegitimate receiver (Eve) is greater than CP. Thus, this causes inter-symbol-interference (ISI), loss of orthogonality, and overall performance degradation at Eve. The simulation results show that the presented technique can provide a significant BER performance gap between Bob and Eve, and can provide Quality of Service (QoS) based security. The design is shown to be robust against channel imperfections and can provide spectral and power efficiency beside enhancing security.Institute of Electrical and Electronics EngineersIEEE Communications Societ

Secret key generation using channel quantization with SVD for reciprocal MIMO channels

The generation of secret keys from reciprocal wireless channel by exploiting their randomness nature, is an emerging area of interest to provide secure communication. One of the main challenges in this domain is to increase the secret key length, extracted from the shared channel coefficients between two legitimate communication parties, while maintaining its randomness and uniformity. In this work, we develop a practical key generation method, based on channel quantization with singular value decomposition (CQSVD), which is capable of significantly increasing the generated secret key in MIMO systems. This is achieved through quantizing the phases and amplitudes of the estimated MIMO channel coefficient's matrix by using an alternative form of SVD, where the key sequence is extracted from the orthogonal basis functions of the decomposed channel. In this method, it is shown that for an M ×M antenna system, with M2 independent channel fading coefficients, a secret key sequence of length 2M3 can be generated. The extracted key sequence is transformed to a random phase sequence, which is then used to manipulate the transmitted data on a symbol level basis rather than bit level-basis, to provide more secure communication. The comparative simulation results show that the proposed CQSVD method outperforms the state of the art secret key generation methods

Multi-cell, multi-user, and multi-carrier secure communication using non-orthogonal signals’ superposition with dual-transmission for IoT in 6G and beyond

Considering the advancements of the internet of things (IoT) in 6G and beyond communications, data transmission security in IoT devices has received extensive interest because of their significant features, such as low computational complexity, led by low power requirements. In such devices, the conventional cryptographic techniques may fail to provide secure communication. To fight this drawback, physical layer security (PLS) has remarkable potential to provide security solutions suitable for such applications. In this work, a highly effective PLS technique is proposed for providing secure communication against external and internal eavesdroppers in a downlink multi-cell, multi-user, and multi-carrier IoT communication system. In our proposed system, we considered two base stations, where each base station uses a single radio frequency (RF) chain to link two antennas that are used for the transmission of data. Further, we transmit the data in two rounds, and each round of transmission occurs through a single active antenna of each base station. A different antenna is used for each round of transmission to communicate with two single antenna IoT devices/users in the presence of a passive eavesdropper. In the proposed algorithm, frequency selective channel-based pre-coder matrices and the dual transmission approach are jointly employed. The dual-transmission is performed simultaneously from two base stations to provide security against internal and external eavesdroppers. The proposed system is suitable for IoT-based applications. Also, the potential capabilities of our proposed algorithm are proved by extensive mathematical and simulation analysis.No sponso