AI-assisted secure data transmission techniques for next-generation HetNets: A review

With the uninterrupted revolution of communications technologies and the great-leap-forward development of emerging applications, the ubiquitous deployment of Internet of Things (IoT) is imperative to accommodate constantly growing user demands and market scales. Communication security is critically important for the operations of IoT. Among the communication security provisioning techniques, physical layer security (PLS), which can provide unbreakable, provable, and quantifiable secrecy from an information-theoretical point of view, has drawn considerable attention from both the academia and the industries. However, the unique features of IoT, such as low-cost, wide-range coverage, massive connection, and diversified services, impose great challenges for the PLS protocol design in IoT. In this article, we present a comprehensive review of the PLS techniques toward IoT applications. The basic principle of PLS is first briefly introduced, followed by the survey of the existing PLS techniques. Afterwards, the characteristics of IoT are identified, based on which the challenges faced by PLS protocol design are summarized. Then, three newly-proposed PLS solutions are highlighted, which match the features of IoT well and are expected to be applied in the near future. Finally, we conclude the paper and point out some further research directions.

Physical layer security and covert communication in UAV-ISAC networks: A comprehensive survey

The physical layer security techniques have made great progress in the past few years. The essential idea of physical layer transmission is to maximize the randomness of undesired channels. The 4-D antenna arrays formed by introducing time as the fourth controlling degree of freedom can be used to regulate the radiated fields in space, time, and frequency domains simultaneously. Thus, 4-D antenna arrays are an effective carrier for achieving physical layer secure transmission. However, the traditional secure transmission approach based on 4-D antenna arrays always inevitably leads to high sidelobe levels (SLLs) of radiated power or less channel randomness. Aimed at this problem, a novel physical layer secure transmission approach based on 4-D antenna arrays is proposed, which combines the advantages of traditional phased arrays and 4-D arrays. The approach can be used to reduce the SLL of radiated power and improve the channel randomness by optimizing the time sequences and static amplitude weighting. Moreover, the signal distortion caused by time modulation can be compensated in the desired direction by premodulating the transmitted signals. Both the numerical and experimental results demonstrate the effectiveness of the proposed approach.

This paper study the secure optimal QoS routing (SOQR) in wireless ad hoc networks (WANETs) based on the physical layer security techniques. Specifically, we consider a multi-hop WANET with malicious eavesdroppers and cooperative jammers, and formulate the SOQR as an optimization problem. To deal with this problem, we first derive the closed-form expressions of connection outage probability (COP) and secrecy outage probability (SOP) for any given end-to-end path, which serve as the performance metrics of communication QoS and transmission security, respectively. Then, we explore the minimum COP conditioned on that SOP is below a pre- specified threshold and obtain the corresponding achievable power allocation strategy. With the help of analysis of a given path, we further propose the SOQR algorithm which selects the secure path between a pair of source and destination nodes in a distributed manner to achieve the optimal QoS performance. Finally, numerical simulations are conducted to validate the efficiency of our theoretical results, as well as to illustrate the QoS-security tradeoffs.

Non-orthogonal multiple access (NOMA) is emerging as a popular radio access technique to serve multiple users under the same resource block to improve spectral efficiency in 5G and 6G communication. But the resource sharing in NOMA causes concerns on data security. Since power domain NOMA exploits the difference in channel properties for bandwidth-efficient communication, it is feasible to ensure data confidentiality in NOMA communication through physical layer security techniques. In this work, we propose to ensure resistance against internal eavesdropping in NOMA communication through a secret key derived from channel randomness. A unique secret key is derived from the channel of each NOMA user; which is used to randomize the data of the respective user before superposition coding (SC) to prevent internal eavesdropping. The simulation results show that the proposed system provides very good security against internal eavesdropping in NOMA.

Smart energy systems are becoming an important component of smart cities. The wide adoption of existing computing technologies and communication standards by a smart energy system exposes it to the plethora of threats that exist in cyberspace. In this article, we investigate the vulnerabilities and threats associated with smart energy system components, including Internet of Things enabled devices, as well as relevant communication standards, and we discuss countermeasures against adversarial attacks. We found that the existing literature has reported various attacks, including modification, denial-of-service, malware, and message replay, which can cause malfunctioning of different components of a smart energy system. In addition, we propose a framework for securing the physical layer of the smart energy system. The framework is based on advanced key generation, machine learning, and physical layer security techniques, which enhance the security of smart energy systems across different applications.

Radio frequency identification (RFID) systems are gaining more attention in new frontiers of applications due to their simplicity, low size factor and low cost of deployment. One of the emerging frontiers of applications of RFID is the healthcare system. In this paper, we propose a novel physical layer security technique (PLS) to secure radio frequency identification (RFID) tags used in healthcare systems. To achieve secure communications for RFID systems, directional modulation (DM) scheme is exploited at the reader side. The proposed system maintains the simple circuity and processing nature of passive tags. The results obtained demonstrate that DM techniques can achieve physical layer security for RFID systems.

In the new generation wireless communication systems, when multiple users are served, information security among them should be considered to protect each user’s privacy. In this case, physical layer security techniques can be adopted for this mutual confidence problem. Unlike other traditional physical layer security methods, the proposed scheme improves secrecy rate with the information of users’ access statuses (i.e., being served or idle), and it is denoted as SRT-AS. In the SRT-AS, appropriate parameters expressing users’ actual access statuses are introduced, and an adaptive transmitter and receiver design strategy is used to increase security. It can be found that no iterative process is included in the SRT-AS, moreover, performance analysis and simulation results illustrate that the SRT-AS is feasible for the multi-user system.

Chapter 3 - HetNet/M2M/D2D communication in 5G technologies

As a physical layer security technique, directional modulation (DM) is normally realized using a fully digital structure due to its easy and flexible hardware design. However, for a large antenna array, such as the case of massive MIMO, to reduce the cost and power consumption, a hybrid digital and analog beamforming structure is widely adopted. In this paper, the DM design problem is studied based on such a hybrid implementation for the first time. As a representative example, the interleaved subarrays are used for the proposed design. Design examples are provided to show the effectiveness of the proposed design.

Heterogeneity is one of the key features that characterizes the future generation of cellular networks, 5G and beyond. However, streaming high-quality bandwidth-hungry multimedia contents over bandwidth-constrained 5G heterogeneous networks (5G HetNets) involves various significant challenges, including long video start time, video start failures, frequent buffering and stalling, and low quality of experience (QoE). Traditional multimedia streaming technologies, however, do not pay attention to either the available network bandwidth or the interaction between content characteristics and resources. To reduce network strain and improve QoE, we propose “Context-Aware Streaming over 5G HetNets ( CASH )” that allows us to achieve a tradeoff between content-context and network-context. The proposed CASH fundamentally works in a multi-step process. First, the CASH comes with an integrated architecture that includes a media server, a flow scheduler, and a single radio controller (SRC). The SRC and the user equipment (UE) of interest cooperatively prepare a metadata file that contains the network-context. Second, based on the metadata file, which can be accessed from the SRC in the media preparation server, we analyze and cluster the contents based on the content-context, e.g., the actual bitrate of each scene. The metadata file is then updated by adding the content-context information. Third, the flow scheduler basically controls the flow of the clusters of the contents in the server-push mode and conveys that to the appropriate radio access technology (RAT) conforming to the bitrate of the clusters and bandwidth delivered by RATs. Finally, the UE will aggregate the received packets and will play-back the content. We analytically show the validity of CASH. Also, extensive simulations are performed to demonstrate that CASH offers substantial performance improvements compared with exiting works in terms of peak data rate, latency, users’ experiences, and spectral efficiency.

Ultra-reliable low-latency communication (uRLLC) emerges as one of the three service categories in fifth-generation (5G) wireless networks, with a potential to support multiple advanced services for latency-sensitive communications. The inherent openness of the wireless environment makes security in 5G unprecedentedly urgent to be addressed. Accordingly, the physical layer security (PLS) technique exploits the randomness characteristics of the wireless channel to fulfill security and confidentiality of information transmission. Different from many current works, which ignored the significance of security in uRLLC, this paper studies secrecy improvement strategy design in uRLLC scenarios. First, we propose suitable performance metrics for evaluating PLS of uRLLC and make a compromise between reliability, latency, and security, while maximizing the network throughput. Next, we identify the key challenging issues for achieving PLS in the context of uRLLC, and discuss the role of cooperative communication and mobility in terms of possible solutions. To the best of our knowledge, this is the first paper to make a trade-off among reliability, security and network throughput. Simulations validate the theoretical analyses.

With the rapid proliferation of the Internet of Things (IoT), small devices in various applications generate, process, and exchange security and safety-critical data as well as privacy-sensitive information. However, due to limited hardware capabilities of such small devices, the IoT networks are inherently vulnerable to security attacks. In this context, the analog cooperative beamforming (ACB)-based physical layer security (PLS) technique can be a suitable solution to guarantee security in the IoT networks by creating a virtual antenna array with multiple IoT devices. Nevertheless, such techniques suffer from poor secrecy performance, when an eavesdropper is located within the main beam toward the legitimate receiver. Motivated by this limitation, in this article, we propose a fully distributed null-steering beamformer, which is suitable for IoT networks following decentralized architecture. Through analysis and simulation, we show that the proposed PLS algorithm outperforms the existing ACB-based PLS scheme. Furthermore, we show that there exists an optimal degree of nulling that maximizes the secrecy performance, which can be estimated based on the analytical results.

In the next generation (5G) new radio (NR) systems, beamforming is an enabling technology for millimeter wave communications which require beam sweeping for transmission. When user equipment (UE) uses discontinuous reception (DRX) to save power, the UE may be informed of incoming services or updating system information through a paging procedure. A next generation NodeB (gNB) transmits the same paging message on multiple beams in discrete time slots to notify the target UE. As the paging is transmitted through beam sweeping, paging transmission occupies multiple time slots and the resources in paging occasion. Additionally, increasing number of time slots make the UE wake up longer to monitor the paging occasion, and this directly increases the power consumption of the UE. In this paper, we propose an efficient beam sweeping paging mechanism taking beam sweeping overhead and UE power consumption into consideration. Mathematical analysis and simulation experiments show that the proposed mechanism enhances the performance of power saving while reducing the overhead of paging sweeping beams.

The wireless networks lack a physical boundary due to the broadcasting nature of wireless transmissions. The security has become a critical concern in the physical layer of wireless networks. Physical-layer security techniques are effective in resolving the boundary, efficiency and link reliability issues, but they can not be able to guarantee security with probability 1. In this work, we present a cross-layer security scheme for STBC system. By introducing a distort signal set the sender randomly flip-flops between the distort signal set and the orthogonal code set to confuse the attacker. The physical-layer security is enhanced as a result. In the proposed scheme the physical-layer may rely on upper-layer encryption techniques for security, which results in a cross-layer security scheme. Our approach can guarantee enhanced security with probability 1 in the wireless networks.