ABSTRACT The real‐time reconfigurable characteristics of meta‐surface antennas can be used to separate multi‐stream signals under the condition of single radio frequency (RF). However, with the increase of the symbol rate and the number of antenna arrays in the future, it will face the problem that the state switch rate of the electromagnetic unit is not enough to reach the upper limit of array effective degrees of freedom (DOF) of the meta‐surface antenna. To solve this problem, a theory of asynchronous control meta‐surface antenna is proposed in this paper. By designing the starting time of different element state switching, different electromagnetic element states are staggered to improve the array effective DOF of the meta‐surface antenna. Then, an electromagnetic unit state design algorithm of asynchronous control meta‐surface antenna based on the minimum condition number of equivalent channel matrix is proposed. We improve the sparrow search algorithm to solve the condition number minimization problem in order to obtain the better multi‐stream signal separation performance. The simulation results show that compared with the synchronous control meta‐surface antenna, theory proposed in this paper can improve the effective DOF of array under the condition of limited switch rate, and can effectively reduce the receiving bit error rate and improve spectral efficiency when separating multi‐stream signals.

Reconfigurable intelligent surface (RIS), which can manipulate the wireless environment, has recently been integrated into physical-layer key generation (PKG) systems to establish randomness symmetric keys in static environments. However, few studies have jointly considered the optimization and randomization of the RIS elements to simultaneously achieve a high key generation rate (KGR) and communication performance. This study proposes a RIS-assisted communication and security-integrated protocol for dual-function integration of communication enhancement and PKG in static environments. The protocol partitions RIS elements for beamforming and random beams for parallel execution, utilizing a sparsity adaptive matching pursuit-based channel estimation algorithm to obtain individual channel state information. Subsequently, an optimization problem is formulated for KGR maximization while satisfying quality of service (QoS) requirements. The non-convex optimization problem is addressed through monotonicity analysis and triangle inequality. We validate the efficacy of the proposed protocol by developing a 4.9 GHz RIS-assisted PKG prototype system, comprising modular hardware and flexible software. The field trials demonstrate a 30.81 bit/s KGR for static environments with an average received power increase of 10.6 dB, achieving effective simultaneous integration of communication and security.

Abstract Confidentiality and authentication are two important security properties of wireless communication. There are currently two types of research in wireless communication security: one is based on cryptography, which can be too complicated for some wireless systems; the other is based on physical layer characteristics, which has some security problems and cannot work as well as the cryptography‐based method. In this paper, a lightweight encryption and message authentication framework for wireless communication is proposed. The proposed framework has lower complexity than the cryptography‐based method and works more securely and efficiently than the classical physical layer method. For the encryption, a physical layer offered chain key (PHYLOCK) structure is proposed to generate one‐time keys, which are then XOR‐ed with the plaintext to generate the ciphertext. A security analysis of PHYLOCK is performed and it is proved that it has better security features than the traditional physical layer key generation. For the message authentication, three types of PHYLOCK‐CRC‐based message authentication schemes are developed whose generator polynomial is determined by one‐time keys generated by PHYLOCK. PHYLOCK‐CRC‐based message authentication detects not only random errors introduced by noises but also malicious attacks. The error‐detecting and anti‐attack capabilities are analyzed mathematically. Compared to the standard CRC, PHYLOCK‐CRC‐based message authentication has a decline in error correction capability but is enhanced with cryptographic security features. Monte‐Carlo simulations are provided to evaluate the proposed scheme.

Physical layer key generation (PKG) technology leverages reciprocal channel randomness to generate shared secret keys. However, multipath fading at the receiver may degrade the correlation between legitimate uplink and downlink channels, resulting in a low key generation rate (KGR). In this paper, we propose a PKG scheme based on the pattern-reconfigurable antenna (PRA) to boost the secret key capacity. First, we propose a reconfigurable intelligent surface (RIS) based PRA architecture with the capability of flexible and reconfigurable antenna patterns. Then, we present the PRA-based PKG protocol to improve the KGR via mitigation of the effects of multipath fading. Specifically, a novel algorithm for estimation of the multipath channel parameters is proposed based on atomic norm minimization. Thereafter, a novel optimization method for the matching reception of multipath signals is formulated based on the improved binary particle swarm optimization (BPSO) algorithm. Finally, simulation results show that the proposed scheme can resist multipath fading and achieve a high KGR compared to existing schemes. Moreover, our findings indicate that the increased degree of freedom of the antenna patterns can significantly increase the secret key capacity.

Abstract The propagation of electromagnetic waves will produce multi‐path fading of wireless channel, which degrades communication performance substantially. If multi‐path can be separated, better signal transmission and reception strategies can be designed to weaken or eliminate fading and improve signal transmission performance. However, it is challenging for communication nodes with limited number of antennas. A general multi‐path separation and measurement framework based on single dynamic metasurface antenna is established which rapidly changes patterns within a single pilot symbol period so that equivalent multi‐dimensional received signals can be obtained. Based on the framework, a multi‐path channel estimation scheme is proposed. Specifically, the parameter estimation problem is formulated and present the algorithm based on atomic norm minimisation to estimate parameters including angle of arrival and complex gain of each propagation path. Simulation results illustrate that single dynamic metasurface antenna can approach the capability of a conventional multi‐antenna array, and even using single dynamic metasurface antenna with 1‐bit coding can estimate angle of arrivals and complex gains of multi‐path components accurately.

Existing handover authentication schemes are implemented in the upper layer through cryptographic techniques with different protocols and parameters involved under different handover scenarios, introducing high latency and complexity especially in the next generation (5G) highly heterogeneous network (HetNet). The authors propose to introduce wireless link signatures decided by users' locations as handover authentication data to achieve unified and fast handover authentication at the physical layer in 5G software defined networking‐based HetNet. Specifically, the unique wireless channel characteristics between a user and the serving access point (AP) are extracted as the secure context information (SCI) and transferred to the target AP. The latter determines whether the user is the legitimate one who has already been authenticated according to the received SCI. They then analyse the authentication performance relating to multiple attributes and results demonstrate that the authentication strength can be adaptively adjusted. Furthermore, they find that optimum performance can be achieved by setting a proper decision threshold and derive the sub‐optimal performance by iterative search. Lastly, analysis and simulations on latency and overhead compared with existing ones are conducted and results prove the effectiveness of the proposed scheme.

Delay and security are both highly concerned in massive internet of things (IoT) which is a promising application scenario in 5G wireless communication system. In this study, the authors develop an integrated framework to study delay performance and secrecy performance in massive IoT. First, stochastic geometry and queuing theory are applied to model the spatially location of IoT devices and the temporal arrival of packets. To enhance the physical layer security of massive IoT with limited overhead increment at IoT devices, a low‐complexity noise injection scheme is applied. Then, the packet delay and packet secrecy outage probability are derived to characterise delay performance and secrecy performance. It is demonstrated that the IoT device intensity and power allocation coefficient arouse a tradeoff between the delay and security. Furthermore, optimal power allocation coefficient that maximises secrecy transmission rate can be derived, which can improve the delay‐security tradeoff. The analytical and simulation results show the effects of power allocation coefficient and IoT device intensity on the tradeoff between delay performance and secrecy performance.

In this paper, the physical layer security of uplink non-orthogonal multiple access transmission in cellular Internet of Things is analyzed. Using the stochastic geometry model where the location of users and eavesdroppers are respectively modeled by poisson cluster process and poisson point process, reliable performance and secrecy performance are analyzed in terms of coverage probability and secrecy outage probability, taking both intra-cell interference and inter-cell interference into consideration. Moreover, average effective secrecy throughput is analyzed which comprehensively characterize the network reliable performance and secrecy performance. The analytical and simulation results show that increasing intensity of base station bring an opposite effect to reliable performance and secrecy performance, thus there exist an optimal intensity of base station that maximizes the average effective secrecy throughput. In addition, our analysis allows an optimum selection of the system parameters like the intensity of base station and wyner's code rates.

Recent researches show that millimeter wave (mmWave) communication offers the promise of orders of magnitude increases in the cellular network capacity. Due to the severe path loss, relay aided transmission has been regarded as an effective way to extend mmWave communication range. In this paper, we apply an opportunistic relay selection (ORS) scheme for range extension to mmWave networks and develop a framework to analyze the connection outage probability (COP) and secrecy outage probability (SOP) using stochastic geometry. We first introduce the ORS scheme where each base station transmits its data in first time slot and the best relay is selected by competition to forward the infirmation in second time slot. Then the COP, SOP and secrecy throughput in direct transmission and ORS transmission are derived, respectively. By comparing the reliability and security performance of the two transmission schemes, it is demonstrated that ORS scheme enhances the reliability of the communication, but unfortunately increases the risk that confidential information be intercepted by an eavesdropper. We also find the secrecy throughput of ORS scheme is higher than that of direct conventional transmission.