Recently, the noise modulation scheme and active anti-jamming (AAJ) scheme have shown the potential advantages, such as high anti-jamming performance, low transmitter complexity and low power consumption. Inspired by the prior schemes, this paper proposes a novel hybrid noise and jamming modulation (NJM) scheme that enables reliable communication under diverse jamming scenarios. Specifically, this scheme encodes information bits through a noise modulated transmitter and the amplification factor of a programmable gain amplifier (PGA), achieving robust anti-jamming performance. Theoretical bit error rate (BER) is conducted to derive the optimal decoding thresholds for different jamming strategies, and the approximate optimal threshold proposed for practical implementation using training symbols. Furthermore, we formulate and solve the power allocation optimization problem to enhance BER performance by properly splitting power between the two modulation components. To comprehensively evaluate the scheme, we provide the capacity analysis for the hybrid NJM scheme under three jamming strategies. Simulation results show that the theoretical results match well with the simulated ones, which demonstrates the correctness of our BER performance analysis. Moreover, the hybrid NJM scheme can achieve the superior BER performance and the channel capacity under the jamming attacks compared with the benchmark schemes.

Unmanned Aerial Vehicles (UAVs) have achieved considerable popularity due to their maneuverability and versatility. However, UAV swarms often face challenges from external malicious jamming and internal co-channel interference when performing reconnaissance missions. Aiming to counteract malicious jamming and co-channel interference, effectively enhancing the anti-jamming transmission capability of UAV networks, this paper proposes UAV deployment schemes based on congestion game model, which adjust the transmitting power of UAV while optimizing the deployment position. By defining the utility function of the UAVs and analyzing the conditions for achieving Nash equilibrium, the optimal deployment strategy and power strategy are realized. Experimental results show that this method effectively improves the data collection efficiency and power efficiency of UAV swarms.

Recently, the noise modulation scheme and active anti-jamming (AAJ) scheme have shown the potential advantages, such as high anti-jamming performance, low transmitter complexity and low power consumption. This paper proposes a novel hybrid noise and jamming modulation (NJM) scheme, which aims to effectively resist the jamming attack in wireless communications. Specifically, the information bits are conveyed by the noise modulated transmitter and the amplification factor of the programmable-gain amplifier (PGA). Then, the optimal threshold is derived for decoding the messages in the receiver node. We formulate the power allocation problem of the hybrid NJM scheme as an optimization problem, which aims to obtain the optimal bit error rate (BER) performance by accurate transmit power splitting for two modulation components. Simulation results show that the theoretical results of BER fit well with the simulated ones, which verifies the effectiveness of the derivation. Moreover, the hybrid NJM scheme outperforms in BER performance against the jamming attack compared with other anti-jamming schemes.

High mobility feature in communication scenario encourages the emergence of the orthogonal time frequency space (OTFS) modulation. The Cyclic prefix (CP) in OTFS systems is used to combat Inter-Symbol Interference (ISI) and Intercarrier Interference (ICI), which simplifies the design of the equalizer by restoring circulant convolution relationship between symbols and the channel. However, the overhead of CP weighs the burden of spectral efficiency and latency. In this paper, an improved CP-free OTFS framework is designed combined with a dual-component Weighted Fractional Fourier transform (DCWFRFT) precoder and an enhanced detector. DCWFRFT precoder enables more evenly distributed signal energy to achieve better performance. To ensure the reliability of CP-free OTFS, the enhanced detector firstly truncates the ISI contaminated portion and then reconstructs these symbols from the reliable one. Finally, the reliable portion and reconstructed portion are combined to be detected and decoded. Furthermore, the normalized mean square error (NMSE) and bit error rate (BER) performance of the proposed detector and CP-free OTFS system are simulated. Results show that the proposed OTFS framework improves spectral efficiency by discarding CP while maintaining satisfactory BER performance compared with CP-OTFS.

Index modulation based frequency hopping spread spectrum (IM-FHSS) has shown the attractive anti-jamming capability. With the aid of jamming detection, IM-FHSS becomes efficient to defend various malicious jamming attacks, especially the reactive jamming. In this paper, we propose two jamming detection approaches for IM-FHSS to efficiently detect reactive jamming. Specifically, the pilot symbols for channel estimation are used in the first detection approach, where a single frame to calculate the optimal test statistic and make the decision. Second, the proposed approach II collects the pilot symbols from many data frames to detect the reactive jamming. Moreover, we theoretically derive the closed-form expressions of the optimal thresholds and the probabilities of detection, and provide the complexity comparison. Simulation results validate the correctness of our performance analysis and show that the proposed approaches outperform the prior detection schemes.

This article focuses on the serious threat to security of key-based physical-layer authentication (PLA) by an eavesdropper using an elaborate impersonation attack, which aims to pass the authentication process illegally. To prevent the eavesdropper from decreasing the authentication performance, we propose a robust channel-phase-based PLA scheme for multicarriers transmission, which contains a novel two-level decision. Specifically, the first level decision is used to protect legitimate users from high-receiver power caused by the elaborate attack of the eavesdropper, and the second one is used to further authenticate the user. The optimal threshold for accurately detecting the response signal with high-receiver power is derived. Moreover, we provide the theoretical performance analysis for the proposed scheme, and derive the closed-form expressions of the probability of detection and false alarm via the numerical statistic and the proper approximation. Simulation results show the robustness of our proposed scheme and verify the effectiveness of the theoretical analysis.

Due to the threat of various jamming attacks in wireless communications, the efficient and general anti-jamming schemes are required to guarantee communication the quality of wireless networks. To this end, this paper proposes the efficient index modulation based frequency hopping spread spectrum (IM-FHSS) scheme. Unlike the classical IM-FHSS which only considered the reactive jamming, the efficient IM-FHSS scheme extends the anti-jamming capacity to various jamming models. Specifically, we firstly derive the closed-form expressions of bit error rate (BER) performance of the IM-FHSS under three jamming models in an additional white gaussian noise (AWGN) channel and a Rayleigh fading channel, which enables the design of anti-jamming strategies. Then, the unified anti-jamming framework is provided for designing the efficient anti-jamming system. Based on the framework, we further provide the strategies of the efficient IM-FHSS for reactive jamming, constant and random jamming. Simulations show that the theoretical derivations match well with the simulated results, which validates the performance analysis. Moreover, the efficient IM-FHSS has demonstrated the superior anti-jamming performance for three typical jamming models, which is also energy-efficient and reliable for achieving targeted bit error rate (BER) performance.

Recently, symbol level jamming (SLJ) has been proposed and studied as an effective jamming technique. However, the detection performance estimation and efficient detection schemes for SLJ have not been investigated in the literature. This paper proposes a novel active detection scheme for SLJ to enhance the detection capability of the legitimate user, where the detection performance estimation and target detection performance can be actively obtained. Specifically, based on a preset tolerant threshold of the bit error rate (BER) and necessary inputs, the threatening jamming power level (TJPL) for SLJ is obtained for the legitimate user, and then the TJPL is used for active performance estimation and adaption. We first derive the theoretical detection performance for QPSK modulated SLJ and noise modulated SLJ. Moreover, the TJPL required for detection is derived based on BER expressions and analytical results. Thereafter, two modes of active detection scheme are discussed, aiming to actively estimate the detection performance and obtain expected detection performance, respectively. Simulation results show that the active detection scheme can accurately estimate the jamming detection performance. Additionally, it can achieve expected detection performance, which adapts well to different preset thresholds, SNR regions and the modulation types.

To defend against eavesdropping and spoofing attacks, the physical layer authentication (PLA) techniques utilize the unique attributes of channel or device for identifying attackers. Among these techniques, the PLA schemes based on channel phase responses use the secret key driven channel phase to authenticate the legitimate user, which have a better performance than the channel amplitude based schemes. However, the prior phase-based schemes only consider the perfect channel correlation coefficient between the two successive timeslots, which differs from the real scenarios. Meanwhile, the closed-form expressions of the theoretical analysis results are not comprehensive in the prior schemes, which are also not tight especially at low signal-to-noise ratio (SNR) regions. In this paper, we propose a PLA scheme based on the channel phase response, aiming to offset the performance loss introduced by the channel correlation coefficient. Moreover, we derive the closed-form expressions of the theoretical analysis results, such as the mean value, the variance and the probability density functions (PDFs), which can be utilized to provide the closed-form threshold for making decision instead of a great ideal of testing. Then, the security analysis is provided to verify the resistance of the proposed scheme under the attacks. Simulation results show that the proposed scheme outperforms the benchmarks and the proposed theoretical results match well with the simulated results even under low SNR regions.

In secret key generation of physical layer security technology, it is challenging to achieve high key capacity and low bit inconsistency rate. This paper investigates intelligent reflecting surface (IRS)-assisted secret key generation, which aims to maximize the secret key capacity by adjusting the placement of the IRS units. Specifically, we first analyze and deduce the key capacity expression of the IRS-assisted system from the perspective of information theory. Then we investigate how to use the channel state information (CSI) to place the IRS units effectively so as to maximize the secret key capacity. Simulation results show that our scheme could improve the quality of secret key generation significantly.

In recent years, orthogonal frequency division multiplexing with index modulation (OFDM‐IM) has been proposed due to its extra diversity gain. Specially, OFDM with all index modulation (OFDM‐AIM) was proposed, which removed symbol bits and enhanced the diversity order compared to typical OFDM. However, the security issue of OFDM‐AIM has not been given full attention. This paper proposes an encrypted subblock design aided OFDM with all index modulation (ESD‐OFDMAIM) scheme to enhance physical layer security. Firstly, an encryption process of subblock design was put forward, which creates a random look‐up table and thus the mapping rule of ESD‐OFDM‐AIM between information bits and subblock realisations becomes random and time varying. Moreover, the scrambling and rotation encryption based on chaotic sequences from channel state information is utilised to prevent the eavesdropper from stealing the information via wireless channel. For eavesdroppers, parameters of ESD‐OFDM‐AIM such as spectral efficiency (SE), constellation points and the length of look‐up table are concealed by the encryption. Finally, analyses of attack models and the information entropy of constellations are also provided to measure the security of ESD‐OFDM‐AIM. Simulation results show that ESD‐OFDM‐AIM can effectively improve the system security without the affecting bit error rate performance.