This work introduces a novel blind channel estimation (CE) scheme for intelligent reflecting surface (IRS)-assisted networks with heterogeneous communications and sensing devices. The proposed approach operates in two stages: the first stage is dedicated to transmitting the sensing data, and the second to transmitting communications data. By leveraging the fact that sensing information typically has less stringent quality of service (QoS) requirements compared to communication data, the sensing data transmission stage is leveraged for blind CE. The CE is performed using a specific frame structure, where the modulated sensing symbols collaborate to estimate the channel coefficients for all IRS elements blindly and jointly. The performance of sensing data transmission is evaluated in terms of average bit error rate (BER), with exact closed-form expressions derived for the considered modulation schemes. For the communications data, the BER is analyzed, and a tight lower bound is derived. Additionally, an accurate closed-form expression is derived for the mean-squared-error (MSE) of the proposed CE. The MSE results demonstrate that the proposed blind CE outperforms state-of-the-art schemes.

This article presents a physical layer security (PLS) technique for non-orthogonal multiple access (NOMA), which can provide joint secrecy, fairness, and bit error rate (BER) improvement. The approach employs power hopping (PH), where users’ power coefficients are dynamically varied according to the instantaneous channel conditions. By randomizing both the detection order and the effective power allocation, PH obscures the underlying NOMA structure from a passive eavesdropper (Eve), thereby severely degrading the data detection capability. To enable secure coordination, a precoding-based mechanism is developed for sharing the PH patterns among legitimate users, leveraging the random and independent nature of wireless channels. The BER and secrecy outage probability (SOP) of the proposed framework are analytically characterized and compared to conventional NOMA under various channel and eavesdropping configurations. The obtained analytical results, corroborated by Monte Carlo simulations, confirm the effectiveness of the proposed scheme, where the SOP of legitimate users is never compromised regardless of Eve’s channel conditions, while incurring only negligible additional complexity compared to conventional NOMA. Furthermore, the fairness and BER performance of stronger users are significantly improved through the combined use of PH and optimal power allocation.

Reliable, long-range mesh networks are critical for emerging Air-to-Ground (A2G) applications that require high-throughput, infrastructure-free communication. We present WiLong-Air, a long-range aerial mesh platform built using commercial off-the-shelf hardware and open-source software, which integrates 5 GHz IEEE 802.11 radios with high-gain omnidirectional antennas. Using 802.11s mesh mode with B.A.T.M.A.N. Advanced routing, WiLong-Air enables scalable aerial connectivity. Field evaluations across outdoor aerial experiments validate its effectiveness: sustained throughputs above 20 Mbps at 700 m in partial NLoS, and reliable video and data transmission from multiple aerial nodes. Furthermore, with six concurrent transmitters, increased jitter, contention, and loss were observed, motivating architectural innovations. Moreover, apart from communications- related hardware and software improvements, the video streaming parameters were also optimised. For instance, it was seen that while variable bitrate mode of video transport improves perceptual quality, constant bitrate modes support steadier link behaviour. These results position WiLong-Air as a robust platform for A2G mesh research.

This work proposes an efficient two-stage jamming detection and channel estimation algorithm for orthogonal frequency division multiplexing (OFDM)-based unmanned aerial vehicles (UAVs) communications. The proposed scheme is designed based on the unique time and frequency domain statistical characteristics of OFDM signals. In the time domain (TD), a likelihood ratio test (LRT)-based decision rule is derived as a function of the inherent correlation between the cyclic prefix (CP) samples and their counterparts in the OFDM symbol. In addition, in the frequency domain (FD), a closed-form joint jamming detection and channel estimation scheme is derived using the maximum a posteriori probability (MAP) principle as a function of the statistics of the received pilots and virtual subcarriers (VSCs) signals, which is then re-expressed using the generalized MAP ratio test (GMAPRT). The system’s complexity is reduced by applying the two stages sequentially, where the possible implementation of the second stage is conditioned on the outcome of the first stage. The performance of the proposed algorithm is evaluated using Monte Carlo simulations, where the results demonstrate its effectiveness compared to the TD-only and FD-only approaches. The results confirm the superior performance of the proposed scheme compared to the cyclostationary feature (CF)-based technique under various operating scenarios.

Mesh networks enables quick on-demand infrastructure creation and help achieve vital last-mile connectivity. Wi-Fi integration can further enhance the potential and compatibility for the pervasive connectivity requirements in next-generation applications. Despite advancements, Wi-Fi standards still need efforts to meet long-range requirements. Accordingly, this paper proposes a customized handheld platform named WiLong for constructing long-range Wi-Fi Mesh networks in the unlicensed higher bands, 2.4 and 5 GHz. The proposed platform can offer versatile radio profiles by leveraging commercially available hardware and open-source software components, augmented with the addition of IEEE 802.11s mesh link and the B.A.T.M.A.N. advanced routing protocol. Experimental evaluations of the said platform have been conducted across various practical environments, including indoor/outdoor spaces, urban & open bay areas, multi-floor basement car parking, and dense mesh deployments. The experimental results underscore the effectiveness of the WiLong platform in improving long-range Wi-Fi performance while emphasizing the significance of multi-hop networking in demanding ground-to-ground scenarios. These findings highlight the platform’s robustness and versatility. In a selected urban route scenario, the WiLong platform achieved 80% voice and 63% video call bandwidth. Additionally, when configured with 2.4 GHz, the platform reached two floors below in a multi-floor basement car parking.

This paper proposes a physical layer-based authentication scheme that exploits multiple features from the RF-front-end for wireless mesh networks. Specifically, we engineer the in-phase and quadrature-phase (IQ) samples of the legitimate nodes by generating specific ranges of carrier frequency offset (CFO), phase offset (PO), and DC offset (DCO). This engineered IQ governs all multiple legitimate node transmissions (to cover the entire ranges of CFO, PO, and DCO) and follows a specific probability mass function (PMF). We then obtain an optimal function based on the MSE criterion that closely fits the engineered IQ data, which serves as a reference for authenticating network nodes. In the authentication phase, the optimal function obtained from the IQ data transmissions of the respective node requesting authentication is compared with the optimal reference function. Successful authentication occurs when the difference between the optimal function and reference optimal function falls within predefined thresholds of absolute difference, MSE, and correlation coefficient parameters. Specifically, a node is deemed legitimate only when all three criteria meet the threshold requirements. The node undergoes a second authentication check if only one or two criteria are met. Otherwise, it is marked as a possible intruder. We generated extensive I and Q datasets following the IEEE 802.11 standard waveform to validate the proposed scheme, and the necessary metrics were evaluated. The results showed that instead of being used individually when the underlying criteria of MSE, correlation coefficient, and absolute difference are used together can guarantee better authentication, detection, and false detection rates. The findings indicate that the proposed approach attains a 100% authentication rate at a 5 × 10–2threshold MSE, which represents a 20% improvement over the individual use of MSE.

This paper examines physical layer security of a secure reconfigurable intelligent surfaces (RIS) enabled wireless communication system. Particularly, we explore a wiretap communication system wherein a source node transmits its confidential information to the legitimate destination node using an RIS-based relay terminal, and at the same time, a passive eavesdropper overhears this information from both source and RIS. Under this system setup, we first derive the closed-form expressions of the cumulative distribution function and probability density function of the end-to-end signal-to-noise ratios (SNRs) at the destination and eavesdropper by adopting the method of moments. Utilizing these distributions, we further deduce the exact expression of the secrecy outage probability (SOP) under Rayleigh fading channels. Moreover, to obtain the system’s secrecy diversity order, we present the asymptotic SOP analysis under two scenarios, viz., 1) high SNR regime, and 2) when average channel gains of main link go to infinity and average channel gains pertaining to wiretap links are fixed. It is revealed that the secrecy diversity order reduces to zero under high SNR regime, whereas a secrecy diversity order of 0. 805N can be achievable for large values of average channel gains of main link, where N is the number of RIS elements. Finally, the theoretical findings are validated via numerical and simulation studies. Our results show the impact of various involved parameters on the system’s SOP performance.

UAVs are increasingly appearing in swarms or formations to leverage cooperative behavior, forming flying ad hoc networks. These UAV-enabled networks can meet several complex mission requirements and are seen as a potential enabler for many of the emerging use-cases in future communication networks. Such networks, however, are characterized by a highly dynamic and mobile environment with no guarantee of a central network infrastructure which can cause both connectivity and security issues. While wireless mesh networks are envisioned as a solution for such scenarios, these networks come with their own challenges and security vulnerabilities. In this paper, we analyze the key security and resilience issues resulting from the application of wireless mesh networks within UAV swarms. Specifically, we highlight the main challenges of applying current mesh technologies within the domain of UAV swarms and expose existing vulnerabilities across the communication stack. Based on this analysis, we present a security-focused architecture for UAV mesh communications. Finally, from the identification of these vulnerabilities, we discuss research opportunities posed by the unique challenges of UAV swarm connectivity.

The authors investigate the secrecy performance of a cooperative relaying network, wherein a fixed source communicates with a fixed destination via an amplify‐and‐forward mobile relay in the presence of a passive mobile eavesdropper. They assume that the source‐to‐relay channel and relay‐to‐destination channel experience Nakagami‐ m fading, whereas relay‐to‐eavesdropper link follows double Nakagami‐ m fading. Under such a mixed fading environment, they derive the novel tight closed‐form expressions for the secrecy outage probability (SOP), probability of non‐zero secrecy capacity, and intercept probability of the considered system. They also deduce the asymptotic secrecy outage and intercept probability expressions in the high signal‐to‐noise ratio regime to highlight the impact of fading parameters and channel conditions on the secrecy diversity order. It is shown that the system can achieve secrecy diversity order of min( ) in terms of SOP, and in terms of intercept probability, where and represent the fading severity parameters between source and relay and between relay and destination, respectively. They also formulate and investigate analytically two optimisation problems, namely, optimal relay location with fixed power allocation and optimal power allocation with fixed relay location, to minimise the system SOP. They verify analytical findings via numerical and simulation results.