Simultaneous wireless information and power transmission (SWIPT)-enabled vehicle-to-vehicle (V2V) systems use radio frequency (RF) signals for both information transmission and power. It reduces energy consumption, increases spectrum efficiency, and optimizes resource allocation to improve overall system performance. In this article, we investigate the physical-layer security (PLS) for a SWIPT enabled V2V cooperative communication system in which a source vehicle (S) transmits information to a destination vehicle (D) through an intermediate vehicle treated as relay node (R). During analysis, it is assumed that two independent vehicular nodes in the same road, i.e., eavesdroppers ($E_{1}$and$E_{2}$) are trying to intercept the information from different legitimate channels. The communication links are assumed to follow the double Nakagami-m (DNm) fading distribution. The study examines the security performance of the networks by calculating the secrecy outage probability (SOP), strictly positive secrecy capacity (SPSC), intercept probability (IP), and connection outage probability (COP). Next, we extend to the analysis of tradeoff between security and reliability as well as tradeoff between secrecy rate and secrecy outage which are termed as security and reliability tradeoff (SRT) and effective secrecy throughput (EST). For a comprehensive analysis, the results are produced for different values of the fading parameter$(m)$, power splitting factor$(\rho)$, and secrecy thresholds. The results clearly indicate that an increase in m leads to an enhancement in the secrecy performance. Additionally, the results show that secrecy performance improves as$\rho $decreases. Finally, the Monte-Carlo simulation results are presented to verify our proposed analytical models.

Abstract This study analyses the interference effect in a visible light‐non‐orthogonal multiple access (VL‐NOMA) network that considers the signal power parameters performance for near and far users. The light‐emitting diode (LED) as a carrier transmits signals, and we investigate the interference effect. The interference effect challenge is a result of unaligned signal power parameters, thereby producing noise or echo during the signal transmission. The signal power parameters are successfully aligned, and NOMA techniques are deployed, which improves the signal performance in terms of bit‐error rate (BER), achieved data rate, and signal‐to‐interference plus noise ratio (SINR). Furthermore, the deployed NOMA techniques, such as power allocations (PA) to assign the signals appropriately, then superposition coding (SC) encodes the entire signal, and successive interference cancellation (SIC) cancels the interference within the signals. The signal behavior of the aligned and the unaligned signal power parameters performance are used to investigate the interference effect. We observed that unaligned signal power parameters reduce the signal performance of achieved data rate, BER, and SINR. Further, the aligned signal power parameter with NOMA techniques improves the signal performance. Moreover, in the aligned signal power scenario of NOMA, the near user performed better than the far user.

Abstract A novel frequency regime of the spectrum from 0.1 to 10 THz enables an emerging paradigm of modern wireless communication referred as 6G communication networks. However, to assure the success of 6G communication networks, ever‐growing development and deployment of nano‐machines, leading to ultra‐dense nano‐network, is witnessed. Nevertheless, the potential feature analysis of such ultra‐dense nano‐network in the presence of interference limited scenarios, by virtue of ultra‐dense deployment of nano‐machines, under the performance improvement techniques is missing from the reported literatures. Therefore, in this article, several performance metrics for an ultra‐dense nano‐network under the selection combining (SC) diversity technique is presented. The analytical expressions for error rates of different modulation schemes such as BPSK/BFSK, DPSK/ NFSK, Q‐PSK and M‐QAM under SC diversity technique for the considered nano‐network in the presence of interference limited ecosystems are presented. In addition, analytical expressions of capacity under constant power with optimal rate adaptation (C ora ) and capacity under channel inversion with fixed rate (C cifr ) are explored. It is worthy to mention that the proposed analytical expressions are generic in nature for the considered scenarios, in which severity and shaping parameters in both the multipath fading and shadowing are included. Numerically simulated results support mathematical formulation.

Abstract Currently, cancer is a large contributing factor in the increased mortality rates and at present the predictions are estimating an increased trend. The conventional medical cancer imaging modalities, for example X-Ray and Computed Tomography use ionizing radiation which is not tissue friendly for repeated assessments. The Terahertz (THz) cancer imaging offers novel opportunities for non-ionizing, non-invasive and early cancer detection, or diagnosis as well as improved cancer patient treatment follow-ups. In this review, a broad overview is given on the potential of THz radiation-based imaging and sensing as a technique for detection of various cancers cells. The THz radiation dynamics and interaction mechanisms with biological systems as well as parameter extraction and modelling for the observed THz image contrast are studied. The experimental studies on THz imaging and sensing are investigated with the goal approach to investigate the ex vivo, in vitro, and in vivo observations. The use of advanced analytic algorithms, specifically deep learning, is proposed for improved detection, discrimination of complex tissue with overlapping dielectric properties and development of clinical decision support systems. Research gaps in the THz imaging studies are identified based on recent trends, latest strategies suggested and the roadmap for future research direction provided.

Abstract Cooperative Non‐orthogonal Multiple Access (C‐NOMA) is projected as the dominant technology for 5G and beyond. Also, physical layer security, due to the presence of eaves‐dropper, is a bottleneck security concern for any open link wireless system. This manuscript presents a novel Decode & Forward (DF)‐based C‐NOMA system in the presence of two eavesdroppers. Moreover, both half duplex and full duplex schemes are included in the analysis. Thereby, separate expressions for Secrecy Outage Probability (SOP), being among the most crucial performance measures in physical layer security, are produced and examined for the system under consideration. Specifically, first of all, novel expression of SOP for C‐NOMA systems under both Half Duplex (HD) and Full Duplex (FD) schemes is derived for the case when only eavesdropper one (E1) attacks on link source to device one (S‐D1). Thereafter, expressions of SOP for the C‐NOMA system under both HD and FD schemes are derived, considering presence of E1 and E2 on the links, source to device one (S‐D1) and source to device two (S‐D2), respectively. Further, for both the duplexes, the effect of eavesdropper one (E1) and eavesdropper two (E2) on the links, S‐D1 and S‐D2, respectively, is analyzed. The presented analysis is useful in the technological development level of C‐NOMA in the presence of multiple eavesdroppers. The simulated results show perfect agreement with the theory.

In this article, we have employed an energy detector (ED)‐based cooperative spectrum sensing (CSS) with multi‐antenna for cognitive radio network (CRN). The spectrum sensing error and energy efficiency (EE) are the key performance parameters in CRN which are affected by the threshold selection method, number of antennas employed at each cognitive user (CU), reporting error probability and cooperative fusion‐rule applied at fusion center (FC). Therefore, we have derived the expression for sensing error by considering the effect of all these parameters and have optimized the cooperative fusion‐rule at FC by formulating mathematical expression for optimal K in k‐out‐of‐M rule to minimize the sensing error. Since CSS improves the sensing performance of CRN at the cost of increased overhead bits due to more CUs reporting to FC, results reduced EE. We have employed censoring approach to reduce the energy consumption and hence increase the EE of CSS technique. Further, we have illustrated the sensing error and EE improvement achieved under the censoring approach when different threshold selection approaches are employed at each CU. The percentage EE enhancement in censoring approach are 19.53% and 19.9% with constant false‐alarm rate (CFAR) and minimized‐error probability (MEP) approaches, respectively in comparison to that of the non‐censoring approach.

This paper has collectively exploited cognitive radio (CR), non‐orthogonal multiple access (NOMA) and multiple‐input‐multiple‐output (MIMO) communication systems in order to propose a spectral‐and interference‐efficient framework which is named as MIMO‐based CR–NOMA communication system. The proposed framework is analysed for the uplink and downlink scenarios. Further, the closed‐form expressions for throughput at each user due to the number of transmitting‐and receiving‐antennas are derived numerically for the downlink‐and uplink‐scenarios. In addition to this, the total/sum throughput for different frameworks such as CR–NOMA, CR–MIMO and MIMO‐based CR–NOMA systems is derived for both the downlink and uplink scenarios. Moreover, in order to satisfy the interference constraints at the primary user due to cell‐edge/far‐user [cognitive user (CU)‐4] transmission in the uplink scenario, a new metric known as interference efficiency is derived. Furthermore, the proposed frameworks are simulated for downlink and uplink scenarios and the relationship between throughput of cell‐centred/near‐user (CU‐1) and CU‐4 are presented. Moreover, the total throughput for different frameworks and interference efficiency is also illustrated with the simulation results. The simulation results reveal that the proposed MIMO‐based CR–NOMA system outperforms the existing MIMO–NOMA, CR–NOMA and CR–OMA systems in terms of the CUs' individual throughput, total throughput and interference efficiency of the system.

Communication industry demands the frameworks, which allow significant improvement in energy efficiency with spectral efficiency, however, these two do not always coincide and may even conflict sometimes in cognitive radio networks. In addition to this, the distributed network structures are preferred over centralised structures due to ease of deployment as well as less information exchange between the cognitive users which reduce the network‐overhead. Therefore, in this study, the authors have proposed a framework to enhance the spectral as well as energy efficiency by exploiting the novel frame structure in the distributed cognitive radio networks. A self‐scheduled multichannel‐medium access control (SMC‐MAC) protocol has been proposed in which the contention and sharing intervals are exploited for the efficient spectrum and energy utilisation. Moreover, the closed‐form expressions of the spectral efficiency, power consumption and energy efficiency for the proposed SMC‐MAC protocols are derived. Furthermore, the relation between energy and spectral efficiency for the proposed framework is also derived. The numerically simulated results are presented to validate the proposed work and Monte‐Carlo simulations are performed for the random events in order to support the numerically simulated results.

The spectrum‐monitoring is a prominent technique to detect the reappearance of the primary user (PU) during the cognitive users’ (CUs) data transmission. However, the imperfect spectrum monitoring (SM) causes a delay in the identification of PU that introduces interference at PU as well as data‐loss. The cooperation among CUs for SM is a proficient solution to diminish these impairments of imperfection. Thus, in this study, a scenario of the heterogeneous cognitive radio network (CRN) is presented in which the CUs perform cooperation among them for SM and have analysed the impact of cooperation on several performance metrics such as the data‐loss, interference efficiency and energy efficiency. An algorithm is presented for the evaluation of data‐loss for different circumstances of the traffic intensity of PU and probability of SM error in the proposed heterogeneous CRN. In addition to this, the closed‐form expressions for the cooperative and non‐cooperative SM of these metrics are derived. Furthermore, the simulation results are illustrated for different state‐of‐affairs of the probability of SM error and traffic intensity.

In this study, a repeated correlative coding scheme is proposed to combat the inter-carrier interference (ICI) caused by the frequency offset in orthogonal frequency division multiplexing (OFDM) communication systems. This proposed scheme combine two ideas of the well-known methods, which are the coding of adjacent subcarriers with antipodal of the same data symbol (ICI self-cancellation) and correlative coding. A mathematical expression for the carrier-to-interference ratio (CIR) by using this proposed repeated correlative coding scheme is derived. The simulated result of CIR for the proposed scheme is significantly improved compared to the correlative coding as well as a self-cancellation scheme. The bit-error-rate (BER) of the proposed scheme is also compared with the ICI self-cancellation scheme and correlative coding scheme, which is comparable to that of the ICI self-cancellation scheme and better than the correlative coding scheme.