Wireless power transfer (WPT) has emerged as a solution for sustainable IoT deployments by harvesting energy from controllable RF signals, unlike unpredictable renewable sources. However, EH circuits exhibit sensitivity and saturation limitations, making non-linear EH models more realistic than conventional linear models. Motivated by this, this work investigates physical layer security in a dual-hop mixed FSO-RF system with simultaneous eavesdropping on both FSO and RF links. The considered system consists of a source communicating with a destination through a PB-powered relay, where the RF and FSO channels are modeled using Nakagami-mand Gamma-Gamma fading distributions, respectively, while incorporating atmospheric turbulence and pointing errors. Closed-form and asymptotic expressions for secrecy outage probability (SOP) are derived to characterize secrecy performance. Furthermore, the impacts of EH saturation, fading severity, turbulence, pointing errors, detection techniques, and eavesdropper SNR on SOP and secrecy throughput (ST) are analyzed, along with a comparison between linear and non-linear EH models. Monte Carlo simulations validate the analytical results. In addition, a DNN-based framework is developed for real-time SOP prediction, offering a low-complexity alternative to conventional analytical methods for secure IoT-enabled wireless networks.

Error performance of hybrid subcarrier intensity modulation (hybrid‐SIM) in optical free‐space satellite downlink has been studied in this work. Bit error rate (BER) is improved by aperture averaging and spatial receiver diversity and it is found out be effective in strong turbulence regime. Subsequently, the reduction in scintillation index has been investigated by implementing a single large receiver and an array of point receivers of length with the same effective aperture area. Moreover, the BER at different turbulence conditions is compared with minimum shift keying and multiple levels of pulse position modulation pertaining to aperture averaging. Upon analysing the single input multiple outputs (SIMO) system, the desired response is obtained above a certain threshold in average received irradiance. At different zenith angles and turbulence strengths for , the threshold is 4.59 and 3.35 dB, respectively, and it rises by 13.6 and 26.43 dB when is increased to 9. This constraint can be exploited to optimise the number of receivers concerning system requirement and availability. Further, the pointing error effects are also investigated for SISO and SIMO systems, which takes into account both atmospheric turbulence and misalignment induced fading.

Channel selection is a challenging task in cognitive radio vehicular networks. Vehicles have to sense the channels periodically. Due to this, a lot of time is wasted which could have been utilised for transmission of data. Employing road side units (RSUs) in sensing can prove to be useful for this purpose. The RSUs may select the channel and allocate it to the vehicles on demand. However, this sensing should be proactive. RSUs should know in advance the channel to be allocated when requested. For this purpose, a deep reinforcement learning algorithm namely deep reinforcement learning based optimal channel selection is proposed in this study for training the network according to the previously sensed data. Proposed protocol is simulated and results are compared with the existing methods. The packet delivery ratio is increased by 2%, throughput is increased by 1.8%, average delay is decreased by 2% and primary user collision ratio is reduced by 3.2% when compared with similar recent work by varying number of vehicles. On the other hand, when compared with similar recent work by varying channel availability, the packet delivery ratio is increased by 4.5 %, throughput by 4.3%, average delay is decreased by 3% and PU collision ratio by 5.5%.

In this study, the authors have developed an analytical model for reducing the peak‐to‐average‐power ratio (PAPR) using non‐linear companding transform (NCT) based on inverse hyperbolic sine function. As a consequence of non‐linear transform, this study compensates the system bit error rate (BER) degradation with the help of an error efficient hybrid modulation. By means of an inflexion point and companding parameter, more design flexibility is achieved; as a result, a trade‐off between PAPR and BER has reasonably been more precise. To the best of the authors’ awareness, no findings have yet been reported on the performance evaluation of the optical orthogonal frequency division multiplexing (OOFDM) system using a hybrid modulation technique. To find out the advantages of hybrid modulation with NCT, the authors inspect the nature of PAPR reduction, and BER improvement through numerical simulations. The numerical BER results exhibit roughly 3 dBm decay in the power efficiency of hybrid modulation with NCT over discrete Fourier transform (DFT) precoding technique. On the other hand, the NCT technique with hybrid modulation has 6 dB less PAPR than the DFT precoding technique.

There are different types of messages containing different priorities in vehicular ad hoc networks. Hence, queue rescheduling is required according to priorities of arrived messages. In this study, a data structure with less computational complexity is proposed to minimise queuing delay. Further, to maintain quality of service, preemptive priority is applied to time‐bound safety messages by transferring non‐safety messages to other bands using the concept of cognitive radio technology. The time‐bound messages are transmitted using the dedicated short‐range communication spectrum without the need for spectrum sensing by vehicles. The other messages with no deadline constraint are switched to other bands near‐dedicated short‐range communication spectrum. The results show that 6.25% improvement in packet delivery ratio of cognitive radio‐enabled preemptive priority is achieved in comparison to existing cognitive radio protocol. The delay shows a slight increment of 1.1%. The packet delivery ratio of cognitive radio‐enabled non‐preemptive priority is improved by 3.24% while the delay is improved by 3.17%. The data storage required for storing sensing data of 50 channels for 10 days is only 45 Mb.

In this study, a hybrid modulation technique called PPM–GMSK, based on the pulse position modulation (PPM) and phase‐sampled Gaussian minimum shift keying (GMSK) technique, is investigated by considering log‐normal and gamma–gamma turbulence as the channel‐fading statistics. The analytical bit error rate (BER) and outage probability of the proposed hybrid modulation are derived. The results show that the hybrid modulation technique is an efficient technique to improve the performance of optical wireless communication for a cellular backhaul channel. Compared to 2‐PPM and minimum shift keying (MSK), the proposed hybrid scheme has a less BER and a reduced amount of outage probability. Moreover, to achieve a reliable voice communication at 2 Gbps bit rate and BER of under a weak turbulence effect, the PPM–GMSK has a coverage distance of about 3 km, whereas for PPM and MSK it is 2.6 and 2.4 km, respectively.

This paper presents multiple beacon vectors based robust detection schemes for cooperative spectrum sensing (CSS) in multiple-input multiple-output (MIMO) cognitive radio (CR) networks under channel state information (CSI) uncertainty. The inaccuracies in the estimate of the CSI are modeled as the standard ellipsoidal uncertainty set. We develop a multiple beacon vector based linear discriminant framework to obtain robust detectors for the problem of primary user detection in MIMO cognitive radio networks under ellipsoidal CSI uncertainty. Next, we employ this framework to develop signaling scheme based application specific detectors, namely the antipodal signaling based robust detector and on-off signaling based robust detector, along with their closed form expressions. Further, for the two signalling schemes, we even present allied detectors that are advantageous under low signal-to-noise ratio (SNR) conditions. Simulation results demonstrate a superior detection performance of the proposed robust detection schemes in comparison to the uncertainty agnostic matched filter detector for CSS in MIMO cognitive radio networks.

When a mobile network changes its point of attachments in Cognitive Radio (CR) vehicular networks, the Mobile Router (MR) requires spectrum handoff. Network Mobility (NEMO) in CR vehicular networks is concerned with the management of this movement. In future NEMO based CR vehicular networks deployment, multiple radio access networks may coexist in the overlapping areas having different characteristics in terms of multiple attributes. The CR vehicular node may have the capability to make call for two or more types of nonsafety services such as voice, video, and best effort simultaneously. Hence, it becomes difficult for MR to select optimal network for the spectrum handoff. This can be done by performing spectrum handoff using Multiple Attributes Decision Making (MADM) methods which is the objective of the paper. The MADM methods such as grey relational analysis and cost based methods are used. The application of MADM methods provides wider and optimum choice among the available networks with quality of service. Numerical results reveal that the proposed scheme is effective for spectrum handoff decision for optimal network selection with reduced complexity in NEMO based CR vehicular networks.

Majority of research contributions in wireless access in vehicular environment (WAVE)/IEEE 802.11p standard focus on life critical safety-related applications. These applications require regular status update of vehicle’s position referred to as beaconing. Periodic beaconing in vehicle to vehicle communication leads to severe network congestion in the communication channel. The condition worsens under high vehicular density where it impacts reliability and upper bound latency of safety messages. In this paper, WAVE compliant enhancement to the existing IEEE 802.11p protocol is presented which targets prioritized delivery of safety messages while simultaneously provisioning the dissemination of nonsafety messages. Proposed scheme relies on dynamic generation of beacons to mitigate channel congestion and inefficient bandwidth utilization by reducing transmission frequency of beacons. Through the use of clustering mechanism, different beaconing frequencies and different data transmission rates are assigned to prioritize vehicular mobility. Through extensive simulation results, the performance of the proposed approach is evaluated in terms of a wide range of quality of service (QoS) parameters for two different transmission ranges. Results show that the proposed protocol provides significant enhancement and stability of the clustered topology in vehicular ad hoc network over existing standard and other protocols with similar applications.

In mobile networks, when the mobile terminal (MT) has an active call while crossing the boundary of two systems, it is required that the existing connection should not be lost. To meet this demand, the signalling protocol of mobility management must be designed for supporting location registration and call delivery for roaming users who move beyond their home network. The objective of this study is to provide a modified boundary location register (MBLR) signalling protocol for inter-system roaming. The idea of generating routing number in advance plays a key role for the proposal. The location registration and call delivery process of the new protocol are proposed which tries to reduce the signalling cost and latency. An analytical model is developed for comparative performance analysis of the boundary location register and MBLR protocol. However, this will result in increased processing requirements at the database server. Thus, trade-off between signalling, database access costs and processing overheads must be recognised.

A partially overlapping super location area (POSLA) Scheme is suggested to overcome the varying updation problem of Overlapping Super Location Area (OSLA) Scheme. In this scheme, the LA is partially overlapped by its surrounding LAs and the location updates will be done based on the minimum distance from the center cell. The suggested scheme, POSLA, shows the reduction in the location update cost as compared to OSLA scheme.

In this paper a new channel allocation scheme is proposed and analyzed for real time traffic. There is no division of channels into groups. Two thresholds (lower and higher) are taken depending on the signal strength of the mobile host in the cell. The handoff calls have the right of preemption over the originating calls with signal strength less than the lower threshold value. The performance of the system is evaluated in terms of handoff dropping probability, originating call blocking probability and the channel utilization.