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Passively harmonic mode-locking has been experimentally demonstrated in an erbium-doped fiber laser with large normal dispersion using single-multi-single mode structure as artificial saturable absorber. By increasing the pump power under the same polarization setting, the mode-locking operation can switch from fundamental mode-locked to 5th order harmonic mode-locked. Highest repetition rate of 4.26 MHz (5th order harmonic) is observed, with pulse width and pulse energy ascertained at 290 fs and 3.0 nJ, respectively. Excellent signal-to-noise ratio (SNR) of above 50 dB is observed for all harmonic orders. The findings validated that SMS structure can be used to generate stable and switchable high order of harmonic mode-locked. The low-cost SMS fiber for harmonic mode-locked generation technique could lay the groundwork for future sustainable industrial growth. [ABSTRACT FROM AUTHOR]

Simultaneous wireless information and power transmission (SWIPT) allows the use of RF signals for both information detection and energy harvesting. Integration of cooperation, NOMA and SWIPT can provide energy-efficient, reliable, and spectral-efficient networks. Therefore, this study aims to design energy harvesting-enabled cooperative NOMA (C-NOMA) networks. This work investigates relay selection for multiple relay downlink C-NOMA networks with SWIPT in the presence of interference. The analytical closed-form outage probability expressions for the proposed relay selection are derived. Subsequently, the impact of various parameters, including the number of available relay nodes, energy harvesting parameters, and energy conversion efficiency, is analyzed on the performance of proposed networks. The finding showed that system performance improves with the number of intermediate relaying nodes, transmit power, and energy conversion efficiency. Comparative analysis of NOMA and time division multiple access TDMA proved the superiority of NOMA over traditional OMA schemes. [ABSTRACT FROM AUTHOR]

Ensuring communication infrastructures always alive during disaster mitigation and recovery is of paramount importance. In this case, Unmanned Aerial vehicle (UAV) will be the ideal substitute for the malfunctioning ground base station due to disaster. Henceforth, we suggest a multi‐UAV and Search and Rescue (SAR) collaboration model in this letter. To improve its connectivity, we propose an optimal SAR elevation angle for the multi‐UAV and SARs to administer larger disaster areas effectively and efficiently. We evaluate the performance of the proposed model in terms of path loss, throughput, and coverage probability. The results demonstrate that the proposed model achieves a significant enhancement in serving the SARs. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a passively mode-locked all-fiber laser utilizing a multimode interference effect in graded-index multimode fiber (GIMF). The mode-locking is obtained due to the Kerr effect in GIMF, which induces the intensity modulation inside the ring cavity laser. We obtain stable soliton mode-locked pulses at a center wavelength of 1574.1 nm, with a fixed repetition rate of 22 MHz and a pulse duration of 650 fs, when the pump power is changed in the range from 66.2 to 140.0 mW. The maximum average output power and pulse energy are recorded at 9.82 mW and 448 pJ, respectively, at a pump power of 140 mW. This proves that a nonlinear optical response in GIMF can be used as a new modulation mechanism for obtaining ultra-short pulses based on all-fiber ring cavity. [ABSTRACT FROM AUTHOR]

The sixth-generation (6G) wireless cellular network integrates several wireless bands and modes with the objectives of improving quality of service (QoS) and increasing network connectivity. The 6G environment includes asymmetrical heterogeneous networks (HetNets) with the intention of making effective use of the available frequencies. However, selecting a suitable gNB and a communication channel that works for users in the network is an enormous challenge in 6G HetNets. This paper investigates a joint user association (UA) and channel allocation (CA) problem in two-tier HetNets by considering the downlink scenario to improve QoS. Our study presents an innovative scheme for user association and channel allocation, wherein the user can be connected to either the macro base station (MBS) or a possible small base station (SBS) in a direct or relay-assisted link. Furthermore, the proposed scheme identifies the optimal channel to be allocated to each user so that the overall network QoS can be maximized. A symmetric matching game-based user association is proposed to find the optimal association for users. Moreover, a modified auction game is applied to allocate the optimal channel by considering the quota of each gNB. Regarding connection probability, throughput, energy efficiency (EE), and spectrum efficiency (SE), the simulation results show that the proposed approach performs well over the state-of-the-art techniques. [ABSTRACT FROM AUTHOR]

The tremendous advancement in distributed computing and Internet of Things (IoT) applications has resulted in the adoption of fog computing as today’s widely used framework complementing cloud computing. Thus, suitable and effective applications could be performed to satisfy the applications’ latency requirement. Resource allocation techniques are essential aspects of fog networks which prevent unbalanced load distribution. Effective resource management techniques can improve the quality of service metrics. Due to the limited and heterogeneous resources available within the fog infrastructure, the fog layer’s resources need to be optimised to efficiently manage and distribute them to different applications within the IoT network. There has been limited research on resource management strategies in fog networks in recent years, and a limited systematic review has been done to compile these studies. This article focuses on current developments in resource allocation strategies for fog-IoT networks. A systematic review of resource allocation techniques with the key objective of enhancing QoS is provided. Steps involved in conducting this systematic literature review include developing research goals, accessing studies, categorizing and critically analysing the studies. The resource management approaches engaged in this article are load balancing and task offloading techniques. For the load balancing approach, a brief survey of recent work done according to their sub-categories, including stochastic, probabilistic/statistic, graph theory and hybrid techniques is provided whereas for task offloading, the survey is performed according to the destination of task offloading. Efficient load balancing and task-offloading approaches contribute significantly to resource management, and tremendous effort has been put into this critical topic. Thus, this survey presents an overview of these extents and a comparative analysis. Finally, the study discusses ongoing research issues and potential future directions for developing effective management resource allocation techniques. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a new Q-switched thulium-doped fiber laser (TDFL) by utilizing a passive saturable absorber (SA) based on Molybdenum–Aluminium boride (MoAlB). The MoAlB is a metal–ceramic-based material; it is embedded in polyvinyl-alcohol (PVA) material to operate as the SA. The laser successfully generates stable Q-switched pulses operating at 1974.7 nm with a maximum repetition rate of 57.7 kHz and a minimum pulse width of 1.79 μs. A maximum pulse energy of 90.2 nJ is recorded at 436 mW pump power. Our experiment is the first demonstration on the use of MoAlB for the pulse laser generation in the 2 μm wavelength region. [ABSTRACT FROM AUTHOR]

The sixth generation (6G) mobile communication system is expected to meet the different service needs of modern communication scenarios. Heterogeneous networks (HetNets) have received a lot of attention in recent years due to their potential as a novel structure for evolutionary networks. When compared to homogeneous networks, HetNets provide more potential for spatial spectrum reuse and higher quality of service (QoS). However, effective resource management (RM) solutions are essential to prevent interference and accomplish spectrum sharing due to mutual interference. This paper presents a comprehensive review of resource management in 6G HetNets. The study aims to give crucial background on HetNets to aid in the creation of more effective methods in this field of study. First, a detailed examination of recent work is presented in resource management aspects such as power allocation, user association, mode selection, and spectrum allocation. Second, we identify the most severe challenges associated with the current resource management methods and propose suitable solutions. Finally, several open issues and emerging areas of research are highlighted. [ABSTRACT FROM AUTHOR]

We demonstrate the Q-switched and mode-locked pulse generation, using Molybdenum Aluminum Boride (MoAlB) material as a saturable absorber (SA). The SA film was obtained by mixing MoAlB with a polyvinyl alcohol (PVA) solution and then evaporating the mixture on a petri-dish. The prepared MoAlB PVA thin film exhibits a saturable absorption characteristic of 10.4%. Being introduced into an Erbium-doped fiber laser (EDFL) cavity, the MoAlB PVA thin film provides a stable Q-switched pulse at 1559 nm, which is achieved by adjusting the pump power above the threshold equal to 30.2 mW. The pulse has a maximum repetition frequency of 82.92 kHz, a minimum pulse width of 2.14 μm, and a maximum energy of 27.49 nJ at the pump power equal to 83.8 mW. Also we obtain the mode-locked pulse at 1560.1 nm, when the cavity length is extended to 205 m. The repetition frequency, pulse width, and time bandwidth product of the mode-locked pulse are 0.989 MHz, 3.82 ps, and 0.329, respectively. To the best of our knowledge, this is the first time that Q-switched and mode-locked pulses are obtained in a fiber laser based on MoAlB material. [ABSTRACT FROM AUTHOR]

A silver sulfide saturable absorber (SA) was successfully employed in an Erbium‐doped fiber laser (EDFL) cavity for short and ultrashort pulse generations. The Q‐switched laser was obtained with an operation wavelength of 1566 nm, pulse rate of 93.81 kHz, and pulse duration of 1.68 μs at a 187.04 mW pump. As the EDFL cavity was optimized for mode‐locking operation by adding 100 m long single mode fiber, a stable soliton pulse train operating at 1564 nm was realized with a constant repetition rate of 1.88 MHz and pulse duration of 3.01 ps. The good nonlinear characteristics of the SA make synergetic contributions to the generation of high‐performance Q‐switched and mode‐locked lasers. [ABSTRACT FROM AUTHOR]

Beyond Fifth Generation (B5G) networks are expected to be the most efficient cellular wireless networks with greater capacity, lower latency, and higher speed than the current networks. Key enabling technologies, such as millimeter-wave (mm-wave), beamforming, Massive Multiple-Input Multiple-Output (M-MIMO), Device-to-Device (D2D), Relay Node (RN), and Heterogeneous Networks (HetNets) are essential to enable the new network to keep growing. In the forthcoming wireless networks with massive random deployment, frequency re-use strategies and multiple low power nodes, severe interference issues will impact the system. Consequently, interference management represents the main challenge for future wireless networks, commonly referred to as B5G. This paper provides an overview of the interference issues relating to the B5G networks from the perspective of HetNets, D2D, Ultra-Dense Networks (UDNs), and Unmanned Aerial Vehicles (UAVs). Furthermore, the existing interference mitigation techniques are discussed by reviewing the latest relevant studies with a focus on their methods, advantages, limitations, and future directions. Moreover, the open issues and future directions to reduce the effects of interference are also presented. The findings of this work can act as a guide to better understand the current and developing methodologies to mitigate the interference issues in B5G networks. [ABSTRACT FROM AUTHOR]

Establishing a wireless communication network (WCN) is critical to saving people's lives during disasters. Since the user equipment (UE) must transfer their information to the functioning area, their batteries will be significantly drained. Thus, technologies that can compensate for battery power consumption, such as the energy harvesting (EH) strategy, are highly required. This paper proposes a framework that employs EH at the main cluster head (MCH) selected by the enhanced clustering technique (CFT) and simultaneously transmits information and power wirelessly to prolong the lifetime of the energy-constrained network. MCH harvests energy from the radio frequency signal via the relay station (RS) and uses the harvested energy for D2D communications. The suggested framework was evaluated by analyzing the EH outage probability and estimating the energy efficiency performance, which is expected to improve the stability of the network. Compared to the UAV scenario, the simulation findings show that when RS is in its optimal location, it enhances the network EH outage probability performance by 26.3%. Finally, integrating CFT with wireless communications links into cellular networks is an effective technique for maintaining communication services for mission-critical applications. [ABSTRACT FROM AUTHOR]

Self-starting Q -switching, Q -switched mode-locking and mode-locking operation modes are achieved sequentially in an all-fiber erbium-doped fiber laser with thulium-doped fiber saturable absorber for the first time. The central wavelengths of Q -switching, Q -switched mode-locking and mode-locking operation modes are 1569.7 nm, 1570.9 nm, and 1572 nm, respectively. The mode-locking operation of the proposed fiber laser generates stable dark soliton with a repetition rate of 0.99 MHz and signal-to-noise ratio of 65 dB. The results validate the capability of generating soliton pulse by doped fiber saturable absorber. Furthermore, the proposed fiber laser is beneficial to the applications of optical communication and signal processing system. [ABSTRACT FROM AUTHOR]

Future wireless communication networks will be largely characterized by small cell deployments, typically on the order of 200 meters of radius/cell, at most. Meanwhile, recent studies show that base stations (BS) account for about 80 to 95 % of the total network power. This simply implies that more energy will be consumed in the future wireless network since small cell means massive deployment of BS. This phenomenon makes energy-efficient (EE) control a central issue of critical consideration in the design of future wireless networks. This paper proposes and investigates (the performance of) two different energy-saving approaches namely, adaptive-sleep sectorization (AS), adaptive hybrid partitioning schemes (AH) for small cellular networks using smart antenna technique. We formulated a generic base-model for the above-mentioned schemes and applied the spatial Poisson process to reduce the system complexity and to improve flexibility in the beam angle reconfiguration of the adaptive antenna, also known as a smart antenna (SA). The SA uses the scalable algorithms to track active users in different segments/sectors of the microcell, making the proposed schemes capable of targeting specific users or groups of users in periods of sparse traffic, and capable of performing optimally when the network is highly congested. The capabilities of the proposed smart/adaptive antenna approaches can be easily adapted and integrated into the massive MIMO for future deployment. Rigorous numerical analysis at different orders of sectorization shows that among the proposed schemes, the AH strategy outperforms the AS in terms of energy saving by about 52 %. Generally, the proposed schemes have demonstrated the ability to significantly increase the power consumption efficiency of micro base stations for future generation cellular systems, over the traditional design methodologies. [ABSTRACT FROM AUTHOR]

Routing is fundamental in any wireless network for path selection, which provides the most effective way that legitimizes the data to be transmitted from a source to a destination device. In gigantic network demand nowadays, routing is pertinent to ensure fast and reliable data transfer. Ineffective routing may cause route flapping and degrade the overall Quality of Service (QoS). Meanwhile, Device-to-Device communications (D2D) is a technology that allows the devices to be connected without or partial involvement of the conventional cellular network. With these natures of qualities, D2D communication provides a reliable propitious medium that caters for the needs of many different telecommunications scenarios. The interconnectivity of multiple devices creates the Internet of Things (IoT), which will be an essential insistent in future technologies. With the dynamic nature of D2D technology, the routing approach act as a principal architecture that essential to be implemented in every niche D2D aspect. If wrong routing decisions are made in D2D communication, the QoS performance would be worse than the conventional cellular network. This paper present the state of the art of fundamentals, recent progress, current challenges, future directions, and potential routing applications for D2D and Beyond IoT 5G Networks. This review will also act as a guide and reference for future researchers and scientists to explore and integrate the routing technique in D2D communication and Beyond IoT 5G Networks. [ABSTRACT FROM AUTHOR]

The concept of the Internet of Things (IoT)-based Wireless Sensor Network (WSN) is rapidly gaining wide-spread recognition and acceptance in our day-to-day lives. Nowadays, the application of the IoT sensor nodes in various domains of endeavors such as health-care, smart homes, industrial and production sectors, control networks, and in many other fields has continued to increase steadily. In IoT-based WSN, sensor nodes dynamically join the internet and collaborate to accomplish a mission by sensing and collecting event data from the application field. The sensor nodes thus forward the collected information to the sink nodes or to the nearest base station for further transmission. However, one of the significant drawbacks of the IoT-based WSN networks is that the battery life of the sensor nodes is often short-lived due to the energy-limited nature of the electronic sensors, resulting in the network's short lifetime. Thus, prolonging the lifetime duration of the sensor nodes becomes a fundamental task. Whether the battery life of a sensor node is extended for a reasonable length of time or depleted in a moment depends mainly on the energy efficiency of the underlying routing protocol. Therefore, the issue of network lifetime can be fundamentally addressed by implementing an efficient and robust energy-aware routing protocol for sustainable and prolonged network operation time in a WSN based IoT network scenario. In this paper, a cluster-based Backpressure routing (CBPR) scheme has been proposed, which targets to prolong the network lifetime and enhance the data transmission reliability using energy load-balancing mechanism. For every cluster of the sensor node, the CBPR scheme elects a cluster head which has the highest energy level and the shortest distance to the sink node. The proposed CBPR routing scheme further utilizes a very robust data aggregation algorithm to checkmate and prevent the circulation of redundant data packets in the network while also exploiting the Backpressure scheduling machine for data packets queueing and for route selection, which allows it to select the next-hop sensor node based on the queue length value of the sensor nodes. Extensive simulations have been performed to evaluate the efficiency of the proposed CBPR routing scheme, which was compared with that of other well-known routing schemes such as the Information Fusion Based Role Assignment and Data Routing for In-Network Aggregation in terms of throughput, energy consumption, and packet delivery ratio. [ABSTRACT FROM AUTHOR]

The whispering gallery mode (WGM) based micro-bottle resonator (MBR) sensor has been proposed and demonstrated for relative humidity measurement by using an agarose gel as a transducer. MBR was fabricated by using a soften-and-compress method to form a 190 µm bulge bottle. The micro-bottle was optically excited by a 3 µm tapered fiber and it exhibits a resonance with a Q factor in an order of 105. The agarose coated MBR produces a good sensing response towards humidity with the sensitivity of 0.107 dB/%RH and linearity of 99.614%. The agarose hydrophilic nature and its changing porosity and refractive index with increasing relative humidity made the coated MBR structure to be more sensitive than the uncoated structure. This humidity sensor has a simple fabrication and is showing good sensitivity, linearity, resolution, response time and operational in a wide humidity range. [ABSTRACT FROM AUTHOR]

The much-awaited year—2021 that promises to deliver a great deal on the 5th generation (5G) wireless systems' expectations is finally here. Several solutions have been proposed to deal with the energy challenges in the evolving wireless systems, especially in 5G and beyond. These solutions have considered among other approaches, design of new network architecture based on the employment of new radio access techniques called cloud radio access networks (C-RAN), the use of heterogeneous networks approaches, the introduction of renewable energy (RE) as an alternative source of power, etc. Nonetheless, this paper's focus is ultimately on the approaches to achieve optimal energy-efficient (EE) in 5G and beyond networks based on an emerging design philosophy that promises higher overall system capacity at a low energy cost. It focuses on four key EE solutions for future wireless systems: EE resource allocation, network planning, RE, and C-RAN. It discusses various related work, research challenges and possible future work for these four areas. Moreover, the advantages and limitation of new proposed 5G and beyond RON architecture are also reviewed. It is expected that the readers of this study will understand different EE solutions to achieve an optimal EE network. [ABSTRACT FROM AUTHOR]

With the increase in the number of communication devices, the requirement for higher bandwidth is essential. To achieve this goal, research and industrial communities have both suggested that future wireless systems will take advantage of the numerous emerging technologies. Utilization of Cognitive Radio (CR) for the next-generation Fifth Generation (5G) communication technology is the major advancement for getting a higher bandwidth in a cellular communication network. In this paper, we present a comprehensive study of CR from the perspectives of spectrum allocation schemes, impact and role of MAC layer in spectrum sensing and sharing, CR application in multi-hop wireless networks, and challenges associated with channel selection and packet routing in multi-hop heterogeneous CR networks. This paper also presents the analysis, in literature, of a range of intelligent routing protocols that are considered viable for packets routing in CR networks. The need to address the issue of spectrum depletion and the apparent underutilization of available scarce spectrum resources in existing wireless networks is the primary motivation behind this study. Considering the fact that CR technology can potentially maximize the utilization of bulk of the unused communication spectrum bands for the future 5G of wireless network and beyond. [ABSTRACT FROM AUTHOR]

In order to mitigate the power consumption issue for the sensor's nodes, an efficient power optimized routing protocol is needed. Therefore, this paper proposes a network coding backpressure routing (NCBPR) routing scheme for a large-scale Internet of Things (IoT) networks, which exploits the backpressure algorithm in order to divert packets flow. In the network, the packets are flowing from the highly congested node to low congested node, which helps to balance the load and optimized the fair use of the battery power of all the participating nodes. It divides the network into the small clusters, where the selection of clusters head depends upon an additional parameter of battery power apart from other optimum path parameters. It also employs an efficient data aggregation mechanism, which improves the throughput of the network by eliminating redundant packets. The network has been designed by considering 300 nodes in a network and the results have been drawn in terms of network throughput, packet delivery ratio and energy consumption. The results are presented in comparison with conventional well-known information-fusion-based role assignment (InFRA) and data routing for in-network aggregation (DRINA) routing schemes. The results prove that the proposed NCBPR scheme delivers significant improvement, such as throughput which increased by 21.38 and 12.13%, packet delivery ratio improved by 24.73 and 11.38%, and sensors node's energy consumption is decreased by 61.46 and 44.35% as compared to conventional InFRA and DRINA schemes, respectively. [ABSTRACT FROM AUTHOR]

In Mobile Ad hoc Networks (MANETs), nodes' mobility, traffic congestion, and link quality estimation of the intermediate nodes are very crucial factors for establishing a reliable forwarding path between a source and destination node pairs. The unpredictable movement of nodes and random data traffic flow at a single node can cause congestion and network topology instability, which significantly lowers the performance of the ad hoc network. Indeed, the above-highlighted issues can be mitigated by implementing a more reliable mobility-centric, contention, and link quality-aware routing protocol for efficient data transmissions in a mobile network. This paper proposes a routing strategy called Mobility, Contention window, and Link quality sensitive multipath Routing (MCLMR) in MANETs, which considers the nodes mobility, contention window size, and link quality estimated value of the intermediate nodes in the optimal route selection. Also, Technique for Order of Preference by Similarity to Ideal Solution; a multicriteria decision-making technique, which provides weights according to node mobility, contention window size, and link quality estimated values, is also employed for the selection of intermediate nodes, whereas the Expected Number of Transmissions metric is used to minimize the effect of control message storm. The extensive simulations results prove that the proposed MCLMR routing scheme outperforms the conventional Multipath Optimized Link State Routing (MP-OLSR) and MP-OLSRv2 routing schemes in terms of network throughput, end-to-end delay, energy consumption, and packets loss ratio. [ABSTRACT FROM AUTHOR]

In this paper, we propose a data aggregation back pressure routing (DABPR) scheme, which aims to simultaneously aggregate overlapping routes for efficient data transmission and prolong the lifetime of the network. The DABPR routing algorithm is structured into five phases in which event data is sent from the event areas to the sink nodes. These include cluster-head selection, maximization of event detection reliability, data aggregation, scheduling, and route selection with multi attributes decision making metrics phases. The scheme performs data aggregation on redundant data at relay nodes in order to decrease both the size and rate of message exchanges to minimize communication overhead and energy consumption. The proposed scheme is assessed in terms of packet delivery, network lifetime, ratio, energy consumption, and throughput, and compared with two other well-known protocols, namely "information-fusion-based role assignment (InFRA)" and "data routing for in-network aggregation (DRINA)", which intrinsically are cluster and tree-based routing schemes designed to improve data aggregation efficiency by maximizing the overlapping routes. Meticulous analysis of the simulated data showed that DABPR achieved overall superior proficiency and more reliable performance in all the evaluated performance metrics, above the others. The proposed DABPR routing scheme outperformed its counterparts in the average energy consumption metric by 64.78% and 51.41%, packet delivery ratio by 28.76% and 16.89% and network lifetime by 42.72% and 20.76% compared with InFRA and DRINA, respectively. [ABSTRACT FROM AUTHOR]

Full‐duplex (FD) assisted multiple‐input–multiple‐output relaying increases the spectral efficiency through efficient spectrum utilization. The major concerns for the FD assisted relay system are the cancellation of inter‐relay interference (IRI) and relay self‐interference (RSI). Previous works were idealized only on the basis of either RSI or IRI; hence, all other realistic models to overcome the RSI or IRI were unappreciated. This paper aims to reduce the interference‐to‐signal ratio. We propose the joint relay's receive beamforming based on oblique projection to mitigate the RSI and IRI in multihop environments. Applying first orthogonal projectors to the relay's received signal, the relay's received signals are divided into interference subspace and signal subspace. Then, the desired signal is recovered from signal subspace by using oblique projection that cancels out the RSI and IRI. The geometric interpretation of oblique projection is analyzed to understand its properties. The major merit of this method is that it can be adopted even when the RSI and IRI channels are unknown. In comparison to the existing interference cancellation methods, the signal‐to‐interference ratio of our proposed method does not deteriorate even when the transmit power is high. Additionally, we demonstrate that the oblique projection output is equivalent to an orthogonal projection using geometrical interpretation, simulation, and theoretical derivation. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA) scheme is emerging as a favourable multiple access scheme for future 5G networks. Compared to orthogonal multiple access techniques, NOMA provides spectral efficiency, user fairness, better connectivity, enhanced data rate and reduced latency. Thus, NOMA can be a suitable multiple access technique for 5G networks. On the other hand, in wireless networks, cooperation is a well-recognized proven technique for performance enhancement. Cooperative networks offer multiple desirable advantages, including high performance, reliability and greater coverage area. It is believed that in future 5G systems, many existing wireless technologies will be combined with new technologies. Power domain-NOMA (PD-NOMA) has features that can provide opportunities of improved performance and better spectral utilization for downlink cooperative networks. Recently, research works of incorporating PD-NOMA in cooperative networks have gained attention of researchers around the globe. This article surveys the recent research trends in PD-NOMA based cooperative network by reviewing related recent research on performance analysis of cooperative PD-NOMA systems, resources allocation, and impact of relay selection. Additionally, this review article discusses the performance of cooperative PD-NOMA networks when they are integrated with other 5G technologies including cognitive radio, full duplex radio and wireless energy harvesting. Furthermore, some unaddressed issues are highlighted for future research in this area. [ABSTRACT FROM AUTHOR]

In mobile ad hoc networks, limited energy resources and traffic congestion at the nodes are crucial issues due to the nodes being battery operated and flooding the network with packets, respectively. These issues degrade network routing performance in terms of quality of service. In this study, we proposed a contention window and residual battery-aware multipath routing scheme to enhance network performance. Our proposed routing scheme has successfully diverted the traffic load from a low energy node to a high energy node while also controlling congestion among intermediate nodes. A multi-criteria decision-making technique was also used for the selection criteria of an intermediate node in the optimal path, based on the mobility and window size contention of nodes. Eventually, the contention window and residual battery-aware multipath routing scheme has enhanced throughput, attenuated the packet loss ratio, and reduced the energy consumption in comparison to a conventional multipath optimized link state routing protocol routing scheme. [ABSTRACT FROM AUTHOR]

The future wireless Fifth Generation (5G) communication network required a higher bandwidth in order to achieve greater data rate. It will be largely characterized by small cell deployments, typically in the range of 200 meters of radius/cell, at most. The implementation of small size networks delivers various advantages such as high data rate and low signal delay. However, it also suffers from various issues such as inter-cell, intra-cell, and inter-user interferences. This paper discusses the issues related to interference management for 5G network from the perspective of Heterogeneous Network and Device-to-Device communication, by using enabling techniques, such as Inter-cell Interference Coordination, Coordinated Multipoint, and Coordinated Scheduling. Furthermore, several pertinent issues have been critically reviewed focusing on their methodologies, advantages and limitations along with the future work. Future directions proposed by the 3rd Generation Partnership Project for interference mitigation has also been outlined. This review will act as a guide for the researchers to comprehend various existing and emerging enabling interference mitigation techniques for further exploration and smooth implementation of 5G wireless network. [ABSTRACT FROM AUTHOR]

In order to resolve the issue of coverage limitation for the future fifth-generation network, deploying a relay node within a cell is one of the most capable and cost-effective solution, which not only enhances the coverage but also improves the spectral efficiency. However, this solution leads to the undesired interferences from nearby base station and relay nodes that affects user's signal-to-interference-plus-noise ratio and can cause the ambiguous received signal at the user end. In this article, we have analyzed a relay-based interference-limited network at millimeter wave frequency and proposed a Poisson point process-based model using a stochastic geometrical approach. The results for the proposed Poisson point process model have been evaluated in terms of success probability, network ergodic capacity, and outage probability, compared with the ideal grid model and conventional multiple-antenna ultra-dense network model. The results proved that the success probability and ergodic capacity for the proposed model are 3.5% and 2.3% higher as compared to the most commonly used model for the high-density network, respectively. Furthermore, the results have been analyzed at different multiple-input-multiple-output antenna configuration, which validates the model in the improvement of overall network performance even for higher number of antennas. [ABSTRACT FROM AUTHOR]

Training sequence is used in multiple antenna systems to estimate channel state information and mitigate channel distortion between transmitter and receiver. However, the training sequence or pilot must be limited to a certain size in order to reduce the impact of overhead loss due to limited channel coherence length in mobile users. In this paper, we proposed to use training size optimization in cell-free massive MIMO system. In addition, we proposed and compared the performance of different training size optimization algorithms, namely exhaustive search optimization, bisection optimization and min–max optimization, with each method has different level of calculation complexities. The results showed that in general, all of the 3 training length optimization methods improved the downlink rate compared to the conventional pilot length method. We also showed that the training optimization methods are more effective when the coherence length is small or the number of users is very large. In the case of large number of users or small coherence length, the exhaustive search has the best median downlink rate, followed closely by min–max optimum and finally the bisection method. Even though the exhaustive search optimization has the best downlink rate, we showed that the proposed reduce optimization complexity methods has significantly less calculation complexity. In addition, the median downlink rate performance of min–max optimization method is only slightly less than that of the exhaustive search method for various number of users and coherence length. [ABSTRACT FROM AUTHOR]

To facilitate connectivity to the internet, the easiest way to establish communication infrastructure in areas affected by natural disaster and in remote locations with intermittent cellular services and/or lack of Wi-Fi coverage is to deploy an end-to-end connection over Mobile Ad-hoc Networks (MANETs). However, the potentials of MANETs are yet to be fully realized as existing MANETs routing protocols still suffer some major technical drawback in the areas of mobility, link quality, and battery constraint of mobile nodes between the overlay connections. To address these problems, a routing scheme named Mobility, Residual energy and Link quality Aware Multipath (MRLAM) is proposed for routing in MANETs. The proposed scheme makes routing decisions by determining the optimal route with energy efficient nodes to maintain the stability, reliability, and lifetime of the network over a sustained period of time. The MRLAM scheme uses a Q-Learning algorithm for the selection of optimal intermediate nodes based on the available status of energy level, mobility, and link quality parameters, and then provides positive and negative reward values accordingly. The proposed routing scheme reduces energy cost by 33% and 23%, end to end delay by 15% and 10%, packet loss ratio by 30.76% and 24.59%, and convergence time by 16.49% and 11.34% approximately, compared with other well-known routing schemes such as Multipath Optimized Link State Routing protocol (MP-OLSR) and MP-OLSRv2, respectively. Overall, the acquired results indicate that the proposed MRLAM routing scheme significantly improves the overall performance of the network. [ABSTRACT FROM AUTHOR]

Realization of a simple integrated and low-cost intensity modulation/direct detection-based humidity and vapor detection system utilizing zinc oxide (ZnO) nanorods as the active material is demonstrated. The sensing device comprises of ZnO nanorods optimally grown on a glass substrate and mounted on 3D printed platform for the alignment with a green light-emitting diode setup for an edge excitation. An Arduino platform was used for the signal processing of the detection of the transmitted light. Both forward and backward scattering are affected due to light leakage while propagating through the glass substrate which are further attenuated in the presence of humidity. In this paper, backward scattering was found to be dominant, and thus, with increasing humidity, a reduction in the transmitted light was monitored. When the sensor was tested in a humidity controlled environment, it was found that the output voltage drops by approximately 750 mV upon changing the relative humidity (RH) level from 35% to 90% in a non-linear fashion. The average sensitivity of the sensor was observed to be −12 mV/% throughout the tested RH levels. Sensitivity was found to be higher at −24.6 mV/% for RH’s beyond 70%. An average response time of 3.8 s was obtained for RH levels of 85% with respect to the standard ambient humidity conditions (RH 50%), which showed a quicker recovery time of 2.2 s. The proposed sensor device provides numerous advantages, including low-cost production, simplicity in design, ease of use, and stability during handling. [ABSTRACT FROM AUTHOR]

A glass substrate coated with ZnO nanorods via a hydrothermal method for formaldehyde vapor sensing is reported. The proposed sensor device was characterized against formaldehyde vapor concentrations varying from 1% to 5% with a reference point as 0% (pure water) at room temperature. A significant sensing response was observed where the output voltage reduced by 0.0856 V via scattering effect by ZnO nanorods upon exposure to the maximum tested concentration (5%). The sensitivity and linearity of the sensing response were recorded to be approximate values of −0.0168 V/% and 98.06% correspondingly. The sensor device was found to have good measurement stability in measuring as low as 1% of concentration for a prolonged time of 600 s. This proposed sensor has potential applications in monitoring air pollution caused not only by formaldehyde vapor but also by other harmful and toxic vapors or gases. [ABSTRACT FROM AUTHOR]

A soliton-locked Erbium-doped fiber laser is demonstrated for the first time using a pure Antimony (Sb) film as a saturable absorber (SA). The SA device is fabricated by depositing a 5 μm Sb layer onto a polyvinyl alcohol thin film via Physical vapor deposition process. Self-starting soliton mode-locked pulses train with a constant repetition rate of 0.99 MHz is obtained as the pump power increased from 101 mW to 142 mW. The laser operates at 1559 nm with a pulse width of 3.53 ps. At the pump power of 142 mW, the maximum peak power and pulse energy are calculated as 5.83 kW and 20.59 nJ, respectively. The obtainable pulse is very stable with a signal-to-noise ratio (SNR) of 70 dB. Our experimental results manifest that the pure Sb thin film-based SA is able to generate mode-locked pulsed laser at the 1.55-micron laser regime. [ABSTRACT FROM AUTHOR]

Long Term Evolution (LTE) is the prominent technology in Fourth Generation (4G) communication standards, which provides higher throughput and better Quality of Service (QoS) to all users. However, users in the cell-edge area are receiving comparatively low QoS due to the distance from eNodeB (eNB) and bad channel conditions. The Conventional Modified Largest Weighted Delay First (MLWDF) algorithm is unable to resolve this issue, as it does not consider the location of the user. This paper proposes an extended MLWDF (EMLWDF) downlink scheduling algorithm to provide better services to the cell-edge user as well as to the cell-center user. The proposed algorithm divides the eNB cell area into inner and outer regions. It includes the distance of the user from attached eNB, received Signal to Interference plus Noise Ratio (SINR) and error probability into the original algorithm. The simulated results are compared with other well-known algorithms and the comparison shows that the proposed algorithm enhances overall 56.23% of cell-edge user throughput and significantly improves the average user throughput, fairness index, and spectral efficiency. [ABSTRACT FROM AUTHOR]

Long term evolution-advanced (LTE-A) system introduces carrier aggregation (CA) technique to improve the user throughput by aggregating multiple component carriers (CCs). Previous research works related to downlink radio resource allocation with carrier aggregation have not considered the delay factor and the error probability. Therefore, the previous methods are unable to provide better quality of service (QoS) compared to the LTE-A standard. This paper considers the radio resource management problem by zooming into the head of line delay, probability of packet loss, and the delay threshold for different types of data. In doing this, several constraints are imposed following the specifications of LTE-A system. Hence, an improved method is developed in this study to enhance the system throughput and to maintain the computational complexity. Extensive simulations were carried out with other well-known methods to verify the overall performance of the proposed method. The result obtained indicates that the proposed method outperforms the previous methods in the measurement of average user throughput, average cell throughput, fairness index, and spectral efficiency. [ABSTRACT FROM AUTHOR]

Online bit error rate (BER) estimation (OBE) has been used as a stopping iterative turbo decoding criterion. However, the stopping criteria only work at high signal-to-noise ratios (SNRs), and fail to have early termination at low SNRs, which contributes to an additional iteration number and an increase in computational complexity. The failure of the stopping criteria is caused by the unsuitable BER threshold, which is obtained by estimating the expected BER performance at high SNRs, and this threshold does not indicate the correct termination according to convergence and non-convergence outputs (CNCO). Hence, in this paper, the threshold computation based on the BER of CNCO is proposed for an OBE stopping criterion (OBEsc). From the results, OBEsc is capable of terminating early in a varying SNR environment. The optimum number of iterations achieved by the OBEsc allows huge savings in decoding iteration number and decreasing the delay of turbo iterative decoding. [ABSTRACT FROM AUTHOR]

In cognitive radio (CR), cooperative spectrum sensing (CSS) has been extensively explored to be accounted for in a spectrum scanning method that permits secondary users (SUs) or cognitive radio users to utilize discovered spectrum holes caused by the absence of primary users (PUs). This paper focuses on optimality of analytical study on the common soft decision fusion (SDF) CSS based on different iterative algorithms which confirm low total probability of error and high probability of detection in detail. In fact, all steps of genetic algorithm (GA), particle swarm optimization (PSO), and imperialistic competitive algorithm (ICA) will be well mentioned in detail and investigated on cognitive radio cooperative spectrum sensing (CRCSS) method. Then, the performance of CRCSS employing GA-, PSO-, and ICA-based scheme is analysed in MATLAB simulation to show superiority of these schemes over other conventional schemes in terms of detection and error performance with very less complexity. In addition, the ICA-based scheme also reveals noticeable convergence and time running performance in comparison to other techniques. [ABSTRACT FROM AUTHOR]

Pulse repetition interval (PRI) analysis based on histogram method is widely used in electronic intelligence (ELINT) systems for emitter recognition. The identification of PRI modulation types using the statistical histogram method has faced inaccurate recognition due to error caused by missing and spurious pulses. In this study, the modelling for the statistical prediction of spurious and missing pulses is done to estimate their distributions density of occurrences that can be related to the robustness of the PRI analysis method. The statistical modelling is simulated using the histogram PRI analysis method and the proposed model is tested for its feasibility using Monte-Carlo simulation. The results obtained show that the proposed model can be used to estimate the presence of missing and spurious pulses, and can be used for testing of the robustness of PRI analysis methods. [ABSTRACT FROM AUTHOR]

Spectrum scarcity is a major challenge in wireless communications systems requiring efficient usage and utilization. Cognitive radio network (CRN) is found as a promising technique to solve this problem of spectrum scarcity. It allows licensed and unlicensed users to share the same licensed spectrum band. Interference resulting from cognitive radios (CRs) has undesirable effects on quality of service (QoS) of both licensed and unlicensed systems where it causes degradation in received signal-to-noise ratio (SIR) of users. Power control is one of the most important techniques that can be used to mitigate interference and guarantee QoS in both systems. In this paper, we develop a new approach of a distributed power control for CRN based on utility and pricing. QoS of CR user is presented as a utility function via pricing and a distributed power control as a non-cooperative game in which users maximize their net utility (utility-price). We define the price as a real function of transmit power to increase pricing charge of the farthest CR users. We prove that the power control game proposed in this study has Nash Equilibrium as well as it is unique. The obtained results show that the proposed power control algorithm based on a new utility function has a significant reduction in transmit power consumption and high improvement in speed of convergence. [ABSTRACT FROM AUTHOR]

Recent trends show that it is a major challenge to predict the exact propagation path accurately and efficiently for three-dimensional (3D) indoor environments. Therefore, this study introduces a new 3D ray tracing algorithm based on a red-black tree with facet mining and object bouncing techniques. The red-black tree data structure offers a faster object searching operation while repeatedly performing intersection tests. On the other hand, extensive ray-facet intersection tests can be eliminated by using object and facet bouncing techniques, whereas the facet mining makes it easier to trace the transmitted ray paths accurately. The proposed method is compared with ray launching, bidirectional path tracing, modified angular Z-buffer, and binary space partitioning-based modified wavefront decomposition techniques and it is found that it obtains better prediction results in terms of computation time, the number of predicted rays, and radio propagation path loss. [ABSTRACT FROM AUTHOR]

The classification of pulse repetition interval (PRI) modulation types using transformation techniques has some disadvantages, whereby PRIs can be misclassified. In this study, classification of PRI modulation types is done using the power spectrum of the Walsh-Hadamard transform (WHT). The generated spectrums are downsampled to reduce sampling errors and sub-harmonics, resulting in decimated Walsh-Hadamard transform (DWHT) spectrums. A template of DWHT spectrums is developed for the most common PRI modulation types, which are; constant, jittered and staggered. In this template, each pulse sequence is given a unique DWHT spectrum as its identity. The template can be used as rule-based classifier for accurate identification of signals. [ABSTRACT FROM AUTHOR]

Interference resulting from Cognitive Radios (CRs) is the most important aspect of cognitive radio networks that leads to degradation in Quality of Service (QoS) in both primary and CR systems. Power control is one of the efficient techniques that can be used to reduce interference and satisfy the Signal-to-Interference Ratio (SIR) constraint among CRs. This paper proposes a new distributed power control algorithm based on game theory approach in cognitive radio networks. The proposal focuses on the channel status of cognitive radio users to improve system performance. A new cost function for SIR-based power control via a sigmoid weighting factor is introduced. The existence of Nash Equilibrium and convergence of the algorithm are also proved. The advantage of the proposed algorithm is the possibility to utilize and implement it in a distributed manner. Simulation results show considerable savings on Nash Equilibrium power compared to relevant algorithms while reduction in achieved SIR is insignificant. [ABSTRACT FROM AUTHOR]