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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]

• Combination of single-mode fibre with step-index multimode fibre as saturable absorber. • The Q-switching is caused by the Kerr-effect of multimode interference. • Repetition rate of the Q-switched laser is tunable from 87 to 158 kHz. • The minimum pulse width is 2.5 µs. A passively Q-switched Erbium-doped fiber laser (EDFL) was successfully demonstrated using SMF (single-mode fiber)-SIMF (step-index multimode fiber)-SMF or SMS structure as a saturable absorber (SA). The SMS structure operates on the Kerr-effect of multimode interference (MMI). To modulate the cavity loss, a 158 mm length of SIMF was fusion spliced into a ring cavity. By properly adjusting the in-line polarization controller (PC) that holds the SIMF, we were able to generate steady Q-switched pulses. As the input pump power increased from 115 to 343 mW, the repetition rate of the Q-switched laser increased from 87 to 158 kHz, while the corresponding pulse width decreased from 4.2 µs to 2.5 µs. The signal-to-noise ratio (SNR) of the fundamental mode for the pulsed laser was around 72 dB at a central wavelength of 1530 nm. Our results indicate that the SMS structure can be used as an SA to generate stable Q-switched EDFL with very simple cavity settings. [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]

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]

• Thulium-doped fiber (TDF) as saturable absorber for ultrashort pulse generation. • 12 cm-long TDF is incorporated into Erbium-doped fiber laser cavity. • The SA has a modulation depth of 3.6% • The mode-locked laser operates at 1568.2 nm with a pulse width of 2.27 ps. • The dark pulse with 220 ns pulse width and 1.85 MHz repetition rate. • The maximum peak power and pulse energy are calculated as 1.75 kW and 3.93 nJ. Generation of ultrashort pulses in an all-fiber Erbium-doped fiber laser (EDFL) cavity with doped fiber saturable absorber (DFSA) is demonstrated for the first time. The doped fiber saturable absorber is fabricated by a single-mode 12 cm-long thulium-doped fiber (TDF). The optical characteristic of TDF indicates a saturable absorption of 3.6 %, which indicates it's capability to function as a mode-locker. Continuous wave, mode-locked and combined-mode operations are observed sequentially with the increase of pump power. The mode-locked erbium-doped fiber laser operates at 1568.2 nm with a pulse width of 2.27 ps. A mode-locked pulse train with a constant repetition rate of 0.99 MHz is obtained as the pump power increased from 96 mW to 178 mW. At the pump power of 178 mW, the maximum peak power and pulse energy are calculated as 1.75 kW and 3.93 nJ, respectively. The obtained pulse train is very robust with a signal-to-noise ratio (SNR) of 63 dB. The experimental results attest that utilizing doped fiber saturable absorber can achieve ultrashort pulses and possess the potentially increasable power of mode-locked operation in all-fiber lasers. [ABSTRACT FROM AUTHOR]

Abstract: Multiple antenna transmission methods are currently being developed all around the world for evolving 3G wireless standards. Space–Time Trellis Code (STTC) has been proven to use transmit diversity efficiently. It effectively exploits the effects of multipath fading to increase the information capacity of the multiple antenna transmission systems. STTC is a channel coding technique that maximises the ‘distance’ between different symbol matrices such that the probability of transmission errors are decreased when transmitting redundant symbol or in other words, to maximise the minimum determinant. Maximising the minimum determinant is equivalent to obtaining optimal generator matrix G. Instead of using state diagrams, optimal generator matrix G discussed in this paper is obtained using an improved algorithm which is based on Lisya tree structure. Optimal generator matrix G in this paper has a minimum determinant of 48 which is the highest coding gain obtained so far. [Copyright &y& Elsevier]

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]

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]

Packet scheduling has drawn a great deal of attention in the field of wireless networks as it plays an important role in distributing shared resources in a network. The process involves allocating the bandwidth among users and determining their transmission order. In this paper an uplink (UL) scheduling algorithm for the Mobile Worldwide Interoperability for Microwave Access (WiMAX) network based on the cyclic polling model is proposed. The model in this study consists of five queues (UGS, ertPS, rtPS, nrtPS, and BE) visited by a single server. A threshold policy is imposed to the nrtPS queue to ensure that the delay constraint of real time traffic (UGS, ertPS, and rtPS) is not violated making this approach original in comparison to the existing contributions. A mathematical model is formulated for the weighted sum of the mean waiting time of each individual queues based on the pseudo-conservation law. The results of the analysis are useful in obtaining or testing approximation for individual mean waiting time especially when queues are asymmetric (where each queue may have different stochastic characteristic such as arrival rate and service time distribution) and when their number is large (more than 2 queues). [ABSTRACT FROM AUTHOR]

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]

Coping with the skyrocketing needs for massive amounts of data for the future Fifth Generation (5G) network, Device-to-Device (D2D) communications technology will provide seamless connectivity, high data rates, extended network coverage, and spectral efficiency. The D2D communications are a prevalent emerging technology to achieve the vision of symmetry in the Internet of Things (IoT) services. However, energy resource constraints, network stability, traffic congestion, and link failure of the devices are the crucial impediments to establish an optimal route in the D2D communications based IoT 5G network. These obstacles induced packet drop, rapid energy depletion, higher end-to-end delay, and unfairness across the network, leading to significant route and network performance degradation. Therefore, in this paper, an energy, mobility, queue length, and link quality-aware routing (EMBLR) approach is proposed to overcome the challenges and boost network performance. Moreover, a multicriteria decision making (MCDM) technique is utilized for the selection of the intermediate device in an optimal route. Extensive simulation has been conducted and proven that the proposed routing approach significantly enhances network performance. Overall, results have been carried out in Quality of Service (QoS) performance metrics and compared with other well-known routing approaches. [ABSTRACT FROM AUTHOR]

MAX phase materials have garnered significant attention due to their corrosion resistance, impressive antioxidation and high electrical and optical conductivity. One such material, Titanium Tin Carbide (Ti 2 SnC), has demonstrated notable nonlinear optical properties. The saturable absorption of Ti 2 SnC, embedded into a polyvinyl (PVA) film, was measured to assess its potential. The Ti 2 SnC -PVA film exhibited a calculated modulation depth of 7.8%. In the context of practical applications, the Ti 2 SnC-PVA film was employed as a saturable absorber (SA) in an Erbium-doped fiber laser (EDFL) cavity. This configuration enabled the generation of stable Q-switched and mode-locked pulse trains. Q-switched operation occurred in a pump power range of 51.67 mW–83.83 mW, reaching a peak pulse energy of 110.94 nJ. Transitioning to mode-locking operation, the laser cavity demonstrated efficiency in the pump power range of 105.27 mW–196.39 mW. At a pump power of 196.39 mW, the fiber laser cavity achieved its highest pulse energy of 5.42 nJ, characterized by a pulse width of 2.32 ps and a pulse repetition rate of 1.825 MHz. These results highlight the promising potential of Ti2SnC-PVA thin film as a cutting-edge material for applications in pulsed laser systems. The material's excellent nonlinear optical properties make it a compelling candidate for advancing the field of pulsed laser technology. • The Ti 2 SnC embedded into a polyvinyl (PVA) film, exhibited a modulation depth of 7.8%. • Q-switched operation occurred in a pump power range of 51.67 mW–83.83 mW, reaching a peak pulse energy of 110.94 nJ. • Transitioning to mode-locking operation in the pump power range of 105.27 mW–196.39 mW. • Mode-locked pulses exhibit a pulse width of 2.32 ps and a repetition rate of 1.825 MHz. • At 196.39 mW, the mode locked EDFL achieved its highest pulse energy of 5.42 nJ. [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]

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]

A dual-wavelength Q-switched fiber laser is successfully demonstrated by utilizing an all-fiber configuration based on fiber saturable absorber (SA). An 18 cm-long Tm-doped fiber (TDF) is employed as a fiber SA since it presents an apparent nonlinear optical characteristic at near-infrared wavelength with 180 MW∕cm2 saturable intensity and 2% modulation depth. After splicing the TDF into an Erbium-doped fiber laser (EDFL) cavity, a stable dual-wavelength Q-switched pulses is generated with the aid of polarization controller as an optical wavelength selector. It operates at wavelengths of 1532.6 nm and 1557 nm (with wavelength spacing as wide as 24.4 nm). To the best of our knowledge, this is the dual-wavelength fiber laser with widest wavelength spacing reported so far. Furthermore, single-wavelength Q-switched operations of 1532 nm and 1558 nm are also realized, which can be flexibly switched between the two wavelengths just by merely manipulating the intra-cavity birefringence. The results attest that TDF SA combined with nonlinear polarization rotating technique can provide a simple and practical method for a switchable single/dual-wavelength all-fiber laser. The proposed all-fiber laser could be applied in terahertz communication, manufacturing, laser radar, and so on. • Dual-wavelength Q-switched pulse generation in Erbium-doped fiber laser (EDFL) cavity. • 18 cm-long Tm-doped fiber (TDF) as a passive saturable absorber (SA). • The SA has a saturation intensity of 180 MW/cm2 and a modulation depth of 2%. • A switchable single/dual-wavelength Q-switched fiber laser has been achieved at 1532.6 nm and 1557 nm. [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]

We successfully generated short pulse in an erbium-doped fiber laser (EDFL) cavity utilizing a new saturable absorber (SA) based on chromium gallium carbide (Cr 2 GaC). The SA film was prepared by implanting the Cr 2 GaC compound into a polyvinyl alcohol (PVA) matrix. Upon integration into the laser's cavity, we achieved a stable mode-locked laser centered at 1558.24 nm. This stability was maintained within a pump power range of 53.7–95.2 mW. Operating at a fixed repetition rate of 1.82, matching the cavity length, the laser consistently delivered pulses with a duration of 3.04 picoseconds. At its peak performance with a pump power of 95.2 mW, the laser exhibited an average power output of 6.81 mW, a peak power of 1.08 W, and a pulse envelope energy of 3.74 nJ. A noteworthy aspect of our study is the exceptional stability demonstrated by the laser. This stability is evidenced by a signal-to-noise ratio of 71.7 dB for the fundamental frequency. Importantly, this research represents a significant milestone as it marks the first instance of achieving soliton pulses in a laser cavity utilizing Cr 2 GaC as a SA. [ABSTRACT FROM AUTHOR]

Recent trend shows that one of the crucial problems faced while using radio frequency to track the objects is the inconsistency of the signal strength reception, which can be mainly due to the environmental factors and the blockage, which always have the most impact on the tracking accuracy. Besides, three dimensions are more relevant to a warehouse scanning. Therefore, this study proposes a highly accurate and new three-dimensional (3D) radio frequency identification-based indoor tracking system with the consideration of different attenuation factors and obstacles. The obtained results show that the proposed system yields high-quality performance with an average error as low as 0.27 m (without obstacles and attenuation effects). The obtained results also show that the proposed tracking technique can achieve relatively lower errors (0.4 and 0.36 m, respectively) even in the presence of the highest attenuation effect, e = 3.3 or when the environment is largely affected by 50% of the obstacles. Furthermore, the superiority of the proposed 3D tracking system has been proved by comparing with other existing approaches. The 3D tracking system proposed in this study can be applicable to a warehouse scanning. [ABSTRACT FROM AUTHOR]

The article discusses a proposed method developed to automatically detect optic disc (OD) and other bright lesions used in the computer assisted diagnosis of retinal diseases. Topics covered include details relating to the preprocessing, marker construction, and watershed algorithm stages of the proposed method, the advantages of using the proposed method, and the test results obtained in developing the proposed method.

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]

Proactive content caching in a fog radio access network (F-RAN) is an efficient technique used to alleviate delivery delay and traffic congestion. However, the symmetric caching of the content is impractical due to the dissimilarity among the contents popularity. Therefore, in this paper, a multi-objective random caching scheme to balance the successful transmission probability (STP) and delay in wireless backhauled F-RAN is proposed. First, stochastic geometry tools are utilized to derive expressions of the association probability, STP, and average delivery delay. Next, the complexity is reduced by considering the asymptotic STP and delay in the high signal-to-noise ratio (SNR) regime. Then, aiming at maximizing the STP or minimizing the delay, the multi-objective cache placement optimization problem is formulated. A novel projected multi-objective cuckoo search algorithm (PMOCSA) is proposed to obtain the Pareto front of the optimal cache placement. The numerical results show that PMOCSA outperforms the original multi-objective cuckoo search algorithm (MOCSA) in terms of convergence to a feasible Pareto front and its rate. It also shows that the proposed multi-objective caching scheme significantly outperforms the well-known benchmark caching schemes by up to 40 % higher STP and 85 % lower average delay. [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]

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 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]

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]

• Generation of soliton dark pulses using a Molybdenum Aluminium Boride (MoAlB) as saturable absorber (SA). • MoAlB was coated onto side-polished fiber to improve the birefringence and nonlinearity. • The dark pulses are generated based on cubic-quintic nonlinear Schrödinger equation mechanism. • The SA has a modulation depth of 6.5 %, a saturation intensity of 100 MW/cm2 and non-saturable loss of 50%. • The laser operated at 1560.6 nm with a pulse duration of 152 ns and repetition rate of 1.87 MHz. We demonstrate the generation of dark pulses from an Erbium-doped fiber laser (EDFL) using a Molybdenum Aluminium Boride (MoAlB) as a saturable absorber for the first time. Molybdenum Aluminium Boride (MoAlB) was coated onto side-polished fiber (SPF) to improve the birefringence and nonlinearity inside the EDFL cavity with net anomalous dispersion. The soliton dark pulses are obtained from the laser cavity based on cubic-quintic nonlinear Schrödinger equation (CQNLSE) mechanism. The laser operated at 1560.6 nm with a pulse duration of 152 ns and repetition rate of 1.87 MHz as the pump power is set within 200 mW to 370 mW. At the maximum pump power, the average output power and pulse energy are recorded at 6.93 mW and 3.77 nJ, respectively. We think that this research is the first to show MoAlB 's potential for dark pulse generation. [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]

Dual-wavelength neodymium-doped fiber laser at 1.08 μm based on bismuth-doped fiber in a ring cavity has been experimentally demonstrated. Using bismuth-doped fiber as a spectral filter introduces intensity-dependent gain to alleviate mode competition caused by homogeneous gain broadening in neodymium-doped fiber. A pure sinusoidal continuous wave with repetition rate of 9.1 MHz was generated at the output. At room temperature, the consistency in output intensity and the wavelength proves the steadiness of the proposed fiber laser. The system is simple, compact and in all-fiber configuration. • Dual-wavelength neodymium-doped fiber laser operating at 1.08 μm. • A bismuth-doped fiber is used as a spectral filter to induce intensity-dependent gain. • The laser produces repetition rate of 9.1 MHz. • The system is simple, compact and in all-fiber configuration. [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]

We successfully demonstrated a stable Q-switched erbium-doped fiber laser (EDFL) using Molybdenum Aluminum Boride (MoAIB), a metal ceramic-based material as saturable absorber (SA). The thin layer of MoAIB was obtained by mechanical exfoliation method and acquired onto the end surface of a standard FC/PC fiber connector to function as SA. The features of MoAIB-SA are experimentally evaluated in two output coupling ratios, which are 50:50 and 95:5. From the experimental results, MoAIB-SA is well-functioning as SA to modulate the CW lasing into Q-switching operation. The 95:5 coupler setup presented better pulse quality, in term of pulse repetition rate and pulse width. Additionally, 50:50 coupler setup allows higher pump power and pulse energy to extract from the fiber laser system. [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]

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]

A stable passive Q‐switched thulium‐doped fibre laser (TDFL) operating at the 1900 nm region is demonstrated by using a multi‐layer graphene film‐based saturable absorber (SA). The graphene is synthesised by electrochemical exfoliation of graphite at room temperature in 1% sodium dodecyl sulphate aqueous solution. Graphene flakes obtained from the process are mixed with polyethylene oxide as the host polymer to produce free standing composite thin film which acts as a passive Q‐switcher in the TDFL ring cavity. At 793 nm pump power of 186 mW, the TDFL generates an optical pulse train with a repetition rate of 7.5 kHz, pulse width of 19.7 μs and a pulse energy of 66.6 nJ. A higher performance Q‐switched TDFL could be achieved with the optimisation of the graphene SA and the laser cavity. [ABSTRACT FROM AUTHOR]

• WGMs based humidity sensor by integrating microsphere resonator on the ZnO nanorods coated glass surface. • Solve issues pertaining to complicated handling of microfiber during the coating process. • ZnO nanorods growth using hydrothermal method and microfiber fabrication using flame brushing technique. • Superiority in term of ultra-high Q factor of microsphere which enhanced interactions between the light and the external environment. A humidity sensor is proposed by integrating a microsphere resonator onto ZnO nanorods coated glass surface. The glass substrate was coated with ZnO nanorods for 12 h using the hydrothermal method and the microsphere was set at a diameter of 234 µm. The proposed sensor produced sensitivity of 0.0748 dBm/%RH and 0.0142 nm/%RH when exposed to humidity level ranging from 35 %RH to 85 %RH. Standard deviation and resolution of the proposed sensor improve by a factor of 1.7 and 2.4 respectively as compared to the straight microfiber laid on the ZnO nanorods coated glass. It utilized the ultra-high Q factor of microsphere and the changeable refractive index of the ZnO nanorods coated glass. Combination of these elements enhanced the interaction between the whispering gallery mode evanescent components with surrounds analyte. It also solves the issues pertaining to the complicated handling of microfibers during the coating process. The proposed sensor has shown exceptional experiment results for humidity sensing applications. [ABSTRACT FROM AUTHOR]

• Humidity sensor based on microfiber laid on a ZnO nanorods coated glass surface. • Employs the evanescent wave coupling between the microfiber and the ZnO nanorods coated glass. • ZnO nanorods growth using hydrothermal method and microfiber fabrication using flame brushing technique. • Reduced the hassle to access the interaction of the ZnO coating layer and the evanescent wave. In this paper, a proposed humidity sensor is fabricated by integrating the microfiber and the glass surface coated with Zinc Oxide (ZnO) nanorods. The silica fiber diameter was reduced to 6 μm using the flame brushing technique, and the glass surface was coated with ZnO nanorods using a hydrothermal method. A significant response to humidity level concentration ranging from 35 %RH to 85 %RH has been observed. The proposed sensor's output power has decreased linearly from -16.32 dB m to -18.68 dB m with a linearity of 95.87 %. The sensitivity and the resolution of the ZnO coated glass improved by a factor of 2.8 and 7.5, respectively, as compared to the uncoated glass substrate. The proposed humidity sensor successfully employs the interaction between the ZnO nanorods surface and the microfiber's evanescent field from the microfiber, which reduce the striving effort in handling the microfiber during the synthesis process. The proposed sensor has shown an excellent sensing performance as a humidity sensor based on the experimental results. [ABSTRACT FROM AUTHOR]

The application of super-hydrophobic nanomaterials for synthesizing membranes with unique physiochemical properties has gained a lot of interest among researchers. The presence of super-hydrophobic materials inside the membrane matrix can play a vital role not only in the separation of toxins, but also to achieve higher water flux with lower fouling tendencies required for an efficient membrane distillation process. In this research, super-hydrophobic carbon nanomaterials (CNMs) were synthesized using powder activated carbon (PAC) as a precursor, whereby the growth was initiated using a bimetallic catalyst of iron (Fe) and molybdenum (Mo). Until recently, no research has been conducted for synthesis and to observe the catalytic influence of bimetallic catalysts on the physiochemical characteristics of the derived CNMs. The synthesis process was carried out using the chemical vapor deposition (CVD) process. The CVD process was optimized using Box–Behnken factorial design (BBD), whereby 15 experiments were carried out under different conditions. Three input variables, which were percentage composition of catalysts (percentage of Fe and Mo) and reaction time (tr), were optimized with respect to their impact on the desired percentage output of yield (CY) and contact angle (CA). Analysis of variance (ANOVA) testing was carried out. It was observed that the developed model was statistically significant. The highest CY (320%) and CA (172°) were obtained at the optimal loading of 5% Fe and 2% Mo, with a reaction time of 40 min. Surface morphological features were observed using field emission scanning electron microscopic (FESEM) and transmission electron microscopic (TEM) analysis. The images obtained from FESEM and TEM revealed the presence of two types of CNMs, including carbon nanofibers (CNFs) and multiwall carbon nanotubes (CNTs). Thermogravimetric analysis was carried out to observe the temperature degradation profile of the synthesized sample. Raman spectroscopic analysis was also used in order to have a better understanding regarding the proportion of ordered and disordered carbon content inside the synthesized sample. [ABSTRACT FROM AUTHOR]

This paper describes a smart ray-tracing method based on the ray concept. From the literature review, we observed that there is still a research gap on conventional ray-tracing methods that is worthy of further investigation. The herein proposed smart 3D ray-tracing method offers an efficient and fast way to predict indoor radio propagation for supporting future generation networks. The simulation data was verified by measurements. This method is advantageous for developing new ray-tracing algorithms and simulators to improve propagation prediction accuracy and computational speed. [ABSTRACT FROM AUTHOR]

The Millimeter-Wave (mmW) technology is going to mitigate the global higher bandwidth carriers. It will dominate the future network system by the attractive advantages of the higher frequency band. Higher frequency offers a wider bandwidth spectrum. Therefore, its utilizations are rapidly increasing in the wireless communication system. In this paper, an indoor mmW propagation prediction is presented at 38 GHz based on measurements and the proposed Three-Dimensional (3-D) Ray Tracing (RT) simulation. Moreover, an additional simulation performed using 3-D Shooting Bouncing Ray (SBR) method is presented. Simulation using existing SBR and the proposed RT methods have been performed separately on a specific layout where the measurement campaign is conducted. The RT methods simulations results have been verified by comparing with actual measurement data. There is a significant agreement between the simulation and measurement with respect to path loss and received signal strength indication. The analysis result shows that the proposed RT method output has better agreement with measurement output when compared to the SBR method. According to the result of the propagation prediction analysis, it can be stated that the proposed method's ray tracing is capable of predicting the mmW propagation based on a raw sketch of the real environment. [ABSTRACT FROM AUTHOR]