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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.

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.

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.

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.

With the rapid development of future wireless networks, device-to-device (D2D) technology is widely used as the communication system in the Internet of Things (IoT) fifth generation (5G) network. The IoT 5G network based on D2D communication technology provides pervasive intelligent applications. However, to realize this reliable technology, several issues need to be critically addressed. Firstly, the device’s energy is constrained during its vital operations due to limited battery power; thereby, the connectivity will suffer from link failures when the device’s energy is exhausted. Similarly, the device’s mobility alters the network topology in an arbitrary manner, which affects the stability of established routes. Meanwhile, traffic congestion occurs in the network due to the backlog packet in the queue of devices. This paper presents a Mobility, Battery, and Queue length Multipath-Aware (MBMQA) routing scheme for the IoT 5G network based on D2D communication to cope with these key challenges. The back-pressure algorithm strategy is employed to divert packet flow and illuminate the device selection’s estimated value. Furthermore, a Multiple-Attributes Route Selection (MARS) metric is applied for the optimal route selection with load balancing in the D2D-based IoT 5G network. Overall, the obtained simulation results demonstrate that the proposed MBMQA routing scheme significantly improves the network performance and quality of service (QoS) as compared with the other existing routing schemes.

Fog Radio Access Network (F-RAN) is a promising technology to address the bandwidth bottlenecks and network latency problems, by providing cloud-like services to the end nodes (ENs) at the edge of the network. The network latency can further be decreased by minimizing the transmission delay, which can be achieved by optimizing the number of Fog Nodes (FNs). In this context, we propose a stochastic geometry model to optimize the number of FNs in a finite F-RAN by exploiting the multi-slope path loss model (MS-PLM), which can more precisely characterize the path loss dependency on the propagation environment. The proposed approach shows that the optimum probability of being a FN is determined by the real root of a polynomial equation of a degree determined by the far-field path loss exponent (PLE) of the MS-PLM. The results analyze the impact of the path loss parameters and the number of deployed nodes on the optimum number of FNs. The results show that the optimum number of FNs is less than 7% of the total number of deployed nodes for all the considered scenarios. It also shows that optimizing the number of FNs achieves a significant reduction in the average transmission delay over the unoptimized scenarios.

The millimeter wave (mmWave) frequency spectrum is being considered as the most promising communication systems to fulfill the bandwidth requirements for the next-generation wireless network. However, the mmWave frequency band has encountered several issues like fading, scattering, atmospheric absorption, and penetration losses as compared to the currently using frequency spectrum, which is under 6 GHz. Therefore, optimizing the propagation channel path at the mmWave band is seemed to be the only solution, which can help the operators to distinguish the signal behavior before practically implement the 5G networks. In this regard, this study aims to analyze the propagation characteristics for 26 GHz frequency band for the outdoor Single Side Parking (SSP) and Double Side Parking (DSP) environment. It utilizes the most potential propagation path loss models i.e., Close-In (CI) and Floating Intercept (FI). The results prove that the CI model can produce better results and delivers higher network performance as compared to the FI model.

The drastic increase in the number of wireless devices and bandwidth requirements, most networks have evolved to distributed networks rather than central client-server configuration. In order to cater a larger number of devices, that is not centrally controlled, a routing scheme is needed that can work with limited configured devices, supports fully dynamic and distributed configurations, and does not overwhelm the network with control messages for the destination that exists in the network but has no message to send. Similarly, this work is focusing on performance analysis of Ad hoc on-demand Distance Vector (AODV) routing protocol to create a mobile ad hoc network (MANET) environment. The simulation has been designed for the real environment of NED University of Engineering and Technology, Karachi, Pakistan, where several buildings of various departments need to communicate with each other without compromising the node's performance with the change in the network occur. The simulation results show that the AODV provides better network performance with fewer packet drops and consistent throughput through the network for varying speeds and locations. The results proved that as compared to Destination-Sequenced Distance Vector (DSDV), the end-to-end delay had shown not much improvement, but comparative delays are observed.

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&ndash, 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&deg, ) 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.

The fully accomplished standardization of the new mobile generation has led to the deployment of fifth-generation (5G) wireless networks to gratify enormous traffic volume for Internet services. The current centralized mobility system could not be sufficient to manage an explosive increase in data volume and is considered a steadily rising issue in modern wireless communication. A new technique that can affluently handle traffic problems and completely avoid network breakdown chances is indispensable. Recently, distributed mobility management (DMM) was introduced to overcome the inevitable obstacles that destructively impact the existing networks. Specifically, a novel design based on the deployment of distributed mobility anchors, closer to the terminal points, was introduced. Several works have been proposed to build DMM solutions with different focuses for 5G-and-beyond networks (B5G), which are also referred to as sixth-generation solutions (6G). In this paper, we present the potential and benefits of flat network design for efficient and fast routing of traffic and furnish the effectiveness of the scheme toward mobility management in B5G by delineating recent research works. We also present the current limitations, challenges, and future research directions for seamless mobility to achieve the desired objectives in the current 5G and upcoming 6G cellular communications.

The surge in global population is compelling a shift toward smart agriculture practices. This coupled with the diminishing natural resources, limited availability of arable land, increase in unpredictable weather conditions makes food security a major concern for most countries. As a result, the use of Internet of Things (IoT) and data analytics (DA) are employed to enhance the operational efficiency and productivity in the agriculture sector. There is a paradigm shift from use of wireless sensor network (WSN) as a major driver of smart agriculture to the use of IoT and DA. The IoT integrates several existing technologies, such as WSN, radio frequency identification, cloud computing, middleware systems, and end-user applications. In this paper, several benefits and challenges of IoT have been identified. We present the IoT ecosystem and how the combination of IoT and DA is enabling smart agriculture. Furthermore, we provide future trends and opportunities which are categorized into technological innovations, application scenarios, business, and marketability.

Fog computing is considered a promising technology to reduce latency and network congestion. Meanwhile, Millimeter-wave (mmWave) communication owing to its potential for multi-gigabit of wireless channel capacity could be employed to further improve the performance of fog computing networks. In this context, we study the feasibility of using 28 GHz and 38 GHz mmWaves in fog radio access networks (F-RANs). The multi-slope path loss model is used to calculate the interference impacts because it provides a more accurate approximation of the wireless links. Simulations are carried out for uplink scenario considering the following fog node (FN) deployment models: Poisson point process (PPP), Ginibre point process (GPP), square grid, and ultra-dense network (UDN). The results depict that at low FN densities the massive accumulation of interference components severely impacts the performance. However, the performance can be improved by increasing the FN density and choosing a deployment strategy with high degree of regularity. Based on the results, we verify that it is feasible to use 28 GHz and 38 GHz mmWaves in F-RANs when the density of the interfering users is less than 150 user/km 2 where capacities higher than 1 Gbps are achieved for all considered scenarios.

The fog radio access network (F-RAN) is considered an efficient architecture for caching technology as it can support both edge and centralized caching due to the backhauling of the fog access points (F-APs). Successful transmission probability (STP), delay, and energy efficiency (EE) are key performance metrics for F-RAN. Therefore, this paper proposes a proactive cache placement scheme that jointly optimizes STP, delay, and EE in wireless backhauled cache-enabled F-RAN. First, expressions of the association probability, STP, average delay, and EE are derived using stochastic geometry tools. Then, the optimization problem is formulated to obtain the optimal cache placement that maximizes the weighted sum of STP, EE, and negative delay. To solve the optimization problem, this paper proposes the normalized cuckoo search algorithm (NCSA), which is a novel modified version of the cuckoo search algorithm (CSA). In NCSA, after generating the solutions randomly via Lévy flight and random walk, a simple bound is applied, and then the solutions are normalized to assure their feasibility. The numerical results show that the proposed joint cache placement scheme can effectively achieve significant performance improvement by up to 15% higher STP, 45% lower delay, and 350% higher EE over the well-known benchmark caching schemes.

With an extensive growth in user demand for high throughput, large capacity, and low latency, the ongoing deployment of Fifth-Generation (5G) systems is continuously exposing the inherent limitations of the system, as compared with its original premises. Such limitations are encouraging researchers worldwide to focus on next-generation 6G wireless systems, which are expected to address the constraints. To meet the above demands, future radio network architecture should be effectively designed to utilize its maximum radio spectrum capacity. It must simultaneously utilize various new techniques and technologies, such as Carrier Aggregation (CA), Cognitive Radio (CR), and small cell-based Heterogeneous Networks (HetNet), high-spectrum access (mmWave), and Massive Multiple-Input-Multiple-Output (M-MIMO), to achieve the desired results. However, the concurrent operations of these techniques in current 5G cellular networks create several spectrum management issues; thus, a comprehensive overview of these emerging technologies is presented in detail in this study. Then, the problems involved in the concurrent operations of various technologies for the spectrum management of the current 5G network are highlighted. The study aims to provide a detailed review of cooperative communication among all the techniques and potential problems associated with the spectrum management that has been addressed with the possible solutions proposed by the latest researches. Future research challenges are also discussed to highlight the necessary steps that can help achieve the desired objectives for designing 6G wireless networks.

Supplemental material, Appendix__I for Interference cancelation for high-density fifth-generation relaying network using stochastic geometrical approach by MHD Nour Hindia, Faizan Qamar, Talib Abbas, Kaharudin Dimyati, Mohamad Sofian Abu Talip and Iraj Sadegh Amiri in International Journal of Distributed Sensor Networks

It has been widely speculated that the performance of the next generation based wireless network should meet a transmission speed on the order of 1000 times more than the current cellular communication systems. The frequency bands above 6 GHz have received significant attention lately as a prospective band for next generation 5G systems. The propagation characteristics for 5G networks need to be fully understood for the 5G system design. This paper presents the channel propagation characteristics for a 5G system in line of sight (LOS) and non-LOS (NLOS) scenarios. The diffraction loss (DL) and frequency drop (FD) are investigated based on collected measurement data. Indoor measurement results obtained using a high-resolution channel sounder equipped with directional horn antennas at 3.5 GHz and 28 GHz as a comparative study of the two bands below and above 6 GHz. The parameters for path loss using different path loss models of single and multi-frequencies have been estimated. The excess delay, root mean square (RMS) delay spread and the power delay profile of received paths are analyzed. The results of the path loss models show that the path loss exponent (PLE) in this indoor environment is less than the free space path loss exponent for LOS scenario at both frequencies. Moreover, the PLE is not frequency dependent. The 3GPP path loss models for single and multi-frequency in LOS scenarios have good performance in terms of PLE that is as reliable as the physically-based models. Based on the proposed models, the diffraction loss at 28 GHz is approximately twice the diffraction loss at 3.5 GHz. The findings of the power delay profile and RMS delay spread indicate that these parameters are comparable for frequency bands below and above 6 GHz.

High Quality of Service is one of the most highlighted expectations of the next generation. Providing users with full coverage and variant demands, even during their movement between adjacent cells, is considered challenging tasks in 5G. The high-speed mobility, one of the transportation’s trends in the future, relocates this challenge to a different level. This work suggests a mechanism of sequential steps to strengthen the handover process. Considering two threshold levels rather than the traditional solo one is used to distinguish between the phase of the triggering the handover process and making the handover decision. Taking advantage of Doppler frequency is also used to minimize the target cells list. Finally, a function combined of different weighted measures taken from the target list to make the vertical handover decision. Adopting more metrics, in addition to the conventional received signal strength, reduces the number of handover trials between the cells and overcomes the ping-pong phenomenon. Cooperation between neighbor cells is required to re-allocate the resources in a manner that ensures the fairness between the users and also to successfully perform a necessary handover. Thus, the short target cells’ list degrades the complexity, the required processing time and the total consumed power by the overall system.

In a high-density wireless communication network, the amount of received signal is degraded due to various scattering and path loss issues. Among the several mitigation techniques, Cooperative Relay (CR) network provide a significant solution which provides a decent cost-effective solution, better spectral efficiency and also enhances the cell coverage size. However, this technique leads to many undesired power consumption issues when it operates in Amplify and Forward (AF) mode, due to extensive use of more relay nodes (RNs) in a network. In a cooperative relaying network, most of the recent researches mainly focus on reducing the power utilization, enhancing diversity gain and minimizing the symbol error rate (SER). In this paper, we proposed a power allocation (PA) scheme which controls channel overheads with the exchange of partial channel State information (CSI) by using particle swarm optimization (PSO) technique. The proposed technique estimates the fitness function of PSO and allocates power to RNs with the help of global best value of the PSO. The results have been evaluated in terms of SER and power consumption for different signal to noise ratio (SNR) and various numbers of RNs. The results prove that the proposed PSO technique gives significantly lower SER and less power utilization as compared to the conventional equal PA technique.

The use of the Millimeter Wave (mm-wave) frequency band brings various scattering, fading, atmospheric absorption and penetration losses issues. These issues can be mitigated easily if we can predict the behavior of the propagation channel, in a particular environment. In this regard, this paper studies the propagation characteristics of 38 GHz mm-wave band for semi-open corridor real environment for both Line of Sight (LOS) and Non-Line of Sight (NLOS) scenarios. The measurements have been conducted by using highly directional horn antenna at the transmitter and receiver side in University Technology Malaysia, Kuala Lumpur campus. It gives a comparison results, based on real measurement data for Close-In (CI) free space path loss and Floating-Intercept (FI) path loss models that are considered as the most potential and very common propagation model in order to characterize the large-scale fading propagation environment for 5G network. The results show that the CI is more appropriate for the semi-open corridor environment owing to its simplicity and accuracy.

5G systems aim to greatly enhance the data rate as one of its promising features compared to currently available technologies. The high data rate is achieved by the utilization of frequencies above 6 GHz, which provides enough bandwidth for each individual user to support faster transfer rates as compared to currently used Long Term Evolution-Advance (LTE-A). Performance of the wireless systems can be improved by optimizing the channel propagation parameters. In this paper, the potential ability of propagation channel for the large-scale outdoor urban environment is presented by utilizing Multiple Input Multiple Output (MIMO) in the frequency band of 15 GHz. Okumura Hata model is used in rural areas, while microcell path propagation model is used in urban areas as the path loss models. Results have been recorded from multiple simulations concerning the capacity of users to evaluate the cell-edge user throughput, average user throughput, average cell throughput, spectral efficiency and fairness index for different MIMO antenna array. Results are then analyzed and compared to predict the channel behavior for urban, suburban and rural areas. The paper paved the path for 15 GHz to be set as a viable option when considering future 5G networks due to its ability to provide ample amount of throughput due to the diversity of multiple antennas for transmission.

With the ever evolving mobile communication technology, achieving a high quality seamless mobility access across mobile networks is the present challenge to research and development engineers. Existing algorithms are used to make handover while a mobile station is roaming between cells. Such algorithms have some handover instability due to method of making handover decision. This paper proposes an enhanced handover algorithm that substantially reduces the handover redundancy in vertical and horizontal handovers. Also, it enables users to select the most appropriate target network technology based on their preferences even in the worst case where the mobile station roams between cell boundaries, and has high ability to have efficient performance in the critical area full of interferences. The proposed algorithm uses additional quality of service criteria, such as cost, delay, available bandwidth and network condition with two handover thresholds to achieve a better seamless handover process. After developing and testing this algorithm, the simulation results show a major reduction in the redundant handover, so high accuracy of horizontal and vertical handovers obtained. Moreover, the signal strength is kept at a level higher than the threshold during the whole simulation period, while maintaining low delay and connection cost compared to other two algorithms in both scenarios.

The advent of fifth-generation (5G) systems and their mechanics have introduced an unconventional frequency spectrum of high bandwidth with most falling under the millimeter wave (mmWave) spectrum. The benefit of adopting these bands of the frequency spectrum is two-fold. First, most of these bands appear to be unutilized and they are free, thus suggesting the absence of interference from other technologies. Second, the availability of a larger bandwidth offers higher data rates for all users, as there are higher numbers of users who are connected in a small geographical area, which is also stated as the Internet of Things (IoT). Nevertheless, high-frequency band poses several challenges in terms of coverage area limitations, signal attenuation, path and penetration losses, as well as scattering. Additionally, mmWave signal bands are susceptible to blockage from buildings and other structures, particularly in higher-density urban areas. Identifying the channel performance at a given frequency is indeed necessary to optimize communication efficiency between the transmitter and receiver. Therefore, this paper investigated the potential ability of mmWave path loss models, such as floating intercept (FI) and close-in (CI), based on real measurements gathered from urban microcell outdoor environments at 38 GHz conducted at the Universiti Teknologi Malaysia (UTM), Kuala Lumpur campus. The measurement data were obtained by using a narrow band mmWave channel sounder equipped with a steerable direction horn antenna. It investigated the potential of the network for outdoor scenarios of line-of-sight (LOS) and non-line-of-sight (NLOS) with both schemes of co- (vertical-vertical) and cross (vertical-horizontal) polarization. The parameters were selected to reflect the performance and the variances with other schemes, such as average users cell throughput, throughput of users that are at cell-edges, fairness index, and spectral efficiency. The outcomes were examined for various antenna configurations as well as at different channel bandwidths to prove the enhancement of overall network performance. This work showed that the CI path loss model predicted greater network performance for the LOS condition, and also estimated significant outcomes for the NLOS environment. The outputs proved that the FI path loss model, particularly for V-V antenna polarization, gave system simulation results that were unsuitable for the NLOS scenario.

The past couple of years have seen an explosion in mobile data traffic as a result of the growth of mobile devices such as smartphones, tablets, and those that are capable of monitoring, record, provide, and transfer Zetta Bytes of data on a yearly basis. As a solution, researchers focus toward the frequency band above 6 GHz bands to propose a new band that can offer larger bandwidth. However, to choose the optimum operation frequency for 5G network needs several channel investigations in terms of large scale and small scale model. In this paper, the power decay is investigated based on path loss and the dispersion of 5G wideband channel. The path loss and time dispersion are estimated for 5G channel at 19 GHz frequency for a line of sight (LOS) and non-line of sight (NLOS) environment. An extensive measurement is conducted using wideband channel sounder within 1 GHz bandwidth. Two different types of antennas are used for collect the received signal directional and omnidirectional antenna. The results reveal that the path loss exponent values in the range of 0.2 to 2.1 depend on the antenna configuration and environment scenarios. For time dispersion analysis, it is found that the omnidirectional antenna is more suitable for RMS delay spread than using the horn antenna at the receiver side.

In the last few years, several works have investigated the performance of cooperative wireless systems with various types of channel codes such as Low Density Parity Check (LDPC), Turbo, CRC, convolutional and recently Reed Solomon (RS) codes. These cooperative schemes give power to single antenna mobiles to originate virtual multiple antennas transmitter, MIMO system, by sharing their antennas so that diversity gain is achieved. The most common cooperative schemes are decode and forward (DF) and coded cooperation (CC). Concatenated Reed Solomon and convolutional codes have been used by several wireless communication standards like digital video broadcasting (DVB) standards and IEEE 802.16e WiMAX standard. In this paper, we develop two different coded cooperation schemes and apply them to the mandatory structure of physical layer specifications of IEEE 802.16e WiMAX. The results attained for both coded cooperation schemes present magnificent diversity gains over non-cooperative scheme.

The importance of small cells deployments in cellular systems are becoming more apparent days after days since the benefits in terms of number of users that can be supported, the offered bandwidth and power consumption are obviously enormous as the wireless networks continue to get more congested. In this paper, a number of well-known scheduling schemes namely, Round Robin (RR), Proportional Fairness (PF), Best-channel Quality Identification (Best-CQI) and Maximum Throughput (Max-TP) are studies and compared and their impact on macro-femto-cells over the LTE-A network is investigated. It is noteworthy that, this paper should be considered as an optimum solution for the cell congestion in LTE-A.

The congestion at the frequency band below 6 GHz and the enormous amount of available raw bandwidth above 6 GHz, directed researchers to utilize millimeter-wave spectrum as an option to increase mobile broadband capacity. Thus the needs to investigate the ultra-wide band frequency for different scenarios are become a critical issue nowadays. In this paper, an investigation of the car reflection case study for a different number of the parking lot rows at 26 GHz frequency band is proposed. The measurement campaigns were conducted at the University Technology Malaysia (UTM), Kuala Lumper, Malaysia and used the directional horn and omni antennas for transmitter and receiver side, respectively. The close in free space (CI) and floating intercept (FI) path loss models are investigated at 26 GHz frequency band. Then the new path gain factor is proposed to display the power degrading with respect to the number of car rows. The results show that CI model is more suitable compared to FI model at the particular scenario.

A new optical orthogonal frequency division multiplexing technique with spectrum amplitude coding optical code division access (SAC-OCDMA) system is developed to enhance the channel data rate, reduce power, and increase the number of SAC-OCDMA system users. The average received signal-to-noise ratio with inter-modulation distortion of subcarriers is derived. Theoretical results are evaluated based on bit error rate, number of users, data rate, and amount of power saved. The proposed system is then compared with the traditional hybrid sub-carrier multiplexing (SCM)/SAC OCDM. The results show that the proposed system reduces approximately −8 dBm of power and doubles the number of users at a higher data rate than the SCM/SAC-OCDMA system. Proof-of-principle simulations of the proposed system are successfully implemented. Overall, the proposed system performed better than the SCM/SAC-OCDMA system. The system is designed based on modified double weight code, which provides better performance than Hadamard and modified frequency-hopping codes.