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With the point in evaluating the performance of the On-the-Move (OTM) Satellite Communication and Light Fidelity (SatCom-LiFi), an extensive study of measurement has been conducted to give a wide vision of the SatCom-LiFi potential under a tropical region. As the interest for OTM network connectivity to offload the C-band capacity arises due to frequency spectrum scarcity, satellite networks offer to balance topographical requirements under tropical environment as the Next Generation Networks (NGN) trend for OTM communication system solutions. To date, mobile satellite terminal propagation model was carried out at temperate regions where further experimental measurement is needed under the OTM scenario in tropical region. This paper discusses on the areas where there are limited real-time data under the OTM scenario (e.g. rain attenuation, power arch) at Ka-band frequency. Integration infers, to be specific, the use of new elements capable in providing performance analysis of all systems involved and to take possible decision, in determining the need for a technically feasible solution. Measurement results reveal that, throughput data rate of 15 Mbps were able to be delivered for more than 80% of the time under the speed of 150 km/h with shielded mesh antenna. In addition to that, this paper reveals the favorable circumstances and inadequacies of OTM network quality, in which the measurement presented plays an important role for future researchers in distinguishing highly accurate predictions.

This paper studies a new amplify-and-forward cooperative overlay cognitive radio (CR) non-orthogonal multiple access (AFCO-NOMA) system, where a primary network shares its license spectrum with a secondary network by using NOMA principles. An approximate closed-form expression for the outage probability of the proposed system is analyzed. Asymptotic expressions for the outage probability in high signal-to-noise ratio (SNR) regime of both secondary and primary destinations are derived assuming channel estimation error (CEE) and imperfect successive interference cancellation (SIC). Further, the optimal power allocation coefficients to maximize the system throughput for different target rates are determined to ensure priority to the primary user. The diversity order at the primary and secondary destinations are also derived. Moreover, the AFCO-NOMA system is compared with the OMA-based cooperative overlay system in terms of outage probability. The paper also studies the impact of various parameters such as power allocation coefficients, CEE, and detection threshold, on the outage performance of the proposed system. Monte Carlo simulations are used to confirm the correctness of the derived analytical results.

In this paper, we are proposing and validating “mobTHE” protocol that is designed to fill the gap in handling seamless mobile communication for on-body nodes. Therefore, “mobTHE” protocol tackles the dis-connectivity problem resulted from the sensor nodes' mobility while keeping an eye on the network's sustainability in terms of maximum packet throughput, prolonged node lifetime, and low temperature. To provide such a balanced trade-off, we utilize two Coordinator Nodes (CNs), namely, CN1 and CN2. Both of these CNs are working as Serving CN (SCN) to its closest nodes and as Neighbour CN (NCN) to the sensor nodes located far from these CNs, which enable collecting data from different sensor nodes continuously. The challenge here is the synchronization between the two CNs in such a way to optimize network resources via minimizing packet transmission duplication and packet drop rate, which is the main contribution of this paper. We present a novel Handover (HO) mechanism during the sensor node mobility and changing between the two CNs. That HO mechanism is capable of minimizing the redundancy of packets and leading to minimization in the packet drop rate. Considering the worst-case scenario where the sensor node is out of the two CNs range, we exploit two-hops data transmission. Parent Node (PN) is selected “on demand” to carry only the data of the moving node which moves away from both CNs rather than carrying the data of all sensor nodes which conserves the energy of the PN nodes as well as the moving node. The simulation analysis depicted that “mobTHE” protocol outperforms the conventional “THE” and “iM-SIMPLE” protocols in terms of temperature control, WBAN lifetime, throughput, and overall residual energy.

As the manufacturing industry gradually expands and tends to be intelligent, the industrial networks have been greatly applied and are of paramount importance. Furthermore, taking the advantages of wireless networks into account, such as flexible deployment, low cost, and easy maintenance, etc., this paper is dedicated to the research of industrial wireless networks. Facing the problem of limited radio resource, in order to make full use of frequency band, this paper proposes a resource scheduling scheme with puncturing, which guarantees the reliability of subsequent ultra-reliable and low-latency communications (URLLC) services under the conditions of existing enhanced mobile broadband (eMBB) services. By optimizing the bandwidth pre-allocation for eMBB services, puncture weight and transmit power, this scheme can effectively meet the needs of the system. Specifically, the purpose of this paper is to minimize the decoding error rate of the devices carrying URLLC service while ensuring the demand for throughput of eMBB services. The problem proposed is a nonlinear stochastic optimization problem involving complex Q-function. The closed-form expression of the objective function is obtained through linear approximation and probability theory, which is further decoupled into three sub-problems. To this end, a block coordinate descent optimization (BCDO) algorithm is proposed to obtain the optimal bandwidth allocation, puncture weight and transmit power. The simulation results verify the rationality of the theoretical analysis and the effectiveness of the proposed algorithm, and also elaborate the influence of different parameters on the decoding error rate of the URLLC devices.

To improve the utilization of spectrum and system capacity, non-orthogonal multiple access (NOMA) is considered as a promising multiple access method for emerging communication technologies. Its advantageous benefits are implemented in two-way wireless networks. Power allocation factors assigned to multiple users play a key role in the successful deployment of fairness balance in NOMA. This paper considers fixed power allocation, and performance degradation is predicted in worse situation in which non-optimal power scheme and the imperfect channel state information (CSI) happen. More challenging issue happens in this system, and this paper addresses the situation of NOMA supporting multi-pair of users, in which group of users can communicate to other users to achieve acceptable throughout in two kinds of mode, i.e. delay-limited mode and delay-tolerant mode. Two performance metrics have been considered, namely, ergodic rate and outage probability. For both metrics, we derived closed-form analytical expressions as well as asymptotic performance. Numerical results show that the proposed system presents benefits to cellular networks by extending ability to serve more users who have different demands on data communication. Monte Carlo simulations are provided throughout to validate the accuracy of the derived analytical expressions.

Diversified interest in the low-cost broadband satellite has overgrown to support a wide range of services in the satellite network. There is a need to explore alternative parts of optical communication towards Light Fidelity (LiFi) to offload the overcrowded radio frequency segments and improve the overall throughput. Ad hoc networks are the most suitable solution to provide a non-trivial challenge towards system design due to efficiency and quality of service (QoS). Both contention and congestion issues can severely affect the performance of a multicast network where video streaming becomes part of the day-to-day life. In this paper, we present network congestion characterization related to LiFi and High Throughput Satellite (HTS) under the Ka-band modulation schemes during adverse weather conditions in the tropical region. The heterogeneous network performance presented in this paper comprehensively provides systematic information for Satellite communication (SatCom) & LiFi and optimization of throughput by reducing network contention ratio. The measurement results have shown that when Deep Packet Inspection (DPI) policy is applied, an improvement of 80.26% in the packet delivery ratio is achieved as compared when without a DPI policy. However, using an on-premise Software-defined-wide access network (SD-WAN) alone provides 58.20% improvement in the overall network system. As a result, DPI provides a well managed QoS approach to manage the entire hybrid network, mainly in the tropical environment region.

Millimeter-wave (mmW) communication has great potential in expanding channel capacity, increasing transmission rates, enhancing anti-interference capabilities, and reducing delay. Therefore, it has been the subject of much attention and research, and it has been adopted as a core technology of 5G. So far, researchers have experimentally verified that high throughput can be achieved with 5G mmWs. However, compared to those of traditional medium- and low-frequency base stations, the propagation characteristics of mmWs have caused link instability and interference problems in large-scale networks, which brings new challenges to the industrial capability of the mmW band and puts forward new requirements for the performance evaluation of mmW base stations. In this paper, based on the signal characteristics of the mmW band and applicable scenarios of mmW base stations, a performance evaluation method for mmW base stations in commercial networks is comprehensively presented. Using the evaluation system described in this paper, we conduct measurements on commercial mmW base stations, evaluate the performance of these stations, and provide comprehensive guidance for their design and actual deployment.

International audience; Vehicular ad-hoc networks (VANETs) are promising research areas which mainly include three communication modes: vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I) and hybrid vehicle communication (HVC). But most of the current research on HVC mode in which vehicle nodes and infrastructures coexist only focuses on the analysis of the optimal single-type relay selection schemes. Inspired by this, in order to design an optimal multi-relay selection scheme which can select different types of relays simultaneously, and to compare it with single-type schemes, this paper firstly introduces a more practical network scenario by proposing a four-node system model which considers communication links between relays and building different channel models for different types of links. Four optimal relay selection protocols, which are named as Non-OR, SOR-AP, SOR-V and DOR-APV respectively, are then designed from the perspective of the different types and numbers of selected relays. The exact expressions of outage probability for each protocol are calculated based on the automatic repeat request (ARQ) protocol to evaluate the link interruption of the four protocols. Furthermore, this paper establishes a generalized 2-dimensional discrete time Markov chain (DTMC) model and analyzes the one-step state transition probability for each protocol. The closed-form expressions of system throughput and energy efficiency are derived by calculating the steady state distribution of the DTMC. Finally, the simulation results summarize the suitable network scenarios for which the four proposed protocols are recommended by comparing their system performance, so as to provide some suggestions for the future design and optimization of vehicle mobile networks.

Having the ability to provide seamless coverage and alleviate the frequency scarcity, the cognitive satellite terrestrial network becomes a promising candidate for future communication networks. In the cognitive network, spectrum sensing plays an important role in detecting the channel state for opportunistic utilization, where cooperative spectrum sensing is employed to improve the sensing performance. Additionally, it is critical for battery-powered satellite mobile terminals to diminish energy consumption costs. In this regard, this paper proposes a novel sensing-based cognitive satellite terrestrial network (SCSTN), which integrates the cognitive satellite terrestrial network with the distributed cooperative spectrum sensing network. Specifically, we focus on energy-efficient cooperative sensing in the SCSTN, which maximizes the energy efficiency (EE) of the cognitive satellite network by a tradeoff between the average throughput and the average energy consumption. In the SCSTN, the energy detection threshold of the sensing node and the rule threshold of fusion affect the average throughput and the average energy consumption. Hence, the objective of this paper is to identify the energy detection threshold of the sensing node and the rule threshold of fusion to achieve the maximum EE. We first study the EE formulation of the rule threshold of fusion when the energy detection threshold of the sensing node is given, and transform the ratio-type objective function of EE into a parametric formulation. Subsequently, by exploring the relationship between the two formulations and making use of the monotonicity of the parametric formulation, an algorithm to obtain the optimal rule threshold of fusion for the original problem is developed. Furthermore, we study the optimal formulation of the energy sensing threshold of the sensing node and discuss the effect of the sensing duration and the number of distributed cooperative terminals on the EE. Lastly, the performance of the proposed method is evaluated through numerical simulation results.

A traffic matrix (TM) is a source of critical traffic throughput information for traffic engineering activities and network management tasks such as traffic prediction, capacity planning, network provisioning, and anomaly detection. However, estimating TM poses several challenges for network engineers. One of the challenges is that traffic data statistics are constantly changing, and their aggregation for real-time monitoring becomes a difficult task. This paper presents a near real-time TM estimation approach for OpenFlow (OF) networks. It makes use of Big Data techniques based on MapReduce operations to tackle the aggregation problem. The proposed method uses traffic data statistics collected from OF switches through an SDN controller as input and aggregates these data in a Big Data streaming processing environment. This paper explores the benefits of the distributed MapReduce computing model to provide an estimate of the TM for all origin-destination (OD) pairs of hosts in the network in two ways: 1) the accumulated throughput and 2) the throughput between two sequential TM estimates. This procedure enables network engineers to monitor the behavior and evolution of the throughput on each OD pair in the network and on each link in the path between each OD pair. The generated TM is persisted in a NoSQL database and can be made available for a variety of network traffic monitoring applications. The results of the simulations show the potential of the proposed MapReduce approach for TM estimation.

This paper presents the design and implementation of a Multi-level Time Sensitive Networking (TSN) protocol based on a real-time communication platform utilizing Data Distribution Service (DDS) middleware for data transfer of synchronous three phase measurement data. To transfer ultra-high three phase measurement samples, the DDS open-source protocol is exploited to shape the network's data traffic according to specific Quality of Service (QoS) profiles, leading to low packet loss and low latency by synchronizing and prioritizing the data in the network. Meanwhile the TSN protocol enables time-synchronization of the measured data by providing a common time reference to all the measurement devices in the network, making the system less expensive, more secure and enabling time-synchronization where acquiring GPS signals is a challenge. A software library was developed and used as a central Quality of Service (QoS) profile for the TSN implementation. The proposed design and implemented real-time simulation prototype presented in this paper takes in consideration diverse scenarios at multiple levels of prioritization including publishers, subscribers, and data packets. This allows granular control and monitoring of the data for traffic shaping, scheduling, and prioritization. The major strength of this protocol lies in the fact that it's not only in real time but it's time-critical too. The simulation prototype implementation was performed using the Real Time Innovation (RTI) Connext connectivity framework, custom-built MATLAB classes and DDS Simulink blocks. Simulation results show that the proposed protocol achieves low latency and high throughput, which makes it a desired option for various communication systems involved in microgrids, smart cities, military applications and potentially other time-critical applications, where GPS signals become vulnerable and data transfer needs to be prioritized.

In this paper, we develop novel precoder and combiner schemes for multi-user hybrid digital-to-analog (D-A) beamforming for uplink massive multiple-input multiple-output millimeter wave (mm-Wave) systems, where the number of radio frequency chains is much smaller than the number of antennas each transceiver is equipped with. Industry 4.0 targets to accelerate the digitalization of manufacturing processes by allocating fixed and mobile robotics which use wireless communication. Such development requires high data throughput for which the utilization of short distance wireless communication such as mm-Wave system is crucially required. Based on our measurements, the probability of mm-Wave propagation waves to be reflected and refracted from metallic surfaces are shown to be significantly high. Consequently, uplink transmissions from different users such as robotics, machines, and sensors can go through paths sharing the same physical scatters, some transmission paths of different users may have overlapped angle of arrivals (AoAs) at the base station. Under such circumstance, the correlation between the channel vectors also increases considerably, which affects the achievable uplink rate severely. Therefore, the intrinsic focus is on substantially maximizing the desired signal while reducing the system interference. The proposed analog precoders and combiners are designed by using the power iteration and the Riemannian optimization method based on Stiefel manifold algorithms, respectively. The proposed digital combiner adapts the minimum mean-square error by judiciously exploiting the effective uplink analog channel gains. Furthermore, the channel estimation is investigated through a newly designed two-step procedure. In each scattering point, there is the strongest power point which is detected and then used to improve the accuracy by employing an angular domain scheme. The impact of this paper will be the boosting of the achievable uplink rate in industrial environme...\ud

In smart home networks, the traffic is often asymmetric (i.e., the uplink traffic load of a node is not equal to its downlink traffic load). This paper is concerned with how to achieve asymmetric transmission for a full-duplex (FD) IoT network (where the AP and nodes are FD-enabled). Most existing related schemes considered a partial FD network consisting of an FD AP and half-duplex (HD) nodes and achieved asymmetric transmission via PHY-layer mechanisms such as power control. However, for an FD network, the MAC-layer scheduling mechanism might be better to achieve asymmetric transmission than the PHY-layer power-control mechanism which will introduce complex interference management. To this end, we propose a simple and novel MAC scheduling scheme called AT-MAC to support asymmetric transmission in an FD IoT network. In our design, we differentiate uplink-dominant (UD) and downlink-dominant (DD) nodes. Upon receiving a packet, a receiver determines whether to execute a reverse transmission to the peer or to initiate a new transmission to a third node according to the type of UD and DD nodes. Next, we develop a theoretical framework to evaluate the throughput of AT-MAC. The extensive simulations verify that our design is very effective (namely, it can achieve the asymmetric transmission, while fully utilizing the FD gain to maximize the system throughput and lower the packet delay) and our theoretical model is very accurate. This paper is very helpful for designing quality-of-service-oriented FD MAC protocols.

Device-to-Device communications (D2D) are being used to improve the spectral efficiency and to reduce the load of the base station (BS) by reutilizing the licensed spectrum. However, the primary cellular users may face high interference from D2D users. There is also a scarcity of licensed spectrum due to the dense deployment of smart devices. To alleviate this problem, in this paper, we are extending the D2D users to the unlicensed band. In this scenario, the D2D users are allowed to reuse the licensed spectrum or share the unlicensed spectrum with the incumbent WiFi users. However, cellular and WiFi users experience high interference if an efficient interference management scheme is not used. In this paper, we propose a joint mode selection, channel allocation, and power control algorithm using particle swarm optimization to manage the interference and improve the overall throughput of cellular and D2D users such that the minimum data rate requirement of WiFi users is guaranteed. Through numerical simulations, we show that the proposed algorithm can significantly mitigate the interference and improve the throughput of the system.

This paper investigates wireless powered communication network (WPCN) systems aided by unmanned aerial vehicle (UAV) where a UAV-mounted access point (AP) serves multiple energy-constrained ground terminals (GTs). Specifically, the UAVs first transmit the wireless energy transfer (WET) signals to charge the GTs in the downlink. Then, by utilizing the harvested energy, the GTs send their wireless information transmission (WIT) signals to the UAVs in the uplink. In this paper, depending on the operations of the UAVs, we consider two different scenarios, namely integrated and separated UAV WPCNs. First, in the integrated system, a UAV acts as a hybrid AP in which both energy transfer and information reception are performed at a single UAV. In contrast, for the separated UAV WPCN, we consider two UAVs each of which behaves as an information AP and an energy AP independently, and thus the information decoding and the energy transfer are separately processed at two different UAVs. In each system, we formulate two optimization problems taking into account a linear energy harvesting (EH) model and a practical non-linear model. To maximize the minimum throughput of the GTs, we jointly optimize the trajectories of the UAVs, the uplink power control, and the time resource allocation for the WET and the WIT. Since the formulated problems are non-convex, in the linear EH model-based system, we apply the concave-convex procedure by deriving appropriate convex bounds for non-convex constraints and identify the suboptimal solution for the problem by a proposed iterative algorithm. In the non-linear model-based system, we propose another algorithm to obtain an efficient solution by adopting the successive convex approximation method with the alternating optimization framework. Simulation results demonstrate the efficiency and the performance of the proposed algorithms compared to conventional schemes.

This paper discusses the impact of spatial reuse and carrier sense threshold (CST) optimization on the performance of wireless local area networks using stochastic geometry analysis. The adjustment of the CST is a promising approach to improve spatial reuse, and has been proposed for the IEEE 802.11ax standard. Considering the situation where each access point (AP) individually adjusts its CST based on the individual received power, this paper derives the probability of transmission success and the density of successful transmissions (DST). The evaluation results of these metrics reveal that the optimal setting is to increase the CST linearly (in terms of dB) with respect to the average received signal power. Because the maximization of the DST causes unfairness from the viewpoint of success of transmission, the maximization of the product of the transmission success probabilities is proposed to improve the performance of the entire system and restrain unfairness. Using the trend of the optimal CST function, the impact of the density of APs on the optimal CST function is determined. Moreover, individual CST adjustment is found to improve spatial reuse compared with identical adjustment, i.e., setting the CST of all APs to an identical value.

Wireless and power line communication hybrid networking can complement each other, save construction costs, and satisfy the needs of different services. Few studies have investigated the MAC layer mechanism when the two networks are mixed. This paper proposes an improved CSMA/CA algorithm suitable for power line and wireless hybrid networking scenarios. The algorithm is compatible with the CSMA/CA algorithm in the existing standards, namely, IEEE 1901 and 802.11, and adopts a two-choice method of the power line and wireless first idle. As long as one of the wireless and power line channels is in the idle state, it can be levied to transmit a data packet. Based on the decoupling hypothesis, this paper establishes a system analysis model of the algorithm, uses simultaneous nonlinear equations to calculate the throughput and collision probability performance of the algorithm, and provides a uniqueness analysis of the solution. This paper also determines the latency of the algorithm. Finally, simulation verifies the effectiveness and reliability of the algorithm model and analyzes the performance in terms of throughput, time delay, and collision probability. Compared with the existing wireless and power line CSMA/CA algorithm, the proposed algorithm can improve the throughput and ensure the effectiveness of the network.

In this paper, we focus on an interesting E-Health monitoring system that efficiently utilizes the concept of the Internet of Things (IoT). Wireless body area network (WBAN) composed of a set of target-oriented sensors placed around the human body and transmit its collected data to a coordinator that carries it to some cloud system. WBAN standardized with the newly emerged IEEE802.15.6 with its specifications for Physical (PHY) and medium access control (MAC) layers only. Regrettably, the Network layer is not addressed by the standard where it plays an important role in the overall performance. In this paper, we design the temperature heterogeneity energy (THE) aware routing protocol for WBAN as a complement for the standard. “THE” aims to control the temperature raising caused by the on-body sensor and affects the skin comfortableness. In the meantime, “THE” maintains the network in high-performance conditions in terms of long node lifetime and high packet throughput. To fulfill these desired tradeoffs, the sensed data is classified into three data levels with variable transmission priority to each level, namely, emergency (abnormal) data priority 7 (highest priority), critical data priority 6, and normal data assigned priority 5. “THE” protocol is based on a utility function that chooses the WBAN's parent node (PN) that has the largest amount of remaining energy, the highest data rate, the minimum distance to the coordinator, and the minimum sensor's temperature. Hopping the data through the parent node (two-hops) is applicable for the data with normal priority while high priority data (critical and emergency) is transmitted to the coordinator in one-hop only. The proposed “THE” protocol's performance validation performed via Monte Carlo simulation analysis which proves that “THE” protocol achieved better performance against conventional protocols (SIMPLE and iM-SIMPLE) in terms of network lifetime, number of dead nodes, total remaining energy, and throughput.

To achieve global network coverage and the need for high-speed communication, the idea of providing Internet access from space has made a strong comeback in recent years. The low earth orbit (LEO) communication satellite constellation is once again on the stage of the world with its unique features and new technology. In order to provide faster and more affordable communication resources, low-orbit satellites need be customized to design satellites. The beam coverage design is essential to the user-customized design. This paper combines the user traffic demand model and the low-orbit satellite beam coverage model to analyze the impact of beam coverage characteristics on the performance of low-orbit satellite systems. The user traffic model bases on the user simulative distribution (uniform, normal) and the user geographic distribution (according to the AIS and ADS-B historical data acquired by STU-2B and STU-2C which are the LEO satellites launched in Sep, 2015, Jiuquan, China). The beam coverage model compares the OneWeb system to the SpaceX system. The beam coverage model takes the variability in performance induced by atmospheric conditions for the user links into account. Follow that this paper proposes a system method to simulate the two satellite system which described by the throughput, delay, access probability. Finally, the sensitivity of beam coverage to user diversification is summarized and discussed.

In this paper, we propose a novel max-weight secure link selection (MWSLS) scheme to enhance physical layer security of decode-and-forward (DF) buffer-aided relay networks. The MWSLS scheme can select the link with the largest weight among all secure and available source-to-relay and relayto-destination links. By modeling the dynamic buffer state transitions as a Markov chain, we derive the closed-form expressions of the secrecy outage probability, the secrecy diversity gain, the average secrecy throughput and the end to end delay, which provide a comprehensive and effective way to evaluate the impacts of different parameters on the secrecy performance. The results of this paper reveal that: 1) For the case with small buffer sizes, a significant enhancement on the secrecy outage performance can be observed compared with the popular max-link secure link selection (MLSLS) scheme. 2) When L ≥ 3, the secrecy diversity gain of the system can achieve 2M, while the MLSLS scheme achieves the same secrecy diversity gain only when L → ∞ (where M denotes the number of relays and L is the buffer size). 3) The MWSLS scheme outperforms the MLSLS scheme in terms of the average secrecy throughput and the end to end delay in the low signal-to-noise ratio (SNR) regime, and obtain the same performance as the latter in the high SNR regime.

This paper investigates a novel architecture of coordinated multi-point (CoMP) transmission in the cognitive satellite-terrestrial network associated with an unmanned aerial vehicle (UAV). We consider the downlink communication where the UAV and base station (BS) cooperatively serve the terrestrial user by sharing the licensed satellite network spectrum. The goal of this paper is to maximize the achievable rate of the terrestrial user by jointly optimizing BS/UAV transmit power allocation and UAV trajectory, subjecting to the interference temperature threshold imposed on satellite network as well as UAV mobility constraint. The formulated problem is shown in a complicated non-convex form, which is hard to tackle. To this end, we decompose the original problem into two sub-problems, and the block coordinate descent method is employed to solve the two sub-problems alternately. Specifically, for the first sub-problem, the optimal BS/UAV transmit power is obtained with a given UAV trajectory by using the Lagrangian dual method. For the second sub-problem, the UAV trajectory is attained with a given BS/UAV power allocation by using the successive convex approximation technique. Simulation results show that our proposed joint CoMP transmission scheme significantly improves the terrestrial network throughput compared with other benchmark schemes.

Harvesting renewable generation (e.g., solar energy) from the ambient environment to achieve a near perpetual operation for embedded systems is being paid more and more attention by academia and industry. However, an immediate problem along with the utilization of renewable energy is the degraded system throughput caused by the intermittent characteristic of renewable generation. On the other hand, energy-harvesting systems (EHSs) deployed in harsh environment are more vulnerable to transient and permanent faults. This paper aims at scheduling dependent tasks on a multicore platform for throughput maximization under energy and reliability constraints. The target of this paper is to design algorithms that optimize system throughput under the energy, reliability, as well as task precedence constraints. To achieve this goal, we propose a mixed-integer linear programming (MILP) approach for allocating and scheduling precedence constrained tasks on the multicore to maximize the throughput of EHS. However, the MILP may find the optimal solution in an exponential time. To overcome this difficulty, we propose a polynomial-time heuristic algorithm to solve the MILP-based throughput maximization problem. In this heuristic algorithm, the uncertainty in energy sources is considered and the allocation and scheduling of tasks are determined based on system energy state. The extensive simulation experiments are carried out to validate our MILP approach and throughput-aware heuristic algorithm. The simulation results justify that the MILP approach achieves an up to 92.9% improvement of system throughput when compared with a baseline method, and the proposed heuristic improves system throughput by up to 32.1% on average when compared with the four representative existing approaches.

In this paper, we consider a relay-enabled wireless-powered communication network (WPCN), consisting of a relay-hybrid access point (RHAP), harvesting and transmitting nodes, and a base station (BS). Contrary to conventional networks, the nodes rely on the energy signal of the RHAP to harvest energy, and they transmit information to the BS via the RHAP. The nodes work on the principle of harvest-transmit-to-cooperate protocol, in which a node harvests energy from a power source in the downlink and transfers information to a relay in the uplink to convey data to the BS. In this paper, we propose a new distributed medium access control (MAC) mechanism in a relay WPCN, based on carrier sense multiple access with collision avoidance, a binary exponential random backoff mechanism. In the proposed scheme, the nodes and the RHAP contend to access the channel with different contention window sizes. Furthermore, the RHAP is given more preference to access the channel by giving a smaller contention window size than the nodes. We propose a Markov chain model for the proposed-MAC and a Markov chain model for the energy states of the nodes. It models the behavior of changing states between energy harvesting and data transmission. The analysis and simulations show the effectiveness of the proposed MAC in terms of throughput and energy efficiency.

Cognitive satellite communications (SatCom) is considered to be able to alleviate the bottleneck of spectrum resource shortage due to traditional spectrum allocation. This paper focuses on a special scenario where the frequency band of SatCom is recommended by the terrestrial terminal according to its spectrum sensing results. Further speaking, frequency bands preferred by terminals in each coverage beam of the satellite may be random, which on the whole forms diverse recommended channels problem that poses a great challenge to traditional multi-beam satellites. To make reasonable use of available resources in this scenario, this paper targetedly proposes a beam hopping (BH) scheme, which is capable of providing services on each frequency band. Based on the BH scheme, two 4-D [i.e., time, frequency, power, and dedicated spot (DS) beam] resource allocation (RA) schemes are presented, which adopt maximizing throughput (MT) and minimizing demand-supply variance (MDSV) as objectives, respectively, corresponding to the fact that satellite resources may be relatively rich or scarce. Both of the RA problems belong to mixed-integer nonlinear programming. By decomposing them, three levels of problems, namely, frequency band selection (FBS) problem, dedicated beam allocation (DBA) problem, and time-power allocation (TPA) problem are successively formed. For the FBS and DBA problems, we correspondingly propose heuristic algorithms to quickly distribute frequency bands and dedicated beams. Whereas for the TPA problem, Lagrangian dual algorithm and water-filling-assisted Lagrangian dual algorithm are respectively adopted to solve the convex problem for MT and the nonconvex problem for MDSV. Taking also spectrum sensing errors into account, numerical simulations show that the proposed schemes and algorithms perform well, and a significant gain can be achieved in cognitive SatCom.

Software-defined networking (SDN) is a networking scenario which changes the traditional network architecture by bringing all control functionalities to a single location and making centralized decisions. Controllers are the brain of SDN architecture, which perform the control decision tasks while routing the packets. Centralized decision capability for routing enhances the network performance. Through this paper, we presented a review report on various available SDN controllers. Along with the SDN introduction, we discuss the prior work in the field. The review states how the centralized decision capability of the controller changes the network architecture with network flexibility and programmability. We also discuss the two categories of the controller along with some popular available controller. For each controller, we discuss the architectural overview, design aspects, and so on. We also evaluate the performance characteristics by using various metrics, such as throughput, response time, and so on. This paper points to the major state-of-the-art controllers used in industry and academia. Our review work covers major popular controllers used in SDN paradigm.

In order to overcome the problem that the traditional linear energy harvesting (EH) model is not practical, this paper presents a practical nonlinear EH model, which considers the sensitivity and saturation characteristics of the circuit. Furthermore, for purpose of solving the problem of spectrum requirement and energy consumption of wireless relays, the proposed model in this paper is used for studying the full-duplex (FD) decode-and-forward relay system. The expression of the outage probability of the system is deduced and the outage throughput of the system is calculated. According to different system quality of service (QoS) requirements, this paper further discusses the optimal scheme of non-linear EH based on outage performance and gives the closed expression of the optimal solution to minimize the outage probability of the FD system. And the optimal solution to maximize the outage throughput of the system is obtained based on the golden section method. The simulation results verify the correctness of the theoretical work, and the simulation results also show that the performance of the FD system under the proposed model is quite different from that of the traditional linear model.

Device-to-Device (D2D) communication has been a promising technology for the fifth generation (5G) wireless network owing to the higher throughput, less energy consumption, and lower latency. As the 5G network becomes denser, the interference in a hybrid D2D and cellular communication system becomes much severe and more difficult to deal with. In this paper, a novel feasibility aware partial interference alignment (FA-PIA) scheme is investigated. Partial IA has already been studied to manage severe interference for symmetric interference network or simple asymmetric network with limited users. In this paper, we consider an asymmetric interference network with an arbitrary number of D2D users transmitting concurrently. We aim to boost the degrees of freedom and achievable sum rate. To achieve this goal, a lower complexity three-step-based scheme is proposed. Specifically, the pressure transfer tree-based interference selection algorithm is first developed, which is to select the appropriate interference links to be aligned under the IA feasibility constraints. Then, the minimum interference leakage-based iterative partial IA scheme is given to mitigate the selected interference. At last, a constrained concave convex procedure-based iterative power optimization algorithm is provided to further manage the residual interference. Numerical results demonstrate that the proposed three-step-based FA-PIA scheme can significantly improve the achievable sum rate.

To alleviate the problem of scarce spectrum resources and meet the ever-increasing of mobile broadband data traffic demands, Licensed Assisted Access (LAA)-Long Term Evolution (LTE), operating in the unlicensed spectrum, is a promising solution. Considering that the unlicensed spectrum is shared by a few incumbent systems, such as IEEE 802.11 (i.e., WiFi), one main target is to guarantee the friendly and harmonious coexistence of LTE with other wireless systems in the unlicensed spectrum. Both listen-before-talk (LBT) and duty cycle methods are regarded as effective ways to solve the coexistence problem in academia and industry so far. Although there are a large number of theoretical researches on LTE in unlicensed spectrum (LTE-U), field trail results are still lacking. In this paper, an experimental testing platform is deployed to model the realistic environment. This paper focuses on three aspects. First, a typical indoor field trial scenario in 5.8 GHz unlicensed bands is deployed, and the performance of LTE-U and WiFi, including coverage and capacity, is evaluated. Specifically, a methodology to determine the proper clear channel assessment energy detection (CCA-ED) threshold for LTE-U is proposed to implement the friendly coexistence between LTE-U and WiFi systems. Second, supplementary downlink (SDL) and Cell ON/OFF mechanisms are investigated to verify the fair coexistence between LAA and WiFi in the unlicensed spectrum. Third, the Enhanced Cell ON/OFF scheme, which introduces Clear to Send (CTS)-to-Self (CTS2S) message, is discussed and evaluated. Based on the built testbed, we obtain threefold conclusions. First of all, introducing LTE into unlicensed spectrums can greatly improve the spectrum efficiency and optimize wireless resources. Furthermore, test results and analyses show that a proper CCA-ED threshold is necessary for coexisting friendly and fairly among different systems, and experiments are also provided to validate the feasibility of the suggested method in various scenarios. Second, experimental results show that SDL mechanism guarantees relatively friendly and harmonious coexistence between LAA and WiFi only in the sparse scenario, while basic Cell ON/OFF mechanism is more effective to ensure coexistence between LAA and WiFi than the SDL. Finally, with the introduction of CTS2S message, the Enhanced Cell ON/OFF scheme is able to achieve more peaceful coexistence between LTE and WiFi users employed in the same bands compared with the Basic Cell ON/OFF scheme.