Massive multiple-input multiple-output (MIMO) is currently entering the practical implementation phase, and key implementation issues for this technology have yet to be fully addressed. Crucial among these is the practical problem of frequency synchronisation, which refers to the adjustment of the clock frequency of local nodes to the clock frequency of a reference node by estimating and compensating

Fog computing (FC) with a distributed architecture plays an essential role in Internet-of-Things (IoT). This paradigm utilises the processing abilities of Fog devices (FDs) and decreases latency. The large volume of data and its process in IoT can cause network failures. Researchers tend to consider communication reliability to reduce fault effects and achieve high performance. Fault tolerance becomes

Goal-oriented Luby transform (LT) codes are required in different scenarios. Based on the random walk model, analysis of ripple size evolution provides an effective method to design LT codes. However, the ripple addition in each step depends on both the number of symbols released in the current step and the ripple size in the last step, leading to distortion. Therefore, the authors propose a random

In this article, we have employed an energy detector (ED)-based cooperative spectrum sensing (CSS) with multi-antenna for cognitive radio network (CRN). The spectrum sensing error and energy efficiency (EE) are the key performance parameters in CRN which are affected by the threshold selection method, number of antennas employed at each cognitive user (CU), reporting error probability and cooperative

This paper has collectively exploited cognitive radio (CR), non-orthogonal multiple access (NOMA) and multiple-input-multiple-output (MIMO) communication systems in order to propose a spectral-and interference-efficient framework which is named as MIMO-based CR–NOMA communication system. The proposed framework is analysed for the uplink and downlink scenarios. Further, the closed-form expressions for

The authors incorporate Alamouti space-time block coded orthogonal frequency division multiplexing (OFDM) with signal space diversity (SSD) in order to significantly strengthen the physical layer security of the communication network. The coordinate interleaving step of SSD is performed amongst OFDM subcarriers, according to distinct strategies that make the correlation coefficients between the subcarrier

In this study, the authors consider the user rate optimisation for wireless powered communication networks (WPCNs). To improve the user rate, a novel minimum mean square error (MMSE)-based transmission method is proposed for WPCNs. For maximising the user rate, a user rate optimisation problem with MMSE constraints in the uplink transmission is formulated, which is considered as a convex optimisation

Relay-assisted device-to-device (D2D) communications have been proposed as a supplement for direct D2D communications to enhance traffic offloading capacity. In this study, the authors propose a joint mode selection, relay selection and resource allocation for relay-assisted D2D communications. They aim at maximising the overall system throughput while guaranteeing the power limitation and signal-

Unmanned aerial vehicle (UAV)-assisted communications have been regarded as a promising technology, which can be used in dynamic heterogeneous networks, since the UAVs can be applied as mobile base stations (MBSs). It is more efficient to set the UAVs as MBSs in different layers according to their functions. Due to the ability in communicating with other vehicles or facilities, vehicle-to-everything

With self-interference cancellation (SIC), a wireless full-duplex terminal is allowed to transmit and receive signal simultaneously in the same frequency band. In this study, the authors first briefly described the impact on the conventional analogue SIC method from the interested signal. To solve this problem, they propose a new practical analogue SIC scheme for full-duplex systems, which is then

This study presents a mobile edge computing (MEC)-enabled UAV communication system, where a number of UAVs are served by terrestrial base stations (TBSs) equipped with computation resource in the non-orthogonal multiple access manner. Each UAV has to offload its computing tasks to the proper TBS due to the limited energy supply. For this, the authors aim at minimising the sum of transmission energy

The cooperative device-to-device (D2D) network employing non-orthogonal multiple access (NOMA) is expected to play an important role in the next-generation wireless networks. In this work, the authors derive outage probability expressions of a cooperative NOMA D2D network which employs decode-and-forward relaying. A wireless link experiencing Nakagami- m fading is considered which is further assisted

VANETs are so-called vehicular ad hoc networks, they enable cost-effective, scalable solutions, and hence, they can be applicable in entertainment and transportation platforms with the assistance of multi-hop wireless communications from vehicle-to-vehicle. Conversely, in VANET circumstance, the multi-hop communication development is still a challenging one because of the quick change in topology and

Coprime array exhibits many advantages over the uniform linear array (ULA) with the same number of physical sensors in resolution performance and interference suppression capability. In this study, the authors take the advantages of coprime array to improve the robustness of adaptive beamformer. In the coprime virtual ULA (CV-ULA), they prove that a constructed Toeplitz matrix can be taken as the sample

The heterogeneous network structure is a promising paradigm to improve the quality of service across the entire network. Nevertheless, such a structure is challenging due to the presence of multiple-tier secondary users (SUs). In this study, the authors investigated the effect of spectrum allocation in heterogeneous cognitive radio networks with a primary network and two-tier secondary networks, and

Contention-based carrier sense multiple access (CSMA) and contention-free time division multiple access (TDMA) protocol are two typical access protocols of media access control in vehicular ad hoc network (VANET). They all show their unique advantages under specific conditions. TDMA has high transmission reliability, CSMA has a low transmission delay in the communication environment with low packet

Presently, the single-carrier frequency division multiplexing (SCFDM)-based visible light communication (VLC) system is extensively implemented for secure and high-speed data transmission. However, the effect of additive white Gaussian noise in VLC with white light-emitting diode is high, due to a high peak to average power ratio (PAPR). To address this difficulty in 5G networks, two objectives were

In this study, the authors consider the problem of secure and reliable communication with uncertain channel state information (CSI) and present a new solution named active secure coding which combines the machine-learning methods with the traditional physical-layer secure coding scheme. First, the authors build a detectable wiretap channel model by combining the hidden Markov model with the compound

As the standard specification for substation, IEC61850 utilises the abstract communication service interface to map to the manufacturing message specification (MMS) to communicate between the substation level and the bay level. The conventional MMS adopts the client/server model, which results in a relatively large transmission delay. In order to solve this problem, the data distribution service (DDS)

This study considers the Gaussian cognitive interference channel (IC), in which one of the two users operates in cognitive mode. In addition, to transmit its signal, the cognitive sender can cooperatively forward the primary signal to its destination, the primary receiver. Moreover, the transmission over this IC also experiences interference from a third source, which is commonly known as the common

Due to the time-varying property of the underwater acoustic (UWA) channel, the significant Doppler spread will severely degrade the performance of direct-sequence spread-spectrum (DSSS) communications. The relative velocity variation between the transmitter and the receiver will cause both the phase rotation and the magnitude loss of correlation peak, during the long transmission of the DSSS packet

Ambient backscatter which utiliees the ambient radio-frequency signals to enable transmissions between battery-less devices has attracted considerable attention in academia and industry. This study addresses the questions of full-duplex (FD) and self-interference cancellation (SIC) for ambient backscatter which adopts dual-antenna structure to achieve persistent information transmission and energy

The non-orthogonal multiple access (NOMA) approach enables a number of users to share the same resource via superposition coding in the transmitter and successive detection in the receiver. In this study a power allocation (PA) approach based on the proportional fair division technique is proposed. In this regard, power is assigned to users such that it ensures the fairness of NOMA follows that of

The widely acceptable problem in wireless sensor networks (WSNs) is to develop a practical scheme for data aggregation in the massive range of sensor nodes that are randomly distributed over a network region. The essential operation of cluster heads (CHs) in such a network is to transmit the aggregated data to the sink node through multi-hop communication, thus the energy to be used in a better way

Exact expressions for the probability density function (PDF) and cumulative distribution function (CDF) of cascaded Rayleigh fading channels with arbitrary correlation but not necessarily identically distributed are derived. Furthermore, the PDF and CDF of the instantaneous signal-to-noise ratio are obtained. The cascaded channels are assumed to have slow frequency non-selective arbitrarily correlated

In recent years, we have witnessed fast-growing unmanned aerial systems (UAS) based applications. To better facilitate these applications, many efforts have been made to enhance the capability of UAS from various aspects, including communications, control and networking, and so on. Nevertheless, most of these studies neglect the computation aspect. Recently, the UAS-enabled mobile edge computing (MEC)

Mobile edge computing (MEC) is to process, analyse, store and calculate the network data at the edge of the network. When the ground infrastructure is damaged in an emergency, the unmanned aerial vehicle (UAV) formation can be rapidly deployed to undertake the task of MEC. However, there are some potential problems to be considered in UAV-enabled MEC, such as the trust among UAVs from different sources

With the popularity of unmanned aerial vehicles (UAVs), more and more valuable data can be collected by UAVs. In order to balance the data usage and communication cost, the data can be preprocessed in UAVs rather than directly transmitting to the data centre in the edge computing paradigm. Users can obtain information of interest by accessing the data centre remotely by authenticating themselves to

Remote sensing by unmanned aerial vehicles (UAVs) is significantly important in emergency rescue applications and operations. Particularly, the on-site images from UAVs can provide valuable information for hazard identification and disaster assessment. In this study, the authors propose a novel method by using back propagation neural networks with feature fusion to detect landslides from UAV images

By offloading video streaming from the centralised cloud to the edge, mobile edge computing (MEC) servers offer new opportunities for real-time video transmission. Deploying on the edge of users can ensure low latency transmission, however, the limited storage and computing ability cannot adapt to the currently used video transmission technologies such as video transcoding or simulcast. To solve this

In this study, an update code using vehicles joint unmanned aerial vehicle (UC-VU) scheme is proposed to disseminate code for smart sensing devices (SSDs) in the smart city. The innovations of the UC-VU scheme are as follows. (i) The unmanned aerial vehicle (UAV) is adopted to disseminate code at the beginning of code dissemination for the SSDs which are difficult to get code through mobile vehicles

With the popularity of computationally intensive applications, more and more computing resources are required. Mobile edge computing (MEC) is widely applied as an effective method to meet the increasing computing demands. In a relatively stable state, MEC can provide computing services with low latency and energy consumption. However, in special cases such as communication traffic, the unmanned aerial

The implementation of computation offloading is a challenging issue in the remote areas where traditional edge infrastructures are sparsely deployed. In this study, the authors propose a unmanned aerial vehicle (UAV)-enabled edge computing framework, where a group of UAVs fly around to provide the near-users edge computing service. They study the computation migration problem for the complex missions

Unmanned aerial vehicles (UAVs) have been recently considered as a flying platform to provide wide coverage and relaying services for mobile users (MUs). Mobile edge computing (MEC) is developed as a new paradigm to improve quality of experience of MUs in future networks. Motivated by the high flexibility and controllability of UAVs, in this study, the authors study a multi-UAV-enabled MEC system,

In this study, the air–ground integrated deployment method is studied for the unmanned aerial vehicle (UAV)-enabled mobile edge computing (MEC) system. The UAV can help to reduce the delay and energy consumption of MEC. However, the limited coverage range of UAV limits the quality of data offloading. To improve the efficiency of data transmission, a hierarchical game model is designed. Ground nodes

Unmanned aerial vehicles (UAVs)-based sensor network is an effective mechanism for recognising and tracking of manoeuvring targets as well as expanding the monitoring coverage in the battlefield. However, there exists redundancy among the spectrum data collected by a UAV monitor within a data collection period, which may waste storage space and reduce the speed of data uploaded to the control centre

Mobile edge computing (MEC) has been envisaged as a promising technique in fifth generation (5G) and beyond wireless networks. In order to alleviate the explosive growth of computation and spectrum demand, cognitive radio (CR) and unmanned aerial vehicles (UAV) are studied in MEC-aware networks. In this study, considering a local computation and partial offloading scheme, a UAV-enabled CR-MEC framework

Wireless power transfer (WPT) and mobile edge computing (MEC) are two prospective technologies to enhance the computing power and endurance of mobile devices. Integrating unmanned aerial vehicle (UAV) into wireless powered MEC system, the energy collection efficiency can be effectively improved with the short-distance line-of-sight path power transfer. However, WPT is susceptible to the ‘double near-far’

With the high mobility, flexibility and manoeuvrability, unmanned aerial vehicles (UAVs)-enabled mobile edge computing (MEC) plays an important role in many applications that lack of available terrestrial infrastructures, such as disaster response, emergency relief and military scenarios. However, the high mobility of UAVs may severely degrade the implementation of UAV-enabled MEC in computation-intensive

This study investigates the opportunistic joint source-pair and relay selection policy for cooperative networks. The investigation considers multi-user pair and multiple bi-directional amplify-and-forward based relays in the system model. The strategy selects an appropriate user-pair and relay among N candidate user-pairs and R available relays based on the maximum achievable sum-rate of each user

In today's time, there is a need to continually monitor the ocean shore in real time for different applications such as coastal monitoring , disaster prevention , assisted navigation etc. This requires a high data rate (order of Mbps) communication for transfer of data from an underwater environment to surface. This cannot be achieved using the traditional acoustic networks as the data rate offered

Huge demand for bandwidth and capacity is exhibited by various wireless users and applications, for that purpose now the light-fidelity (Li-Fi)-based technologies are developing. In visible light communication, the hybrid networks based on Wi-Fi and Li-Fi has emerged recently. It is based on the concept of integrating small cell Li-Fi networks with large coverage radio frequency (RF) communication

In this study, the authors investigate the secure coding issue for a wiretap channel model with fixed main channel and varying wiretap channel, by assuming that legitimate parties can obtain the wiretapping channel state information (CSI) with some delay. For the symmetric degraded delay CSI case, they present an explicit weak security scheme by constructing secure polar codes on a one-time pad chaining

Analogue only beamforming generally refers to a structure of analogue phase shifters that have no control over the amplitude of the signals and are utilised in millimetre-wave massive multi-input multi-output systems to reduce the cost and power consumption. Conventional analogue only beamforming methods are based on beam-training and subspace sampling where the transmitter and receiver select the

In positioning research based on the orthogonal frequency division multiplex (OFDM) system, the observed time difference of arrival positioning method is a widely studied direction. The terminal measures the reference signal sent by the base station to calculate the time of arrival (TOA). Using TOA information, the location of the terminal can be identified. So the accuracy of the positioning is highly

Networks (wireless sensor networks) an important challenge of network design is maximising the network lifetime. In this study, the performance of the network is enhanced by proposing an adaptive immune-inspired energy-efficient cross-layer routing (AIEECR) protocol. For data transmission, three layers are considered which include the physical layer, transport layer, and data link layer. For the clustering

The design of transceiver impedances is very important to improve the performance of the power line communication (PLC) system. In this study, it infers an expression of signal-to-noise ratio (SNR) related to transceiver impedances for broadband PLCs, and the optimal transceiver impedances are obtained by solving a maximisation problem. By the comparison of the SNR of PLC system with the proposed transceiver

In current research of device-to-device (D2D) caching strategies, when terminals request and receive files within the transmission range, the effect of file redundancy and idle loss rate of the cache in terminals are rarely considered. In this study, the authors establish a motion and the transfer model of D2D terminals, and define a loss function considering cache idle loss and file redundancy. Then

The authors evaluate the outage probability, ergodic capacity, and symbol error rate (SER) performances of an amplify-and-forward relaying system equipped with a non-ideal variable gain single relay with hardware (HW) distortions at both the transmitter and receiver sides with the derivations of the instantaneous end-to-end signal-to-noise-and-distortion ratios. More specifically, they analytically

The large amount of devices deployed for the Internet of Things (IoT) cause a tremendous traffic burden on the cloud server. Caching content at the edge of IoT networks is a promising technology to alleviate the traffic load. However, how to further improve the successful transmission probability (STP) of cache-enabled IoT networks is still an open issue. In this study, the authors propose a novel

Millimetre-wave (mmWave) communications have been regarded as a key technology for the next-generation cellular systems since the huge available bandwidth can potentially provide the rates of multiple gigabits per second. Conventional precoding and combining techniques are impractical at mmWave scenarios due to manufacturing costs and power consumption. Hybrid alternatives have been considered as a

Today's, a promising solution, namely wireless network-on-chip (WiNoC) is utilized in multi-core systems to overcome the constraints of conventional on-chip networks. In WiNoC architectures, wireless routers (WRs) provide high capacity wireless links to reduce the latency of multi-hop communications. However, the buffer size of the WR antenna is limited, and under heavy traffic loads, it's filled and

In this study, a relay assisted order energy harvesting-based non-orthogonal multiple access (NOMA) network is considered where the relay harvests energy from radio frequency signal of the source. A transmit antenna selection scheme is considered at the source under imperfect channel state information (CSI). The outage probability of order NOMA network is analysed and a closed-form expression of it

In this study, the authors propose a novel architecture based on the combination of peak-to-average power ratio (PAPR) reduction with digital beamforming (BF) for mm-wave massive multiple-input multiple-output (MIMO) systems. In order to keep the power amplifiers (PAs) working at the same input back-off thus maximising the system power efficiency, they propose to perform time-domain transmit beam-steering

Spectrum sensing plays a key role in cognitive radio technology to acquire information on the occupancy status of the channel. Cyclostationary spectrum sensing is considered one of the most promising approaches. However, its performance is severely degraded by a mismatch between the actual and the nominal cyclic frequency [i.e. cyclic frequency offset (CFO)]. This is particularly true for vehicular

Discrete fractional Fourier transform (DFRFT) based orthogonal frequency division multiplexing (OFDM) system significantly outperforms the conventional discrete Fourier transform (DFT) based OFDM system in the presence of carrier frequency offset (CFO). However, to achieve the interference-free performance, the residual interference remaining after the channel equalisation in the fractional Fourier

In this study, the authors secure the mixed radio frequency/free space optical (FSO) relay-aided interference aligned system using a proposed physical layer security algorithm. This algorithm reduces the quality of the received signal at the eavesdropper through two procedures. First, it minimises the data transmission power from the legitimate users and the relays. Second, it jams the eavesdropper

Rich scattering of the signals in the ultraviolet (UV) band of electromagnetic spectrum enables non-line-of-sight (NLOS) outdoor wireless connectivity. It eliminates the line-of-sight requirement of the links which are using the signals in the infra-red band. Besides scattering losses, UV signals also suffer from atmospheric turbulence-induced fading. The turbulent atmospheric channel causes fluctuations

In this study, a novel closed expression of direction of arrival (DOA) information (DI) in a single-source scenario is proposed, which is more convenient than the theoretical expression to evaluate the performance of DOA estimation. Firstly, the authors give a uniform linear array system model, where the DI is expressed as the mutual information between the source and the received signal with complex

In this study, a serially concatenated scheme of polar codes with convolutional codes is proposed to improve the error correction performance. The novel belief propagation (BP) decoding algorithm addresses two issues that are present in the currently available BP decoding algorithms. The first issue is the poor performance of the BP decoding algorithms, in particular the introduction of an error floor