In recent years, Wireless Sensor Network (WSN) have expanded as foundation infrastructure for Internet of Things (IoT). However, integrating WSN into IoT is a challenging task due to its poor network lifetime and high energy consumption. To address these shortcomings, our proposed work performs five sequential processes: Initially, we split the network region into multiple partitions using Quad Tree combined Binary Tree (QTcBT) partitioning algorithm. We carry out Weight based Cluster Head Selection (WCHS) method to select a cluster head in each partition. A novel Pair based Sink Relocation Scheme (PSRS) is proposed to relocate the sink node which effectually increases the network lifetime. We execute Destination Oriented Directed Acyclic Graph (DODAG) based route adjustment that adjusts route by considering three rules. Finally, we perform Type 2 Fuzzy based Adaptive MAC Scheduling (T2FAMS) that is handled by the cluster head. At last, we evaluate the performance of our proposed work in terms of metrics including Energy consumption, End to End delay, Network lifetime, Delivery success ratio and Number of nodes alive. From the evaluation, we conclude that our work reduces energy consumption up to 20% and improves network lifetime up to 30% compared to the existing QDVGDD and GR methods.

In this study, vehicle-to-vehicle (V2V) radio channel measurements at 5.9 GHz were conducted on a suspension bridge and a beam bridge. Given that a different structure of the two bridges will result in different channel properties, the authors study small-scale and large-scale propagation characteristics for the bridge scenarios based on measurement data. By using Akaike's information criteria, the study determines optimal small-scale fading distribution. Owing to that Ricean distribution occupies the dominant position, Ricean K-factors in the two bridge scenarios are modelled separately and compared with each other. Afterwards, power delay profiles, Doppler power spectral densities, root-mean-square (RMS) delay spread and RMS Doppler spread are estimated and analysed in different cases. They employ bimodal Gaussian mixture distribution (BGMD) to model the RMS delay spreads and the RMS Doppler spreads. Fitting results of the BGMDs show good matching levels. For the large-scale propagation characteristics, path loss model for the beam bridge scenario is proposed based on the two-ray theory. On the other hand, path loss for the suspension bridge scenario is modelled by using an empirical function derived from WINNER II. Finally, grey relational grade–mean absolute percentage error, and RMS error criteria prove the effectiveness of the two proposed path loss models.

The authors introduce a novel hybrid precoding algorithm based on Gram–Schmidt orthogonalisation (GSO) in millimetre-wave massive MIMO systems. Specifically, the columns of array response matrix orthogonalised by the GSO process are considered as a set of candidate analogue precoders, then traditional orthogonal matching pursuit (OMP) is utilised to find the optimal analogue and digital precoders. Since GSO is a recursive process that depends on the order in which the matrix columns are selected. A heuristic solution to the order of columns selection is suggested according to the array response vector along which the fully-digital precoder has the maximum projection. The proposed algorithm, not only constrained to uniform linear arrays, can avoid the matrix inversion in designing the digital precoder compared to OMP. Simulation results show that the spectral efficiency and bit error rate of the proposed hybrid precoding solutions are close to that obtained with fully digital architectures. Furthermore, the results indicate that the proposed hybrid precoding solutions outperform the orthogonality-based matching pursuit, which uses the columns of the DFT matrix as a set of candidate analogue precoders.

This study investigates the co-channel interference effects on the leakage rate based untrustworthy relay selection strategies. The investigation considers half-duplex, full-duplex, and hybrid leakage rate-based untrustworthy relay selection strategies. The hybrid-based selection strategy dynamically switches between half-duplex and full-duplex modes. The investigation also considers a dual-hop untrustworthy amplify-and-forward based half/full-duplex bi-directional wireless relaying network in the system model. In addition, a finite number of friendly jammers and co-channel interference affect to the untrustworthy relay terminals. According to analytical, asymptotic, and Monte-Carlo simulation results, the co-channel interference slightly degrades the outage probability performance curves and causes system coding gain losses in high signal-to-noise ratio regimes. Results also show that the co-channel interference degrades the system achievable rate performance and causes additional system coding gain losses in high SNR regimes. Results also show that co-channel interference does not have any effect on the system security trade-off performance.

In this study, the authors investigate the joint design problem of interference alignment (IA) and power splitting (PS) in simultaneous wireless information and power transfer (SWIPT) networks. The existing joint design method is generally divided into two steps. First, IA is performed, and then the PS ratio is optimised. To obtain IA and SWIPT, a new joint design multi-objective alternating optimisation (MOAO) algorithm is proposed. Different from the existing joint design method, the proposed MOAO algorithm not only maximises the sum harvested power after PS, but also maximises the sum signal-to-intereference-plus-noise ratio (SINR) by jointly designing the transmitting precoding matrices, the receiving interference suppression matrices, and the PS ratio. For this multi-objective optimisation problem, a weighted optimisation method is proposed, which compromises between maximising the sum harvested power and maximising the sum SINR. Simulation validates that the sum achievable rate and sum harvested power of the proposed MOAO algorithm are significantly superior to those of the current scheme under the reasonable weighting coefficients.

With the development of big data, the authors have witnessed the great success of the mobile internet that the number of intelligent mobile devices (MDs) has increased dramatically and the data that needs to be transmitted grows exponentially. The traditional end-to-end communication mechanism in social networks is difficult to satisfy enormous communication demands. Therefore, opportunistic social networks proposed that message applications should choose relay nodes to perform effective data transmission processes. Currently, some routing algorithms that utilise contextual information associated with nodes need to handle heavy computing tasks and manage large numbers of messages, which usually results in higher network overhead and network latency. Furthermore, the computing power of MDs is usually limited, message carriers may not be able to quickly find the suitable relay node because of their insufficient computing power, resulting in higher network latency and network overhead. In this study, they construct a cooperative-routing mechanism based on node classification and task allocation for opportunistic social networks. In their proposed strategy, the reliable relay nodes can be obtained by classifying nodes according to the social attributes of the nodes. The task of node classification will be uniformly assigned to other idle nodes according to their computing power.

Exploiting mobile sink (MS) for data gathering in the wireless sensor networks has been extensively studied in the recent researches to address energy-hole issues, thereby facilitating balanced energy consumption among nodes and so prolonging network lifetime. However, such approaches suffer from an extended data collection delay causing buffer overflow problem. In this regard, finding the optimal number of locations (i.e. rendezvous points (RPs) where the MS sojourns for data collection), is not only of utmost importance, but also a challenging task. A novel scheme for trajectory design of MS for data collection is presented in this study. The authors' primary goal is to optimise the number of RPs and their locations to minimise the travelling length of the MS. First, they reduced the problem size by using a combination of breadth-first search and Tarjan's algorithm and then applied spectral clustering to find the optimal set of RPs to plan the tour for the MS. They have performed extensive simulations, and the results are compared with relevant existing schemes. The comparative results confirm the effectiveness of their approach in terms of the number of RPs, path length, the variance of RPs, and energy consumption per round.

With the evolution of the fifth generation (5G) and beyond heterogeneous wireless networks, telecommunications operators and researchers are driven to develop advanced transmission technologies that enable the coexistence of multiple radio access technologies (multi-RATs). By employing the efficient implementation of filter-bank multi-carrier (FBMC) transceiver and the scalable matrix transformation (SMT) module, in this study, a unified multiple access architecture termed as FBMC-SMT is proposed, which is capable of flexibly integrating with both 3G and 4G transmission schemes and improving the system performance. As a special case of FBMC-SMT, the performance evaluation of FBMC-CDMA is conducted by extensive simulation. It is verified that FBMC-CDMA with 16 subbands allocated outperforms the traditional single carrier wideband code division multiple access when the number of code channels assigned is larger than 5. Moreover, the signal-to-interference-plus-noise ratio analysis of FBMC-SMT is also given and matches the simulation results very well. Hence, the proposed FBMC-SMT can serve as a unified architecture to flexibly integrate multi-RATs, thus to meet variable application requirements in 5G and beyond heterogeneous wireless networks.

Security becomes increasingly important due to various attacks from adversaries in wireless sensor networks. This work considers a resilient distributed estimation of an unknown parameter with a cluster-based approach when some agents are adversarial. A two-phase algorithm is adopted to perform parameter estimation and detect attacks. First, a cluster scheme is proposed to make sure that each cluster is connected. Then, the attack is detected and estimation is achieved with a consensus+innovation estimator in each cluster. Finally, the cluster heads combine the consensus estimates in each cluster and exchange with other cluster heads to achieve unknown parameter estimation. In addition, the detection sensitivity under different cluster schemes is also compared. Numerical examples illustrate that the proposed cluster-based approach can improve the convergence rate and detection sensitivity.

So far, the research of wireless powered communication networks (WPCNs) mainly considers the scenarios with a single radio-frequency (RF) energy transmitter (ET) and a single sink. However, in practice, there are many applications where multiple ETs and sinks need to be deployed. This study focuses on large-scale WPCNs having multiple RF ETs and sinks. Specifically, the authors aim to minimise the total energy provision by optimising ETs' transmit powers with the node-throughput demand and sum-throughput demand, respectively. For the node-throughput demand case, they firstly formulate it to be a convex optimisation problem, then transform it to be a linear programming (LP) problem, and finally present a distributed algorithm to obtain the optimal solution. For the sum-throughput demand case, they firstly formulate it to be a non-linear optimisation problem, then prove its convexity and finally propose an efficient dual subgradient algorithm to obtain the optimal solution. Simulation results demonstrate that compared to the sum-throughput demand, imposing the node-throughput demand can effectively alleviate the throughput unfairness at the cost of increased energy provision; the proposed optimal algorithms can substantially decrease the total energy provision of ETs; the energy provision reduction percentage achieved by their schemes increases as the number of ETs increases.

In this study, the authors investigate the performance of an energy harvesting cognitive cooperative multiple relays network with spectrum sensing, where secondary user accesses the licensed spectrum according to the spectrum sensing results. Particularly, if the spectrum hole is detected, the secondary nodes harvest energy from the ambient environment, otherwise, the secondary source and relays transmit with the energy collected from the primary signals. Taking the imperfect spectrum sensing results into account, exact closed-form expressions for the total outage probability and capacity of the secondary network are derived under the context of Rayleigh fading channels, where the proposed modified selective cooperative decode-and-forward relaying transmission schemes are adopted. Compared with the conventional cognitive relay network, the authors must undertake the correlations among the received signal-to-noise ratios or signal-to-interference-plus-noise ratios caused by both the presence of primary user's interference and energy harvesting for the system understudy. It is shown that spectrum sensing phase and data transmission phase are mutual influence and mutual restraint.

Large and rapidly changing Doppler shift poses a huge challenge on fast carrier acquisition for hypersonic vehicle communications. In this study, a novel Doppler shift acquisition method is proposed to increase the acquisition probability and reduce the acquisition time simultaneously. Firstly, the Doppler rate is estimated with a proposed fast blind estimation algorithm. The order of Doppler shift is reduced though twice instantaneous delay autocorrelation operation on the received signal and the modulated information is cancelled, and the Doppler rate can be obtained by the corresponding spectrum analysis. Secondly, the received signal is compensated by the estimated Doppler rate. Finally, the maximum value of the average power spectrum of the compensated result over multiple symbols is detected, and the Doppler shift and Doppler rate can be jointly determined. Furthermore, to improve the acquisition speed, a corrected narrower range, which is determined by the flight conditions of the hypersonic vehicles, is proposed to constrain the search range of the power spectrum peak. Simulation results indicate that, under typical hypersonic flight conditions, the acquisition probability of the Doppler rate increases from 0.52 to 0.86 under  − 20 dB. The processing speed can be improved by 75.47% when the length of the combined symbols is 1000.

The growth in mobile network data traffic is even more noticeable in networks compatible with the Long-Term Evolution (LTE) standard. As such, both academia and industry seek mechanisms aimed at improving new communications systems, therefore, new test benches are required. The emulators are candidates to validate the proposals without affecting the real central systems. However, many papers that seek to address LTE emulation ignore the not-so-insignificant effect of wireless media propagation features. In this work, a characterization of the main propagation models used by typical emulation systems has been carried out. The network simulator three tool using indoor propagation models, has compared the outcomes achieved compared with the results obtained in a real test bench. Since most mobile data in the coming years is forecast to be mobile video traffic, this study focuses on a live video streaming service, considering both real-time message protocol and real-time streaming protocol transmission protocols. From the results, we demonstrate that only one of the propagation models under study is able to equate with a real LTE system performance. Thereby, the emulation system under this specific setup is well suited to conducting performance tests of LTE networks supporting video streaming services in indoor scenarios.

Cloud computing platforms propose applied directional information technology services to its clients. It provides services according to demands by which shared resources, data, software, and other tools are to be made available based on the client's request. Load balancing is considered as one of the main issues in cloud computing. The quality of service (QoS) factors such as resources application, answering time, process time, scalability, throughput, the durability of the system, and energy consumption are improved by the balanced load. The cloud tasks scheduling and load balancing are considered as an NP-hard issue. Therefore, in this study, a new energy-aware cloud load balancing method is proposed by usage of preference alignments and ant colony optimisation algorithm. This approach aims at balancing the virtual machines workload and energy consumption of cloud data centres and also assures QoS for users. CloudSim simulator is used to confirm the performance of the method. It shows that the proposed method reduces waiting time and energy consumption on a virtual machine.

The indoor positioning method based on received signal strength indication (RSSI) ranging is a lack of systematic quantitative research on the factors affecting the characteristics of indoor RSSI, which affect the accuracy of positioning. This paper quantitatively analyzes the characteristics of the 2.4 GHz RSSI collected in indoor scenes from the following four aspects: antenna orientation of the receiver, type of wireless network interface card (NIC) of the receiver, time period of the data measurement and height difference between the transmitting and receiving antenna. The experimental results show that: (i) the RSSI value measured is the strongest when the antenna of the receiver is vertically oriented to the antenna of the transmitter, while the weakest when the antenna is vertically back-facing and the difference between the strongest signal and the weakest signal is 20–25% at the same test point; (ii) the wider the measurement range of NIC, the more conducive to data collection; (iii) the distribution of RSSI signals generated by an access point at a fixed position is inconsistent with time; (iv) when the height of receiving antenna is 0.5 m different from each other, the path loss index of ranging model produces a deviation of about 10%.

A practical implementation and the maximum likelihood detection analysis of the blind cyclic-feature detection (BCD) in cognitive radios is presented in this study. The sum of the magnitude squared of the cyclic spectral density (SCSD) is the merit criterion for the maximum likelihood detection. The authors show that the SCSD can be conveniently obtained from the autocorrelation of the power spectral density for a cyclostationary process. Unfortunately, this is not true for a stationary process. For a white Gaussian noise process, the SCSD exhibits non-zero values for all cyclic frequencies although the noise process does not have any cyclic features. To ameliorate the challenge, the authors introduce noise elimination methods in the BCD. The simulation results show that the receiver operating characteristics of the BCD are considerably superior to the energy detection especially in signal-to-noise ratio fluctuation. With a moderately increased computational complexity, the BCD can be very beneficial for millimeter-wave cognitive radios with fast fading.

Considering its simplicity and the uniform distribution of signal energy and interference after transformation, the weighted fractional Fourier transform (WFRFT) has been gradually applied to the field of communication. With in-depth study of WFRFT, the number of weighted terms can be extended from the original four terms to any number. This is called a multi-WFRFT (M-WFRFT). As the number of weighted terms plays an important role in the receiving system, research into an M-WFRFT reception method compatible with different weighted terms is critical. In view of the high complexity of communication systems based on M-WFRFT, in order to solve the general receiving problems of the receiver when the parameters of the transmitter are not fixed or when multiple transmitters share the same receiving system, a regenerative transformation scan method for M-WFRFT signals is established. This is accomplished by adapting to dynamic processing conditions and avoiding the problem of high complexity. In this method, the 4-WFRFT mechanism is introduced, regeneration weighting coefficients are constructed, and the regeneration order is given by combining the inherent relationship between the weighting coefficients and the order. The new method can achieve the purpose of receiving M-WFRFT signals with different number of items and different orders.

Non-orthogonal multiple access (NOMA) is recognised as an improved multiple access technique as compared with OMA technique to fulfil the requirements of fifth-generation wireless communication systems. In this study, the outage probability and sum-rate analysis of downlink multi-user NOMA system over the generalised fading channels, i.e. η–µ and κ–µ, are presented. Specifically, the outage probability of NOMA is analysed with fixed target rate and OMA rate. The mathematical expressions for the outage probability and sum rate with a fixed set of power allocation coefficients are derived and verified through the simulation results. The impact of system parameters such as number of users, power allocation coefficients, fading parameters etc. on the performance of NOMA system is investigated. NOMA with given fixed target rate offers better outage performance as compared with OMA. However, NOMA with OMA rate offers better outage performance for the near user only. The sum rate and near user rate of NOMA improves with signal-to-noise ratio; however, the far user rate does not follow the same trend.

To improve information throughput conventional single-pulse M -ary pulse-position-modulation (PPM) scheme, multi-pulse PPM has been proposed on the optical intensity-modulated and direct-detection channel. Although the multi-pulse M -ary PPM scheme significantly enhances throughput performance, nevertheless, the symbol error rate (SER) increases due to the loss of orthogonality between different pairs of symbols. In this study, the authors first derive the SER performance of general L pulses M -ary PPM scheme under Poisson channel statistic. Moreover, as the green radio is essential in future network, energy efficiency becomes the major concern. Hence, they evaluate L pulses M -ary PPM scheme by the number of reliable bits transmitted per joule of energy consumed. They analyse the trade-off between throughput and power consumption.