Millimeter wave (mmWave) has been claimed as the viable solution for high-bandwidth vehicular communications in 5G and beyond. To realize applications in future vehicular communications, it is important to take a robust mmWave vehicular network into consideration. However, one challenge in such a network is that mmWave should provide an ultra-fast and high-rate data exchange among vehicles or vehicle-to-infrastructure (V2I). Moreover, traditional real-time channel estimation strategies are unavailable because vehicle mobility leads to a fast variation mmWave channel. To overcome these issues, a channel estimation approach for mmWave V2I communications is proposed in this paper. Specifically, by considering a fast-moving vehicle secnario, a corresponding mathematical model for a fast time-varying channel is first established. Then, the temporal variation rule between the base station and each mobile user and the determined direction-of-arrival are used to predict the time-varying channel prior information (PI). Finally, by exploiting the PI and the characteristics of the channel, the time-varying channel is estimated. The simulation results show that the scheme in this paper outperforms traditional ones in both normalized mean square error and sum-rate performance in the mmWave time-varying vehicular system.

Although there have been many researches and corresponding degrees of freedom (DoF) analysis on multiple pairwise users exchanging data by one-hop relaying through one or more relays, the two-hop relay system still needs further exploring. In this paper, we design a communication scheme for multiple pairs of users in the two-tier heterogeneous networks (HetNets) with wireless backhaul link, which includes four phases: two multiple access (MAC) phases and two broadcast (BC) phases. Firstly, a new transmission and coding-decoding scheme combining generalized signal alignment (GSA), zero forcing (ZF) and physical layer network coding (PLNC) is proposed, which jointly takes account of users, small base-stations (SBSs) and macro BS (MBS). Furthermore, we analyze the sum rate for users relayed by SBS or also helped by MBS, the influence of the number of antenna configurations on the DoF, and the constraints that antenna should meet. Besides, compared with the traditional SSA scheme, the superiority of this scheme is highlighted. Meanwhile, simulation results illustrate that the proposed scheme can achieve much higher system sum rate than ZF scheme.

In recent years, considerable studies have been devoted to physical‐layer network coding (PLNC) in a two‐way relay channel (TWRC) network with the symmetric channel. However, it may not be appropriate for the asymmetric channel in which the source‐to‐relay channels are not equally strong and the two sources may utilise different modulation. In this study, the authors studied the heterogeneous PLNC design in the asymmetric TWRC network with high‐order modulation and proposed a relay denoising mapping approach to reduce the decoding error probability. Firstly, they put forward a cluster maximisation algorithm to enlarge one cluster by sucking the neighbour points, which satisfy the exclusive law. Then, based on this algorithm, they designed the heuristic nearest‐neighbour denoising mapping (HNDM) approach. The HNDM algorithm divides the nearest neighbour superimposed constellation points into the same cluster as far as possible. Points in the same cluster are coded into a new symbol by a specific mapping that achieves a many‐to‐one mapping. Performance results are provided in terms of symbol error rate. Under diversity channel conditions, the performances of 16‐quadrature amplitude modulator (16‐QAM)‐8‐phase‐shift keying and 16‐QAM‐quadrature phase‐shift keying are evaluated.

Millimetre wave (mmWave) communication is a promising technique for fifth generation networks. Hybrid precoding is introduced to mmWave communication systems to provide a reasonable trade‐off strategy between system performance and energy cost. The hybrid precoder with the partially‐connected structure has relatively low hardware complexity and less energy consumption. In this study, the authors decompose the optimisation problem of analogue precoder into several subproblems, and introduce a heuristic method to find the solution. Then, they obtain the digital precoder according to the product of the channel matrix and analogue precoding matrix. Numerical simulations show that the proposed algorithm performs well in most cases. Considering the error of channel estimation or the finite resolution of phase shifters, the proposed algorithm is able to provide acceptable spectral efficiency as well.

Hybrid precoding, combining the digital and analogue precoding, is a key enabler to reach a compromise between system performance and hardware complexity in millimetre wave (mmWave) massive multiple‐input multiple‐output (MIMO) systems. Most previous studies on hybrid precoding considered narrowband channels. However, mmWave systems are expected to operate on wideband channels with frequency selectivity. In this study, the authors focus on the hybrid precoding design in mmWave massive MIMO systems using orthogonal frequency division multiplexing (OFDM). By transforming the hybrid precoding problem into a series of sub‐problems, they propose a low‐complexity algorithm to design the digital precoder and analogue precoder alternately. In particular, a phase pursuit method is introduced to seek this solution of analogue precoding matrix with the constant amplitude constraint. Simulation results and complexity evaluations reveal that the proposed algorithm can obtain better performance and lower complexity than some existing solutions in mmWave OFDM systems.

Following successful adoption of cloud computing, many service providers (SPs) are now using high-performance Virtual Machines (VMs) located in large datacenters owned by public cloud infrastructure providers to deploy their virtual network functions (VNFs). Since using these VMs has a cost depending on utilization time, a complex problem of VNF placement and scheduling (VPS) must be addressed to achieve satisfactory network performance (e.g., latency) while minimizing the cost paid to lease VMs. In this study, a cost-efficient VPS scheme (CE-VPS) is proposed to address the VPS problem in public cloud networks considering dynamic requests of ordered sequences of VNFs. Our CE-VPS scheme goes beyond existing solutions as it models some important practical aspects such as an additional latency incurred by booting a VM and installing a VNF instance. Also, CE-VPS considers that VNFs can be multi-threaded or single-threaded, and that their throughput as a function of allocated computing resources must be modeled differently. CE-VPS is formulated as a mixed inter linear program (MILP) and also as an efficient heuristic algorithm. CE-VPS achieves lower cost and latency than conventional Best-Availability and Cost-Efficient Proactive VNF Placement schemes, and a better trade-off between resource consumption and latency performance than a conventional Low-Latency scheme.

In radar communication integrated (RCI) systems, multi-carrier shared signals based on OFDM-LFM have been widely used. However, there is a severe problem that the peak-to-average power ratio (PAPR) is too high. Although applying the conventional selective mapping (SLM) algorithm to the OFDM-LFM-RCI system can greatly reduce the probability of high PAPR and have a good PAPR suppression effect, the computational complexity is too high. In order to reduce the computational complexity and improve the PAPR suppression effect, a judgment-based cascaded SLM algorithm (J-Ca-SLM) is proposed in this paper. The proposed J-Ca-SLM algorithm is composed of a two-level cascaded SLM modules and a judgment mechanism between the two levels. For the judgment mechanism, if the PAPR of the first level output sequence is less than the threshold PAPRth, then the sequence is directly used as the transmit sequence, otherwise it will be transferred to the second level for further processing. The simulation results show that the J-Ca-SLM algorithm can not only greatly reduce the computational complexity, but also have better PAPR suppression effect without reducing the communication and radar performance of OFDM-LFM-RCI integrated system.

Millimetre wave (mmWave) multiple‐input multiple‐output (MIMO) systems have been proposed to enable Gbps communication for next‐generation cellular systems and local area networks. To compensate for the severe propagation loss of the mmWave channel, a cost‐effective hybrid precoding architecture, combining a digital precoder and an analogue precoder, is widely used in mmWave MIMO systems. In this study, two hybrid precoding algorithms based on particle swarm optimisation (PSO) algorithm will be proposed for two different hybrid precoding structures, i.e. the fully connected and partially connected structures. First, the authors use the phase of the analogue precoding variable to replace the corresponding variable with the constraints of the unit norm to solve the non‐convex constraints skillfully. Then they design analogue precoding by using PSO algorithm and compute the digital precoding based on the least squares solution. Finally, the proposed algorithms are compared with the existing advanced algorithms. Simulation results demonstrate that the proposed algorithms can approach the optimal performance under the corresponding structure.

This study explores the feasibility of linear interference alignment (IA) for a ( M × M , 1) K system with multi‐frequency independent channels. The authors prove that number of users K ≤ 2 M − 2 is a necessary condition for ( M × M , 1) K multi‐frequency IA system, which is less than that of ( M × M , 1) K multiple‐input–multiple‐output system (i.e. K ≤ 2 M − 1). The conclusion can be extended to all cases with the diagonal channel matrix. They also reveal that the traditional frequency division multiplexing method is inefficient in spectrum utilisation. They apply max‐SINR (signal to interference plus noise ratio) and iterative IA algorithms and the author's simulation results verify that IA algorithms work well in ( M × M , 1) 2 M –2 IA system.

ABSTRACT This article focuses on improving the system capacity of 60‐GHz wireless personal area networks (WPANs) and presents an effective time slot allocation scheme for spatial reuse, which combines the existing exclusive region (ER)‐based scheduling algorithm with simple power control. In the study, the concept of ER for concurrent transmissions is introduced first. Considering the large path loss in the millimeter‐wave band and the characteristics of typical indoor multipath channels, we generalize the signal propagation model as well as ER radius for 60‐GHz WPANs. Then, we propose an improved ER‐based scheduling algorithm, which employs power control instead of constant transmitting power. In this algorithm, devices are assumed to receive data at the receiver sensitivity, which refers to the minimum receiving power to ensure the reliability for communications. Implementation feasibility is provided within the current standards framework. Some more practical analysis based on the beamforming codebook specified by of the IEEE 802.15.3c standard is also developed. In addition, the impact of the antenna radiation efficiency and receiver sensitivity is discussed. Computer simulations validate the excellent performance of the proposed scheme, which can significantly improve the channel capacity under different antenna configurations. Copyright © 2012 John Wiley & Sons, Ltd.

In this article, we suggest an efficient beam switching technique for the emerging 60GHz wireless personal area networks. Given the pre-specified beam codebooks, the beam switching process, aiming to identify the best beam-pair for data transmissions, is formulated as a global optimization problem in a two-dimension plane that is formed by the potential beam pattern index. As the analytical gradient information of the objective reward function is practically unavailable, Rosenbrock numerical algorithm is properly adopted to implement beam searching, by implicitly approaching and exploiting the gradient descent direction through the numerical pattern-search mechanic. In order to enhance search performance, furthermore, a novel initialization process is presented to provide the feasible initial solution for Rosenbrock search. Inspired by the appealing conception of small-region dividing and conquering, this pre-search algorithm can efficiently reduce the search scope and hence improve the success probability. The developed beam switching technique, i.e. an initialization process followed by Rosenbrock search, exhibits a much lower complexity than the current state-of-the-art strategies. It is demonstrated from both theoretical analysis and numerical experiments that, compared with the existing popular methods, the required protocol overhead of the new beam-training procedure can be significantly reduced, accompanying the power consumption of 60GHz devices.

A compressed sensing radar detection scheme for closing vehicle detection is proposed in this paper. Because most of the man-made signals are cyclostationary, the cyclic autocorrelation domain of the target return signal is sparse. The compressed sensing radar detection scheme in this paper is designed based on the sparsity of the cyclic autocorrelation of the target return signal. From the measurements based on the compressed sensing of the cyclic autocorrelation, the actual cyclic autocorrelation of the signal can be reconstructed. From the simulation, the dissertation can be made that a very simple OMP algorithm can get a high probability of detection.

Modern communication engineering has brought forward impractical requirements on powerful computation engines as well as simple implementations. Apparently, the two aspects are contradicted in most realistic applications. Because of the dispersive multipath propagation in underwater acoustic channels, traditional coherent and adaptive receivers are computationally intensive and, hence, inapplicable to the large-scale underwater sensor networks. Inspired by quantum computing and nature intelligence that are incorporated with the concept of culture evolution, in this paper, we suggest a novel quantum memetic algorithm (QMA) built with more qualified problem-solving ability. Instead of classical gene representations, the quantum bit structure is employed by chromosomes to enhance the population diversity of genetic searching. The quantum gate rotating is then explored to update chromosomes in an efficiently parallel way. As a hybridization strategy, quantum-rotation-based local search is integrated in the lifetime learning to further refine individuals' performance and accelerate their convergence toward the global optimality. As a significant real-world application, we develop a noncoherent underwater signal receiver that is based on a QMA framework. From a pattern recognition aspect, the suggested detection scheme includes two sequential phases: Features extraction and pattern classification. Finally, the highly computational optimization problem is elegantly addressed by QMA. Providing favorable robustness to various parameter configurations, QMA can considerably reinforce the search performance and improve the underwater signal detection. It is demonstrated from numerical experiments that QMA is much superior to genetic algorithm (GA) in this high-dimensional optimization. Meanwhile, QMA shows remarkable advantages in search performance, even to the current state-of-the-art quantum-inspired GA and memetic algorithm.

Many-to-one transport results in congestion in wireless sensor networks (WSNs). This is due to the sudden impulse of information flowing to a single destination by single branch. More attention has been paid to congestion control in WSN, but most research works in the past were apt to handle it by controlling output sending rate, and seldom sought solutions on utilizing the idle resources of non-congestion branch. In this paper, an Active Congestion Help (ACOH) mechanism is designed to find and build an auxiliary routing when congestion. For fairness and flow balancing, Adaptive Flow Allocation algorithm (AF) is designed to distribute flow as adaptive proportion between the main routing and the auxiliary. AF is considering the transmitting-receiving rate of congestive and auxiliary node, and quickly converges to a fair and efficient proportion. In ACOH, a simple backpressure is used to handle the data flow which exceeds the maximum throughput. Simulation results validate the effectiveness of our ACOH.

In this paper, we propose a novel multi-tier clustering strategy using cultural-based multiobjective particle swarm optimization (Cultural-MOPSO) for maximizing the longevity of wireless sensor networks. We take into account the distribution of surviving nodes and define three objective functions based on multi-tier cluster hierarchy to fully evaluate every clusterhead election. Simulation results demonstrate that our proposed strategy can achieve energy-efficient multi-tier cluster hierarchy and outperform two other PSO-based clustering schemes in terms of a new metric of network longevity.

A new pulse for cognitive radio-ultra wideband (CR-UWB) using multiple modified transform domain communication system (M-TDCS) is presented in this paper. Utilizing multiple M-TDCS to sense the electromagnetic environment and UWB as a versatile PHY layer to adapt various wireless channel conditions, this pulse can avoid interference to/from the existing wireless systems or noise. This pulse can be implemented using surface acoustic wave (SAW) devices and some other accessorial devices. The bit error ratio (BER) performance of system using this pulse can be observably improved for UWB systems.

In this paper, a statistical analysis of the peak-to-average power ratio (PAPR) of Polynomial cancellation coded OFDM (PCC-OFDM) signals is presented. PCC-OFDM has the good performance of compressing intercarrier interference (ICI) at the cost of high PAPR. The most PAPR analysis assume the subcarriers to be identically and independently distributed (i.i.d). However, the correlation between adjacent pairwise subcarriers of PCC-OFDM causes the assumption not valid. The adjacent partial transmit sequence (PTS) with parameter constraints can be used to reduce the PAPR of PCC-OFDM. The simulation results show that the theoretic analysis is very close to experimental results. The PAPR of PCC-OFDM signals with 128 subcarriers exhibit near 2 dB higher than the same type normal OFDM. PTS based method proposed in this paper can reduce the PAPR of PCC-OFDM to the normal complex-value OFDM level while keeping PCC relation.