This paper proposes a resource-allocation technique for Gaussian multiple-input multiple-output, orthogonal- frequency-division-multiplexing (MIMO-OFDM) multiple-access channel (MAC). Zero-forcing generalized decision-feedback equalizers (ZF-GDFE) are employed at the receiver to cancel completely the interferences produced by all the other users, while a novel matrix decomposition method based on the generalized channel singular-value-decomposition (SVD) is used to find the precoding matrices at each user's transmitter. The achievable rate region is obtained by solving a series of weighted sum-rate maximization problems, and the associated users' power distributions are efficiently found by a Lagrange dual- decomposition method along with a per-tone-based exhaustive search of decoding orders among users. The complexity can be further reduced by replacing the exhaustive search with a greedy algorithm. Simulation results show that the achievable rate region obtained by the greedy algorithm is very close to that achieved by the exhaustive search. Therefore, with a significant computational complexity reduction over the canonical minimum-mean- squared-error (MMSE) -based GDFE, the proposed algorithm provides an ideal scheme for practical systems such as uplink wireless MIMO-OFDM systems and upstream vectored digital subscriber lines (DSL).
To solve the operation sequencing problem in CAPP that is a difficult problem, combining the idea of genetic algorithm, an GA-Jaya algorithm is proposed to minimize the total cost. In the GA-Jaya, the population is initialized according to the procedure priority adjacency matrix which makes the population all meet the process priority relationship. Mutation iteration operator and two kinds of crossover iteration operator are designed for process sequence and processing resource evolution. The GA-Jaya algorithm is applied to a typical case, and compared with the existing genetic algorithm, particle swarm optimization algorithm and ant colony optimization algorithm. The results show that the average quality of the solution obtained by the GA-Jaya algorithm is better than the existing genetic algorithm, particle swarm optimization algorithm and ant colony optimization algorithm.
Wireless energy transfer (WET) is potentially a promising solution to provide convenient and reliable energy supplies for energy-constrained networks, and has drawn growing interests recently. To overcome the significant propagation loss over distance, employing multi-antennas at the energy transmitter (ET) to more efficiently direct wireless energy to desired energy receivers (ERs), termed energy beamforming, is an essential technique for WET. However, the achievable gain of energy beamforming crucially depends on the available channel state information (CSI) at the ET, which needs to be acquired practically. In this paper, we study the optimal design of one efficient channel-acquisition method for a point-to-point multiple-input multiple-output (MIMO) WET system, by exploiting the channel reciprocity based on which the ET estimates the CSI via dedicated reverse-link training from the ER. Considering the limited energy availability at the ER, the training strategy should be carefully designed so that the channel can be estimated with sufficient accuracy, and yet without consuming excessive energy at the ER. To this end, we propose to maximize the net energy at the ER, which is the total energy harvested offset by that used for channel training. The optimal training design, including the number of receive antennas to be trained, as well as the training time and power allocated, is derived. Our result shows that training helps only when the following conditions are satisfied: (i) the channel coherence time is sufficiently large; (ii) the number of antennas at the ET is large enough; and (iii) the effective signal-to-noise ratio (ESNR) is sufficiently high; otherwise, no training should be applied and isotropic energy transmission is optimal.
Constant envelope (CE) precoding is an appealing transmission technique, which enables highly efficient power amplification, and is realizable with a single radio frequency (RF) chain at the multi-antenna transmitter. In this paper, we study the transceiver design for a point-to-point multiple-input multiple-output (MIMO) system with CE precoding. Both single-stream transmission (i.e., beamforming) and multi-stream transmission (i.e., spatial multiplexing) are considered. For single-stream transmission, we optimize the receive beamforming vector to minimize the symbol error rate (SER) for any given channel realization and desired constellation at the combiner output. By reformulating the problem as an equivalent quadratically constrained quadratic program (QCQP), we propose an efficient semi-definite relaxation (SDR) based algorithm to find an approximate solution. Next, for multi-stream transmission, we propose a new scheme based on antenna grouping at the transmitter and minimum mean squared error (MMSE) or zero-forcing (ZF) based beamforming at the receiver. The transmit antenna grouping and receive beamforming vectors are then jointly designed to minimize the maximum SER over all data streams. Finally, the error-rate performance of single- versus multi-stream transmission is compared via simulations under different setups.
Millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems can significantly reduce the number of radio frequency (RF) chains by using lens antenna arrays, because it is usually the case that the number of RF chains is often much smaller than the number of antennas, so channel estimation becomes very challenging in practical wireless communication. In this paper, we investigated channel estimation for mmWave massive MIMO system with lens antenna array, in which we use a mixed (low/high) resolution analog-to-digital converter (ADC) architecture to trade-off the power consumption and performance of the system. Specifically, most antennas are equipped with low-resolution ADC and the rest of the antennas use high-resolution ADC. By utilizing the sparsity of the mmWave channel, the beamspace channel estimation can be expressed as a sparse signal recovery problem, and the channel can be recovered by the algorithm based on compressed sensing. We compare the traditional channel estimation scheme with the deep learning channel-estimation scheme, which has a better advantage, such as that the estimation scheme based on deep neural network is significantly better than the traditional channel-estimation algorithm.
No abstract is provided for this article.
Intelligent System (IS) technologies have shown encouraging potential in facilitating very fast power system dynamic security assessment (DSA) in recent years. In general, the development of the IS consists of four stages. This paper conducts a comprehensive and detailed review on each stage and classifies the methods involved in the stages. The classification highlights the differences between the methods and show their advantages and deficiencies. The value of this paper is that it can serve as a useful and practical guideline to assist in developing ISs for very fast DSA. Moreover, the proposed classifications can provide deep insight into the enhancement of the IS towards improved DSA performance.
Radio waves carry both energy and information simultaneously. Nevertheless, Radio-Frequency (RF) transmission of these quantities have traditionally been treated separately. Currently, we are experiencing a paradigm shift in wireless network design, namely unifying wireless transmission of information and power so as to make the best use of the RF spectrum and radiations as well as the network infrastructure for the dual purpose of communicating and energizing. In this paper, we review and discuss recent progress on laying the foundations of the envisioned dual purpose networks by establishing a signal theory and design for Wireless Information and Power Transmission (WIPT) and identifying the fundamental tradeoff between conveying information and power wirelessly. We start with an overview of WIPT challenges and technologies, namely Simultaneous Wireless Information and Power Transfer (SWIPT),Wirelessly Powered Communication Network (WPCN), and Wirelessly Powered Backscatter Communication (WPBC). We then characterize energy harvesters and show how WIPT signal and system designs crucially revolve around the underlying energy harvester model. To that end, we highlight three different energy harvester models, namely one linear model and two nonlinear models, and show how WIPT designs differ for each of them in single-user and multi-user deployments. Topics discussed include rate-energy region characterization, transmitter and receiver architecture, waveform design, modulation, beamforming and input distribution optimizations, resource allocation, and RF spectrum use. We discuss and check the validity of the different energy harvester models and the resulting signal theory and design based on circuit simulations, prototyping and experimentation. We also point out numerous directions that are promising for future research.
One of the most promising approaches of handling constrained optimization problems (COPs) is to adopt multi-objective methods, which can provide a trade-off between the objective and constraints. However, the multi-objective-based constraint-handling techniques take preference over infeasible solutions, some promising feasible solutions cannot survive during the course of search because they are dominated ones. Furthermore, some nondominated infeasible solutions with worse objective values should not be reserved in that they are far from the feasible optimal solution. To address these two problems, this paper proposes a Pareto front transformation model which transforms a part of potential feasible solutions into nondominated ones. Meanwhile, combined with the dynamic multi-objective technique, certain nondominated infeasible solutions with worse objective values will be rejected. In this way, the search can towards the global optimum from both the feasible and infeasible sides of the search space. The proposed Pareto front transformation model is integrated into a multi-objective-based constrained evolutionary algorithm (CEA). The new designed algorithm is named PT-MOEA, and it is compared with seven peer multi-objective-based CEAs and five state-of-the-art CEAs on solving IEEE CEC 2006 and IEEE CEC 2010 test suites, respectively. Experimental results demonstrate the competitiveness of the proposed method in comparison with its competitors for solving COPs.
In order to enhance the business support capability of power distribution Internet of Things and save economic cost, this paper proposes an optimal deployment method for distribution edge computing terminals in software defined network based power distribution Internet of Things. The base station of power wireless private network has abundant data flow and service flow. It has obvious advantage to deploy distribution edge computing terminal by using the site of wireless base station. This paper introduces the software defined network based edge computing architecture of the power distribution Internet of Things, and establishes the service, intelligent terminal and edge computing terminal of the power distribution Internet of things. Furthermore, considering communication mode constraints, delay constraints and hardware configuration constraints, and aiming at minimizing the sum of annual average equipment cost and annual operating cost, an optimal deployment model of distribution edge computing terminals was established. The effectiveness of the proposed method is verified by simulation.
In this paper we establish spatial central limit theorems for a large class of supercritical branching Markov processes with general spatial-dependent branching mechanisms. These are generalizations of the spatial central limit theorems proved in [1], P. for branching OU processes with binary branching mechanisms. Compared with the results of [1], our central limit theorems are more satisfactory in the sense that the normal random variables in our theorems are non-degenerate.
