No abstract is provided for this article.
In this paper, we study simultaneous wireless information and power transfer (SWIPT) in orthogonal frequency division multiple access (OFDMA) systems with the coexistence of information receivers (IRs) and energy receivers (ERs). The IRs are served with best-effort secrecy data and the ERs harvest energy with minimum required harvested power. To enhance the physical layer security for IRs and yet satisfy energy harvesting requirements for ERs, we propose a new frequency domain artificial noise (AN) aided transmission strategy. With the new strategy, we study the optimal resource allocation for the weighted sum secrecy rate maximization for IRs by power and subcarrier allocation at the transmitter. The studied problem is shown to be a mixed integer programming problem and thus non-convex, while we propose an efficient algorithm for solving it based on the Lagrange duality method. To further reduce the computational complexity, we also propose a suboptimal algorithm of lower complexity. The simulation results illustrate the effectiveness of proposed algorithms as compared against other heuristic schemes.
No abstract is provided for this article.
Conventional beamforming with fixed-position antenna (FPA) arrays has a fundamental trade-off between maximizing the signal power (array gain) over a desired direction and simultaneously minimizing the interference power over undesired directions. To overcome this limitation, this letter investigates the movable antenna (MA) array enhanced beamforming by exploiting the new degree of freedom (DoF) via antenna position optimization, in addition to the design of antenna weights. We show that by jointly optimizing the antenna positions vector (APV) and antenna weights vector (AWV) of a linear MA array, the full array gain can be achieved over the desired direction while null steering can be realized over all undesired directions, under certain numbers of MAs and null-steering directions. The optimal solutions for AWV and APV are derived in closed form, which reveal that the optimal AWV for MA arrays requires only the signal phase adjustment with a fixed amplitude. Numerical results validate our analytical solutions for MA array beamforming and show their superior performance to the conventional beamforming techniques with FPA arrays.
The main control methods for helicopter turboshaft engines are cascade feedforward control and model predictive control. The former is difficult to solve the delay of power turbine response caused by the large inertia of the rotor system, while the latter often requires a great amount of computation due to the iteration of the optimal algorithm. To improve the real-time rapidity of power turbine control for turboshaft engines, a control system framework based on thermo-gas-dynamic performance model is proposed in this paper. The calculation of this model is lightweight based on component characteristics, and a double closed-loop feedback control system of the two rotational speeds of gas generator (GG) and power turbine (PT) based on small-step fuel flow (Wf) is further designed. The simulation results show that the power turbine speed is stable, the engine power response is fast, and the control process can be fast and reliable when this control framework is utilized for the acceleration and deceleration processes of the engine.
This paper studies a multiuser multiple-input single-output (MISO) broadcast system for simultaneous wireless information and power transfer (SWIPT), where a multi-antenna access point (AP) sends information and energy simultaneously via beamforming to multiple single-antenna receivers. We maximize the weighted sum-power transferred to energy harvesting (EH) receivers subject to a set of minimum signal-to-interference-and-noise ratio (SINR) constraints at information decoding (ID) receivers. In particular, we consider two types of ID receivers, namely Type I and Type II receivers, without and with the capability of cancelling the interference from energy signals, respectively. For each type of ID receivers, we formulate the joint information and energy transmit beamforming problem as a non-convex quadratically constrained quadratic program (QC-QP), for which the globally optimal solution is obtained by applying the technique of semidefinite relaxation (SDR). It is shown that for Type I ID receivers, dedicated energy beamforming is not needed to achieve the optimal solution, while for Type II ID receivers, employing no more than one energy beam is optimal.
In order to sample precisely the state transition time when simulating non-Markovian system,a new sampling method named Approximate Sampling for Residual Distribution(ASRD) method is put forward,in which several uniform distributions are used to approach general residual life distributions. The approach-coefficient d is used to adjust sampling precision and efficiency. Another method named Forced Transitions(FT) based ASRD(FT-ASRD) simulation method is brought forward to simulate high-reliable non-Markovian systems. FT-ASRD uses FT strategy to get the unreliability parameter. Several examples show that,when 5≤d≤10,FT-ASRD is more efficient and has lower relative error compared with crude simulation methods.
In recent years,our country service computing paradigm has been constant development,cyber source release,network maintenance,cyber source as well as the deployment of the reasonable configuration of cyber source domain and so on are more or less produced very big change.Whether from the personal point of view,or from the point of view of the whole enterprise,users have the old space limit,time limit and limit the great span,and the innovation ability is very good extension.As the current situation of the new generation service computing model,cloud computing for IT and the related industry produced very far-reaching effect,has the profound significance.In the face of the current cloud computing cloud computing will be the myriads of changes,the ecosystem of this concept is good take,cloud computing system,operation mechanism,key factors and its key algorithm good put up,and a cloud storage as the main example,the process of the construction of a good analysis,the possible problems are discussed,and the measures to solve,in this paper,the author study of cloud computing and cloud storage ecosystem.
This letter studies a wireless-powered amplify-and-forward relaying system, where an energy-constrained relay node assists the information transmission from the source to the destination using the energy harvested from the source. We propose a novel two-phase protocol for efficient energy transfer and information relaying, in which the relay operates in full-duplex mode with simultaneous energy harvesting and information transmission. Compared with the existing protocols, the proposed design possesses two main advantages: 1) it ensures uninterrupted information transmission since no time switching or power splitting is needed at the relay for energy harvesting; and 2) it enables the so-called self-energy recycling, i.e., part of the energy (loop energy) that is used for information transmission by the relay can be harvested and reused in addition to the dedicated energy sent by the source. Under the multiple-input single-output (MISO) channel setup, the optimal power allocation and beamforming design at the relay are derived. Numerical results show a significant throughput gain achieved by our proposed design over the existing time switching based relay protocol.
This paper studies the energy management in the coordinated multi-point (CoMP) systems powered by smart grids, where each base station (BS) with local renewable energy generation is allowed to implement the two-way energy trading with the grid. Due to the uneven renewable energy supply and communication energy demand over distributed BSs as well as the difference in the prices for their buying/selling energy from/to the gird, it is beneficial for the cooperative BSs to jointly manage their energy trading with the grid and energy consumption in CoMP based communication for reducing the total energy cost. Specifically, we consider the downlink transmission in one CoMP cluster by jointly optimizing the BSs' purchased/sold energy units from/to the grid and their cooperative transmit precoding, so as to minimize the total energy cost subject to the given quality of service (QoS) constraints for the users. First, we obtain the optimal solution to this problem by developing an algorithm based on techniques from convex optimization and the uplink-downlink duality. Next, we propose a sub-optimal solution of lower complexity than the optimal solution, where zero-forcing (ZF) based precoding is implemented at the BSs. Finally, through extensive simulations, we show the performance gain achieved by our proposed joint energy trading and communication cooperation schemes in terms of energy cost reduction, as compared to conventional schemes that separately design communication cooperation and energy trading.
The six-dimensional movable antenna (6DMA) is a promising technology to fully exploit spatial variation in wireless channels by allowing flexible adjustment of three-dimensional (3D) positions and rotations of antennas at the transceiver. In this paper, we consider a 6DMA-equipped base station (BS) and aim to maximize the average sum logarithmic rate of all users served by the BS by jointly designing 6DMA surface positions and rotations based on statistical channel information (SCI). Different from prior works on 6DMA design which use alternating optimization to iteratively update surface positions and rotations, we propose a new sequential optimization method that first determines the optimal rotations and then identifies feasible positions to realize these rotations under practical antenna placement constraints. Simulation results show that our proposed optimization scheme significantly reduces the computational complexity of conventional alternating optimization (AO), while achieving communication performance comparable to the AO-based approach and superior to existing fixed-position/rotation antenna arrays.
No abstract is provided for this article.
This paper studies the optimal training design for a multiple-input single-output (MISO) wireless energy transfer (WET) system in frequency-selective channels, where the frequency-diversity and energy-beamforming gains can be both achieved by properly learning the channel state information (CSI) at the energy transmitter (ET). By exploiting channel reciprocity, a two-phase channel training scheme is proposed to achieve the diversity and beamforming gains, respectively. In the first phase, pilot signals are sent from the energy receiver (ER) over a selected subset of the available frequency sub-bands, through which the sub-band that exhibits the largest sum-power over all the antennas at the ET is determined and its index is sent back to the ER. In the second phase, the selected sub-band is further trained for the ET to estimate the multi-antenna channel and implement energy beamforming. We propose to maximize the net energy harvested at the ER, which is the total harvested energy offset by that used for the two-phase channel training. The optimal training design, including the number of sub-bands trained and the energy allocated for each of the two phases, is derived.
No abstract is provided for this article.
For more than a thousand years, Chinese people were aware of the transmitted sensations by the application of needles on the body surface. This practice is called acupuncture. Acupuncture had been recorded and transcribed in writings and in drawings, until finally the acupoints were inscribed onto a bronze statue. The bronze statue was called the Meridian Figure. Deeply embodied in the bronze statue is a tripartite confrontation-prism representation of the humans body. This concept was a great scientific achievement in ancient China. The author traces the history of Meridian science described in traditional Chinese medical terms. Then he explores a clear analogy of the meridian pathway (MP) phenomenon. In a model system, by using a simple segmental in vertebrate, certain parallels can be demonstrated with the meridian concept. For example, the author demonstrated a clear correlation rule among the central mechano-sensory channels, and characteristics of positional discrimination in individual nerve cells from different receptive field inputs. The evidence suggests that the MP phenomenon is an objective neurobiological response. To clarify the research objective in this paper, the author suggests that the MP is a bi-directional pathway along which a positional message signal is transmitted. This phenomenon is evoked by physical stimulation, transmitted linearly across the human body segments, and is perceived by the brain. The MP consists of low resistance paths, is connected by the liquid media contained in the apposite membranous structure. At the cellular level, the regulation functions of MP must pass through along this low resistance path. Two aspects of the modern Meridian research are the functional regulation and the mechanism of intercellular liquid modulation at the nanometer level.
