Optimal Online Transmission Policy for Energy-Constrained Wireless-Powered Communication Networks

This work considers the design of online transmission policy in a wireless-powered communication system with a given energy budget. The system design objective is to maximize the long-term throughput of the system exploiting the energy storage capability at the wireless-powered node. We formulate the design problem as a constrained Markov decision process (CMDP) problem and obtain the optimal policy of transmit power and time allocation in each fading block via the Lagrangian approach. To investigate the system performance in different scenarios, numerical simulations are conducted with various system parameters. Our simulation results show that the optimal policy significantly outperforms a myopic policy which only maximizes the throughput in the current fading block. Moreover, the optimal allocation of transmit power and time is shown to be insensitive to the change of modulation and coding schemes, which facilitates its practical implementation.Comment: 7 pages, accepted by ICC 2019. An extended version of this paper is accepted by IEEE TW

The Development and Application of Emotion and Values in Primary School

Based on the effective teaching of primary school English class, this paper starts from studying the application of emotion attitude goal in class, and relies on the human-oriented version of primary school English textbook to discuss how primary school English teachers adopt effective teaching strategies to organize and implement English teaching activities, so as to achieve the goal of “emotion attitude and values” in English teaching. This paper explains the significance of realizing “emotion, attitude and value” in primary school English classroom and how to excavate emotion elements in English textbooks so as to effectively realize the three-dimensional goal of primary school English teaching. By studying the current status of primary school English teaching and existing problems, this paper points out that teachers should update their teaching concepts in time, and discuss and explore the aspects of lesson preparation, class, teaching test evaluation and so on around the theory of “unit integrated design”, so as to improve the efficiency of class and promote students’ emotions, attitudes and values while grasping knowledge. At the same time, the author emphasizes classroom practice, timely reflection after class and timely adjustment of the taught content so as to achieve the ultimate goal of “emotion, attitude and values”

Achieving Covert Wireless Communications Using a Full-Duplex Receiver

Covert communications hide the transmission of a message from a watchful adversary while ensuring a certain decoding performance at the receiver. In this work, a wireless communication system under fading channels is considered where covertness is achieved by using a full-duplex (FD) receiver. More precisely, the receiver of covert information generates artificial noise with a varying power causing uncertainty at the adversary, Willie, regarding the statistics of the received signals. Given that Willie's optimal detector is a threshold test on the received power, we derive a closed-form expression for the optimal detection performance of Willie averaged over the fading channel realizations. Furthermore, we provide guidelines for the optimal choice of artificial noise power range, and the optimal transmission probability of covert information to maximize the detection errors at Willie. Our analysis shows that the transmission of artificial noise, although causes self-interference, provides the opportunity of achieving covertness but its transmit power levels need to be managed carefully. We also demonstrate that the prior transmission probability of 0.5 is not always the best choice for achieving the maximum possible covertness, when the covert transmission probability and artificial noise power can be jointly optimized.Comment: 13 pages, 11 figures, Accepted for publication in IEEE Transactions on Wireless Communication

Numerical analysis of hard rock tunnel excavated by double shield TBM based on CWFS model

In order to study the mechanical response of a hard rock tunnel excavated by double shield tunnel boring machine (DS-TBM), a numerical method was introduced to simulate the TBM excavating process. The failure modes of surrounding rock mass described based on the cohesion weakening and frictional strengthening (CWFS) Mohr-Coulomb strain-softening criterion. The characteristics of stress field and plastic zone on the cross and longitudinal section of the tunnel were analyzed in detail, and the results were compared with those in the intrinsic condition (when TBM model is not activated). The simulation results indicate that the stress paths at the vault are relatively simple, and the stress concentration caused by excavation unloading is obviously reduced by lining and backfill grouting, while the sidewall is less disturbed by the excavation of TBM. The invert experiences three unloading processes, due to excavation, the contact between the rear shield and the bottom of surrounding rock, as well as backfill grouting at gap between the lining and the rock mass. The vault has a larger plastic zone than the invert, attributing to the geometrical difference between the cutter-head and the front shield, as well as the conicity of the front and rear shields. The area of plastic zones gradually increases along the tunnel route, but it becomes stable after the rear shield