Two-way Network Research Articles

Latent Factors in Student–Teacher Interaction Factor Analysis

Classroom interactions between students and teachers form a two-way or dyadic network. Measurements such as days absent, test scores, student ratings, or student grades can indicate the “quality” of the interaction. Together with the underlying bipartite graph, these values create a valued student–teacher dyadic interaction network. To study the broad structure of these values, we propose using interaction factor analysis (IFA), a recently developed statistical technique that can be used to investigate the hidden factors underlying the quality of student–teacher interactions. Our empirical study indicates there are latent teacher (i.e., teaching style) and student (i.e., preference for teaching style) types that influence the quality of interactions. Students and teachers of the same type tend to have more positive interactions, and those of differing types tend to have more negative interactions. IFA has the advantage of traditional factor analysis in that the types are not presupposed; instead, the types are identified by IFA and can be interpreted in post hoc analysis. Whereas traditional factor analysis requires one to observe all interactions, IFA performs well even when only a small fraction of potential interactions are actually observed.

A Two-Way Network Beamforming Approach Based on Total Power Minimization With Symmetric Relay Beamforming Matrices

We study the total transmit power minimization problem for a two-way relay network under two constraints on the transceivers’ received signal-to-noise-ratios. The network considered herein consists of multiple multi-antenna relay nodes and two single-antenna transceivers. Each relay transforms the vector of its received signals, by multiplying this vector with a complex beamforming matrix, thereby obtaining a new vector whose entries are transmitted over different antennas of that relay. Assuming the relay beamforming matrices and the transceivers’ transmit powers as the design parameters, we first study the total power minimization problem under the assumption that the relay beamforming matrices are symmetric. Under such an assumption, we show that the total power minimization problem is amenable to a semi-closed-form solution, and thus, it can be solved efficiently. We then consider the case, where the relay beamforming matrices may not be symmetric and show that in this case, the total power minimization problem can be solved using a computationally prohibitive algorithm which involves a 2-D search over a grid in the space of the transceivers’ transmit powers and semi-definite programming at each vertex of this grid. Our numerical results show that the symmetric assumption on the relay beamforming matrices incurs only insignificant loss, while this assumption allows us to significantly reduce the computational burden of solving the total power minimization problem.

Power splitting based SWIPT in network-coded two-way networks with data rate fairness: an information-theoretic perspective

This paper investigates the simultaneous wireless information and power transfer (SWIPT) for network-coded two-way relay network from an information-theoretic perspective, where two sources exchange information via an SWIPT-aware energy harvesting (EH)relay. We present a power splitting (PS)-based two-way relaying (PS-TWR) protocol by employing the PS receiver architecture. To explore the system sum rate limit with data rate fairness, an optimization problem under total power constraint is formulated. Then, some explicit solutions are derived for the problem. Numerical results show that due to the path loss effect on energy transfer, with the same total available power, PS-TWR losses some system performance compared with traditional non-EH two-way relaying, where at relatively low and relatively high signal-to-noise ratio (SNR), the performance loss is relatively small. Another observations is that, in relatively high SNR regime, PS-TWR out-performs time switching-based two-way re-laying (TS-TWR) while in relatively low SNR regime TS-TWR outperforms PS-TWR. It is also shown that with individual available power at the two sources, PS-TWR outperforms TS-TWR in both relatively low and high SNR regimes.

Enhanced beamforming design and sum-rate maximization for two-way multi-relay networks

In this paper, we investigate an enhanced relay beamforming design for two-way relay networks (TWRN). In order to reduce the computational complexity, we derive a sum of the inverse of the signal-to-noise ratio (SI-SNR) problem equivalent to the objective sum-rate (SR) problem. The SI-SNR problem can be reformulated as a simple optimization problem by using the Cholesky decomposition and Cauchy-Schwarz inequality, and solved by the interior-point method. The numerical results show that the proposed SI-SNR method can not only reduce the computational complexity but also have the same SR performance as that of the conventional works.

On the Capacity Region of Asymmetric Gaussian Two-Way Line Channel

Lattice codes are known to outperform random codes for certain networks, especially in the Gaussian two-way relay channels (GTWRCs) where lattice codes are able to exploit their linearity. As an extension of the GTWRC, in this paper, we consider the asymmetric Gaussian two-way line network where two nodes exchange their messages through multiple relays. We first investigate the capacity region of the full-duplex two-way two-relay line network. The results can be extended to an arbitrary number of relays and to half-duplex scenarios. This channel consists of four nodes: $1\leftrightarrow 2\leftrightarrow 3\leftrightarrow 4$ , where nodes 1 and 4 with the help of two full-duplex relays, i.e., nodes 2 and 3, exchange their messages with each other. Using lattice codes, we design a novel scheme that allows the relay nodes to send the data in both directions simultaneously under an asymmetric rate region. In the proposed scheme, each relay decodes the sum of lattice points and then re-encodes it into another lattice codeword (which satisfies the transmit power constraint at the relay). It is shown that the proposed scheme achieves the capacity region of asymmetric two-way line network within 0.5 bit independent of the number of relays.

개방형 자동 수요 반응 시스템 보안 취약성 분석에 관한 연구

Abstract Technology to optimize and utilize the use and supply of the electric power between consumer and supplier has been on the rise among the smart grid power market network in electric power demand management based on the Internet. Open Automated Demand Response system protocol, which can deliver Demand Response needed in electric power demand management to electricity supplier, system supplier and even the user is openADR 2.0b. This paper used the most credible, cosmopolitanly proliferated EPRI open source and analysed the variety of security vulnerability that developed VEN and VTN system may have. Using the simulator for attacking openADR protocol, the VEN/VTN system that has been implemented as EPRI open source was conducted to attack in a variety of ways. As a result of the analysis, we were able to get the results that the VEN/VTN system has security vulnerabilities to the parameter tampering attacks and service flow falsification attack. In conclusion, if you want to implement the openADR2.0b protocol system in the open or two-way communication environment smart grid network, considering a variety of security vulnerability should be sure to seek security technology and services.

The Effect of the Elastic Fields Caused by a Networks of Dislocations Placed at Interfaces of a Three-Layer Material Cu/Cu/(001) Fe in the Case of Anisotropic Elasticity

The importance of crystal interfaces in the assessment of the effects of elastic fields Eshelby et al. (Acta Meta 1:251–259, 1953) for nanoscale multilayer materials is a topical area that has been the focus of many researchers. This work focuses on the characterization and modeling of interfacial defects on both microscopic and macroscopic scales. From a design perspective, considering such elastic fields has become a critical element in the development of multilayer’s in the industry due to their effect on the properties of materials. The description of elastic fields associated with misfit dislocations in a multilayer involving hetero fields is possible thanks to the inversion of a single set of linear equations. Thus, the aim of this investigation is to evaluate the effects of elastic fields at the level of crystal interfaces for a nanoscale three-layer material under the effect of two-way networks of unidirectional dislocations. These are placed at interfaces accommodating a parametric mismatch which accounts for the particular anisotropic elasticity for each crystal.

Diversity combining in bi‐directional relay networks with energy harvesting nodes

In this study, the authors consider two multiple-antenna transceivers exchanging information through a relay-assisted network using a single-carrier communication scheme. The authors assume that the propagation delay in different relaying path is negligible and the relay nodes are synchronous. As a result, the end-to-end multipath channel is not frequency-selective (time-dispersive) and hence, the successive arriving signals at the transceivers do not interfere with each other. Otherwise, inter-symbol-interference (ISI) will be inevitable and cyclic insertion and removal matrices will be required to combat ISI. In such a two-way network, the relay nodes harvest energy from the surrounding environment and utilise this energy to forward their received messages using a harvest-then-forward protocol. For different receiver diversity combining techniques, the authors design an optimal relay beamforming to maximise the quality of the received signals at the transceivers subject to the energy casualty constraint at the relay nodes (the energy consumed for transmission of each block cannot exceed the accumulative harvested energy). For each diversity combining technique, a closed-form solution is obtained for the optimal signal-to-noise ratio (SNR) that shows how adjusting the data transmission rate of the transceivers and the amount of energy harvested at the relays affects the received SNR.

Joint probability inference algorithms of a Bayesian network and reliability analysis of electronic products

Considering the tedious and complex problem of solving joint probability with the bucket elimination algorithm, a parallel joint probability inference algorithm was proposed. The logical relation was analysed among each node variable and the inverse order method of the bucket elimination was used to introduce the mathematical expressions of joint probability and calculate the probabilities of one or more node failures when the network fails. The method is applied into the example of reliable analysis of electronic products and is demonstrated the simplicity and effectiveness of the method in the process of two-way Bayesian network inference. The results can be used to identify the weak links of electronic products and also provide a theoretical basis for reliability and maintenance strategies for electronic products.

Wireless energy harvesting in two-way network coded cooperative communications: a stochastic approach for large scale networks

In this letter, we study the performance of network coding (NC)-aided cooperative communications in large scale networks, where the relays are able to harvest energy emitted by wireless transmissions. In particular, we derive theoretical expressions for key network performance metrics, i.e., the probability of successful data exchange and the network lifetime gain. The proposed analytical expressions are verified via extensive Monte Carlo simulations, demonstrating the potential benefits of the energy harvested by the wireless transmissions.

Centralized Two-Way AF MIMO Multiple Dispersed Relay Network

This paper considers a two-way amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay network consisting of two sources (each with multiple antennas) and multiple physically dispersed single-antenna relays. A central station finds the optimum relay amplifying matrices and transmit/receive beamforming vectors explicitly and iteratively under the transmit power constraints at the sources and the relays. The minimum-mean-square-error criterion is used. Numerical results show that the proposed scheme outperforms the existing two-way AF MIMO network schemes proposed by Arti et al. and Wang et al.

Analysis of Network Exit Functions for Various Urban Grid Network Configurations

Macroscopic networkwide traffic models have been used to study aggregate traffic behavior on urban networks and to design traffic control strategies. However, less attention has been given to their application in the study of street network design. This paper uses the network exit function (NEF) to analyze traffic performance on an abstract grid network of various street configurations. The NEF is an aggregate relationship between trip completion rate and the number of vehicles circulating in a network. Street configuration is a topic of interest in many cities, especially in the United States, where city planners are considering street network conversions. Three configurations are addressed here: two-way streets, two-way streets with prohibited left turns (TWL), and one-way streets. This work builds on previous studies by incorporating more realistic traffic dynamics with microsimulation software (VISSIM) with dynamic traffic assignment enabled to emulate better the behavior of real drivers. This work finds that NEFs of two-way networks generally are smaller than those of TWL and one-way networks because of reduced capacity at intersections. Comparison of TWL and one-way networks is more nuanced, as traffic performance on these networks depends on route choice. If vehicles are always routed through the path with the shortest travel time, TWL networks offer NEFs with higher trip completion rates; however, if vehicles spread themselves across multiple alternatives, one-way networks provide better results. TWL networks offer a better trade-off between distance traveled and capacity at intersections, and one-way networks offer more shortest-path routing choices between origin–destination pairs.

Functional Requirements in Video-on-Demand Transmission System

Video-on-demand transmission system which is based on IP/DVB technology adopts C/S structure that is easy to operate and maintain for users to manage interactive commands and data transmission. Through interactive control on commands and media flow transmission by IP/DVB technology, it forms instant video-on-demand of transmission platform. The system is designed on the bases of multiple functions such as: response based on user command; analytical transmission of media stream; media stream receiving. Shaoxing radio is one of the digital cable TV pilots approved by the state, and has modified two-way radio and television network equipment. If large number of input network resources are idle, it will bring a lot of loss to radio companies.

Distributed Beamforming for Spectrum-Sharing Systems With AF Cooperative Two-Way Relaying

We consider in this paper distributed beamforming for two-way cognitive radio networks in an effort to improve the spectrum efficiency and enhance the performance of the cognitive (secondary) system. In particular, we consider a spectrum sharing system where a set of amplify-and-forward (AF) relays are employed to help a pair of secondary transceivers in the presence of multiple licensed (primary) users. The set of relays participate in the beamforming process, where the optimal beamformer weights are obtained via a linear optimization method. For this system, we investigate the transmission protocols over two and three time-slots. To study and compare the performance tradeoffs between the two transmission protocols, for both of them, we derive closed-form expressions for the cumulative distribution function (CDF) and the moment generating function (MGF) of the equivalent end-to-end signal-to-noise ratio (SNR) at the secondary receiver. We analyze the performance of the proposed methods where closed-form expressions for the user outage probability and the average error probability are derived for independent and identically distributed Rayleigh fading channels. Numerical results demonstrate the efficacy of beamforming in enhancing the secondary system performance in addition to mitigating the interference to the primary users. In addition, our results show that the three time-slot protocol outperforms the two time-slot protocol in certain scenarios where it offers a good compromise between bandwidth efficiency and system performance.

Advances in Dynamic Traffic Assgmnt: TAC

Traditionally traffic assignment problems (TAPs) have been formulated as non-cooperative games (NCGs), and Wardrop’s user equilibrium (UE) of a TAP as Nash equilibrium (NE) of the corresponding NCG. In this study, in contrast, we propose a mapping from finite NCGs (F-NCGs) to asymmetric TAPs (A-TAPs) on a two-way or urban network, in which the travel cost of one link depends on flows on other links. With the help of three route-based formulations of UE, we show that NE of an F-NCG is equivalent to UE of the corresponding A-TAP. Based on the new relationship, we extend Nash’s fixed point formulation of NE to prove the existence of static UE. This study provides a more complete picture of the relationships between NCGs and TAPs. In the future we will be interested in studying Nash’s fixed point formulation for dynamic UE.

The Overview of Smart Grid

Smart Grid is the newest direction of electric power development, and is regarded as the significant technology innovation and development trend of the electric power system in 21st century. It is also regarded as the inevitable result of the development of economic and technology. It has flexible, clean, safe, economical, and friendly functions. Smart grid is a new "second generation" network, which is built on an integrated basis of two-way high-speed communication networks, through the application of advanced sensing and measurement techniques, equipment technology, control technology and decision support system technology in order to achieve reliable, safe, high-quality, economical, efficient, environmentally friendly and safe using target. Smart Grid’s background, significance key technologies, technical difficulties and prospects are introduced in this paper.

Wireless Energy Harvesting in Two-Way Network Coded Cooperative Communications: A Stochastic Approach for Large Scale Networks

In this letter, we study the performance of network coding (NC)-aided cooperative communications in large scale networks, where the relays are able to harvest energy emitted by wireless transmissions. In particular, we derive theoretical expressions for key network performance metrics, i.e., the probability of successful data exchange and the network lifetime gain. The proposed analytical expressions are verified via extensive Monte Carlo simulations, demonstrating the potential benefits of the energy harvested by the wireless transmissions.

Semi-blind two-way AF relaying over Nakagami-m fading environment

In this paper, we investigate semi-blind opportunistic amplify-and-forward (AF) selection relaying in two-way dual-hop cooperative communication networks on independent Nakagami-m fading channels. This system is compared to channel state information (CSI)-assisted opportunistic AF selection relaying (CSIA-OAF) where the relays use variable gains for the amplification. In semi-blind opportunistic AF scenario (SB-OAF), the relays use partial CSI-fixed gains to amplify the received signals. In this work, we first derive the expression of the signal-to-noise ratio (SNR) in the case of SB-OAF selection relaying. The obtained SNR is used to process the bounds of average sum-rate, outage probability, and average symbol error rate (SER). Numerical results are used to show the performance of the proposed SB-OAF system compared to the CSIA-OAF relaying. The comparison shows that the cost of the significant reduction of the proposed SB-OAF complexity is obtained for a slight loss in performance compared to CSIA-OAF scenario.

On the Secure Outage Performance for Dual-Hop Network Coding Systems with Cooperative Jamming

In this paper, a design of cooperative network coding (NC) and jammer relay (JR) is proposed for this two-way network in order to improve the security of the date exchange. Considering the system over Rayleigh fading channels in the presence of one eavesdropper and two relays, we study secrecy outage (including the probability of non-zero secrecy capacity and secure outage probability), respectively. In this paper, one relay is regarded as NC relay which is used to make codes by xor in order to prevent eavesdropper's interception while the other one is regarded as a jammer relay which can send interference to eavesdropper. We derive exact expressions for the secure outage probability. The accuracy of our performance analysis is verified by simulation results.

An Communication and Battery Performance Evaluation of the Demand Response and Battery Storage Coordination System Potential for Providing Microgrid Tie-Line Smoothing Services

In this paper, an communication and battery performance evaluation is discussed for a demand response and battery storage coordination algorithm, which provides a new way of microgrid tie-line smoothing service. A battery storage system and a total number of 1000 heat pumps are modeled to demonstrate the algorithm. A temperature priority list (TPL) model is used to describe the behavior of the heat pumps. Besides, a control strategy via a two-way communication networks is implemented to smooth the tie-line fluctuations. Then considering in a no ideal communication environment, the impacts of the unexpected changes of the on/off status of the heat pumps on the simulation results are studied. Meanwhile, the impacts of different numbers of batteries and batteries with different charging rates are also referred. The results show that coordinating the heat pumps and batteries can significantly smooth the fluctuations brought by the integration of the renewable resources such as the wind and solar power. The switching status changes of the heat pumps, the numbers and charging rate of the batteries also have great influence on the proposed smoothing performance.