Improving Performance of User Pair Using Reconfigurable Intelligent Surfaces

With the given scope for new use cases and the demanding needs of future 6th generation (6G) wireless networks, the development of wireless communications looks exciting. The propagation medium has been viewed as a randomly behaving entity between the transmitter and the receiver since traditional wireless technology, degrading the quality of the received signal due to the unpredictable interactions of the broadcast radio waves with the surrounding objects. On the other hand, network operators could now manipulate electromagnetic radiation to remove the negative impacts of natural wireless propagation due to the recent arrival of reconfigurable intelligent surfaces (RIS) in wireless communications. According to recent findings, the RIS mechanism benefits nonorthogonal multiple access (NOMA), which can effectively deliver effective transmissions. For simple design, of RIS-NOMA system, fixed power allocation scheme for NOMA is required. The main system performance metric, i.e., outage probability, needs to be considered to look at the efficiency and capability of transmission mode relying on RIS and NOMA schemes, motivated by the potential of these developing technologies. As major performance metrics, we derive analytical representations of outage probability, and throughput and an accurate approximation is obtained for the outage probability. Numerical results are conducted to validate the exactness of the theoretical analysis. It is found that increasing the higher number of reflecting elements in the RIS can significantly boost the outage probability performance, and the scenario with only the RIS link is also beneficial. In addition, it is desirable to deploy the RIS-NOMA since it is indicated that better performance compared with the traditional multiple access technique.

Binary fraction of O and B-type stars from LAMOST data

Binary stars play an important role in the evolution of stellar populations . The intrinsic binary fraction (f bin) of O and B-type (OB) stars in LAMOST DR5 was investigated in this work. We employed a cross-correlation approach to estimate relative radial velocities for each of the stellar spectra. The algorithm described by Sana et al. (2013) was implemented and several simulations were made to assess the performance of the approach. The binary fraction of the OB stars is estimated through comparing the uni-distribution between observations and simulations with the Kolmogorov-Smirnov tests. Simulations show that it is reliable for stars most of whom have six, seven and eight repeated observations. The uncertainty of orbital parameters of binarity becomes larger when observational frequencies decrease. By adopting the fixed power exponents of π = −0.45 and κ = −1 for period and mass ratio distributions, respectively, we obtain that f bin = 0.4 − 0.06 + 0.05 for the samples with more than three observations. When we consider the full samples with at least two observations, the binary fraction turns out to be 0.37 − 0.03 + 0.03 . These two results are consistent with each other in 1σ.

Metode Power Control sebagai Manajemen Interferensi pada Komunikasi Device to Device

Teknologi komunikasi yang sedang berkembang saat ini sudah memasuki generasi ke-5 (5G), dengan salah satu solusi yang ditawarkan adalah komunikasi device to device (D2D). Skema yang digunakan pada makalah ini adalah cooperative D2D dengan Mobile User Equipment (MUE) yang berada jauh dari eNodeB (eNB). D2D User Equipment (DUE) berperan sebagai relay yang membantu MUE dalam meningkatkan kualitas layanan. Efek yang ditimbulkan komunikasi D2D adalah interferensi, sehingga untuk mengatasinya dilakukan metode power control. Makalah ini menggunakan tiga simulasi perbandingan, yaitu Tanpa Power Control, skema Power Control 1, dan Power Control 2. Skema yang digunakan pada Power Control 1 adalah skema fixed power control, sedangkan skema Power Control 2 menggunakan adaptive power control. Dengan menggunakan Cumulative Distribution Function (CDF), diperoleh hasil bahwa skema Power Control 1 mampu memperbaiki SINR sebesar 0,124 dB untuk downlink dan 0,0814 dB untuk uplink, sedangkan skema Power Control 2 mampu menaikkan SINR 0,0316 dB untuk downlink dan 0,0627 dB untuk uplink. Berdasarkan hasil akhir terkait SINR, throughput, dan CDF, metode Power Control 1 memiliki hasil yang lebih baik daripada metode Power Control 2.

A Cross-Mode Universal Digital Pre-Distortion Technology for Low-Sidelobe Active Antenna Arrays in 5G and Satellite Communications

A cross-mode universal digital pre-distortion (CMUDPD) technology is proposed here to linearize low-sidelobe active antenna arrays with non-uniform fixed power levels for each branch, which are desired in satellite communications with stringent requirements to minimize interference. In low-sidelobe arrays formed by nonuniform amplitude excitation, conventional digital pre-distortion (DPD) techniques require multiple feedback paths for either one-to-one or average linearization of the PAs, which increases system complexity and is infeasible for large-scale arrays. This is because the power amplifiers (PAs) usually operate in different modes where the supply voltages, bias voltages, and input power levels are different. The proposed CMUDPD method aims at solving this issue by intentionally arranging the PAs to work in different modes but with shared nonlinear characteristics. Based on the nonlinear correlation established among the PAs’ different operating modes, a single feedback path is sufficient to capture the common nonlinearity of all the PAs and determine the parameters of the CMUDPD module. The concept is explained in theory and validated by simulations and experiments using GaN PAs operating with three significantly different output power levels and two orthogonal frequency division multiplexing (OFDM) signal bandwidths.

PSO-Based UAV Deployment and Dynamic Power Allocation for UAV-Enabled Uplink NOMA Network

Recently, unmanned aerial vehicles (UAVs) have been used as flying base stations (BSs) to take advantage of line-of-sight (LOS) connectivity and efficiently enable fifth-generation (5G) and cellular network coverage and data rates. On the other hand, nonorthogonal multiple access (NOMA) is a promising technique to help achieve unprecedented requirements by simultaneously allowing multiple users to send data over the same resource block. In this paper, we study a UAV-enabled uplink NOMA network, where the UAV collects data from ground users while flying at a certain altitude. Unlike all existing work on this topic, this study consists of two stages. In the first stage, we use the well-known Particle Swarm Optimization (PSO) algorithm, which is a metaheuristic algorithm, to deploy the UAV in 3D space, so that the users’ sum pathlosses are minimized. In the second stage, we investigate the user pairing problem and propose a dynamic power allocation technique for determining the user’s power allocation coefficients, as well as a closed-form equation for the ergodic sum-rate. Results show our PSO-based algorithm prevailing over the Genetic Algorithm (GA) and random deployment methods. The proposed dynamic power allocation strategy maximizes the network’s ergodic sum-rate and outperforms the fixed power allocation strategy. Additionally, the results reveal that the best pairing scheme is the one that keeps uniform channel gain difference in the same pair.

Constituting Intersectional Politics of Reinscription: Women Entrepreneurs’ Resistance Practices in China, Denmark, and the United States

Guided by feminist politics of reinscription and intersectionality theory, this study theorized how women entrepreneurs from China, Denmark, and the United States depicted their situated struggles to resist simultaneous interlocking oppressions in everyday entrepreneuring based on 40 in-depth interviews. Participants described that they experienced inscription whereby multiple power asymmetries of gender, age, culture, race/ethnicity, and so on emerged and entangled to prescribe social scripts that constrained their entrepreneurial agencies. Simultaneously, participants engaged in reinscription to deconstruct intersectional controls and rework hegemonic scripts in situated entrepreneurial activities. They deployed three resistance strategies: recontextualizing their intersectionalities in different discursive contexts to legitimize and elevate their entrepreneur identities; reformulating their intersectionalities by invoking privileged positions to counterbalance marginalization; and re-envisioning by transcending their intersectional subordination to create opportunities for change. Instead of focusing on pre-existing and fixed power structures and identities in intersectional resistance-control processes, we demonstrate how intersectionalities are (re)constituted in situ through complex and fluid inscription-reinscription dynamics in women’s entrepreneurship.

Performance Evaluation of Solar PV Inverter Controls for Overvoltage Mitigation in MV Distribution Networks

The incorporation of real and reactive power control of solar photovoltaic (PV) inverters has received significant interest as an onsite countermeasure to the voltage rise problem. This paper presents a comprehensive analysis of the involvement of active power curtailment and reactive power absorption techniques of solar PV inverters for voltage regulation in medium voltage (MV) distribution networks. A case study has been conducted for a generic MV distribution network in Malaysia, demonstrating the effectiveness of fixed power factor control, Volt–Var, and Volt–Watt controls in mitigating overvoltage issues that have arisen due to the extensive integration of solar PV systems. The results revealed that the incorporation of real and reactive power controls of solar PV inverters aids in successfully mitigating overvoltage issues and support network operating conditions. Furthermore, the comparative analysis demonstrated the importance of employing the most appropriate control technique for improved network performance.

Eco-Friendly Speed Control Algorithm Development for Autonomous Vessel Route Planning

The upcoming autonomous vessel voyage is promising future in the maritime sector. However, so far, the contemporary route decision making technologies rely on human intervention. Therefore, this manuscript proposes the two newly developed speed algorithms: the modified fixed speed control and the wave feed forward speed control in the route decision making procedure for the autonomous vessels. These two algorithms can control the vessel’s speed without human intervention in eco-friendly and economic manner. The first algorithm is the wave feed forward speed control that can predict the speed change according to wave loads and compensate it to reduce the fluctuation of speed, power, and fuel consumption. To develop this algorithm, the real time modeling of the wave added resistance and the wave real time effect on propulsion are analyzed. The efficacy of the developed wave feed forward scheme is validated using the in-house route optimization simulation program through comparisons with the results of conventional speed governor control case. The developed schemes are applied to a 173 K LNG (Liquefied Natural Gas) carrier with twin propulsion. The other proposed speed control algorithm is the modified fixed control algorithm. This algorithm improves the conventional fixed power control algorithm by adding a time marching module to satisfy the required time arrival of the voyage. The two proposed methods are analyzed in the various simulations—ideal environmental conditions and real voyage environments: The Pacific and the Atlantic cases. Based on the results, the suggested methods can reduce fuel oil consumption, gas emission, and wear and tear problem of the propulsion devise of ship. In the study, it is clearly demonstrated that the developed wave feed forward speed control and modified fixed power scheme perform much better than the conventional speed governor control case.