scholarly journals Analytical Framework of CP-Free Multiuser OFDM System for Coordinated Multi-Point at mmWave

2021 ◽  
Vol 11 (16) ◽  
pp. 7605
Author(s):  
Joarder Jafor Sadique ◽  
Saifur Rahman Sabuj ◽  
Shaikh Enayet Ullah ◽  
Md. Akbar Hossain ◽  
Raad Raad ◽  
...  
Keyword(s):  
Channel Coding ◽  
Forward Error Correction ◽  
Average Power ◽  
Analytical Framework ◽  
Papr Reduction ◽  
Achievable Rate ◽  
Cell Edge ◽  
Noise Ratio ◽  
The Impact ◽  
Multiuser Ofdm

In this paper, a coordinated multipoint joint transmission (CoMP-JT) framework at mmWave for a cyclic prefix (CP)-free multiuser OFDM wireless communication system is developed and analyzed. The aim is to provide high-quality service to cell-edge users; otherwise, the cell-users would suffer from significant signal degradation due to undesired interference. The impact of complex Hadamard transform with block diagonalization channel precoding for multiuser interference reduction and designed subcarrier mapping for out-of-band (OOB) reduction are investigated. In addition, the paper studied the input back-off-aided high-power amplifier for peak-to-average power ratio (PAPR) reduction and forward error correction channel coding for improved bit error rate (BER) for cell-edge users at mmWave frequencies. Moreover, signal-to-interference-noise ratio and ergodic achievable rate are estimated both in the presence and absence of CoMP-JT-based transmission technique to verify their significance in terms of transmitted power. Numerical investigations showed an OOB reduction of 312 dB, PAPR reduction from 17.50 dB to 7.66 dB, and improved BER of 1×10−3 in 16-QAM for a signal-to-noise ratio of −6 dB. Hence, the simulation results demonstrated the effectiveness of the developed system.

Iterative Invertible Clipping Method for PAPR Reduction in Wireless MC-CDMA Communication Systems

2019 ◽  
Vol 9 (3) ◽  
pp. 372-387
Author(s):  
Hocine Merah ◽  
Mokhtaria Mesri ◽  
Yacine Merrad ◽  
Larbi Talbi
Keyword(s):  
Channel Coding ◽  
Communication Systems ◽  
Additive White Gaussian Noise ◽  
Average Power ◽  
Papr Reduction ◽  
Power Ratio ◽  
High Power Amplifier ◽  
Papr Performance ◽  
Code Division Multiple ◽  
System Characteristics

Background & Objective: One of the disadvantages of Multi-carrier Code Division Multiple Access (MC-CDMA) system is the high value of Peak to Average Power Ratio (PAPR). This paper proposes an approach called Iterative Invertible Clipping Method (IICM) to address the PAPR for MC-CDMA signal based on wireless communication system characteristics. This is mainly concentrated in clipping function making use of a polynomial of degree three at the transmitter, and its inverse at the receiver, to recover the original signal. Method: A Fast Fourier Transform (FFT)-based frequency domain filter is employed to reduce the overall peak regrowth which is supported by measuring the Adjacent Channel Power Ratio (ACPR) after soft clipping and filtering. This technique is compared with Ragusa method using a polynomial of degree 5. Result: The simulated results of the proposed method showed better performance in terms of PAPR reduction, Bit Error Rate (BER), and computational complexity requiring two iterations only. The Complementary Cumulative Complementary Density Function (CCDF) is served to measure and improve PAPR performance of the system. Conclusion: The channel coding process is applied to strengthen the obtained results in the Additive White Gaussian Noise (AWGN) channel and fading channel (Rayleigh). The High-Power Amplifier (HPA) is used for validation purposes.

scholarly journals DFT-Spread Spectrally Overlapped Hybrid OFDM–Digital Filter Multiple Access IMDD PONs

Sensors ◽  
2021 ◽  
Vol 21 (17) ◽  
pp. 5903
Author(s):  
Abdulai Sankoh ◽  
Wei Jin ◽  
Zhuqiang Zhong ◽  
Jiaxiang He ◽  
Yanhua Hong ◽  
...  
Keyword(s):  
Digital Filter ◽  
Multiple Access ◽  
Forward Error Correction ◽  
Direct Detection ◽  
Transmission Rate ◽  
Signal Transmission ◽  
Average Power ◽  
Direct Consequence ◽  
Papr Reduction ◽  
Power Budget

A novel transmission technique—namely, a DFT-spread spectrally overlapped hybrid OFDM–digital filter multiple access (DFMA) PON based on intensity modulation and direct detection (IMDD)—is here proposed by employing the discrete Fourier transform (DFT)-spread technique in each optical network unit (ONU) and the optical line terminal (OLT). Detailed numerical simulations are carried out to identify optimal ONU transceiver parameters and explore their maximum achievable upstream transmission performances on the IMDD PON systems. The results show that the DFT-spread technique in the proposed PON is effective in enhancing the upstream transmission performance to its maximum potential, whilst still maintaining all of the salient features associated with previously reported PONs. Compared with previously reported PONs excluding DFT-spread, a significant peak-to-average power ratio (PAPR) reduction of over 2 dB is achieved, leading to a 1 dB reduction in the optimal signal clipping ratio (CR). As a direct consequence of the PAPR reduction, the proposed PON has excellent tolerance to reduced digital-to-analogue converter/analogue-to-digital converter (DAC/ADC) bit resolution, and can therefore ensure the utilization of a minimum DAC/ADC resolution of only 6 bits at the forward error correction (FEC) limit (1 × 10−3). In addition, the proposed PON can improve the upstream power budget by >1.4 dB and increase the aggregate upstream signal transmission rate by up to 10% without degrading nonlinearity tolerances.

scholarly journals Droplet impact onto a spring-supported plate: analysis and simulations

2021 ◽  
Vol 128 (1) ◽  
Author(s):  
Michael J. Negus ◽  
Matthew R. Moore ◽  
James M. Oliver ◽  
Radu Cimpeanu
Keyword(s):  
High Speed ◽  
Flexible Substrate ◽  
Practical Importance ◽  
Hybrid Approach ◽  
Hydrodynamic Pressure ◽  
Analytical Framework ◽  
Canonical System ◽  
Linear Process ◽  
Plate Motion ◽  
The Impact

AbstractThe high-speed impact of a droplet onto a flexible substrate is a highly non-linear process of practical importance, which poses formidable modelling challenges in the context of fluid–structure interaction. We present two approaches aimed at investigating the canonical system of a droplet impacting onto a rigid plate supported by a spring and a dashpot: matched asymptotic expansions and direct numerical simulation (DNS). In the former, we derive a generalisation of inviscid Wagner theory to approximate the flow behaviour during the early stages of the impact. In the latter, we perform detailed DNS designed to validate the analytical framework, as well as provide insight into later times beyond the reach of the proposed analytical model. Drawing from both methods, we observe the strong influence that the mass of the plate, resistance of the dashpot, and stiffness of the spring have on the motion of the solid, which undergo forced damped oscillations. Furthermore, we examine how the plate motion affects the dynamics of the droplet, predominantly through altering its internal hydrodynamic pressure distribution. We build on the interplay between these techniques, demonstrating that a hybrid approach leads to improved model and computational development, as well as result interpretation, across multiple length and time scales.

scholarly journals Evaluation of Organ Dose and Image Quality Metrics of Pediatric CT Chest-Abdomen-Pelvis (CAP) Examination: An Anthropomorphic Phantom Study

2021 ◽  
Vol 11 (5) ◽  
pp. 2047
Author(s):  
Nor Azura Muhammad ◽  
Zunaide Kayun ◽  
Hasyma Abu Hassan ◽  
Jeannie Hsiu Ding Wong ◽  
Kwan Hoong Ng ◽  
...  
Keyword(s):  
Image Quality ◽  
Multidetector Ct ◽  
Organ Dose ◽  
Quality Metrics ◽  
Ct Scanner ◽  
Image Quality Metrics ◽  
Tube Current ◽  
Significant Difference ◽  
Noise Ratio ◽  
The Impact

The aim of this study is to investigate the impact of CT acquisition parameter setting on organ dose and its influence on image quality metrics in pediatric phantom during CT examination. The study was performed on 64-slice multidetector CT scanner (MDCT) Siemens Definition AS (Siemens Sector Healthcare, Forchheim, Germany) using various CT CAP protocols (P1–P9). Tube potential for P1, P2, and P3 protocols were fixed at 100 kVp while P4, P5, and P6 were fixed at 80 kVp with used of various reference noise values. P7, P8, and P9 were the modification of P1 with changes on slice collimation, pitch factor, and tube current modulation (TCM), respectively. TLD-100 chips were inserted into the phantom slab number 7, 9, 10, 12, 13, and 14 to represent thyroid, lung, liver, stomach, gonads, and skin, respectively. The image quality metrics, signal to noise ratio (SNR) and contrast to noise ratio (CNR) values were obtained from the CT console. As a result, this study indicates a potential reduction in the absorbed dose up to 20% to 50% along with reducing tube voltage, tube current, and increasing the slice collimation. There is no significant difference (p > 0.05) observed between the protocols and image metrics.

scholarly journals A Novel Hybrid Precoding-Companding Technique for Peak-to-Average Power Ratio Reduction in 5G and beyond

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1410
Author(s):  
Mohamed Mounir ◽  
Mohamed B. El_Mashade ◽  
Salah Berra ◽  
Gurjot Singh Gaba ◽  
Mehedi Masud
Keyword(s):  
Computational Complexity ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Average Power ◽  
Papr Reduction ◽  
Power Ratio ◽  
Error Vector Magnitude ◽  
Hybrid Precoding ◽  
High Power Amplifier ◽  
Reduction Techniques

Several high-speed wireless systems use Orthogonal Frequency Division Multiplexing (OFDM) due to its advantages. 5G has adopted OFDM and is expected to be considered beyond 5G (B5G). Meanwhile, OFDM has a high Peak-to-Average Power Ratio (PAPR) problem. Hybridization between two PAPR reduction techniques gains the two techniques’ advantages. Hybrid precoding-companding techniques are attractive as they require small computational complexity to achieve high PAPR reduction gain. Many precoding-companding techniques were introduced to increasing the PAPR reduction gain. However, reducing Bit Error Rate (BER) and out-of-band (OOB) radiation are more significant than increasing PAPR reduction gain. This paper proposes a new precoding-companding technique to better reduce the BER and OOB radiation than previous precoding-companding techniques. Results showed that the proposed technique outperforms all previous precoding-companding techniques in BER enhancement and OOB radiation reduction. The proposed technique reduces the Error Vector Magnitude (EVM) by 15 dB compared with 10 dB for the best previous technique. Additionally, the proposed technique increases high power amplifier efficiency (HPA) by 11.4%, while the best previous technique increased HPA efficiency by 9.8%. Moreover, our proposal achieves PAPR reduction gain better than the most known powerful PAPR reduction technique with a 99% reduction in required computational complexity.

Influence of Renminbi Internationalization on China’s Monetary Policy Effects: A Theoretical Analysis

2021 ◽  
Vol 13 (8) ◽  
pp. 14
Author(s):  
Huiguan Ding ◽  
Asli Ogunc ◽  
Dale Funderburk ◽  
Shiyou Li ◽  
Zhebie Shi
Keyword(s):  
Monetary Policy ◽  
Open Economy ◽  
Analytical Framework ◽  
Securities Markets ◽  
Republic Of China ◽  
Policy Effects ◽  
The People ◽  
The World ◽  
The Impact ◽  
Rmb Internationalization

For more than a decade, the People’s Republic of China has sought to expand the degree of internationalization of its official currency. In recent decades, China has become the world’s second largest economy, as well as the world’s largest trading nation, and its securities markets are among the largest in the world. Today, the RMB is among the top five as a world payments currency. One of the significant costs of achieving higher degrees of internationalization of a country’s currency is the complicating impact it has on the efficacy and effect of that country’s domestic monetary policy.  However, what is the nature and extent of that complicating impact? This paper employs an IS-LM model of an open economy as an analytical framework, embeds an RMB internationalization factor into that model. Specifically, with this model we examine the impact of RMB internationalization on the effects of China’s monetary policy. 

Human capital accumulation, income distribution, and economic growth: a demand-led analytical framework

2021 ◽  
Vol 9 (3) ◽  
pp. 319-336
Author(s):  
Gilberto Tadeu Lima ◽  
Laura Carvalho ◽  
Gustavo Pereira Serra
Keyword(s):  
Human Capital ◽  
Capital Accumulation ◽  
Analytical Framework ◽  
Output Growth ◽  
Human Capital Accumulation ◽  
Capital Utilization ◽  
Tax Rate ◽  
Long Run ◽  
The Impact ◽  
Long Run Equilibrium

This paper incorporates human capital accumulation through provision of universal public education by a balanced-budget government to a demand-driven analytical framework of functional distribution and growth of income. Human capital accumulation positively impacts on workers’ productivity in production and their bargaining power in wage negotiations. In the long-run equilibrium, a rise in the tax rate (which also denotes the share of output spent in human capital formation) lowers the pre- and after-tax wage share and physical capital utilization, and thus raises (lowers) the output growth rate when the latter is profit-led (wage-led). The impact of a higher tax rate on the employment rate (which also measures human capital utilization) in the long-run equilibrium is negative (ambiguous) when output growth is wage-led (profit-led). In any case, the supply of higher-skilled workers does not automatically create its own demand.

scholarly journals In Search of Alignment: A Review of Impact Studies in Entrepreneurship Education

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Uladzimir Kamovich ◽  
Lene Foss
Keyword(s):  
Empirical Studies ◽  
Entrepreneurship Education ◽  
Analytical Framework ◽  
Future Research ◽  
Impact Studies ◽  
Teaching Objectives ◽  
Teaching Content ◽  
Instructional Processes ◽  
Scant Attention ◽  
The Impact

This study uses the concept of alignment as a framework to examine empirical research on the impact of entrepreneurship education interventions on students. Alignment assumes that effective instruction requires congruence between three instructional components: intended outcomes, instructional processes, and assessment criteria. Given the extant diversity and complexity of entrepreneurship education impact, scholars have not been able to explain how teaching approaches and methods are being adjusted to the variety of expected outcomes. In order to address this gap, we critically reviewed the published empirical studies on entrepreneurship education impact in 20 journals over a 15-year period (2000–2015). We found 16 empirical studies that met our inclusion criteria. Our findings revealed that teaching objectives, teaching methods, and teaching content receive scant attention from researchers. This study will be of value to scholars researching the impact of heterogeneous entrepreneurship education practices and approaches on individuals. Our analytical framework could contribute to less contradictory findings of entrepreneurship education impact studies. We also identify research limitations and suggest avenues for future research.

scholarly journals Shaping Code in Conjunction with DCT for PAPR Reduction in Multicarrier System

2021 ◽  
Author(s):  
Younes Aimer ◽  
Boubakar Seddik Bouazza ◽  
Smail Bachir ◽  
Claude Duvanaud
Keyword(s):  
Power Amplifier ◽  
Power Efficiency ◽  
Average Power ◽  
Nonlinear Behavior ◽  
Signal Amplitude ◽  
Amplitude Distribution ◽  
Papr Reduction ◽  
Radio Link ◽  
Error Vector Magnitude ◽  
Multicarrier System

Abstract Nonlinear behavior and power efficiency of the Power Amplifier (PA) contradictorily depend on the input signal amplitude distribution. The transmitted signal in multi-carrier modulation exhibits high Peak-to-Average Power Ratio (PAPR) and large bandwidths, leading to the degradation of the radio link and additional generation out-of-band interferences, which degrade the quality of the transmission. Practical solutions exist, like a power back-off, but with unacceptable efficiency performances of the transmitter. This paper deals with efficiency and linearity improvement using a new PAPR reduction method based on the combination of Discrete Cosine Transform (DCT) and shaping technique. The main principle is to determine an optimal coding scheme according to a trade-off between coding complexity and performance benefits in the presence of PA non-linearities. Simulation and experimental results in the context of OFDM signal and using a 20W - 3.7GHz Radio-Frequency Power Amplifier (RF-PA) show an improvement on PAPR reduction of about 3.25dB. Also, the communication criteria like BER (Bit Error Rate) and EVM (Error Vector Magnitude) are improved by about one decade and a half and 8%, respectively.

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