Equal Gain Research Articles

A simplified mode diversity coherent receiver based on non-mode-selective photonic lantern and Kramers-Kronig detection

This paper proposes a mode-diversity space optical communication receiver for long-range space optical communication, which can compensate for the effect of atmospheric turbulence and be applied between 2 km and 16 km space optical communication with a low-cost, low-power and low-complexity feature. The receiver uses a non-mode selective photonic lantern as a mode demultiplexer, merging using an equal gain combining (EGC) algorithm and a Kramers-Kronig (KK) detection technique to accomplish the optical detection of high-dimensional modulated format signals. The performance of the receiver under different turbulent conditions is experimentally investigated, showing significant compensation for atmospheric turbulence. The experimental results show that the proposed scheme achieves a gain of 4–5 dB at BER = 3 × 10−3 compared to a single-mode fiber (SMF) receiver under moderately strong turbulent conditions.

Free-Space Optical Communication Based on Mode Diversity Reception Using a Nonmode Selective Photonic Lantern and Equal Gain Combining

This paper experimentally investigates the perform-ance of free-space optical (FSO) communication based on mode diversity reception (MDR) using nonmode selective photonic lantern (NSPL) and equal gain combining (EGC). By employing a mode demultiplexer and combining technology in the receiver, the bit error rate (BER) and outage performance of FSO communication system can be significantly improved. However, different from diversity system with multiple receive apertures, the branches in mode diversity system are non-independent fading signals, which are influenced by not only atmospheric but also the modal crosstalk of mode demultiplexer. Therefore, we take into consideration the difference of mode demultiplexer and study four schemes for FSO mode diversity reception system: 1) NSPL with equal gain combining (NSPL-EGC), 2) NSPL with maximal ratio combining (NSPL-MRC), 3) mode selective photonic lantern with equal gain combining (MSPL-EGC), and 4) mode selective photonic lantern with equal gain combining (MSPL-MRC). Experimental results show that NSPL-EGC is the most suitable scheme for MDR with low implementation complexity, and the performance difference is less than 1 dB compared with the one using MRC at BER = 3.8×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> under turbulence from weak to strong.

English

The spatial diversity techniques are broken down and explained systematically along with its combination which includes Maximum Ratio Combining (MRC), Equal Gain Combining (EGC) and Simple Selection Combining (SC) under the influence of atmospheric-induced turbulence fading in Free Space Optical (FSO) communication. Diversity is a technique used to prevent or reduce multipath. Multipath is a phenomenon describing propagation that results in the signals reaching the antenna by two or more paths. There is an extreme difficulty for a transmitted signal to be detected by a receiver in a case of increased turbulence. This research provides a forum for the receiver with some forms of diversity. The validation of the recommended simulation is through Additive White Gaussian Channel without combiner of the same process. The results display that Maximum Ratio Combining (MRC) has the greatest mitigation level of fading in comparison with others. Consequently, where fading is more dominant like on a terrestrial FSO link, Maximum Ratio Combining (MRC) can be used. Overall, the findings suggest the capability of the model in mitigating atmospheric turbulence especially for the 5G wireless networks in the terrestrial link. Key words: Free Space Optical Communication (FSO), Atmospheric Turbulence, Additive White Gaussian Channel (AWGC), Maximum Ratio Combining (MRC), Equal Gain Combining (EGC), Selection Combining (SC) and Additive White Gaussian Noise (AWGN).

Modified differential overlap factor and modal gain equalization criteria-based comparative analysis of 4M-EDFA 980;1480 nm towards identification of a unique erbium doping profile for the 4M-EDFA1480 nm system

Modified differential overlap factor and modal gain equalization criteria-based comparative analysis of 4M-EDFA 980;1480 nm towards identification of a unique erbium doping profile for the 4M-EDFA1480 nm system

Analysis of Regional Regulations of Sragen Regency Number 8 of 2018 concerning Tourism Organization

Sragen Regency has a very potential tourism area in the form of natural tourism, man-made tourism, cultural tourism, geo-tourism, eco-tourism, water tourism, religious tourism, culinary tourism and superior product tourism whose development needs to be directed in order to realize people's prosperity and welfare, encourage equal opportunity strive and gain benefits, and be able to face the challenges of changes in local, national and global life. This Regional Regulation is stipulated in order to improve services for orderliness and ease of tourism development, create a tourism business atmosphere that pays attention to religious values, customs, and views and values ​​that live in society, then the implementation of tourism in Sragen Regency needs to training, supervision and control.

A Reconfigurable RF Filter With 1%–40% Fractional Bandwidth for 5G FR1 Receivers

This paper presents a radio frequency front-end (RFFE) for 5G New Radio (NR) receivers operating in Frequency Range 1 (FR1). The core of this RFFE is a synthetic fourth-order Q-enhanced RF filter employing gm-boosting, noise-cancelling, capacitive cross-coupling, and forward body-biasing techniques to achieve 1.7 GHz to 6.4 GHz operating range and 1 adjustable fractional bandwidth (FBW). The function of the filter is based on subtracting out-of-phase signals in the passband and in-phase signals in the stopband. Two Q-enhanced LC resonators are utilized for outphasing. The filter is preceded by a low-noise transconductance amplifier, and it is followed by a programmable gain amplifier and a differential buffer stage for the measurement purposes and gain equalization. The experimental results demonstrate that the voltage gain is tunable between 18 and 47 dB with 0.2 dB steps, which leads to an equalized output power in all the filter configurations. Fabricated in 22 nm Fully Depleted Silicon on Insulator (FD-SOI) technology, the RFFE achieves 4.6 dB NF, -14 dBm IB-IIP3, and 26 dBm IB-IIP2 at 4 GHz. Notably, the fourth-order steep roll-off provides 22 dBm OOB-IIP3 at 2WBW frequency offset. The entire RFFE draws 22-45 mA from a 1 V supply and the filter core occupies 0.11 mm2 chip area.

Performance Evaluation of Space Receive Diversity Techniques for Massive MIMO System

This paper presents performance evaluation of massive MIMO system in terms of signal to noise ratio (SNR) and system capacity with respect to increasing number of receive antennas at the base station for a wireless communication between a single transmit antenna of user terminal per time. The analysis performed in MATLAB simulation environment revealed that for M = 128, 256, and 512, the SNR improvement in dB achieved using selective combining (SC) was 7.31, 7.85, and 8.34 respectively, whereas for equal gain combining (EGC) and maximal ratio combining (MRC) the SNRs performance in dB were 19.79 and 20.83, 22.95 and 24, and 25.96 dB, and 27 respectively. Generally, the outcomes of simulations have proven that optimizing the number of receive antenna based on selection by changing the number of antennas at base station (BS) can provide improved SNR and system capacity.

Low Power Consuming Mode Switch Based on Hybrid-Core Vertical Directional Couplers with Graphene Electrode-Embedded Polymer Waveguides

We propose a mode switch based on hybrid-core vertical directional couplers with an embedded graphene electrode to realize the switching function with low power consumption. We designed the device with Norland Optical Adhesive (NOA) material as the guide wave cores and epoxy polymer material as cladding to achieve a thermo-optic switching for the E11, E21 and E12 modes, where monolayer graphene served as electrode heaters. The device, with a length of 21 mm, had extinction ratios (ERs) of 20.5 dB, 10.4 dB and 15.7 dB for the E21, E12 and E11 modes, respectively, over the C-band. The power consumptions of three electric heaters were reduced to only 3.19 mW, 3.09 mW and 2.97 mW, respectively, and the response times were less than 495 µs, 486 µs and 498 µs. Additionally, we applied such a device into a mode division multiplexing (MDM) transmission system to achieve an application of gain equalization of few-mode amplification among guided modes. The differential modal gain (DMG) could be optimized from 5.39 dB to 0.92 dB over the C-band, together with the characteristic of polarization insensitivity. The proposed mode switch can be further developed to switch or manipulate the attenuation of the arbitrary guided mode arising in the few-mode waveguide.

Calibration of the ICARUS cryogenic photo-detection system at FNAL

The calibration of the ICARUS photo-detection system is based on a low power laser diode at 405 nm. Laser pulses arrive to one optical switch and then are sent to 36 UHV flanges, by 20 meters long optical patches. Light is then delivered to the ten PMTs connected to a single flange, by 7 m long injection optical patches. Extensive tests of the used components and care in the design of the optical system have guaranteed to each PMT a sizeable calibration signal with minimal distortion, with respect to the original one. Gain equalization of PMTs has reached a 1% resolution. In this procedure data from background photons were also used. The distribution of the PMTs’ signal arrival time has a distribution with a resolution less than 1 ns, thus allowing a good determination of the absolute event timing. The status of the laser calibration system with its possible upgrades will be reported.

A uniform ion doping air-hole-assisted FM-EDF for low differential modal gain

An air-hole-assisted few-mode erbium-doped fiber (AH-FM-EDF) with a uniform erbium ion doping profile is proposed for gain equalization. By introducing the central air hole, the mode field distribution is strongly modified, contributing to a significant improvement in reducing the differential modal gain (DMG). Numerical results show that the gains of each mode can all reach 20 dB and the DMG is about 0.4 dB at 1550 nm in either core-pumping or cladding-pumping cases. Besides, the amplifier is well-behaved in gain-flattening with a noise figure (NF) of about 4.5 dB over the whole C-band. The proposed fiber shows much flexibility and robustness in gain equalization due to its simple uniform doping profile and pump-mode selection.

Modeling of a ring-core trench-assisted few-mode BDFA for seven-mode signal gain equalization.

In this paper, a ring-core trench-assisted few-mode bismuth-doped fiber amplifier (BDFA) is simulated on the basis of the three-energy level. The fiber is designed to support four modes of signal group transmission for practical considerations, including LP01, LP11, LP21, and LP31. The results suggest that (1) it is possible to obtain gain equalization of the three signal groups by using the LP21 mode pump independently, where the maximum difference in modal gain (MAX DMG) is about 0.9dB, except for the LP31 mode signal; (2) by combining the LP01 and LP31 mode pumps, the average gain of the groups increases by 14%, and the MAX DMG decreases by nearly 60% (3.8 to 1.5dB) compared to the LP01 pump alone; and (3) with the same combination of mode pumps, the ring-core BDFA (1.5dB) achieves better gain equalization than the single-core BDFA (2.8dB). The analysis is informative for the future development of a multimode BDFA.

Heuristic-based optimization framework for customizable design of long-haul data center interconnect networks

With the widespread deployment of data centers, Internet service providers are expecting more efficient design strategies to build long-haul data center interconnect (DCI) networks. In this paper, we propose a heuristic-based optimization framework to design these networks. Through this framework, network designers can obtain a site-type design scheme that arranges customized site types such as in-line amplifiers, dynamic gain equalizers, optical terminal multiplexers, and electrical regenerators, and three strategies are provided for reference. Taking the quality of transmission as the main metric, and the overall cost of the network as the ancillary measurement, we compare the schemes obtained by the proposed framework against the baseline scheme obtained by a traditional periodic design strategy. Simulations are conducted on a topology of the Tencent DCI network. Under the condition that all schemes ensure that the minimum general signal-to-noise ratio (GSNR) remains above the given GSNR threshold, the schemes designed by our framework can achieve overall cost savings up to 25.73%.

Signal quality enhancement in multiplexed communication systems based on the simulation model of the optimum technical specifications of Raman fiber optical amplifiers

Abstract Raman optical amplifiers have more reliability than the repeater in the optical communication networks. In the optical amplifier, the transmission equals the gain bandwidth of the amplifiers. The optical amplifier has functionalities such as WDM amplification (gain equalization), gain control (rapidly variation of the gain), inter-stage access (compensation in the dispersion rate). This paper presents the optimum technical specifications of fiber Raman optical amplifiers (FROAs) with average power system for signal quality improvement in multiplexed systems. The signal has upgraded to a max. Q-factor of 11.47 applied along 1000 m as a range through the free-space optical (FSO) communication channel that has an attenuation rate of 10 dB/km. Our suggested system has clarified the best Q-factor that is greatly increased to reach 49.36 in the presence of the pump laser. The multiplexed communication systems signal quality is enhanced by the percentage ratio of 39.65%.

Improvement of Multiple Antenna Sensing Technique for Detecting the White Space in a Spectrum Sharing System

Exact detection of White Space (WS) is one of the actions in a Spectrum Sharing System (SSS) to determine unused spectrum for proper utilization. However, exact detection of WS is being affected by channel impairments, resulting in harmful interference. The Existing Multiple Antenna Spectrum Sensing (EMASS) technique used in addressing this effect is characterized with noise uncertainty leading to low detection rate due to setting of thresholds that is based on noise variance. Hence, this paper proposes an Improved Multiple Antenna Spectrum Sensing (IMASS) for detecting the WS in a SSS. Various copies of licensed user’s signals are received through the unlicensed user antennas over different antenna configuration. The received signals are combined using a modified equal gain combiner and energy of the combined signal is determined using Parseval’s relation for a discrete time signal. The received signal is used to form a square matrix which is converted to covariance matrix. Characteristic equation is obtained from covariance matrix to determine the minimum eigenvalue. The ratio of energy to minimum eigenvalue of the received signal is obtained and used as test statistics. The IMASS technique is evaluated using Probability of Detection (PD) and Total Error Probability (TEP) by comparing with EMASS. The proposed IMASS technique gives better performance with higher PD and lower TEP values than EMASS at all different antenna configurations.

Probality Density Function Analysis of Multipath Fading with Phase Error over Rayleigh and Rician Fading Channels in Equal Gain Diversity

Probality Density Function Analysis of Multipath Fading with Phase Error over Rayleigh and Rician Fading Channels in Equal Gain Diversity

Beamforming Design and Performance Analysis for Satellite and UAV Integrated Networks in IoRT Applications

Satellite and unmanned aerial vehicle (UAV) integrated networks (SUINs) are considered as a promising method to offer various Internet of Remote Things (IoRT) applications. In this article, we investigate the downlink transmission of SUINs where the satellite-to-UAV link uses the free-space optical (FSO) technology with an equal gain combining (EGC) scheme while the links from UAV to IoRT devices exploit radio frequency (RF) with the space-division multiple access (SDMA) technique. Specifically, considering that only statistical channel state information (CSI) is available, we first formulate an optimization problem to maximize the ergodic sum rate (ESR) of the system, which is constrained by the total transmit power budget and IoRT devices’ rate requirements. Then, a beamforming (BF) scheme based on the alternating direction method of multipliers (ADMM) is proposed to solve the nonconvex problem. Furthermore, a zero-forcing (ZF)-based suboptimal approach is also presented to reduce the implementation complexity. Finally, by assuming that the FSO link and RF links are subject to Gamma–Gamma fading and Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$m$ </tex-math></inline-formula> fading, respectively, we derive closed-form ESR expressions for the considered network with the proposed BF schemes. Simulation results are provided to confirm the accuracy of the theoretical analysis. Moreover, it is revealed that our proposed EGC scheme for FSO communication and BF schemes for RF transmission can both achieve better performance than the existing works.

Fusion Schemes Based on IRS-Enhanced Cooperative Spectrum Sensing for Cognitive Radio Networks

The detection performance of cooperative spectrum sensing (CSS) is poor when there are obstacles blocking. Therefore, fusion schemes based on intelligent reflecting surface (IRS)-enhanced CSS are investigated. Existing fusion schemes can be divided into the soft combination and the hard combination. In the soft combination, each secondary user (SU) uploads the decision statistic to a fusion center (FC). Comparatively, during the hard combination, each SU reports the local 0/1 decision result to FC instead of decision statistic. In this paper, the equal gain combination (EGC) and the selection combination (SC) schemes are studied for the soft combination. The weighted hard combination (WHC) scheme is studied for the hard combination, and an optimal set combination (OSC) scheme is proposed based on signal-to-noise ratio (SNR). By using the definition of the non-centrality chi-square distribution and the moment-matching method, the closed-form expressions for the average probability of detection of all the schemes are derived. Simulation results reveal that the detection performance of IRS-enhanced CSS obviously outperforms the decode and forward (DF) relay case and the no IRS case. In addition, our proposed OSC are superior to the K-rank in terms of the detection performance.

Novel Approximate Distribution of the Sum of Lognormal-Rician Turbulence Channels With Pointing Errors and Applications in MIMO FSO Links

In this paper, an approximate closed-form probability density function expression for the sum of lognormal-Rician turbulence channels with Rayleigh pointing errors is developed. The results of Kolmogorov-Smirnov goodness-of-fit statistical tests show that the proposed approximation is highly accurate across a wide range of channel conditions. Also, the analysis of approximation error is presented in detail, and it indicates that a more efficient approximation can be achieved for larger coherence parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$r$</tex-math></inline-formula> and smaller variance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sigma _{z}^{2}$</tex-math></inline-formula> . To reveal the importance of proposed approximation, the closed-form expressions for the ergodic capacity, outage probability, and bit-error rate are derived in terms of Meijer’s G-function. The performance of multiple-input multiple-output (MIMO) free-space optical (FSO) systems with equal gain combining (EGC) diversity technique are analyzed in detail under different scenarios, including the number of transmit and receive apertures, turbulence channels, and presence of pointing errors. It is observed that MIMO technology can offer a significant improvement in FSO performance when compared with the single-input single-output (SISO) systems. The ergodic capacity and BER performance at high signal-to-noise ratio are also obtained to provide further insights. Numerical results demonstrate the accuracy of the proposed approach.

Spectral-efficient hybrid precoding for multi-antenna multi-user mmWave massive MIMO systems with low complexity

Millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems allow for a data transmission rate of gigabits per second owing to the large bandwidth available in the mmWave spectrum and the antenna gains provided by the massive MIMO system. However, hybrid precoding with high complexity and low spectral efficiency cannot address the challenge of high cost and power consumption of RF chains of multi-user systems. In this paper, we propose a low-complexity hybrid precoding scheme for downlink multi-antenna multi-user mmWave massive MIMO systems, aiming to enhance the sum spectral efficiency (SSE) performance. We first extend the dimension of the analog precoding matrix into a square matrix and find the optimal analog combiner by selecting some of the discrete Fourier transform (DFT) bases, which enhances the equivalent baseband channel matrix gain. Then, we directly aggregate the channel gain through the equal gain transmission (EGT) method to ensure the frequency efficiency performance. Finally, we propose an improved BD scheme to design the digital precoder and combiner to reduce the inter-user interference. We consider both the mmWave channel and the Rayleigh channel to evaluate the performance of the proposed algorithm. The simulation results verify that the proposed scheme enjoys near-optimal achievable sum spectrum efficiency and BER performance in both the mmWave channel and Rayleigh channel and performs even better in Rayleigh channel than in the mmWave channel.

Performance of a free-space optical communication system employing receive diversity techniques in anisotropic atmospheric non-Kolmogorov turbulence

In this paper, bit error rate (BER) performance of a free-space optical communication (FSOC) system operating in anisotropic non-Kolmogorov weak turbulence is investigated together with the spatial diversity techniques. The spatial diversity techniques are implemented as maximum ratio combining (MRC), equal gain combining (EGC), and selection combining (SC) and applied to the receiver. The propagating beam is the Gaussian beam wave, and the modulation scheme is binary phase-shift keying (BPSK). Results are obtained for various parameters such as the anisotropy factor, non-Kolmogorov power law exponent, photodetector responsivity, equivalent load resistor, electronic bandwidth, Gaussian beam radius, wavelength, propagation distance, and turbulence structure constant. It is found that the spatial diversity technique used at the receiver causes significant improvement in the performance of an FSOC system under the conditions of anisotropic non-Kolmogorov atmospheric turbulence. It is also observed that BER performance improves as the atmospheric turbulence becomes more anisotropic. Among the spatial diversity techniques, SC is inferior to EGC and EGC is inferior to MRC in terms of BER performance.