Ciphered BCH Codes for PAPR Reduction in the OFDM in Underwater Acoustic Channels

We propose an effective, low complexity and multifaceted scheme for peak-to-average power ratio (PAPR) reduction in the orthogonal frequency division multiplexing (OFDM) system for underwater acoustic (UWA) channels. In UWA OFDM systems, PAPR reduction is a challenging task due to low bandwidth availability along with computational and power limitations. The proposed scheme takes advantage of XOR ciphering and generates ciphered Bose–Chaudhuri–Hocquenghem (BCH) codes that have low PAPR. This scheme is based upon an algorithm that computes several keys offline, such that when the BCH codes are XOR-ciphered with these keys, it lowers the PAPR of BCH-encoded signals. The subsequent low PAPR modified BCH codes produced using the chosen keys are used in transmission. This technique is ideal for UWA systems as it does not require additional computational power at the transceiver during live transmission. The advantage of the proposed scheme is threefold. First, it reduces the PAPR; second, since it uses BCH codes, the bit error rate (BER) of the system improves; and third, a level of encryption is introduced via XOR ciphering, enabling secure communication. Simulations were performed in a realistic UWA channel, and the results demonstrated that the proposed scheme could indeed achieve all three objectives with minimum computational powerThis research was funded by a grant from the Spanish Ministry of Science and Innovation in the framework of the project “NAUTILUS: Swarms of underwater autonomous vehicles guided by artificial intelligence: its time has come” (PID2020-112502RB / AEI / 10.13039/501100011033). Partial funding for open access charge: Universidad de Málag

Coded-GFDM for Reliable Communication in Underwater Acoustic Channels

The performance of the coded generalized frequency division multiplexing (GFDM) transceiver has been evaluated in a shallow underwater acoustic channel (UAC). Acoustic transmission is the scheme of choice for communication in UAC since radio waves suffer from absorption and light waves scatter. Although orthogonal frequency division multiplexing (OFDM) has found its ground for multicarrier acoustic underwater communication, it suffers from high peak to average power ratio (PAPR) and out of band (OOB) emissions. We propose a coded-GFDM based multicarrier system since GFDM has a higher spectral efficiency compared to a traditional OFDM system. In doing so, we assess two block codes, namely Bose, Chaudari, and Hocquenghem (BCH) codes, Reed-Solomon (RS) codes, and several convolutional codes. We present the error performances of these codes when used with GFDM. Furthermore, we evaluate the performance of the proposed system using two equalizers: Matched Filter (MF) and Zero-Forcing (ZF). Simulation results show that among the various block coding schemes that we tested, BCH (31,6) and RS (15,3) give the best error performance. Among the convolutional codes that we tested, rate 1/4 convolutional codes give the best performance. However, the performance of BCH and RS codes is much better than the convolutional codes. Moreover, the performance of the ZF equalizer is marginally better than the MF equalizer. In conclusion, using the channel coding schemes with GFDM improves error performance manifolds thereby increasing the reliability of the GFDM system despite slightly higher complexity.This research was funded by a grant from the Spanish Ministry of Science and Innovation in the framework of the project “NAUTILUS: Swarms of underwater autonomous vehicles guided by artificial intelligence: its time has come” (PID2020-112502RB/AEI/10.13039/501100011033). The authors would like to thank the Deanship of Scientific Research at Umm Al-Qura University for supporting this work by Grant Code: (22UQU4300148DSR01). Partial funding for open access charge: Universidad de Málag

Comparison of MATLAB Simulink application with PLC application of ‎real-time classical ‎PID controllers in laboratory

Process control is a common area of study for different engineering disciplines. Controllers working ‎with ‎the ‎proportional–integral–derivative (PID) method are generally used in process control. ‎Parameters like ‎level, ‎flow, position, pressure, and temperature are controlled in-process control. PID ‎algorithm can be ‎formed ‎with different microprocessor-based devices. Process control is ‎implemented by using analog input ‎and ‎outputs terminals of PLCs (Programmable logic controller) ‎which is recently the most commonly used ‎in ‎industries. Also, a real-time PID method can be ‎implemented by using a computer-based ‎MATLAB ‎ ‎program in the laboratory.‎ The liquid level and flow control in the laboratory has been done by using PID algorithms and ‎PLC ‎device ‎and MATLAB real-time interface by using an experimental set. Necessary connections ‎and ‎configurations have ‎been prepared to perform process control. (SIMATIC Manager Step7) is ‎used for ‎programming in PLC. ‎Besides, the MATLAB simulation program is configured to implement ‎real-time ‎control to be ‎compatible with the MF624 data acquisition card. Liquid level and fluid flow ‎control ‎experiments were ‎performed separately for the same PID algorithms formed on two different ‎devices, then ‎liquid level ‎detection and liquid flow control results have been collected and ‎investigated. Based on these ‎results, a total ‎of four experiments were compared with both devices ‎considering the ease and difficulties of ‎using PLC and ‎MATLAB.

Analysis and simulation of three MANET routing protocols: A research on AODV, DSR & DSDV characteristics and their performance evaluation

Mobile ad-hoc network allows electronic devices to independently configure the communication; even if the device changes its position, the (MANET) can maintain the connectivity among the devices since it has the capability to arrange a temporary network dynamically. The lack of central infrastructure and the freedom of mobile nodes to move randomly will create several problems, like routing and security issues. MANET requires a stable routing algorithm to adapt to the network that changes its topology randomly at any time. Several studies were conducted with different scenarios to suggest the best protocol for routing. However, a clear performance evaluation is still a missing part, because the dissimilarities in the mechanism of the protocol can lead to important performance differences. This article provides a performance assessment of (DSR), (DSDV), and (AODV) protocols. Research results and the evaluation of the network are made based on network size, mobility, and variable network load by using NS2 application for simulation. The results reveal that the (AODV, DSR) are more efficient than DSDV and reasonably more proper for ad-hoc applications and projects

Unicast based reactive & proactive routing simulation in MANET: A comparative study for protocols in mobility scenarios

A challenging issue for (MANETs) is finding an effective routing mechanism, the wireless connection must have the capability to interact while traveling randomly, since MANETs are self-configuring mobile node networks. Traditional fixed network routing protocols are useless with MANET. Based on this, MANETs introduced new routing protocols. In this study, the routing process was investigated, particularly (DSR), (AODV) and (DSDV). Simulations are implemented in the NS2 simulation environment and evaluated their performance under various scenarios. The results of the simulation study were summarized with a number of graphs using NAM (Network Animation Environment) and Trace Graph programs and a general evaluation was made. The results of the simulation studies presented that DSR and AODV showed better efficiency than the table based DSDV protocol. In addition, DSR and AODV protocols may present a variable performance for the different data packets and network sizes due to their algorithmic differences

Levocarnitine Improves AlCl3-Induced Spatial Working Memory Impairment in Swiss albino Mice

Background: Aluminum, a neurotoxic substance, causes oxidative stress induced-neurodegenerative diseases. Several lines of evidence suggest that levocarnitine has an antioxidant effect and also plays an important role in beta-oxidation of fatty acids. However, the role of levocarnitine in aluminum-induced neurotoxicity has not been well documented. Here we aimed to investigate the effect of levocarnitine on aluminum chloride (AlCl3)-induced oxidative stress and memory dysfunction.Methods: Male Swiss albino mice (n = 30) were treated with either control (saline) or AlCl3 or AlCl3 plus levocarnitine or levocarnitine or astaxanthin plus AlCl3 or astaxanthin alone. The spatial working memory was determined by radial arm maze (RAM). In addition, we measured the lipid peroxidation (MDA), glutathione (GSH), advanced oxidation of protein products (AOPP), nitric oxide (NO) and activity of superoxide dismutase (SOD) in the various brain regions including prefrontal cortex (PFC), striatum (ST), parietal cortex (PC), hippocampus (HIP) hypothalamus (HT) and cerebellum (CB). We used astaxanthin as a standard antioxidant to compare the antioxidant activity of levocarnitine.Results: The RAM data showed that AlCl3 treatment (50 mg/kg) for 2 weeks resulted in a significant deficit in spatial learning in mice. Moreover, aluminum exposure significantly (p < 0.05) increased the level of oxidative stress markers such as MDA, GSH, AOPP and NO in the various brain regions compared to the controls. In addition, combined administration of levocarnitine and AlCl3 significantly (p < 0.05) lowered the MDA, AOPP, GSH and NO levels in mice.Conclusion: Our results demonstrate that levocarnitine could serve as a potential therapeutic agent in the treatment of oxidative stress associated diseases as well as in memory impairment

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication

Assessment and Performance Improvement of Multicarrier Modulation for Underwater Acoustic Communications

Se han considerado dos tipos de receptores: filtro adaptado y ZF. Los resultados presentados muestran que el receptor SF supera al receptor de filtro adaptado a valores altos de relación señal a ruido (Signal-to-Noise Ratio, SNR) para casi todas las configuraciones. Como cuarta contribución, se ha propuesto - y evaluado su rendimiento - un transceptor OFDM basado en modulación de fase continua para comunicación acústica submarina. En nuestra técnica propuesta, el codificador en OFDM tradicional es reemplazado por un modulador CPM (Continuous Phase Modulation). El comportamiento observado del error establece claramente la superioridad de CPM-OFDM sobre los esquemas OFDM tradicionales.En esta tesis doctoral se han propuesto múltiples técnicas para mejorar la viabilidad de un transceptor OFDM para transmisión acústica submarina. En primer lugar, se desarrolla y evalúa un banco de pruebas (o simulador) acústico submarino basado en el transceptor OFDM (Orthogonal Frequency Division Multiplexing) de prefijo cíclico (Cyclic Prefix, CP). El simulador se ha implementado en Matlab. Se supone que el sistema OFDM tiene intervalos de guarda mayores que la dispersión de retardo y se utiliza un igualador ZF (Zero-Forcing), considerando la estimación del canal ideal. Además, el sistema propuesto permite ajustar múltiples parámetros del transceptor y realizar comparaciones de tasa de error de bit (Bit Error Rate, BER) para múltiples escenarios. El diseño propuesto permite la evaluación de una variedad de distintos esquemas de modulación. Como segunda contribución, se ha propuesto un algoritmo de estimación de canal asistido por piloto basado en una estimación de error de mínimos cuadrados (Least Squares Error, LSE). Además, se han considerado dos igualadores para mejorar el rendimiento de error de un sistema de comunicaciones acústicas submarinas basado en OFDM. Ambos igualadores emplean subportadoras piloto para estimar el canal acústico submarino. Uno es un igualador de mínimos cuadrados (LS) y el otro es un igualador ZF. La tercera contribución de este trabajo evalúa el rendimiento de un transceptor GFDM (Generalized Frequency Division Multiplexing) para la transmisión acústica submarina de alta velocidad de transmisión. Se ha analizado el rendimiento del transceptor GFDM propuesto en términos de eficiencia espectral, PAPR (Peak-to-Average Power Ratio), BER y complejidad computacional usando simulaciones. Los resultados obtenidos se han comparado con los correspondientes de CP-OFDM. Se ha desarrollado y evaluado un módem basado en GFDM para comunicación acústica submarina

Pilot-Assisted OFDM for Underwater Acoustic Communication

Multicarrier techniques have made it possible to wirelessly transmit data at higher rates for underwater acoustic (UWA) communication. Several multicarrier techniques have been explored in the past for wireless data transmission. OFDM is known to fight off inter-symbol interference due to the orthogonality of its subcarriers. However, due to time variations, OFDM suffers from intercarrier interference. As the UWA channel is both a time and frequency variant, channel estimation becomes complex. We propose a pilot-based channel estimation technique and explore two equalizers for improving the error performance of an OFDM-based UWA system. Both the equalizers employ pilot subcarriers to estimate the UWA channel. One equalizer is a least squares (LS) equalizer and the other is a zero forcing (ZF) equalizer. Using computer simulations, it is observed that, for an acceptable error performance, the number of pilots should be one-fourth the number of subcarriers. Moreover, if the energy of the pilots is increased without changing the overall symbol energy, the error performance degrades. It is also noted that both the LS and ZF equalizers give an acceptable error performance with the ZF performing marginally better than the LS. Furthermore, the error performance of the proposed system is evaluated as a function of the transmitter-receiver distance and an acceptable error performance is observed even at 1250 m