The Resilience of Massive MIMO PNC to Jamming Attacks in Vehicular Networks

In this article, we investigate the resilience of Massive MIMO Physical Layer Network Coding (PNC) to jamming attack in both sub-6 GHz and millimeter-Wave (mmWave) systems in vehicular networks. Massive MIMO generally is resilient to jamming attacks, and we investigate the impact that PNC has on this resilience, if combined with Massive MIMO. The combination of Massive MIMO and PNC has shown a significant improvement in the bit error rate (BER) in our previous investigation. The corresponding framework is analysed against a barraging attack from a jammer, where the jamming channel is not known to the base station (BS), and the jammer can use any number of transmit antennas. Over Rayleigh channel, our simulation results reveal that Massive MIMO PNC performs better in the lower signal-to-noise ratio (SNR) regions to jamming attacks and this is achieved at twice the spectral efficiency. A similar performance is observed over mmWave channel

Non-orthogonal space-time block coding design for 3 transmit antennas

- Dans cet article, nous proposons un codage spatio-temporel en bloc non orthogonal de rendement symbole 1 pour 3 antennes à l'émission. Ce code permet d'améliorer les performances d'un système de communications sans fil. Le code proposé peut être décodé soit simplement par forçage à zéro soit en utilisant un décodeur à maximum de vraisemblance à complexité réduite. Finalement, nous avons montré que la capacité du code est très proche de la capacité du canal en boucle ouverte

Potential Synergy Activity of the Novel Ceragenin, CSA-13, against Carbapenem-Resistant Acinetobacter baumannii Strains Isolated from Bacteremia Patients

Carbapenem-resistant Acinetobacter baumannii is an important cause of nosocomial infections, particularly in patients in the intensive care units. As chronic infections are difficult to treat, attempts have been made to discover new antimicrobials. Ceragenins, designed to mimic the activities of antimicrobial peptides, are a new class of antimicrobial agents. In this study, the in vitro activities of CSA-13 either alone or in combination with colistin (sulphate), tobramycin, and ciprofloxacin were investigated using 60 carbapenem-resistant A. baumannii strains isolated from bacteremia patients blood specimens. MICs and MBCs were determined by microbroth dilution technique. Combinations were assessed by using checkerboard technique. The MIC 50 values (mg/L) of CSA-13, colistin, tobramycin, and ciprofloxacin were 2, 1, 1.25, and 80, respectively. The MIC 90 (mg/L) of CSA-13 and colistin were 8 and 4. The MBCs were equal to or twice greater than those of the MICs. Synergistic interactions were mostly seen with CSA-13-colistin (55%), whereas the least synergistic interactions were observed in the CSA-13-tobramycin (35%) combination. No antagonism was observed. CSA-13 appears to be a good candidate for further investigations in the treatment of A. baumannii infections. However, future studies should be performed to correlate the safety, efficacy, and pharmacokinetic parameters of this molecule

A Novel Joint Index Modulation and Physical Layer Network Coding Mechanism for Beyond 5G

In beyond 5G communications, besides energy efficiency (EE) and spectral efficiency (SE), latency and reliability, which are among the main metrics that extreme ultrareliable low-latency communications (URLLC) applications must fulfil. Although new techniques are sought after to meet the crunching requirements of URLLC, combining existing physicallayer techniques have become compelling, attractive and cost saving approach in achieving the same goal. In this paper, we describe a novel mechanism in combining Physical Layer Network Coding (PNC) and Index Modulation (IM) to achieving a balance between SE and EE for URLLC applications beyond 5G. PNC has the potential to increase SE because it leverages on interference from many transmissions occurring at the same time. Although fewer resources are required for IM, the capacity gain is the same as if all transmission resources are used, and as a result, both EE and SE can increase simultaneously. Our simulation results show the feasibility of combining these two key physical-layer techniques, affirming the complementary role this approach will play in meeting the performance KPIs of URLLC, beyond 5G

User Selection for NOMA based MIMO with Physical Layer Network Coding in Internet of Things Applications

Non-orthogonal multiple access (NOMA) based multiple-input multiple-output (MIMO), which has the potential to provide both massive connectivity and high spectrum efficiency, is considered as one of the efficient techniques for sixth generation (6G) wireless systems. In massive Internet of Things (IoT) networks, user-set selection is crucial for enhancing the overall performance of NOMA based systems when compared with orthogonal multiple access (OMA) techniques. In this paper, we propose a user-set selection algorithm for IoT uplink transmission to improve the sum data rate of the NOMA based MIMO systems. In order to exchange data between the selected IoT pairs, we propose to employ wireless physical layer network coding (PNC) to further improve the spectral efficiency and reduce the delay to fulfill the requirements of future IoT applications. Performance evaluations are provided based on both sum data rate and bit error rate for the proposed NOMA based MIMO with PNC in the considered massive IoT scenarios

Comparative In Vitro Activities of First and Second-Generation Ceragenins Alone and in Combination with Antibiotics Against Multidrug-Resistant Klebsiella pneumoniae Strains

Objectives: The ceragenins, or CSAs, were designed to mimic the activities of antimicrobial peptides and represent a new class of antimicrobial agent. The aim of this study was to comparatively investigate the antimicrobial activities of first/second generation ceragenins and various antibiotics against multidrug-resistant (MDR) Klebsiella pneumoniae, including colistin-resistant bacteria. Also, the synergistic effects of two ceragenins with colistin or meropenem were investigated with six K. pneumoniae strains presenting different resistant patterns. Methods: Minimal inhibition concentrations (MICs) were determined by the microdilution method according to the CLSI. Antibiotic combination studies were evaluated by the time–kill curve method. Results: MIC50 and MIC90 values of tested ceragenins ranged from 8 to 32 mg/L and 16 to 128 mg/L. Overall, among the ceragenins tested, CSA-131 showed the lowest MIC50 and MIC90 values against all microorganisms. The MICs of the ceragenins were similar or better than tested antibiotics, except for colistin. Synergistic activities of CSA-131 in combination with colistin was found for strains both at 1× MIC and 4× MIC. No antagonism was observed with any combination. Conclusions: First-generation ceragenins CSA-13 and CSA-44 and second-generation ceragenins CSA-131, CSA-138 and CSA-142 have significant antimicrobial effects on MDR K. pneumoniae. Mechanisms allowing resistance to clinical comparator antibiotics like colistin did not impact the activity of ceragenins. These results suggest that ceragenins may play a role in treating infections that are resistant to known antibiotics

Postantibiotic Effects of Tigecycline, Colistin Sulfate, and Levofloxacin Alone or Tigecycline-Colistin Sulfate and Tigecycline-Levofloxacin Combinations against Acinetobacter baumannii

Background: Colistin sulfate and levofloxacin, alone and in combination with tigecycline, were investigated for their in vitro activities and postantibiotic effects (PAEs) on 6 meropenem-resistant Acinetobacter baumannii. Methods: The in vitro activities of colistin sulfate and levofloxacin in combination with tigecycline were determined using a microbroth checkerboard technique. The results were interpreted based on the fractional inhibitory concentration index. To determine the PAEs, A. baumannii strains in the logarithmic phase of growth were exposed for 1 h to antibiotics, alone and in combination. Recovery periods of test cultures were evaluated using viable counting after centrifugation. Results: One synergistic interaction was observed for each of the tigecycline-colistin sulfate and tigecycline-levofloxacin combinations. Colistin sulfate produced a strong PAE ranging from 2.50 to 7.0 h in a concentration-dependent manner. PAEs were induced by levofloxacin (ranging from 0.35 to 2.45 h) and tigecycline (ranging from 0.05 to 1.40 h). In combination, tigecycline slightly changed the PAE of colistin sulfate and levofloxacin against the studied strains. Conclusion: This study's findings could have important implications for the timing of doses during antimicrobial therapy with tigecycline, colistin sulfate, and levofloxacin alone and in combination. copyright (C) 2010 S. Karger AG, Base

In vitro effectiveness of colistin, tigecycline and levofloxacin alone and combined with clarithromycin and/or heparin as lock solutions against embedded Acinetobacter baumannii strains

Objectives: To determine the in vitro stability and efficacy of colistin, tigecycline and levofloxacin alone or in combination with clarithromycin and/or heparin as lock solutions against biofilm-embedded Acinetobacter baumannii strains

Resource Allocation for Underlaying Device-to-Device Communications Using Maximal Independent Sets and Knapsack Algorithm

In this paper, we address the resource allocation problem of device-to-device (D2D) communications underlaying orthogonal frequency division multiple access (OFDMA) based cellular systems by exploiting the efficiency that comes from an ensemble of graph theory and Knapsack problem. It is possible to construct the conflict graph of the D2D pairs by finding the maximal independent sets. Then, we use those independent sets as inputs to Knapsack problem iteratively in order to find D2D groups which allocate the subchannels. In Knapsack problem, we consider a maximum interference level that the base station is exposed at each subchannel. We illustrate that the proposed resource allocation method significantly outperforms graph coloring in terms of average data rate for the high number of underlaying D2D pairs in cellular systems

Post-Antibiotic Effect of Levofloxacin and Tobramycin Alone or in Combination with Cefepime against Pseudomonas aeruginosa

Background: Levofloxacin and tobramycin, alone and in combination with cefepime, were investigated for their in vitro activities and post-antibiotic effects (PAEs) on Pseudomonas aeruginosa. Methods: The in vitro activities of tobramycin and levofloxacin in combination with cefepime were determined by microbroth chequerboard technique against six P. aeruginosa strains that were isolated from patients with bacteremia. The results were interpreted by fractional inhibitory concentration index. To determine the PAEs, P. aeruginosa strains in the logarithmic phase of growth were exposed for 1 h to antibiotics, alone and in combination. Recovery periods of test cultures were evaluated using viable counting after centrifugation. Results: Three synergistic interactions were observed with cefepime-tobramycin and one with cefepime-levofloxacin combinations against tested strains. No antagonism was observed. Levofloxacin produced a PAE ranging from 1.9 to 4.5 h in a concentration-dependent manner. Similar PAEs were induced by tobramycin (ranging from 1.5 to 3.1 h). However, negative PAE values were obtained with cefepime. In combination, cefepime slightly reduced the PAE of tobramycin and levofloxacin against studied strains. Conclusion: The finding of this study may have important clinical implications for the timing of doses during therapy with cefepime, levofloxacin and tobramycin alone and in combination. Copyright (C) 2009 S. Karger AG, Base