Hybrid visible light communication and radio frequency (VLC/RF) networks provide combined benefits of both visible light and radio frequency technologies. This is an eminent technology for providing 5G services in an indoor environment. Because of small coverage range, multiple VLC cells coexist in a close proximity. For efficiently utilizing resources of multiple VLC access points (VLC-APs), a different approach than conventional multi RF-APs based resource allocation schemes is required due to unique characteristics of light. In this paper, we provide an optimized solution for combined power and slot allocation in hybrid VLC/RF networks with the objective of maximizing sum rate for a downlink communication scenario. The resources are optimized on frame by frame basis, instead of per request basis. This frame-based optimization reduces the frequency of optimization and also improves the utilization of the resources. The non-convex problem of joint slot and power allocation is divided into less complex sub problems and solved iteratively. The performance of the joint slot and power allocation (JSPA) scheme has been analyzed for data rate and fairness factor for varying values of network size and minimum quality of service (QoS) requirements. The analysis exhibits on average more than 65% improvement in both fairness factor and average sum rate as compared to single VLC-AP based scheme (SV O RF), in which single VLC-AP is utilized for a user and RF-AP is utilized to offload traffic when VLC resources are not sufficient. Moreover, we propose a hybrid user-centeric and network-centeric (H-Uc/Nc) scheme for slot allocation which entails far less computational complexity. Although, H-Uc/Nc scheme performs inferior to optimized scheme, however, it exhibits much better performance than (SV O RF).
IEEE 802.11 Wireless Local Area Network (WLAN) is one of the most widely deployed wireless network technologies in the world today. However, 802.11 MAC algorithm is unable to support modern multimedia applications which require certain level of quality of service (QoS) guarantees in terms of consistent, timely and reliable data transfer. The 802.11e MAC protocol provides extension for adjustment of MAC parameters that were previously fixed in the standard 802.11 CSMA/CA contention mechanism. In this paper we conduct the evaluation study of 802.11e Enhanced Distributed Channel Access (EDCA) mechanism which supports service differentiation by assigning data traffic with different priorities based on their QoS requirements. The evaluation also includes the study of the role of different parameters IEEE 802.11e EDCA utilizes to realize service differentiation as well as the performance comparison of 802.11 and 802.11e along with its capability to resolve downlink/uplink fairness problem.
IEEE 802.15.4 Wireless Personal Area Networks (WPANs) are envisaged to play an important role in future ubiquitous network applications. When multiple PANs operate in the same area called personal operating space (POS), they are not aware of each other's presence and hence not able to communicate with each other. In this paper, we present a framework for intercommunication of neighboring PANs located in the same area through sensor nodes residing at the border. By time sharing the logical channels, a gating operation is performed by the border sensor nodes of two noninterfering PANs. The framework includes detecting neighboring PAN, identifying border sensor nodes and a gating protocol. The simulation results show improvement in delivery ratio when number of border sensor nodes is increased.
For achieving high bandwidth, fast, and robust communication in 5G, multiple technologies are needed to work under heterogeneous networks. Visible light communication, due to its high bandwidth, low latency, and small interference area, will be a significant part of 5G along with mmwave. In this paper, a new frame structure has been proposed that implements reserve before transmit scheme. In this scheme, the active portion of the frame starts with contention access‐based reservation period (RP) followed by access point response (RES Reply) and TDMA‐based guaranteed time slots for successful nodes. In contrast to fixed slot assignment in TDMA, contention‐based reservation avoids idle slot wastage due to fixed allotment. Moreover, small reserve packets keep medium busy for a short time, the benefit of which is a lower probability of failed channel access. The proposed scheme has been compared with IEEE 802.15.7 for a sufficiently large length of RP. A Markov model of the system has been developed for analyzing the effect of RP length on the network performance. The result depicts that reserve before transmit–based frame structure provides an increase of 170% in reliability and decrease of 80% in channel access delay as compared to existing IEEE 802.15.7 CSMA/CA‐based access.
Escherichia coli is a universal bacterium causing infections in humans and animal and serves as a major pathogen of urinary tract infections (UTI) and Extraintestinal infection. The present study was conducted for current antibiotic resistance pattern of E. coli and molecular detection of resistance related gene in clinical isolates of E. coli. The study was a hospital based, prospective study which was done for a period of twelve months. This study was done by using the standard culture techniques for urine, pus, semen and sputum samples, Maximum number was from samples of urine 73 followed by pus 23 semen 2 and sputum 2. Hundred pathogenic E. coli isolates was further identified by standard microbiology techniques such as colony morphology, Gram staining and biochemical testing methods. Drug resistance was evaluated by disc diffusion method and relevant drug resistance gene detection done by Multiplex PCR. Out of 130 clinical samples total (n=100) isolates were identified as E. coli and their susceptibility patterns for different antibiotics were determined. Results showed that Gentamicin among aminoglycosides and Colistin sulfate among polymyxin were showed relatively less resistance in E. coli. Bacitracin, Ampicillin, trimethoprim, Erythromycin, Tetracycline, Ciprofloxacin, Amoxicillin and Piperacillin were found more resistant. Imepenum, Meropenum among ? lactam were most effective drug. PCR was employed to identify resistance causing gene. Among 100 pathogenic E. coli isolates 87% shown ampicillin resistance encoded by Tem B lactamase gene and 86 % shown tetracycline resistance causing by Tet A gene. Highest level of drug-resistance was observed against ampicillin and tetracycline (AMP-TET) among clinical isolates of pathogenic E. coli collected from hospitalized patients.
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