2-Aminovinyl-cysteine (AviCys) is a thioether amino acid shared by a variety of ribosomally synthesized and posttranslationally modified peptides (RiPPs). Based on investigations into the ...biosynthesis of thioviridamide RiPPs in Streptomyces sp. NRRL S-87, we here report a path for the formation of this unusual thioether residue. This path relies on four dedicated proteins: phosphotransferase TvaCS-87, Lyase TvaDS-87, kinase homolog TvaES-87, and LanD-like flavoprotein TvaFS-87. TvaES-87 plays a critical role in effective AviCys formation. During the posttranslational modifications of the precursor peptide, it works with TvaFS-87 to form a minimum AviCys synthetase complex, which follows the combined activity of TvaCDS-87 for Thr dehydration and catalyzes Cys oxidative decarboxylation and subsequent Michael addition of the resulting enethiol nucleophile onto the newly formed dehydroamino acid residue for cyclization. With TvaES-87, TvaFS-87 activity for Cys processing can be coordinated with TvaCDS-87 activity for minimizing competitive or unexpected spontaneous reactions and forming AviCys effectively.
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•Formation of an AviCys residue in thioviridamides relies on four dedicated proteins•A lyase functionally associates with a phosphotransferase for Thr dehydration•Kinase homolog TvaE plays a critical role in effective AviCys formation•TvaE works with a LanD-like flavoprotein to form a minimum AviCys synthetase complex
Qiu et al. report 2-aminovinyl-cysteine formation in the biosynthesis of ribosomally synthesized thioviridamides. A kinase homolog works with a LanD-like flavoprotein to form a minimum 2-aminovinyl-cysteine synthetase complex. Following combined phosphotransferase-lyase activity for Thr dehydration, this complex catalyzes Cys oxidative decarboxylation and subsequent Michael addition to provide an unsaturated thioether linkage.
Wireless local area networks (WLANs) have become a promising choice for indoor positioning as the only existing and established infrastructure, to localize the mobile and stationary users indoors. ...However, since WLANs have been initially designed for wireless networking and not positioning, the localization task based on WLAN signals has several challenges. Amongst the WLAN positioning methods, WLAN fingerprinting localization has recently garnered great attention due to its promising performance. Notwithstanding, WLAN fingerprinting faces several challenges and hence, in this paper, our goal is to overview these challenges and corresponding state-of-the-art solutions. This paper consists of three main parts: 1) conventional localization schemes; 2) state-of-the-art approaches; and 3) practical deployment challenges. Since all proposed methods in the WLAN literature have been conducted and tested in different settings, the reported results are not readily comparable. So, we compare some of the representative localization schemes in a single real environment and assess their localization accuracy, positioning error statistics, and complexity. Our results depict illustrative evaluation of the approaches in the literature and guide to future improvement opportunities.
A network is a group of hardware devices and software components that are designed to connect devices. To be effective and efficient, a network must meet a number of criteria. The most important of ...these are performance, throughput, delay and security. CIT college network is a well designed and an efficient network but suffers from various problems like hardware failure, bandwidth congestion, application server processing time, quality of data, authentication service and the like. Hence diagnosing network performance issues is part of our daily work. This paper aims to simulate and analyze the performance of LAN network implemented in our college using NETSIM, and to study its performance metrics. A proper study on the network metrics is made and solutions for improvement measures are provided. A considerable increase in throughput and decrease in delay is been noted by modifying the parameters in the application type, switching mode and transport layer of wired and wireless node in the current network structure.
Location information for events, assets, and individuals, mostly focusing on two dimensions so far, has triggered a multitude of applications across different verticals, such as consumer, networking, ...industrial, health care, public safety, and emergency response use cases. To fully exploit the potential of location awareness and enable new advanced location-based services, localization algorithms need to be combined with complementary technologies including accurate height estimation, i.e., three dimensional location, reliable user mobility classification, and efficient indoor mapping solutions. This survey provides a comprehensive review of such enabling technologies. In particular, we present cellular localization systems including recent results on 5G localization, and solutions based on wireless local area networks, highlighting those that are capable of computing 3D location in multi-floor indoor environments. We overview range-free localization schemes, which have been traditionally explored in wireless sensor networks and are nowadays gaining attention for several envisioned Internet of Things applications. We also present user mobility estimation techniques, particularly those applicable in cellular networks, that can improve localization and tracking accuracy. Regarding the mapping of physical space inside buildings for aiding tracking and navigation applications, we study recent advances and focus on smartphone-based indoor simultaneous localization and mapping approaches. The survey concludes with service availability and system scalability considerations, as well as security and privacy concerns in location architectures, discusses the technology roadmap, and identifies future research directions.
Emulating the local area network (LAN) has become a vital requirement for the passive optical network (PON). There are many efforts to establish the optical layer LAN (OLAN) in various PONs. However, ...the existing OLAN schemes generally isolate the LAN function from regular PON, resulting in the rigid allocation of transmission resources. To improve the flexibility of OLAN, this work presents a PON system that can achieve the conversion between PON and LAN. According to different conversions, the system forms three work modes. In addition, a novel bandwidth allocation scheme is proposed for this PON system to determine when to switch its work mode. The proposed bandwidth allocation scheme aims to reuse the idle timeslots due to the half-duplex LAN transmission by sharing the timeslot and wavelength resources between the upstream and LAN transmissions. Simulation results show that the proposed bandwidth allocation scheme can significantly outperform the traditional one in the average latency, network throughput, and load balancing performances.
•A local area network scheme based on passive optical network is proposed.•Achieving flexible conversion between local area network and passive optical network.•A bandwidth allocation scheme sharing wavelength and timeslot is proposed.•The flexible system possesses outstanding latency and throughput performance.
In the IEEE 802.11 specifications, a wireless fidelity (Wi‐Fi) access point (AP) broadcasts a beacon frame every 0.1024 s, and the received signal strength indicator (RSSI) is measured at a user ...terminal. RSSI is used as a metric for AP selection, but it does unlikely correlate with the actual quality of service, as has been pointed out in previous literature. In this letter, a simple metric is proposed that correlates with the effective throughput offered by a public Wi‐Fi AP. Specifically, the number of beacon frames within a time window is counted instead of using RSSI. The proposed metric can be easily calculated as it does not rely on advanced techniques such as machine learning. In a realistic IEEE 802.11a/n/ac network, the correlation coefficient between the proposed metric and the effective total throughput is 0.874 in the time window of 1 s, which is higher than a conventional metric, indicating the potential for low‐latency identification of whether a public Wi‐Fi AP can provide good throughput.
A simple metric is proposed that correlates with the effective throughput offered by a public wireless fidelity (Wi‐Fi) access point. The proposed metric can be easily calculated as it does not rely on advanced techniques such as machine learning. In a realistic IEEE 802.11a/n/ac network, the correlation coefficient between the proposed metric and the effective throughput is 0.874, which is higher than a conventional metric, indicating the potential for low latency throughput estimation.
A Multiband Slot Antenna for GPS/WiMAX/WLAN Systems Cao, Y. F.; Cheung, S. W.; Yuk, T. I.
IEEE transactions on antennas and propagation,
2015-March, 2015-3-00, 20150301, Letnik:
63, Številka:
3
Journal Article
Recenzirano
The design of a four-band slot antenna for the global positioning system (GPS), worldwide interoperability for microwave access (WiMAX), and wireless area network (WLAN) is presented. The antenna ...consists of a rectangular slot with an area of 0.37λ g × 0.14λ g = 48 × 18 mm 2 (where λ g is the guide wavelength), a T-shaped feed patch, an inverted T-shaped stub, and two E-shaped stubs to generate four frequency bands. The radiating portion and total size of the antenna are less than those of the tri-band antennas studied in literature. Parametric study on the parameters for setting the four frequency bands is presented and hence the methodology of using the design for other frequency bands is proposed. The multiband slot antenna is studied and designed using computer simulation. For verification of simulation results, the antenna is fabricated and measured. The simulated and measured return losses, radiation patterns, realized peak gains, and efficiencies of the antenna are presented. Measured results show that the antenna can be designed to cover the frequency bands from 1.575 to 1.665 GHz for the GPS system, 2.4-2.545 GHz for the IEEE 802.11b&g WLAN systems, 3.27- 3.97 GHz for the WiMAX system, and 5.17-5.93 GHz for the IEEE 802.11a WLAN system. The effects of the feeding cable used in measurement and of the cover are also investigated.
Channel bonding is one promising approach to cope with rising WLAN data demand, given scarce spectrum resources. An access point (AP) can aggregate multiple contiguous channels to satisfy demand. We ...discuss how to optimally utilize available frequency bands under uncertainty in AP demands using two stochastic optimization frameworks: a static scheme which minimizes the total occupied bandwidth while satisfying the demand of each AP with probability at least <inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula>, and an adaptive scheme that allows adaptability of the bandwidth allocation in response to the AP demand variations. Given its complexity, we propose a novel framework to solve the adaptive stochastic optimization problem efficiently. The proposed framework exploits the special structure of the problem through decomposition into two subproblems. A particle swarm optimization (PSO)-based algorithm is tailored to the first-stage problem in order to obtain good solutions. The second-stage problem is further decomposed into several subproblems that can be solved independently in parallel. Our numerical results (i) demonstrate the advantages of stochastic compared to deterministic allocation, (ii) illustrate that the proposed framework reaches the optimal solution for the two-stage problem in few iterations, and (iii) explain the bandwidth-user satisfaction trade-off provided by the adaptive allocation approach.
LPWAN is a type of wireless telecommunication network designed to allow long range communications with relaxed requirements on data rate and latency between the core network and a high-volume of ...battery-operated devices. This article first reviews the leading LPWAN technologies on both unlicensed spectrum (SIGFOX, and LoRa) and licensed spectrum (LTE-M and NB-IoT). Although these technologies differ in many aspects, they do have one thing in common: they all utilize the narrow-band transmission mechanism as a leverage to achieve three fundamental goals, that is, high system capacity, long battery life, and wide coverage. This article introduces an effective bandwidth concept that ties these goals together with the transmission bandwidth, such that these contradicting goals are balanced for best overall system performance.
Millimeter-wave (mmWave) with large spectrum available is considered as the most promising frequency band for future wireless communications. The IEEE 802.11ad and IEEE 802.11ay operating on 60 GHz ...mmWave are the two most expected wireless local area network (WLAN) technologies for ultra-high-speed communications. For the IEEE 802.11ay standard still under development, there are plenty of proposals from companies and researchers who are involved with the IEEE 802.11ay task group. In this survey, we conduct a comprehensive review on the medium access control layer (MAC) related issues for the IEEE 802.11ay, some cross-layer between physical layer and MAC technologies are also included. We start with MAC related technologies in the IEEE 802.11ad and discuss design challenges on mmWave communications, leading to some MAC related technologies for the IEEE 802.11ay. We then elaborate on important design issues for IEEE 802.11ay. Specifically, we review the channel bonding and aggregation for the IEEE 802.11ay, and point out the major differences between the two technologies. Then, we describe channel access and channel allocation in the IEEE 802.11ay, including spatial sharing and interference mitigation technologies. After that, we present an in-depth survey on beamforming training, beam tracking, single-user multiple-input-multiple-output beamforming, and multi-user multiple-input-multiple-output beamforming. Finally, we discuss some open design issues and future research directions for mmWave WLANs. We hope that this paper provides a good introduction to this exciting research area for future wireless systems.
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