Single Packet Research Articles

Backward Compatible Physical Layer Protocol Evolution for ADS-B Message Authentication

The automatic dependent surveillance-broadcast system is a pillar of the future air traffic control system. It is a surveillance system in which air planes transmit their information (identity, position, velocity, etc.) in broadcast to any listener equipped with a receiver. Networks of ADS-B receivers have been installed all over the world, producing a clear traffic awareness for air traffic controllers. For historical reasons, this protocol does not have any authentication/encryption mechanism. The aim of this article is to improve the ADS-B system security by introducing a physical layer protocol modification for the introduction of an authentication scheme. The proposed evolution fully complies with the current standard and exploits the phase modulation to increase the number of bits that can be transmitted with a single packet of data. These additional bits can be used to carry authentication information, making the overall system more secure (and safe). The proposed protocol evolution is developed ensuring backward compatibility and respecting the ICAO and RTCA recommendations; it can be introduced and used together with the present standard in a mixed scenario, allowing a smooth transition from the present protocol to the new one. Protocol performances were evaluated by simulations and, moreover, its feasibility and compliance with recommendations were tested using a software-defined radio (as transmitter) and a laboratory ADS-B receiver.

A two-channel slotted sense multiple access protocol for timely and reliable data transmission in industrial wireless sensor networks

In designing a real-time MAC protocol for wireless sensor networks, it is desirable to shorten the data acquisition cycle time to satisfy more applications with a tighter time constraint in data collection. To achieve this, one often tries to improve throughput by employing a slot reuse technique. Meanwhile, the slotted sense multiple access protocol that uses a sharable slot was proven to be advantageous for timely and reliable data delivery. However, since the nodes at lower tree levels process more packets or bigger packets with data aggregation, they need a bigger sharable slot. Thus, it is not easy to employ a slot reuse technique due to the size variation of sharable slots. To tackle this problem, we try to reduce the size of an aggregated packet by limiting the number of packets for aggregation using two channels. If every node is allowed to send a single packet during data acquisition cycle time, an equal-sized sharable slot can be allocated to every tree level. It is shown that the proposed approach can reduce data acquisition cycle time significantly while maintaining good reliability in data transmission compared with slotted sense multiple access and also reduce energy consumption greatly compared with another multi-channel MAC protocol.

A Synchronously Self-Q-Switched and Self-Mode-Locked Fiber Laser with a Compound Resonator

We demonstrate a synchronously self-Q-switched and self-mode-locked output pulse fiber laser based on a linear compound resonator and an LD cladding-pumped Yb-doped double-clad fiber. A maximum average output power of 332.1 mW is achieved. We observe that the maximum pulse envelope width is 8 μs, and the pulse energy is 3.83 μJ for the self-Q-switched pulse envelope. At the same time, the achieved maximum pulse width is 37.8 ns and pulse energy is 17.61 nJ for the self-mode-locked pulse. We observe the pulse splitting of the self-Q-switched envelope as well and achieve 14 subpulse packets for L1 = 180 mm. There are 75 self-mode-locked pulses in single packets.

Query Privacy Preserving for Data Aggregation in Wireless Sensor Networks

Wireless Sensor Networks (WSNs) are increasingly involved in many applications. However, communication overhead and energy efficiency of sensor nodes are the major concerns in WSNs. In addition, the broadcast communication mode of WSNs makes the network vulnerable to privacy disclosure when the sensor nodes are subject to malicious behaviours. Based on the abovementioned issues, we present a Queries Privacy Preserving mechanism for Data Aggregation (QPPDA) which may reduce energy consumption by allowing multiple queries to be aggregated into a single packet and preserve data privacy effectively by employing a privacy homomorphic encryption scheme. The performance evaluations obtained from the theoretical analysis and the experimental simulation show that our mechanism can reduce the communication overhead of the network and protect the private data from being compromised.

Multiple QoS provisioning with pre-emptive priority schedulers in multi-resource OFDMA networks

In this paper, we present an analytical framework for the performance evaluation of a pre-emptive priority scheduler in multi-resource networks, like those using Orthogonal Frequency Division Multiple Access (OFDMA). We focus on Quality of Service (QoS)-guaranteed traffic for which QoS is guaranteed to individual users by restricting the number of admitted users. For this, the QoS-constrained capacity, in terms of the number of supported users, needs to be ascertained a priori. The QoS-constrained capacity is a function of users’ QoS requirements, channel conditions, and radio resource allocation algorithms, which in this work is the pre-emptive priority scheduler. It is, thus, a variable quantity and mostly obtained using time-consuming offline computer simulations. Mathematical models, on the other hand, are timely and accurate, allowing the capacity to be derived in real-time as a function of the current network configuration. Existing works on mathematical modelling of pre-emptive priority schedulers have mostly focussed on single servers or multiple servers where a single server is assigned to each user. In contrast, OFDMA networks have multiple radio resources, i.e., multiple servers and each user may need more than one radio resource for a single packet transmission, i.e. it is a multi-resource system, which has been accounted for in this paper. We classify the users based on their resource requirements and model the pre-emptive priority scheduler as a multi-class, multi-server, multi-resource, non-work conserving queueing system. We derive its QoS metrics like average delay, packet drop probability, throughput, etc., from its continuous-time Markov Chain. We then use the derived QoS metrics to obtain the QoS-constrained capacity and design a threshold based predictive call admission control unit. We have validated the results using extensive discrete event simulations.

Broadcasting a file in a communication network

We study the problem of distributing a file, initially located at a server, among a set of n nodes. The file is divided into mge 1 equally sized packets. After downloading a packet, nodes can upload it to other nodes, possibly to multiple nodes in parallel. Each node, however, may receive each packet from a single source node only. The upload and download rates between nodes are constrained by node- and server-specific upload and download capacities. The objective is to minimize the makespan. This problem has been proposed and analyzed first by Mundinger et al. (J Sched 11:105–120, 2008. https://doi.org/10.1007/s10951-007-0017-9) under the assumption that uploads obey the fair sharing principle, that is, concurrent upload rates from a common source are equal at any point in time. Under this assumption, the authors devised an optimal polynomial time algorithm for the case where the upload capacity of the server and the nodes’ upload and download capacities are all equal. In this work, we drop the fair sharing assumption and derive an exact polynomial time algorithm for the case when upload and download capacities per node and among nodes are equal. We further show that the problem becomes strongly NP-hard for equal upload and download capacities per node that may differ among nodes, even for a single packet. For this case, we devise a polynomial time smash {(1+2sqrt{2})}-approximation algorithm. Finally, we devise two polynomial time algorithms with approximation guarantees of 5 and 2 + lceil log _2 lceil n/mrceil rceil /m, respectively, for the general case of m packets.

Flower traits, habitat, and phylogeny as predictors of pollinator service: a plant community perspective

AbstractPollinator service is essential for successful sexual reproduction and long‐term population persistence of animal‐pollinated plants, and innumerable studies have shown that insufficient service by pollinators results in impaired sexual reproduction (“pollen limitation”). Studies directly addressing the predictors of variation in pollinator service across species or habitats remain comparatively scarce, which limits our understanding of the primary causes of natural variation in pollen limitation. This paper evaluates the importance of pollination‐related features, evolutionary history, and environment as predictors of pollinator service in a large sample of plant species from undisturbed montane habitats in southeastern Spain. Quantitative data on pollinator visitation were obtained for 191 insect‐pollinated species belonging to 142 genera in 43 families, and the predictive values of simple floral traits (perianth type, class of pollinator visitation unit, and visitation unit dry mass), phylogeny, and habitat type were assessed. A total of 24,866 pollinator censuses accounting for 5,414,856 flower‐minutes of observation were conducted on 510 different dates. Flowering patch and single flower visitation probabilities by all pollinators combined were significantly predicted by the combined effects of perianth type (open vs. restricted), class of visitation unit (single flower vs. flower packet), mass of visitation unit, phylogenetic relationships, and habitat type. Pollinator composition at insect order level varied extensively among plant species, largely reflecting the contrasting visitation responses of Coleoptera, Diptera, Hymenoptera, and Lepidoptera to variation in floral traits. Pollinator composition had a strong phylogenetic component, and the distribution of phylogenetic autocorrelation hotspots of visitation rates across the plant phylogeny differed widely among insect orders. Habitat type was a key predictor of pollinator composition, as major insect orders exhibited decoupled variation across habitat types in visitation rates. Comprehensive pollinator sampling of a regional plant community has shown that pollinator visitation and composition can be parsimoniously predicted by a combination of simple floral features, habitat type, and evolutionary history. Ambitious community‐level studies can help to formulate novel hypotheses and questions, shed fresh light on long‐standing controversies in pollination research (e.g., “pollination syndromes”), and identify methodological cautions that should be considered in pollination community studies dealing with small, phylogenetically biased plant species samples.

Echo in a single vibrationally excited molecule

Echo is a ubiquitous phenomenon found in many physical systems, ranging from spins in magnetic fields to particle beams in hadron accelerators. It is typically observed in inhomogeneously broadened ensembles of nonlinear objects, and is used to eliminate the effects of environmental-induced dephasing, enabling observation of proper, inherent object properties. Here, we report experimental observation of quantum wave packet echoes in a single isolated molecule. In contrast to conventional echoes, here the entire dephasing-rephasing cycle occurs within a single molecule without any inhomogeneous spread of molecular properties, or any interaction with the environment. In our experiments, we use a short laser pulse to impulsively excite a vibrational wave packet in an anharmonic molecular potential, and observe its oscillations and eventual dispersion with time. A second delayed pulsed excitation is applied, giving rise to an echo: a partial recovery of the initial coherent wavepacket. The vibrational dynamics of single molecules is visualized by time-delayed probe pulse dissociating them one at a time. Two mechanisms for the echo formation are discussed: ac Stark-induced molecular potential shaking and creation of depletion-induced "hole" in the nuclear spatial distribution. Interplay between the optically induced echoes and quantum revivals of the vibrational wave packets is observed and theoretically analyzed. The single molecule wave packet echoes may lead to the development of new tools for probing ultrafast intramolecular processes in various molecules.

Fast key-frame image retrieval of intelligent city security video based on deep feature coding in high concurrent network environment

Aiming at the problems faced by the connection management module in single packet processing in intelligent city security video retrieval, we firstly propose the traffic locality quantization index based on the traffic characteristics of the backbone link to quantitatively analyze the traffic locality characteristics in the backbone link. And then, a key-frame abstraction and retrieval of videos based on deep learning is proposed to improve the efficiency and accuracy of video retrieval, where an adaptive key-frame selection algorithm is designed and the existing convolutional neural network framework is used to extract the features of key-frames, and unsupervised, semi-supervised and supervised retraining models are designed to improve the effectiveness of the feature extraction of the convolutional neural network and the accuracy of the video retrieval. Experimental results based on the public video datasets show that our proposed key-frame image retrieval model realizes a good precision for key-frame representation, and achieves high accuracy and efficiency for video retrieval.

Hybrid Multilayer Network Traceback to the Real Sources of Attack Devices

With the advent of the Internet of Things (IoT), there are also major information security risks hidden behind them. There are major information security risks hidden behind them. Attackers can conceal their actual attack locations by spoofing IP addresses to attack IoT devices, law enforcement cannot easily track them. Therefore, a method to trace stealth attacks is required. Conventional IP traceback methods that traceback only attackers on the network layer and cannot infer the path information of a packet traversing the switch. This article proposes a method to simultaneously traceback attack sources at the network layer and the data link layer with only one single packet. Even if the core network contains a switch or if multiple attackers launch attacks from different locations, the method can correctly traceback the true devices responsible for the attacks, and its achievements include a zero false negative rate and a low false positive rate.

Testing different Channel Estimation Techniques in Real-Time Software Defined Radio Environment

In modern wireless communication to maximize spectral efficiency and to minimize the bit error rate OFDM (Orthogonal frequency-domain multiplexing) is used. OFDM is used broadly in networks using various protocols, including wireless vehicular environment IEEE 802.11p, IEEE 802.16d/e Wireless Metropolitan Area Networks, Long-Term Evolution 3GPP networks and IEEE 802.11a/g/n Wireless Local Area Networks. The main challenges involved when using OFDM for wireless communications are short channel-coherence bandwidth and the narrow coherence time, and both have a major effect on the reliability and latency of data packet communication. These properties increase the difficulty of channel equalization because the channel may change drastically over the period of a single packet. Spectral Temporal Averaging is an enhanced decision-directed channel equalization technique that improves communication performance (as far as the frame delivery ratio (FDR) and throughput) in typical channel conditions. This paper reports tests of Spectral Temporal Averaging channel equalization in an IEEE 802.11a network, compared with other channel equalization techniques in terms of the FDR in a real-time environment. Herein, a software defined Radio (SDR) platform was used for estimating the channel. This proves that the system can provide over 90% of delivery ratio at 25 db of Signal to Noise Ratio (SNR) for various digital modulation techniques. For this purpose, an experimental setup consisting of software-defined radio, Universal Software Radio Peripheral (USRP) N210 along with wide bandwidth daughter board as hardware and GNU radio is used.

Multiband Massive Channel Random Access in Ultra-Reliable Low-Latency Communication

Ultra-Reliable Low-Latency Communication (URLLC) is challenging due to its extremely higher reliability requirement with stringent short latency packet transmission. In order to overcome this reliability and latency bound, a communication access scheme needs to assure almost error-free and high speed packet transmission. In this paper, a new multiple-access scheme-Orthogonal Frequency-Subcarrier-based Multiple Access (OFSMA)-is proposed with URLLC's high requirement adaptation. In this scheme, the packet diversity concept is incorporated to achieve the expected packet transmission reliability and a diverse number of the duplicated packet are processed with a set of operations and transmitted over randomly selected orthogonal subcarrier frequency channels. Performances of the OFSMA system are measured in terms of applying several numbers of frequency bands, a massive number of subcarrier channels, a different number of packet duplications, and a diverse rate of traffic arrival conditions. We determined the minimum number of subcarrier channels requirement to satisfy the reliability of 99.999% for different packet duplication in presence of different frequency bands. The reliability response for a fixed number of subcarrier channels is evaluated for different frequency band conditions. Finally, the air interface latency of the OFSMA system is measured for single packet uplink transmission and compared with that of a traditional OFDMA system. The performance results in terms of reliability and latency express that the OFSMA scheme can assure the expected reliability and latency defined by URLLC.

A Proposed IoT-Enabled Smart Waste Bin Management System and Efficient Route Selection

Internet of Things (IoT) is an emerging technology that offers promising solutions to modernize the traditional systems. It accords promising result in crystallizing smart cities, smart homes, smart industries, and smart environment. This article presents the smart waste management architecture for smart cities and efficient routing technique considering least delay for the architecture. In wireless sensor networks, end-to-end delay is one of the important Quality of Services (QoS) parameter to overcome delay in data communication. In this article, we consider end-to-end delay minimization in smart waste management application. The term “end-to-end delay” is defined as the total time taken by a single packet to reach the destination node. The proposed scheme considers the interference level, the length of the routing path, and the number of hops along the path. The simulation results show that the proposed scheme outperforms current schemes.

Programmable and robust static topological solitons in mechanical metamaterials

Solitary, persistent wave packets called solitons hold potential to transfer information and energy across a wide range of spatial and temporal scales in physical, chemical, and biological systems. Mechanical solitons characteristically emerge either as a single wave packet or uncorrelated propagating topological entities through space and/or time, but these are notoriously difficult to control. Here, we report a theoretical framework for programming static periodic topological solitons into a metamaterial, and demonstrate its implementation in real metamaterials computationally and experimentally. The solitons are excited by deformation localizations under quasi-static compression, and arise from buckling-induced kink-antikink bands that provide domain separation barriers. The soliton number and wavelength demonstrate a previously unreported size-dependence, due to intrinsic length scales. We identify that these unanticipated solitons stem from displacive phase transitions with periodic topological excitations captured by the well-known {varphi }^{4} theory. Results reveal pathways for robust regularizations of stochastic responses of metamaterials.

An effective practical method for narrowband wireless mesh networks performance

This study presents a new practical measurement method for analyzing narrowband wireless mesh networks (NWMNs) application performance. It investigates a scenario for packet transmissions in NWMNs, leveraging wireless interconnection between two devices. It analyzes the effect of message size and channel spacing on the resulting bitrate, forwarding time and modulation rate through experimental results. We transmit a single packet for one hop, exploiting a versatile radio modem with very-high-frequency radios operating in the bridging or routing modes. The measurement results obtained, with the mentioned critical operating parameters, provide a quicker and clearer idea as well as conclusive evidence for overall network performance.

A New Energy Efficient Clustering Protocol for Life Timemaximization in Wsns

On this paper we have got proposed an energy inexperienced clustering protocol that is dynamic, distribution, self-organizing and further electricity green than gift protocols. Contributors in wi-fi sensor network clusters transport records to their cluster heads using TDMA scheduling. The cluster head transmits the aggregated and compressed packets to the bottom station. The CSMA MAC protocol is traditionally used for data transmission. In the CSMA MAC protocol, whilst the packet arrives on the cluster head it first senses the channel, if it's far loose, the cluster head transmits records that may be every a single packet or a a couple of packet. The cluster is reduced in transmitting unmarried packets from the pinnacle to the bottom station electricity. To make better utilization of sources along with energy more than one packets to be sent in area of transmitting single packet. On this proposed technique, we particularly focused on site visitors at the Cluster heads i.E. Cluster heads with big site visitors are desired for channel project and cluster head site traffic is a great deal much less for backoff time, in this era cluster head may also moreover collect greater records from their individuals. So on this manner strength overall performance is improved via who choose transmission of multiple packets in location of a single packet.In this proposed approach, Fuzzy C-way (FCM) set of rules is accompanied to form clusters inside WSNs. MATLAB software program is used to implement and evaluate the effects of the proposed set of rules with deterministic inexperienced clustering (DEC) set of regulations, Voronoi set of guidelines and LEACH protocol In terms of lifespan and electricity intake. The consequences show that the existence of the proposed algorithm is extended with the beneficial aid of 17%.

Parameterization of a Non-local Crystal Plasticity Model for Tempered Lath Martensite Using Nanoindentation and Inverse Method

Crystal plasticity (CP) models have proven to accurately describe elasto-plastic behavior on micro- and nanometer length scales in numerous applications. However, their parameterization requires series of experiments and inverse analysis of the results. In this regard, nanoindentation promises to be a well-suited tool for realizing a parameterization approach to determine all model parameters. The objective of this work is to develop a parameterization technique for a non-local CP model by means of an accessible and reproducible workflow. To determine its feasibility, tempered lath martensite with two different carbon contents is used as testing material. The workflow combines nanoindentation tests with finite element simulations. First, indentation into single packets of tempered lath martensitic specimen is yielding the load-displacement curves and the residual imprint topology on the surface with the help of atomic force microscopy. In a second step, a finite element simulation of the indentation using non-local crystal plasticity as constitutive model is performed with estimated model parameters. In the next step, non-local CP parameters are systematically adapted in an optimization scheme to reach optimal agreement with experiments. As a final validation step it is successfully demonstrated that the CP model parameterized by nanoindentation is able to predict the macroscopic stress-strain response of polycrystals. Two observations are made: on the one hand, the material properties locally scatter very strongly, which is caused by fluctuations in microstructure and chemistry. On the other hand, a novel method has been demonstrated were an inverse analysis is used to parameterize a non-local CP model for highly complex microstructures as those of tempered lath martensite.

Real-time temporal-spectral analysis of complex dynamics involving multiple soliton states in a dual-wavelength passively mode-locked fiber ring laser

We present an experimental study of complex dissipative solitons dynamics in a passively mode-locked fiber ring laser. Recently, thanks to real-time spectroscopy techniques such as the dispersive Fourier transform (DFT), it has been possible to study the complex internal dynamics of soliton molecules. However, most of the works have been limited to the study of intermolecular or intramolecular dynamics involving a small number of solitons within a single compact soliton packet, to which the DFT technique applies naturally. In this work, we study the dynamics of complex arrangements of multiple solitons, extending the analysis to regimes where multiple soliton packets at different wavelengths coexist and interact in the cavity, probing simultaneously the internal dynamics of various short-lived soliton molecules, as well as the collective dynamics of the different soliton packets distributed in the cavity, all of which is made possible by simultaneous analysis in the temporal and spectral domains. This allows to relate temporal dynamics at different time scales, as well as temporal and spectral events. In particular, we report the experimental observation of the dynamics of the Kelly sidebands that flank the soliton spectra, and relate it to temporal and spectral events such as extinctions of soliton packets with pulsating amplitude, spectral narrowing, and with energy fluctuations.

Efficient Data Broadcast Mitigation in Multisource Named-Content Discovery for Vehicular CPS

Conventionally, a node or vehicle in the Named Data Networking (NDN) sends an interest packet to discover information and receives a single data packet in response. However, in the case of named data Vehicular Cyber-Physical System (VCPS), a vehicle may require content from multiple vehicles in the network. Therefore, NDN forwarding daemon must receive multiple data packets in response to a single interest. Moreover, the data broadcast storm worsens in the named data VCPS due to the broadcast nature of the wireless link. In this letter, we propose the data packet broadcast suppression method for any multisource content discovery in VCPS. The proposed scheme distributively selects the potential data forwarding vehicles based on the neighbor distance, node density, and the closeness to the data forwarding line of sight. Our simulation results show that the proposed scheme alleviates 55% data traffic, 17% average per-hop delay, and achieves 7% more data discovery ratio.

Ns-2'de Farklı Arka Plan TCP Trafik Koşulları Altında VoIP'nin Kullanıcı Düzeyinde Performans Değerlendirmesi

Voice over IP (VoIP) is gaining more and more importance and displaces the traditional telephony. For example, more than 300 million monthly active users worldwide use the popular VoIP application "Skype". However, a big problem in the VoIP environment is the voice quality. The purpose of this study is to investigate the effects of background TCP traffic on perceived voice quality of a VoIP conversation at the user-level using the G.711 codec. Two different playout buffering policies including static buffering and optimal buffering have been applied by the VoIP server. For comparison purposes, the same experiments have also been repeated when no playout buffering policy has been applied by the VoIP server. A three -hop network topology consisting of a source, a transit, and a destination subnetwork was simulated whereas the end-to-end capacity of the entire network was limited by a 1.5 Mbps Asymmetric Digital Subscriber Line ( ADSL) link. Multiple simultaneous TCP connections with different segment sizes were established to simulate the various conditions of background traffic. By using the ns2voip framework, an enhancement to the popular Network Simulator 2 (ns-2), extensive simulation experiments for analyzing the VoIP user-level performance have been carried out and the voice quality has been evaluated by calculating the Mean Opinion Score (MOS). The results show that the voice quality is strongly negatively affected by background TCP traffic, even in the presence of a single TCP flow with 1500 Byte segments. Also, the size of background TCP segments significantly influences the achievable MOSs of VoIP conversations. However, it has also been observed that aggregating multiple speech frames into a single IP packet can increase the MOS. Particularly, depending on the number and segment size of background TCP flows, aggregation of the optimal number of voice frames into the same IP packet improves the MOSs up to 14.61% over a 1.5 Mbps ADSL link.