310 research outputs found
Effects of Time Synchronization Errors in IoT Networks
Internet of Things is a term referring to the wireless connection of people and devices, briefly referred to as âthingsâ. The growth of technology has become so rapid, that people are finding various ways and means to communicate to each other in a fast and reliable way. Industries and other organizations such as hospitals, military, schools and so on, are demanding better, easy and cheaper way to communicate or pass out information.
Time and frequency synchronization are basic demands for all wireless communication system to work accurately. In time synchronization, the receiver terminal determines the correct time at which to sample the incoming signal. For two or more systems to function at same time with high speed, accuracy and reliability, they must be well synchronized, and time sensitive enough so that it will not experience failure at some point in time.
This thesis focuses on the characteristics of IoT technologies, how time-sensitive an IoT network can be, and what time and frequency synchronization solutions there exist. A simulation study is also performed using Binary Phase Shift Keying (BPSK) modulation and Narrowband (NB) and Ultra-Narrowband (UNB) signals.
The simulation-based analysis is done with three error models (constant, random and clock) using MATLAB simulation, where a plot of Bit-Error-Rate (BER) versus Signal-to-Noise-Ratio (SNR) is drawn to investigate the effects of the time synchronization errors with the NB and UNB signals
Homomorphic Filtering for Improving Time Synchronization in Wireless Networks
Wireless sensor networks are used to sample the environment in a distributed way.
Therefore, it is mandatory for all of the measurements to be tightly synchronized in order to guarantee
that every sensor is sampling the environment at the exact same instant of time. The synchronization
drift gets bigger in environments suffering from temperature variations. Thus, this work is focused
on improving time synchronization under deployments with temperature variations. The working
hypothesis demonstrated in this work is that the clock skew of two nodes (the ratio of the real
frequencies of the oscillators) is composed of a multiplicative combination of two main components:
the clock skew due to the variations between the cut of the crystal of each oscillator and the clock
skew due to the different temperatures affecting the nodes. By applying a nonlinear filtering,
the homomorphic filtering, both components are separated in an effective way. A correction factor
based on temperature, which can be applied to any synchronization protocol, is proposed. For testing
it, an improvement of the FTSP synchronization protocol has been developed and physically
tested under temperature variation scenarios using TelosB motes flashed with the IEEE 802.15.4
implementation supplied by TinyOS
10 Gigabit White Rabbit: sub-nanosecond timing and data distribution
Time synchronization is a critical feature for many scientific facilities and industrial
infrastructures. The required performance is progressively increasing everyday, for instance, few tens of
nanoseconds for Fifth Generation (5G) networks or sub-nanosecond accuracy on next family of particle
accelerators and astrophysics telescopes. Due to this exigent accuracy, many applications require specific
timing dedicated networks, increasing the system cost and complexity. Under this context, the new IEEE
1588-2019 High Accuracy (HA) default profile is intensively based on White Rabbit (WR) which can
provide sub-nanosecond accurate synchronization for Ethernet networks. However, current WR solutions
have not been designed to work properly with high data bandwidth delivery services even in 1 Gigabit
Ethernet (GbE) links. On this contribution, the authors propose a new architecture design that enables WR
and, consequently, the IEEE 1588-2019 HA profile to be deployed over 10 GbE links solving the already
identified data bandwidth problem. Furthermore, this work addresses different experiments needed to
characterize the system performance in terms of time synchronization and data transfer. As final result, this
contribution presents for the first time in the literature a new WR system which allows high bandwidth data
exchange in 10 GbE networks while providing sub-nanosecond accuracy synchronization. The proposed
solution maintains the time synchronization performance of existing WR 1 GbE devices with significant
advantages in terms of latency and data bandwidth, enabling its deployment in applications that integrate
data and synchronization information in the same network.European Union (EU)
725490H2020 ASTERICS
653477AMIGA7
RTI2018-096228-B-C3
Recent Trends in Communication Networks
In recent years there has been many developments in communication technology. This has greatly enhanced the computing power of small handheld resource-constrained mobile devices. Different generations of communication technology have evolved. This had led to new research for communication of large volumes of data in different transmission media and the design of different communication protocols. Another direction of research concerns the secure and error-free communication between the sender and receiver despite the risk of the presence of an eavesdropper. For the communication requirement of a huge amount of multimedia streaming data, a lot of research has been carried out in the design of proper overlay networks. The book addresses new research techniques that have evolved to handle these challenges
Industrial Wireless Sensor Networks
Wireless sensor networks are penetrating our daily lives, and they are starting to be deployed even in an industrial environment. The research on such industrial wireless sensor networks (IWSNs) considers more stringent requirements of robustness, reliability, and timeliness in each network layer. This Special Issue presents the recent research result on industrial wireless sensor networks. Each paper in this Special Issue has unique contributions in the advancements of industrial wireless sensor network research and we expect each paper to promote the relevant research and the deployment of IWSNs
Economically sustainable public security and emergency network exploiting a broadband communications satellite
The research contributes to work in Rapid Deployment of a National Public Security and Emergency Communications Network using Communication Satellite Broadband. Although studies in Public Security Communication networks have examined the use of communications satellite as an integral part of the Communication Infrastructure, there has not been an in-depth design analysis of an optimized regional broadband-based communication satellite in relation to the envisaged service coverage area, with little or no terrestrial last-mile telecommunications infrastructure for delivery of satellite solutions, applications and services.
As such, the research provides a case study of a Nigerian Public Safety Security Communications Pilot project deployed in regions of the African continent with inadequate terrestrial last mile infrastructure and thus requiring a robust regional Communications Satellite complemented with variants of terrestrial wireless technologies to bridge the digital hiatus as a short and medium term measure apart from other strategic needs.
The research not only addresses the pivotal role of a secured integrated communications Public safety network for security agencies and emergency service organizations with its potential to foster efficient information symmetry amongst their operations including during emergency and crisis management in a timely manner but demonstrates a working model of how analogue spectrum meant for Push-to-Talk (PTT) services can be re-farmed and digitalized as a âdedicatedâ broadband-based public communications system. The networkâs sustainability can be secured by using excess capacity for the strategic commercial telecommunication needs of the state and its citizens. Utilization of scarce spectrum has been deployed for Nigeriaâs Cashless policy pilot project for financial and digital inclusion. This effectively drives the universal access goals, without exclusivity, in a continent, which still remains the least wired in the world
Ultra-wideband Based Indoor Localization of Mobile Nodes in ToA and TDoA Configurations
Zandian R. Ultra-wideband Based Indoor Localization of Mobile Nodes in ToA and TDoA Configurations. Bielefeld: UniversitÀt Bielefeld; 2019.This thesis discusses the utilization of ultra-wideband (UWB) technology in indoor localization scenarios and proposes system setup and evaluates different localization algorithms in order to improve the localization accuracy and stability of such systems in non-ideal conditions of the indoor environment.
Recent developments and advances of technology in the areas of ubiquitous Internet, robotics and internet of things (IoT) have resulted in emerging new application areas in daily life in which localization systems are vital. The significant demand for a robust and accurate localization system that is applicable in indoor areas lacking satellites link, can be sensed. The UWB technology offers accurate localization systems with an accuracy of below 10 cm and covering the range of up to a few hundred meters thanks to their dedicated large bandwidth, modulation technique and signal power.
In this thesis, the technology behind the UWB systems is discussed in detail. In terms of localization topologies, different scenarios with the focus on time-based methods are introduced. The main focus of this thesis is on the differential time of arrival localization systems (TDoA) with unilateral constellation that is suitable for robotic localization and navigation applications.
A new approach for synchronization of TDoA topology is proposed and influence of clock inaccuracies in such systems are thoroughly evaluated. For localization engine, two groups of static and dynamic iterative algorithms are introduced. Among the possible dynamic methods, extended Kalman filter (EKF), Hâ and unscented Kalman filter (UKF) are discussed and meticulously evaluated.
In order to tackle the non-line of sight (NLOS) problem of such systems, for detection stage several solutions which are based on parametric machine learning methods are proposed. Furthermore, for mitigation phase two solutions namely adjustment of measurement variance and innovation term are suggested. Practical results prove the efficiency and high reliability of the proposed algorithms with positive NLOS condition detection rate of more than 87%.
In practical trials, the localization system is evaluated in indoor and outdoor arenas in both line of sight and non-line of sight conditions. The results show that the proposed detection and mitigation methods can be successfully applied for both small and large-scale arenas with the higher performance of the localization filters in terms of accuracy in large-scale scenarios
- âŠ