Bernhard Etzlinger

Johannes Kepler University Linz | JKU · Institute for Communications Engineering and RF-Systems

This review addresses the role of synchronization in the radio localization problem, and provides a comprehensive overview of recent developments suitable for current and future practical implementations. The material is intended for both, theoreticians and practitioners, and is written to be accessible to novices, while covering state-of-the-art t...

Cooperative localization in agent networks based on interagent time-of-flight measurements is closely related to synchronization. To leverage this relation, we propose a Bayesian factor graph framework for cooperative simultaneous localization and synchronization (CoSLAS). This framework is suited to mobile agents and time-varying local clock param...

Channel based clock synchronization in packet switched networks (PSNs) is considered for, but not limited to, the time and safety/security critical application of power system protection. The synchronization accuracy requirement of power system protection devices used for line current differential protection is 10 mus, which could be achieved in t...

Research evidence in Cyber-Physical Systems (CPS) shows that the introduced tight coupling of information technology with physical sensing and actuation leads to more vulnerability and security weaknesses. But, the traditional security protection mechanisms of CPS focus on data encryption while neglecting the sensors which are vulnerable to attacks...

The Internet of Things (IoT) will seamlessly integrate a large number of densely deployed heterogeneous devices and will enable new location-aware services. However, fine-grained localization of IoT devices is challenging as their computation and communication resources are typically limited and different devices may have different qualities of int...

This paper proposes two deep-learning (DL)-based approaches to a physical tamper attack detection problem in orthogonal frequency division multiplexing (OFDM) systems with multiple receiver antennas based on channel state information (CSI) estimates. The physical tamper attack is considered as the unwanted change of antenna orientation at the trans...

This letter proposes a deep learning approach to detect a change in the antenna orientation of transmitter or receiver as a physical tamper attack in OFDM systems using channel state information. We treat the physical tamper attack problem as a semi-supervised anomaly detection problem and utilize a deep convolutional autoencoder (DCAE) to tackle i...

Mobile contact tracing apps are -- in principle -- a perfect aid to condemn the human-to-human spread of an infectious disease such as COVID-19 due to the wide use of smartphones worldwide. Yet, the unknown accuracy of contact estimation by wireless technologies hinders the broad use. We address this challenge by conducting a measurement study with...

This letter proposes a deep learning approach for detecting a change in transmitters' or receivers' antenna orientation as a physical tamper attack in OFDM systems using channel state information. We treat the physical tamper attack problem as a semi-supervised anomaly detection problem and utilize a deep convolutional autoencoder (DCAE) to tackle...

We propose to add a monitoring system consisting of so-called path- and guard nodes to industrial wireless sensor network (IWSN), to increase the security level by using RSSI measurements. Via these measurements, the monitoring system determines the presence of a mobile sensor node in a predefined area, which can be used to handle access rights and...

A precise decentralized clock synchronization method, referred to as Integrated Cooperative Synchronization (ICS) is proposed in this letter. ICS is a delay compensating method that relies on mean-field (MF) message passing, where the measurement phase is integrated into the message passing phase. By selecting an extended factorization of the under...

This paper considers a passive localization scenario relying on a single transmitter, several receivers and multiple moving targets to be located. The so-called “passive” targets equipped with RFID reflectors are capable of reflecting the signals from the transmitter to the receivers. Existing approaches assume that the transmitter and receivers ar...

In this work we propose a secure communication concept for the protection of critical power supply and distribution infrastructure. Especially, we consider the line current differential protection method for modern smart grid implementations. This protection system operates on critical infrastructure, and it requires a precise time behavior on the...

Modern day networking and computing systems rely increasingly on knowing the location of the user. These include state-of-the art technologies such as navigation of vehicles and robots, traffic planning, or light control in smart home environments. In the future, even more services will appear. The predominant localization technology currently uses...

Timestamp free clock synchronization in a masterslave network, i.e., synchronization where no timestamps are exchanged between the nodes, is considered. For highly accurate synchronization, a novel discrete-valued clock model is introduced. It is based on the observation that clocks are discrete counters in digital wireless radios. Considering this...

In many applications the pulse duration of a periodic pulse signal is the parameter of interest. Thereby, the non-band-limited pulse signal is sampled during a finite observation period yielding to aliasing and windowing effects, respectively. In this work, the pulse duration estimation based on the mean value of the samples is considered, and a cl...

Localization and synchronization are very important in many wireless applications such as monitoring and vehicle tracking. Utilizing the same time of arrival (TOA) measurements for simultaneous localization and synchronization is challenging. In this paper, we present a factor graph (FG) representation of the joint localization and time synchroniza...

We consider the problem of clock synchronization between a pair of nodes using round-trip communication where only the initiating node collects time stamps, and where no time stamps are exchanged. These time stamps are the current timer values at the event of transmission or reception of a signal. Traditionally, the timer is modeled by a continuous...

(work accepted at Asilomar 2015 conference) We consider the passive localization problem in a wireless network, where source nodes at unknown positions are emitting arbitrary signals at unknown time. The receiving asynchronous anchor nodes act passively as they do not cooperate with the source nodes. In order to localize the source nodes, the loca...

(work accepted at Asilomar 2015 conference) We consider the problem of clock synchronization between a pair of nodes using round-trip communication where only the initiating node collects time stamps, and where no time stamps are exchanged. These time stamps are the current timer values at the event of transmission or reception of a signal. Tradit...

In this paper we consider a unique word OFDM (UW-OFDM) system with iterative detection, for which we explore two soft-input soft-output (SISO) detection algorithms: A LMMSE detector and a detector based on the generalized approximate message passing (GAMP) algorithm. For the GAMP based detector we propose additional simplifications suitable for UW-...

Cooperative sensor self-localization (CSL) in wireless networks usually requires the nodes to be equipped with specific ranging hardware including ultra-wideband or ultrasonic distance sensors. Such designs are not suitable for application in low-cost, low-power sensor networks. Here, we demonstrate how low-cost, low-power, asynchronous sensor node...

Clock synchronization and ranging are important topics in the field of wireless networks, where internode time measurement allows both tasks to be completed in one. Such networks are generally time-variant due to possible changes in environmental conditions and mobility of network nodes. We present a fully distributed filtering algorithm for combin...

Many emerging technologies for wireless networks (WNs) require decentralized synchronization and ranging, i.e., distance estimation between neighboring pairs of nodes. Both tasks are related to each other when they are based on time measurements between nodes. Revealing this connection, we present a mean field (MF) message passing algorithm for coo...

We present a factor graph framework and a particle-based belief propagation algorithm for distributed cooperative simultaneous localization and synchronization (CoSLAS) in decentralized sensor networks. The proposed algorithm jointly estimates the locations and clock parameters of the network nodes in a fully decentralized fashion. This estimation...

Localization and synchronization in wireless networks are strongly related when they are based on internode time measurements. We leverage this relation by presenting a message passing algorithm for cooperative simultaneous localization and synchronization (CoSLAS). The proposed algorithm jointly estimates the locations and clock parameters of the...

Synchronization is a key functionality in wireless network, enabling a wide variety of services. We consider a Bayesian inference framework whereby network nodes can achieve phase and skew synchronization in a fully distributed way. In particular, under the assumption of Gaussian measurement noise, we derive two message passing methods (belief prop...

For a bit-interleaved coded MIMO communication system over a frequency-selective channel we present a factorgraph-based joint channel estimation and data detection. In the graph, Gaussian message passing with different message update rules is investigated. We compare the application of belief propagation on the entire graph to a joint application o...

We propose a fully-parallel low-complexity hardware architecture of a soft-input soft-output detector based on message passing on a factor graph. Conventionally, the message computation in the graph nodes consists of complex arithmetic operations on probabilities. Here, we represent probabilities by bit-serial streams and transform the arithmetic o...

In this letter we consider a MIMO communication system with iterative detection over a frequency-selective MIMO channel. We present a soft-input soft-output MIMO detector based on a cyclic factor graph representation and the sum-product algorithm with two different message schedules (serial and parallel). Computer simulations show that both schedul...

In this paper we consider a soft-input soft-output equalizer, for MIMO intersymbol interference channels, used in a turbo equalization scheme. We derive the equalizer on the basis of a cyclic factor graph representation and the sum-product algorithm, with two different message schedules (serial and parallel). In the sum-product algorithm we use Gau...

In this paper, we consider a bit-interleaved coded spatial multiplexing MIMO communication system over a frequency-selective MIMO channel. We present a factor-graph-based derivation of two different equalization algorithms. To this end, we propose a cycle-free factor graph representation of the equalizer, to which we apply the sum-product algorithm...

Factor graphs (FG) are a tool to derive efficient algorithms for complex systems by graphically displaying the structure of the mathematical model. The construction of the graph and the choice of the messages which are passed over its edges significantly determine the performance and the complexity of the derived algorithm. In our work we show the...

The resolution of a pulse based radar system is restricted by the pulse width. Overlapping echoes in time domain of adjacent objects make a wave front evaluation of B-scans difficult. In this paper, a new algorithm for the wave front detection is proposed. Based on a reference impulse response of a large metal plate, the algorithm is able to determ...

Ultra wide band (UWB) radar systems are used to get information from a detected target. This can be done by studying the shapes of incident and reflected pulses. To evaluate the target transfer function, a calibration is necessary to eliminate the influences of the system and the environment. The calibration includes deconvolution operations produc...