Jorge F. Schmidt

• PhD. in Engineering
• Head of 5G & IoT at Digital Factory Vorarlberg GmbH, Austria

Coupled oscillator systems can lead to states in which synchrony and chaos coexist. These states are called “chimera states.” The mechanism that explains the occurrence of chimera states is not well understood, especially in pulse-coupled oscillators. We study a variation of a pulse-coupled oscillator model that has been shown to produce chimera st...

We present experimental results on a private 5G standalone network in an industrial environment. We focus on inter-robotic communication and assess the impact that increasing network traffic has on the achievable link latency and, ultimately, the collaboration capability of the robots. We demonstrate a notable degradation across all tested quality...

The concept of pulse-coupled oscillators for self-organized synchronization has been applied to wireless systems. Putting theory into practice, however, faces certain obstacles, particularly in radio technologies that cannot implement pulses but use common messages for interactions between nodes. This raises the question of how to deal with interfe...

We propose a relaying scheme for a LoRa network’s uplink, where some end devices (EDs) overhear and relay messages from other EDs. The scheme’s salient feature is that it allows the EDs to adjust their relaying behavior according to their energy status, such that EDs with higher energy reserves perform more forwarding. This prevents early depletion...

Resistance welding is known to generate Electromagnetic emissions that can impair wireless transmissions. This poster studies the impact of these emissions on the feasible communication range of ultra-wideband (UWB) technology. Our results are based on extensive packet loss measurements at different link distances and propagation conditions in an i...

This paper explores key parameters of a massive MIMO system and their impact on energy efficiency at transmission. In particular, the effect of the digital to analog converter resolution and peak to average power ratio reduction techniques are addressed, in the context of practical user location distributions for both line and non line of sight cha...

Not all systems of pulse-coupled oscillators converge to synchrony from any initial configuration. The probability of synchronization depends on the network topology and the phase response function. It is often assumed that all oscillators are governed by the same phase response function. We exemplify that the synchronization probability can be sig...

We propose a scheme to reduce and balance the energy consumption of nodes in dense IoT use cases implemented with LoRa. We study a multiple gateways network with nodes uniformly distributed around each gateway, and restricted to use only short spreading factors. Relays using longer spreading factors, are added to the network infrastructure to forwa...

Swarmalators combine two types of distributed coordination - swarming and synchronization - whose mutual coupling leads to the emergence of spatio-temporal patterns. This paper studies issues for implementing swarmalators in the real world. First, the model is discretized in time to achieve limited communication overhead. We propose to apply stocha...

Studies on wireless network synchronization based on the theory of coupled oscillators largely ignore the interference caused by the in-band synchronization signals exchanged between nodes. We show that such interference can play a key role and gain two insights: First, increasing the node transmission power does not necessarily lead to faster sync...

We analyze the reliability and energy consumption of uplink message delivery in bidirectional LoRa networks that employ acknowledgements and retransmissions. Our frame-collision analysis with symbol-level timing accuracy shows that the ACKs—introduced to improve reliability—significantly impact the end devices’ power consumption via the collisions...

Wireless solutions for on-board communications are gaining momentum in the aerospace industry with the aim to further improve flight safety, reduce aircraft costs, and lower environmental impact. Also passenger infotainment services are increasingly realized in a wireless way and call for high-rate connectivity to the Internet. There are many issue...

This article proposes and evaluates a technique to predict the level of interference in wireless networks. We design a recursive predictor that forecasts future interference values at a given location by filtering measured interference at this location. The predictor's parametrization is done offline by translating the autocorrelation of interferen...

We discuss the potential of ultra-wideband (UWB) technology for realizing use cases in industry 4.0 and demonstrate the implementation of an UWB sensor network with off-the-shelf transceivers for machine vibration monitoring.We propose a flexible medium access layer tailored for industrial sensing and show how the choice of its parameters is affect...

We derive the probability distribution of the link outage duration at a typical receiver in a wireless network with Poisson distributed interferers sending messages with slotted random access over a Rayleigh fading channel. This result is used to analyze the performance of random linear network coding, showing that there is an optimum code rate and...

Usage scenarios in industry • Broad range of communication and processing requirements • Emerging use cases require higher data rates • Machinery condition monitoring • Solutions that operate on a battery plus harvested energy • Efficient use of the available energy • Most work with Zigbee, WiFi, GSM→NB-LTE • Some work with UWB, LoRa, BTLE

This paper presents initial results regarding the potential of ultra-wideband (UWB) technology to become an enabler of self-powered industrial sensor networks. Our study uses requirements from vibration monitoring typically implemented today with wired installations. A wireless solution can significantly reduce cost if batteries do not need to be r...

Measurements of ultra-wideband (UWB) communications inside an Ariane 5 launcher are reported, assessing received signal power fluctuations and connectivity in the vehicle equipment bay. This environment is challenging due to shadowing and reflections. Our results highlight the relationship between the multipath delay spread and the UWB signal detec...

This article takes an analytical approach to investigate the temporal dynamics of interference in wireless networks. We propose a framework to calculate the autocorrelation of interference in Poisson networks and derive closed-form expressions for the case of Nakagami fading. The framework takes three correlation sources into account: the location...

A thorough understanding of the temporal dynamics of interference in wireless networks is crucial for the design of communication protocols, scheduling, and interference management. This article applies stochastic geometry to investigate the interference dynamics in a network of nodes that use carrier sense multiple access (CSMA). This type of netw...

This article proposes and evaluates a technique to predict the level of interference in wireless networks. We design a recursive predictor that computes future interference values at a given location by filtering measured interference at this location. The parametrization of the predictor is done offline by translating the autocorrelation of interf...

A thorough understanding of the temporal dynamics of interference in wireless networks is crucial for the design of communication protocols, scheduling, and interference management. This paper applies stochastic geometry to investigate interference dynamics for the first time in a network with nodes that use carrier sense multiple access. This type...

The dynamics of interference over space and time influences the performance of wireless communication systems, yet its features are still not fully understood. This article analyzes the temporal dynamics of the interference in Poisson networks accounting for three key correlation sources: the location of nodes, the wireless channel, and the network...

Experimental results on the connectivity of IEEE 802.15.4-2011 ultra-wideband (UWB) devices are presented in two industrial scenarios: a large-size aircraft assembly hangar and a medium-size production hall. These measurements are the first ones reported for off-the-shelf UWB devices in such setting and shed light on the potential of UWB to support...

Our research investigates the concept of interference prediction as an unprecedented approach for interference management. This paper is a �rst step in this direction: it proposes and evaluates a simple interference prediction technique that is based on lowcomplexity learning. Nodes predict the interference situation they expect to experience in th...

There is a strong demand in the aviation industry to replace cables in airplanes by wireless connectivity to gain flexibility and reduce weight. Such in-plane wireless communications must be reliable and robust against interference. As part of our activities in this domain, we present a proof-of-concept for an ultra-wideband (UWB) sensor network de...

Variable packet delays (VPDs) are the key limiting factor for achieving tight synchronization with Pulse-Coupled Oscillators (PCO) schemes. In this paper, we argue that specific MAC frames should be designed to facilitate PCO synchronization in IEEE 802.15.4 systems. In particular, a customized PCO-MAC frame is proposed to reduce VPDs. We show that...

A time synchronization technique for networked devices with low-precision oscillators and low computational power is proposed and evaluated. We apply a dynamic stochastic model inserted into a Kalman filter formulation to track the clock evolution of oscillators and achieve synchrony to a central time reference. Indoor and outdoor experiments perfo...

We derive closed-form expressions for the bit error rate in an interference-limited wireless network. Users are distributed according to a Poisson point process and communicate over a Nakagami fading channel using the widely employed Gray-coded quadrature amplitude modulation. The way how interference influences the bit error rate provides insight...

This work explores the benefits in terms of energy efficiency that can be provided by device-to-device (D2D) communications in cellular systems. Analyzing a large cellular network through stochastic geometry tools and considering realistic system parameters and Nakagami fading, we explore the reduction in overall network power consumption that can...

We present a wireless sensor network, deployed and tested for real aircraft applications. By employing IEEE 802.15.4-2011 UWB compliant transceivers, with a time slotted channel access protocol, characteristics of indoor propagation are studied. A test setup in an aircraft’s empty passenger cabin is presented and wireless channel features are analy...

Time synchronization is challenging in wireless sensor networks due to the use of low-precision oscillators and the limited computational capacity of resources limited sensor nodes. While several schemes exist, the performance analysis of a majority of them is based on simulations and fail to capture key features of real world deployments. This pap...

Time synchronization provides the basis for several applications in wireless sensor networks but the limited memory and computational power, and the use of low precision oscillators make the task of time synchronization non-trivial. In this demonstration, we present a novel time synchronization scheme that is based on time series analysis. To provi...

Time synchronization provides the basis for several applications in wireless sensor networks but the limited memory and computational power, and the use of low precision oscillators make the task of time synchronization non-trivial. In this demonstration, we present a novel time synchronization scheme that is based on time series analysis. To provi...

Device-to-device (D2D) communications is a promising candidate for increasing the throughput of cellular systems towards 5G. Its current consideration for inclusion in LTE-A is attracting a lot of research interest, including work on mode selection, bandwidth allocation, and power control. Some consider the uplink for D2D operation while others foc...

The Proportional Fair Scheduler (PFS) has become a popular channel-aware resource allocation method in wireless networks, as it effectively exploits multiuser diversity while providing fairness to users. PFS decisions on which mobile station (MS) to schedule next are based on Channel Quality Indicator (CQI) values. Since CQI values are reported by...

We present a low-power design for Active Interference Cancellation (AIC) sculpting of the OFDM spectrum, based on sparse design concepts. Optimal AIC designs compute cancellation weights based on contributions from all data subcarriers. Thus, as the number of subcarriers grows, power consumption becomes a concern, and suboptimal solutions that avoi...

Active interference cancellation (AIC) is a multicarrier spectrum sculpting technique which reduces the power of undesired out-of-band emissions by adequately modulating a subset of reserved cancellation subcarriers. In most schemes online complexity is a concern, and thus cancellation subcarriers have traditionally been constrained to linear combi...

Active Interference Cancellation (AIC) techniques for OFDM spectrum sculpting have gained interest over the last years, and several extensions to the MIMO case have been recently proposed. However, these designs do not fully exploit the spatial diversity provided by the multiple transmit antennas, as canceler allocation is fixed. This paper propose...

Active interference cancellation (AIC) is an effective technique to shape the OFDM spectrum, providing deep notches over protected bands without affecting receiver design. However, AIC typically introduces spectrum overshoot, of concern if compliance with a spectral emission mask is required. Most AIC designs neglect these spectral spurs, focusing...

A novel low complexity active interference cancellation (AIC) scheme for primary user (PU) protection is presented for application to cognitive orthogonal frequency division multiplexing (OFDM) systems, in which out-of-band radiation spilling over the PU protected band is to be minimized. A set of carefully selected cancellation subcarriers are mod...

A novel active interference cancellation (AIC) scheme for primary user (PU) protection is presented for application to cognitive OFDM systems, in which out-of-band radiation spilling over the PU protected band is to be minimized. A set of cancellation subcarriers are modulated by appropriate linear combinations of the remaining data subcarriers. Th...

We present a novel channel estimator/predictor for OFDM systems over time-varying channels using a recursive formulation of a basis expansion model (BEM) based on an approximated discrete cosine transform (DCT). We derive a recursive implementation of the approximated DCT-BEM for tracking time-varying channels based on a filter bank. The recursive...

We present a prediction-based resource allocation algorithm (RA) for orthogonal frequency-division multiple-access (OFDMA) downlink, where inaccuracies in the wireless channel predictions are accounted for in the problem formulation. As the prediction quality significantly degrades with the prediction horizon, we propose a solution based on the his...

We present a prediction-based resource allocation algorithm (RA) for OFDMA downlink over mobile wireless channels, where prediction errors are incorporated in the problem formulation. A solution based on the empirical characterization of the prediction error is proposed. We test the proposed scheme on a realistic scenario using a practical low comp...

We present a novel channel estimator/predictor for OFDM systems over time-varying channels using a recursive for- mulation of a basis expansion model (BEM) based on an approxi- mated discrete cosine transform (DCT). We derive a recursive im- plementation of the approximated DCT-BEM for tracking time- varying channels based on a filter bank. The rec...

We present a prediction-based resource allocation algorithm (RA) for OFDMA downlink over mobile wireless chan- nels, where prediction errors are incorporated in the problem formulation. A solution based on the empirical characterization of the prediction error is proposed. We test the proposed scheme on a realistic scenario using a practical low co...

We present a prediction-based resource allocation algorithm (RA) for orthogonal frequency-division multiple-access (OFDMA) down- link, where inaccuracies in the wireless channel predictions are accounted for in the problem formulation. As the prediction quality significantly degrades with the prediction horizon, we propose a solution based on the h...

We present a novel channel estimator for fading channels using basis function approximations and Kalman filtering. The proposal results in a low complexity estimator that is robust to the shape of the channel Doppler spectrum and allows different Doppler spectra for each channel coefficient in a frequency-selective scenario. The estimator is based...

We present a channel predictor based on a basis function approach formulation of a Kalman filter channel estimator. The estimator models chan- nel variations via truncated discrete cosine transform (DCT), which is robust to the shape of the channel Doppler spectrum. We show that the DCT can be ap- proximated by a set of linear narrow passband filte...