Konferenzbeiträge

Acoustic or visual warning signals for workers in hazardous situations might fail under loud and/or lowvisibility work situations. A warning system that uses electrocutaneous stimulation can overcome this problem. The aim of this pilot study was to find spatio-temporal stimulation patterns for appropriate electrical warning. Eight electrode pairs were attached to the upper right arm of 16 participants. The stimulation was conducted with bi-phasic rectangular pulses of 150 μs and an amplitude of up to 25 mA. Pulse intervals that generate a single pulse, pulsating, vibrating, and continuous perception as well as varying spatial patterns (e.g. alternating between electrode pairs or circumferentially around the arm) were investigated and evaluated with regard to alertness, discomfort, and urgency. The pilot study revealed that a stimulation signal that generates a vibrating perception and is applied as a circumferential signal around the arm showed the highest values of alertness and is therefore considered a potential warning pattern for future studies with larger study groups.

Due to the direct contact between electrode and scalp, dry EEG electrodes are exposed to increased mechanical wear compared to conventional gel-based electrodes. However, state-of-the-art commercial cap systems commonly use permanently fixated electrodes which can lead to downtime of the EEG cap during professional repair and replacement as well as reduced overall lifetime. An easily replaceable EEG electrode would furthermore improve hygiene, especially for newborn and infant applications. We propose a novel replaceable electrode system, consisting of an electrode holder, a snap top, a contact ring fixated inside the electrode holder, and a replaceable electrode. The production process consists of 3D printing, silicone molding, resin casting, and electroless plating. The replaceable electrode system is integrated into a multichannel EEG cap system. A verification study is conducted with 30 volunteers. The operators experienced that the new electrode holder eases adjustment of the electrode to have proper contact with the scalp. During the study, defective electrodes can be replaced without a soldering process. Furthermore, all electrodes stayed in the holder and did not fall off the cap for the whole session. In conclusion, the novel replaceable electrode system is suitable for EEG measurements.

A parallel receiver architecture for multiple input multiple output (MIMO) channel sounding application is presented with a software-defined radio (SDR)-based field-programmable gate array (FPGA) implementation. The receiver covers phase coherent reception via shared local oscillator (LO) and reference clock, a timing scheme synchronous to the antenna switching at the transmitter, and an integrated automatic gain control (AGC) in all receive channels. It is built with SDRs (NI USRP-2955, X310 series with TwinRx daughterboards). The use of these off-the-shelf hardware components reduces the costs of the sounding system. The FPGA implementation together with the system parameters of the chosen hardware allows a minimum AGC update interval of approx. 44.38 μs. Our setup demonstrates the applicability of state-of-the-art SDRs as a sounding system for continuous acquisition of the time variant, space, and frequency selective radio propagation channel.

Satellite communication receives strongly increasing attention for automated and connected driving. Compact size, low power consumption, and high data rates are key performance parameters for such systems. Based on realistic assumptions on user equipment terminal and satellite antenna for low-earth orbiting satellites using large space structures, we present relevant link budget considerations. The high-gain satellite antenna opens the potential to employ compact user equipment antennas of moderate gain and without beam tracking. We study selected C-, Ku-, and Ka-frequency bands for 5G satellite communications based upon usual key performance indicators. Our findings indicate that C-band and Ka-band offer a suitable spectrum, with an uplink data rate of 7 Mbit/s at Ka-band, which is suitable for IoT and broadband mobile access applications.

Slow-feature analysis (SFA) seeks to extract the most slowly varying components of dynamic systems. However, the original definition of SFA implies a linear relationship of system states between adjacent time instants. In this paper, a new approach to SFA, which is called EVOLVE.INFOMAX, is defined, based on which the mutual-information-based SFA (MI-based SFA) is proposed. The optimisation problem can be solved by joint diagonalisation of the mutual-information (MI) matrices. The MI matrices are approximated by quantities related to Rényi entropy that can be calculated using the kernel trick. The case studies show MI-based SFA is better for slow feature extraction, especially for nonlinear systems. This allows a better soft sensor to be developed.