Mobile Communications
In the broad field of mobile communications, our group focuses on major topics within the scope of next-generation mobile cellular networks: link layer measurements and simulations of fifth generation (5G) and beyond mobile communications, simulation and optimization of heterogeneous cellular networks with distributed antennas and reconfigurable intelligent surfaces, traffic analysis and simulation at the IP layer and cross-layer optimizations.
A significant part of our research in the field of mobile communications is financed by the Christian Doppler (CD-)Laboratory for Dependable Wireless Connectivity for the Society in Motion. Together with our corporate partners A1 Telekom Austria AG, Nokia Solutions and Networks and ÖBB Infrastruktur AG, we set our objective within this CD-Lab on significantly contributing to the development of 5G and beyond mobile communications technologies, with a focus on scenarios with (potentially fast) moving (human and machine-type) users (cars, trains, but also pedestrians and cyclists). Our work is partitioned into the following three research modules: 1) In research module 1, we investigate together with Nokia Solutions and Networks, a world market leader for communication networks, possible strategies for enhancing the physical layer of mobile network technologies, especially for high-mobility users. The core topics of this research module are massive multiple-input multiple-output technologies and reconfigurable intelligent surfaces. We are targeting an enhancement of the resource efficiency and the robustness of such technologies for high-mobility scenarios. 2) In research module 2, we examine together with our partners from A1 Telekom Austria AG, the leading Austrian mobile network operator, innovative technologies that have the potential to substantially advance mobile communications. Specifically, our focus is on wireless communications in the millimeter-wave band (approximately 30 to 300 GHz) and on non-orthogonal multiple access schemes. Mobile communication in the millimeter-wave band face countless challenges, but it also has significant potential since a vast amount of untapped spectrum is available in that regime, promising corresponding enhancements in mobile network capacities. Non- orthogonal multiple access, as compared to orthogonal multiple access, has the advantages of potentially providing a lower access latency, as well as, supporting a larger number of simultaneous connections. However, these advantages can only be realized with more sophisticated and complicated signal processing at the transmitters and receivers. 3) In research module 3, we develop together with ÖBB Infrastruktur AG, responsible for Austria’s railroad infrastructure, localization techniques based on wireless communication technologies, utilizing classical signal processing techniques (based on signals times and/or angles of arrival) but also novel machine learning concepts, such as deep neural network learning. These methods facilitate large scale analysis of person flows in public transportations and support a dynamic learning-based self-optimization of the mobile network utilizing spatiotemporal demand variations and predictions.
To enable computer-based investigation of dense heterogeneous cellular networks and facilitate the evaluation of coordination methods developed for such networks, we rely on our Vienna Cellular Communications Simulators (VCCS), a suite of in-house developed Matlab-based mobile communication simulators, publicly available for academic users to download on our webpage. The free simulators are highly popular within the scientific community and a commercial version is in usage by a number of 3GPP companies. In 2021 our main focus was on extending the capabilities of our system-level simulator for 5G networks, building the basis for the research work conducted in our industrial cooperation. New releases of our simulators are continuously made available to our partners, following the newest developments within mobile network standardizations. In 2021 the VCCS-5G system level simulator version 1.2 was published, providing features such as non- orthogonal multiple access, massive MIMO, traffic models and interfaces to related software tools.
In an FFG funded research cooperation with our industry partner A1 Telekom Austria AG, we are developing and refining analytical methods and models for traffic flows in 5G networks. In this BRIDGE project, SEMONE performance benchmarks transform from centrally coordinated measurements to crowdsourced distributed events at the end terminal of the users. The current research challenge is the integration of non-intrusive benchmark measurements for reactive networks. The goal is a distributed setup to analyze, measure and simulate operational mobile networks. In the past year crowdsourcing was finally used to replace parts of common drive-testing.
Internet usage for nomadic customers is becoming a central element for planning in mobile networks. In this context, we continued the cooperation with the Austrian Federal Railways (OEBB-TS). We currently work towards identifying room for improvements for mobile coverage in high-speed trains. In this context, we are also further developing our performance measurement algorithms towards ultra-fast probing to allow tests in motion. Since 2020 we optimize the mobile coverage provided by infrastructure along the rails for service on trains together with the ÖBB-PV. Following these activities, we started cooperation with other international companies in the rail sector. With the Deutsche Bahn AG, and MM-1 we did carry out the development of a measurement methodology for service quality onboard high speed trains.
The demand for new mobile communication services has changed the requirements for the quality monitoring of 5G based networks. In this year, we continued our cooperation action with A1 in this area. The focus is on mobile access technologies, LTE and 5G, and the hybrid combination. The challenge is the current social development towards nomadic home-office usage, which leads to increased use of mobile networks as the last mile. This strong increase in volume generated at the customer side is a challenge for the quality-of-service system of existing solutions. With the help of this research, we develop a method to measure and characterize the traffic flows and optimize their resource consumptions.
Measuring the performance of mobile communications in 3D is a new research challenge we picked up in recent years. We focus on the development of fully autonomous test vehicles collecting measurement data along the optimized path. In 2021, we extended the modified aerial drones with a software module for optimized mission planning. The drone is currently largely autonomous, measuring using artificial intelligence.
The dedicated course plan in mobile communications attracts students from all over the world. International socializing is an activity already in the master program: together with the technical universities in Bratislava and Brno, we offered an International Seminar on Mobile Communications this year due to Covid-19 online and in reduced form. The cooperation with the Technical Universities of Munich and ETH Zurich we conduct as part of the Mobile Communications Seminar lecture will hopefully restart in 2022.
Christian Doppler Laboratory for „Dependable Wireless Connectivity for the Society in Motion“
The Christian Doppler Laboratory for Dependable Wireless Connectivity for the Society in Motion addresses fundamental research questions arising from large numbers of static and mobile wireless users especially within urban agglomerations. The research focus is not only on enhancing mobile network capacity and best-effort high data rate services, but equally on dependable (reliability- and delay-critical) data transmissions. Under these circumstances we focus on questions relating to efficiency, reliability, latency and availability of wireless communications.
The CD-lab started its work in January 2016 with three work modules. Each of the modules is associated to one of our three industrial partners Nokia Solutions and Networks (Module 1), A1 Telekom Austria AG (Module 2) and Kathrein-Werke KG (Module 3). In January 2019 the Lab was extended by a fourth research module with the industrial partner ÖBB Infrastruktur AG. The main scope of the laboratory is on 5G mobile communication technologies. Since 2020, our research additionally focuses on the most promising 6G candidate technologies. Our research work within the CD-lab encompasses measurement-based wireless channel characterizations, especially at higher carrier frequencies, optimization of transmitter and receiver signal processing on link level, as well as, large-scale network analyses on a system level. The CD-lab currently finances six doctoral students and eight Master-level students. In addition, we cooperate with many Universities and research institutions within and outside of Europe. We also regularly organize scientific events to share our results with other researchers and to promote our work. After a successful scientific 5-years evaluation in October of 2020, the CD-lab is now in its final extension phase until the end of 2022.
Flexible Wireless Systems
In the meanwhile, 5G is generally available. The Internet has become mobile and allows the transmission, distribution, storage, and manipulation of information. The next challenges for “digitalization” concern 5G applications for production, transportation, distribution, storage, and manipulation of objects (“internet of things”). Wireless technologies need to become dependable. This requires major improvements in availability (coverage) and transmission latency, packet delivery guarantees, guaranteed data rates, as well as energy efficiency and cost structure. Therefore, we investigate 5G/6G transmission techniques, notably in the centimeter and millimeter wave bands, dependable connectivity for highly mobile users, their behavior at high network load, as well as energy efficient data transmission.
The use of MIMO transmission using antenna array technology has become the commercial state of the art in mobile communications. Major improvements compared to 3G have been achieved in 4G networks in terms of spectral efficiency by dynamic resource allocation which takes into account the current system load, advanced precoding techniques, and spatial multiplexing. Massive MIMO transmission and reconfigurable meta-surfaces will be core 5G/6G technologies.
Direct radio communication between mobile entities enjoys a renaissance in connection with the recent interest in peer-to-peer and ad-hoc networks. This is especially true for cooperative vehicle- to-anything (C-V2X) communication to enable advanced active safety. The institute leads the project consortium “Intelligent InterSection”. This project establishes an intersection traffic system to improve road safety and traffic efficiency for all road users. Through a broad, inclusive, inter- disciplinary human-centered design approach, all stakeholders’ needs, goals, and limitations are captured and cast into quantitative key performance indicators and a technical problem description. Novel methods and tools to model, calibrate, simulate, estimate, predict and control heterogenous intersection traffic, as well as novel means and use cases of 5G communication will be combined to optimize the traffic situations in real time. The resulting real-world benefits of the intelligent intersection will be studied via detailed co-simulations, real-world validation and demonstration tests, and re-assessed with all stakeholders. Hence, the project provides a sound basis for later realization in urban traffic systems that improves road safety and efficiency alike, for all users. Co-operative systems have become an important field of research in the area of telematics. Wireless networking of sensors and instrumentation enables new application fields: Intelligent Transport, Smart Metering, Intelligent Production, etc.
Nonlinear detection techniques offer resource efficient solutions in communication systems. The nonlinearity is adapted to the interference scenario, such that the interference is discriminated whereas the information of interest is detected largely unperturbed. Such communication systems are interference resilient.
One family of wireless systems features extreme bandwidths and low power spectral densities. These ultra-wideband (UWB) transmission techniques enable energy efficient communication among electronic sensors and actuators over short ranges in buildings. They cause little interference to existing small bandwidth systems. Here, the spectral efficiency is of less importance than the power efficiency of the transmission scheme in short-range links. Key applications are low-power sensor networks and robust embedded systems which require neither batteries, nor external antennas. We explore UWB impulse-radio techniques experimentally with integrated on-chip antennas for power- efficient short-range wireless communication, sensing, and localization. Thus, UWB technology provides a dependable association of data with objects: A key to the Internet of Things.
