Frank Wollenschläger

60 GHz Ultrawideband Polarimetric MIMO Sensing for Wireless Multi-Gigabit and Radar

Polarimetric radio wave processing becomes of increasing interest for very high-data rate wireless transmission and for short-range radar at millimeter-waves (mm-W). This goes along with the huge bandwidth of 7 to 9 GHz, which is available worldwide in the 60 GHz unlicensed band. In this paper, we propose a 60 GHz ultra-wideband (UWB) polarimetric multiple-input-multiple-output (MIMO) sensing system architecture and polarimetric signal processing for short-range communications and radar. Demonstration measurements were made by using an UWB radar interface. By measurements in multipath rich environments it is demonstrated that tap-wise polarimetric filtering in delay domain can enhance the 60 GHz link budget by filtering some paths and then reducing shadowing due to human activity. Additionally, optimum MIMO polarimetric filtering is proposed to reduce heavy clutter for mm-W radar, increasing by about 30 dB the signal-to-clutter-plus-noise-ratio.

Over-the-Air Testing of Cognitive Radio Nodes in a Virtual Electromagnetic Environment

This paper provides an overview of ongoing research in over-the-air (OTA) testing for next-generation communication and data transmission devices with special consideration of cognitive radio (CR). Existing state-of-the-art techniques and their merits and limitations are discussed. We identify the requirements and issues for the OTA test in a virtual electromagnetic environment (OTAinVEE) which needs to address the more complex scenario of future networks, where interference emulation becomes a highly challenging task. A complex interference scenario arises due to the attempt to simultaneously utilize several opportunity dimensions such as frequency, time, direction (space), and polarization, in a dynamic manner in a multiuser scenario. Although MIMO-OTA testing addresses many limitations of single antenna-conducted test systems, more dimensions and parameters to be addressed in the new scenarios imply further increase in cost and complexity. Closed-loop OTA test setups for CR evaluation are discussed along with an overview of other test scenarios.

60 GHz-Ultrawideband Real-Time Multi-Antenna Channel Sounding for Multi Giga-Bit/s Access

60 GHz technology has been proposed recently for multi-Giga-bit/s access within different application scenarios, e.g. in crowded multi-user public transportation (PT) environments. Hence, channel sounders that are used to investigate multipath propagation and multi-user access techniques including spatial diversity and beam-forming in time-variant shadowing environments require ultra-wideband (UWB) operation, multiple antennas, and real-time. This paper presents probably the first channel sounder architecture fulfilling these requirements. Moreover, an experimental study is described which is performed for planning purposes and deployment of 60 GHz WLAN/WPAN networks in PT scenarios. Coverage analysis based on different PHY channelization schemes, including multiple access point configurations and antennas is addressed for the Airbus 340 cabin. Additionally, distributions of time dispersion, coherent bandwidth, and Rice K-factor in the in-cabin coverage area are presented. Specifically, a brief analysis under dynamic channel conditions due to human activities is introduced. The suitability of the 60 GHz-UWB channels sounder for PT scenarios is demonstrated. Besides, some channel results for finding the most suitable system parameters for 60 GHz access deployment of in-flight-entertainment (IFE) systems are given.

60 GHz short-range communications: channel measurements, analysis, and modeling

This article presents measurement and analysis results for 60 GHz short-range wideband radio channels. We consider two scenarios, referred to as “very-high-rate extended-range” (VHR-E) and “ultra-high-rate cordless” (UHR-C). The VHR-E measurements aimed at 60 GHz fixed networks for an Airbus A340 cabin both under static and dynamic (shadowing due to passenger movement) channel conditions. We describe the channel sounder used for the VHR-E measurements and present a simple multipath model derived from the measurements. Furthermore, simulations show the feasibility of the raytracing approach for this kind of channel. As a typical UHR-C use case, a data kiosk scenario was investigated. Various propagation conditions are analyzed with respect to channel gain, time dispersion, and frequency selectivity.

Emulation of virtual radio environments for realistic end-to-end testing for intelligent traffic systems

We consider two approaches for real-time end-to-end over-the-air testing for intelligent traffic systems using virtual radio environments. One approach is based on coherent wavefield synthesis, while the other aims at emulating the essential features of a realistic radio channel in vehicular ad-hoc networks. Due to finite hardware resources, the former is limited to electrically small systems-under-test, while the latter is suited for typical vehicle-to-vehicle scenarios. Three major aspects of the emulation of radio environments in our facilities in Ilmenau, Germany, are described: 1. Emulation hardware, 2. Channel sounding, modeling, and feature extraction, 3. Emulation methods.

Over-the-air testing of Car-to-Car and car-to-infrastructure communication in a virtual electromagnetic environment

This paper provides an overview of over-the-air (OTA) testing for next generation communication devices with special consideration of Car-to-Car (C2C) and Car-to-Infrastructure (C2I) communication. Existing state-of-the-art techniques, their merits, and limitations are discussed. We identify the requirements for the OTA test in virtual electromagnetic environment (OTAinVEE) for the C2C/C2I communication scenario, where interference emulation becomes a highly challenging task. We propose systematic test procedure and closed-loop OTA set-up applicable for such scenario. Since the main test challenge in C2C/C2I communication is the modeling of highly time variant channel, we discuss channel modeling concepts and propose a framework appropriate for such communication. The ongoing activities in Ilmenau towards simulation and testing for C2C/C2I communication is also briefly discussed.

A broadband 60 GHz aperture-coupled patch array integrated in multilayer ceramics technology

The ISM band at 60 GHz provides sufficient bandwidth for wireless transmission of data rates in the Gbps range. To fully utilize this unlicensed frequency range, the design of suitable antennas has to account for application-specific demands in terms of frequency bandwidth and antenna gain. We present a successful implementation, based on a compact patch array approach, meeting realistic requirements. The measured S-parameters indicate an impedance bandwidth of 10.5% for the antenna array. The measured gain amounts to 11.8 dBi with a flatness of 2.1 dB over the impedance bandwidth.

Virtual electromagnetic environment for over-the-air testing of car-to-car and car-to-infrastructure communication

This paper provides an overview of over-the-air (OTA) testing for Car-to-Car (C2C) and Car-to-Infrastructure (C2I) communication. We identify the requirements for OTA tests in virtual electromagnetic environments (OTAinVEE) for C2C/C2I communication scenarios, where emulation of known and unknown interference in addition to multipath becomes a highly challenging task. We propose a systematic test procedure and closed-loop OTA set-up applicable for such scenario. We discuss channel modeling concepts applicable to C2C/C2I communication scenario and propose an appropriate framework. The ongoing activities in Ilmenau towards simulation and testing for C2C/C2I communication are also briefly discussed.