Martin Jacob

Performance Analysis of Future Multigigabit Wireless Communication Systems at THz Frequencies With Highly Directive Antennas in Realistic Indoor Environments

In this paper, a simulation environment encompassing realistic propagation conditions and system parameters is employed in order to analyze the performance of future multigigabit indoor communication systems at tetrahertz frequencies. The influence of high-gain antennas on transmission aspects is investigated. Transmitter position for optimal signal coverage is also analyzed. Furthermore, signal coverage maps and achievable data rates are calculated for generic indoor scenarios with and without furniture for a variety of possible propagation conditions.

Diffraction in mm and Sub-mm Wave Indoor Propagation Channels

Current indoor wireless communication systems are shifting from classical microwave bands towards mm wave frequencies, whereas here the 60 GHz band is of special interest. Future systems are expected to work at even higher carrier frequencies in the sub-mm band beyond 300 GHz. In indoor wave propagation channels of such systems, diffraction occurs at a multitude of objects and hence must be considered for propagation simulations. Although the relevance of diffraction has been thouroughly studied at lower frequencies, it has not yet been analyzed methodically in the mm and sub-mm wave frequency range. This paper presents an extensive measurement campaign of the diffraction at objects like edges, wedges and cylinders for frequencies of 60 and 300 GHz. Different materials, realistic antennas as well as transmission through the objects are taken into account. Theoretical approaches are validated against the measurement results. Furthermore, shadowing of rays by persons is investigated and modeled with the help of diffraction. Finally, ray tracing is applied in an office scenario in order to evaluate the impact of diffraction on mm and sub-mm wave indoor channel characteristics.

Diffuse Scattering From Rough Surfaces in THz Communication Channels

Recent years have seen a tremendous increase in the demand for wireless bandwidth. To support this demand by innovative and resourceful use of technology, future communication systems will have to shift towards higher carrier frequencies. Due to the tight regulatory situation, frequencies in the atmospheric attenuation window around 300 GHz appear very attractive to facilitate an indoor, short range, ultra high speed THz communication system. In this paper, we investigate the influence of diffuse scattering at such high frequencies on the characteristics of the communication channel and its implications on the non-line-of-sight propagation path. The Kirchhoff approach is verified by an experimental study of diffuse scattering from randomly rough surfaces commonly encountered in indoor environments using a fiber-coupled terahertz time-domain spectroscopy system to perform angle- and frequency-dependent measurements. Furthermore, we integrate the Kirchhoff approach into a self-developed ray tracing algorithm to model the signal coverage of a typical office scenario.

Channel and Propagation Measurements at 300 GHz

Ultrabroadband Terahertz communication systems are expected to help satisfy the ever-growing need for unoccupied bandwidth. Here, we present ultra broadband channel measurements at 300 GHz for two distinct indoor scenarios, a point-to-point link of devices on a desktop and the connection of a laptop to an access point in the middle of an office room. In the first setup, measurements are taken with regard to distance, different antenna types and device displacements. Additionally, an interference constellation according to the two-ray model is examined. In the second setup, the focus is on the detection and characterization of the LOS- and the NLOS-paths in an indoor environment, including a maximum of two reflections. Temporal channel characteristics are examined with regard to maximum achievable symbol rates. Furthermore, ray obstruction due to objects in the transmission path is investigated.

Reverberation and Absorption in an Aircraft Cabin With the Impact of Passengers

Using a similar approach to that applied in acoustics and in microwave reverberation chambers, a theory of wideband propagation in a closed environment is discussed. Here, a room environment is viewed as a lossy cavity, characterized by diffuse scattering from walls and internal obstacles. For experimental results, measurements from 3 to 8 GHz were performed in a 24 passenger section of an aircraft cabin. This UWB system has the transmitter at ceiling height and the receivers at armrest and headrest positions. The measurements were performed for the cabin being unoccupied and fully occupied. In the theoretical model, the closed room environment is characterized by the reverberation time and volume, and these parameters allow derivation of the the remaining parameters such as path loss and average passenger absorption. The RMS delay spread and mean excess delay are also studied. For the mean power the agreement between the theory and measurements is good to within 1-2 dB, indicating the excellent accuracy of the method, which extends to estimating body absorption in real world environments. The total absorption from the seated passengers is dominated by the few who are near the transmitter. In general, this absorbed power is relatively small, so the effect of passengers is marginal for this configuration of a cabin communication system.

A dynamic 60 GHz radio channel model for system level simulations with MAC protocols for IEEE 802.11ad

This paper presents a dynamic 60 GHz radio channel model for system level simulations with MAC Protocols. It is based on radio propagation measurements investigating the influence of moving humans on the 60 GHz channel, which has been performed in the framework of IEEE 802.11ad 60 GHz WLAN standardization.

Ultra broadband indoor channel measurements and calibrated ray tracing propagation modeling at THz frequencies

Ultra broadband communication systems operated at THz frequencies will require the thorough knowledge of the propagation channel. Therefore, an extensive measurement campaign of 50 GHz wide indoor radio channels is presented for the frequencies between 275 and 325 GHz. Individual ray paths are resolved spatially according to angle of arrival and departure. A MIMO channel is recorded in a 2×2 configuration. An advanced frequency domain ray tracing approach is used to deterministically simulate the THz indoor propagation channel. The ray tracing results are validated with the measurement data. Moreover, the measurements are utilized for the calibration of the ray tracing algorithm. Resulting ray tracing accuracies are discussed.

A comparison of indoor channel measurements and ray tracing simulations at 300 GHz

This paper presents ultra broadband channel measurements in a typical office room. The measured channel impulse response and transfer function is compared to a ray tracing simulation performed with a 3D model of the scenario. Additionally, we show reflection losses of the building materials in the room which are required as input data for the ray tracing algorithm.

Application of ray tracing to derive channel models for future multi-gigabit systems

Applications of future multi-gigabit systems using frequencies at 60 GHz and beyond will also cover operational environments with non-line-of-sight conditions. Due to the high diffraction losses at millimetre-wave frequencies and beyond, establishing radio links in shadowing situations will require beam forming in order to exploit scattering and reflection processes. For the development and standardisation of these systems, double directional spatial channel models for non-line-of-sight situations have to be derived. Double directional channel models contain information both about angle of arrival at the receiver and angle of departure at the transmitter. An attractive possibility currently pursued both in research projects and standardisation is to derive these channel models based on ray-tracing simulations. This paper presents results from indoor channel measurements and shows the potential of ray tracing for 60 GHz channel modelling.

An Integrated Simulation Environment for the Investigation of Future THz Communication Systems: Extended Version

The first stages of developing indoor communication systems operating at frequencies beyond 300 GHz are currently undeway. In this paper, an integrated simulation environment is introduced, where the system parameters of future THz communication systems can be estimated under realistic hardware and propagation conditions. It is shown how this simulation environment can be used to determine the most critical parameters in the whole system and may be used to derive requirements for the development of hardware components. Exemplary simulation results, taking into account various factors of influence (different modulation schemes, antenna gains and wall materials), are presented.