Sebastian Priebe

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.

Stochastic Modeling of THz Indoor Radio Channels

Providing the basis for fast system simulations and the adequate design of upcoming THz communication systems, a novel stochastic 300 GHz indoor channel model is introduced. It combines both the modeling in time as well as in frequency domain in order to account for the significant frequency dispersion of ultra broadband THz channels. Not only amplitude, phase and temporal, but also spatial channel information is considered. That way, MIMO systems as well as novel antenna concepts can be simulated. Verified and calibrated frequency domain ray tracing simulations in an office scenario provide the data basis for the derivation of model parameters. Model channel realizations are tested against ray tracing predictions and channel measurements. A complete scenario-specific parameter set is given for the considered environment, so that the model can be implemented for further use and future THz communication links can be designed under consideration of realistic propagation conditions.

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.

Performance evaluation of 60 GHz WLAN antennas under realistic propagation conditions with human shadowing

In this paper, the evaluation of different 60 GHz WLAN antenna designs is presented. Based on ray tracing and human blockage the radio propagation in a living room scenario is modeled. Then simulated 3D antenna patterns of conventional and smart antennas are linked to the radio channel data. The performance of the antennas is compared in terms of the coverage probability within the living room.

An Overview of Ongoing Activities in the Field of Channel Modeling, Spectrum Allocation and Standardization for mm-Wave and THz Indoor Communications

This paper gives an overview of current issues in the field of mm-wave and THz communications. A concept for radio channel modeling is presented together with the latest channel investigation results in this frequency range. In addition we discuss the status quo of standardization activities and the worldwide ongoing spectrum allocation plans.

From broadband ray tracing propagation modeling to physical layer simulations of THz indoor communication systems

Allowing for the conception of future THz indoor communication systems, a simulation environment combining an accurate ray tracing propagation model as well as a physical layer simulator is introduced. Frequency domain ray tracing is demonstrated for a wireless LAN setup in an indoor environment at frequencies from 300 to 350 GHz. On the basis of the results, arising challenges of such ultra broadband communication channels as well as specialties with respect to system simulations are illustrated. Exemplary system simulations employing the realistic ray tracing channel are performed to assess system aspects such as coding schemes, antenna types and phase noise requirements.

Measurement of channel and propagation properties at 300 GHz

The constantly growing need for unoccupied and unregulated bandwidth will lead to the extension of operation frequencies of ultrabroadband communication systems into the lower Terahertz frequency range. Here we present first channel measurements at 300 GHz for two simple indoor scenarios, a point-to-point link on a desktop and a connection from a desktop to an access point within an office room. For the first scenario measurements are taken depending on distance, antenna types and transmitter/receiver placement. For the second scenario, measurements are obtained to identify line-of-sight and non-line-of-sight paths with up to two reflections and obstruction due to objects in the transmission path. From the channel transfer function, temporal channel characteristics are derived to estimate maximum achievable symbol rates.