In this paper, comprehensive double-directional channel measurements at 300 GHz in various usage scenarios in corridor environments, such as Access, Device-to-device (D2D), and Backhaul over 40 different receiver (Rx) positions using an in-house developed channel sounder, are presented. The measurement results are analyzed and validated by ray tracing (RT) simulation. The quasi-optical propagation properties at 300 GHz make an accurate estimation of relatively simple propagation in a corridor environment possible by using ray optics theory. However, even though non-trivial quadruple-bounce specular reflection paths can be identified in both scenarios, propagation phenomena other than reflection exist irrespective of the Rx positions. Thus, to model the propagation mechanism appropriately, a quasi-deterministic (QD) channel model comprising deterministic and random components is also proposed. The results generated using the proposed model are found to agree well with our prior observations and measurement results. Finally, the paper concludes by characterizing and comparing the channel for all the investigated scenarios in terms of path loss (PL) and large-scale parameters (LSP). On analyzing the measurement results using synthesized power spectra, proposed QD model, and evaluated PL and LSP it is observed that the Access and D2D scenarios share almost similar propagation mechanisms. Furthermore, in the Access and Backhaul scenario the LoS is observed to be affected by the unresolvable ceiling-reflected components. This study, across three different scenarios, can aid the design of next-generation communication systems operating in the THz spectrum.

This paper presents a novel localization technique—Multipath-radio tomographic imaging (RTI)—based on millimeterwave (mm-wave) radio systems, such as 5G mobile and WiGig LAN systems. Because of their high delay and angle resolutions, mm-wave radio systems can realize highly accurate device-free localization (DFL) for smart home/smart building applications. They can thus easily separate the multipath components. The Multipath-RTI can drastically reduce the number of anchor nodes using virtual nodes created by multipaths. This paper established the signal processing procedure for RTI image generation and position estimation using Multipath-RTI. Then, a practical signal processing scheme, ray-tracing-assisted Multipath-RTI, is presented, and the DFL results obtained by multilink double-directional channel sounding measurements are shown. Here, the position estimation errors in the measurements were less than 0:5 m for all target positions. Furthermore, the empirical position estimation errors for a single target under various conditions obtained by simulations were less than 0:5 m in 96.2 % and 88.0 % of the areas in an L-shaped room and a room with an obstacle in the center, respectively. The position estimation accuracy for multiple targets was also evaluated, where, for example, the errors for three targets were less than 0.1 m at 50 % probability with failure rates of less than 20 %.

To design a reliable communication system utilizing millimeter-wave (mm-wave) technology, which is gaining popularity due to its ability to deliver multi-gigabit-per-second data rate, it's essential to consider the site-specific nature of the mmwave propagation. Conventional site-general stochastic channel models are often unsatisfactory for accurately reproducing the channel responses under specific usage scenarios or environments. For high-precision channel simulation that reflects sitespecific characteristics, this paper proposes a channel model framework leveraging a widely accepted 3GPP map-based hybrid channel modeling approach, and it provides a detailed recipe to apply it to an actual scenario using some examples. First, an extensive measurement campaign was conducted in typical urban macro and micro cellular environments using an inhouse dual-band (24/60 GHz) double-directional channel sounder. Subsequently, the mm-wave channel behavior was characterized, focusing on the difference between the two frequencies. Then, the site-specific large-scale and small-scale channel properties were parameterized. As an essential component for improving prediction accuracy, this paper proposes an exponential decay model for power delay characteristics of non-line-of-sight clusters, of which powers are significantly overestimated by deterministic prediction tools. Finally, using the in-house channel model simulator (CPSQDSIM) developed for grid-wise channel data (PathGridData) generation, a significant improvement in prediction accuracy compared with the existing 3GPP map-based channel model was demonstrated.

This letter tries to address the fundamental questions on the feasibility of multipath communication and achievable capacity for line-of-sight (LoS), obstructed-line-of-sight (OLoS), and non-line-of-sight (NLoS) scenarios in an outdoor setting for futuristic communication networks. In this context, a relevant measurement campaign at 300 GHz is conducted, and the results are presented in terms of the number of nontrivial propagation streams available for signal transmission. Encouraged by the obtained results, the average achievable channel capacity for such multi-stream channels is evaluated with and without passive reflecting surfaces (PRS). It is observed a multi-antenna system provides a significant improvement in average capacity compared to a single-antenna system with PRS providing additional enhancement.

In this paper, a newly developed 300 GHz channel sounder is presented followed by a detailed description of test measurements and the subsequent results obtained to validate its working. An elucidation of the high-resolution double-directional channel measurement in a typical conference room scenario precedes the comparison of the results obtained for the current campaign to that obtained from an earlier campaign at 60 GHz for a similar setup. It is observed that a similar number of clusters for both the bands under investigation for all the transmitter (Tx) and receiver (Rx) positions are obtained from the generated power spectra. Any deviation is theorized to be caused either due to the usage of lower measurement bandwidth in the 60 GHz campaign or due to limited elevation expanse in the 300 GHz measurement. To identify the interacting objects (IOs) causing the clusters, environment-embedded angular power spectra (APS) and ray tracing simulations are used. The large-scale parameters (LSPs) are also evaluated for both campaigns. It is observed that signal propagation in the terahertz (THz) band is dominated more by the line-of-sight (LoS) path compared to the millimeter wave (mm-wave) band (below 100 GHz). The results are also compared with other similar results from the literature.

Currently, millimeter-wave (mm-wave) based wireless communications in the 30 to 300 GHz frequency band are attracting new attention because the existing frequency band below 6~GHz is very congested. In order to use the mm-wave bands for designing and assessing next-generation mobile systems, it is essential to characterize its propagation channel considering the spatial consistency (SC) for non-stationary user equipment in an outdoor environment. Since the mm-wave band has different characteristics from the microwave band, 3GPP has proposed an SC procedure that provides spatial correlation to clusters for beam-tracking evaluation in dynamic scenarios. However, this letter reports on the evaluation of SC of clusters in terms of cluster visible region based on the obtained measured data in two different mm-wave frequencies, 24 GHz and 60 GHz, in urban environments. The visible region is estimated by tracking the available clusters using the fourth-dimensional spatiotemporal multipath parameters: the departure/arrival angles (azimuth), delay time, and cluster power. The obtained visible regions for two different frequencies and scenarios are compared and confirmed the dependencies of SC of the clusters on frequency and environment.