In this paper, we present a detailed description of a propagation channel measurement campaign performed in an office workstation environment and provide a comprehensive channel model for this environment. To facilitate the measurement campaign, we developed a dual-band frequency-domain channel sounder system, which utilizes 4×4 virtual Multiple-Input-Multiple-Output (MIMO) and Single-Input-Single-Output (SISO) antenna configurations. The measurements were conducted at millimeter-wave (mm-wave) frequencies of 28-36 GHz and 58-66 GHz, and Terahertz (THz) frequencies of 140-160 GHz and 200-220 GHz for both Line-of-sight (LOS) and Obstructed-Line-of-Sight (OLOS) scenarios. Propagation channel parameters such as distance-dependent pathloss exponent, frequency-dependent pathloss component, shadowing gain and root-mean-squared (rms) delay spread statistics along with the small-scale fading statistics were extracted and presented in the paper. Furthermore, the channel model presented in this work was validated using delay spread statistics. The information provided in this work will be relevant to the development of Device-to-Device (D2D) wireless communication systems operating at THz and mm-wave frequencies in an office workstation environment.

The THz band (0.1-10 THz) has attracted considerable attention for next-generation wireless communications due to the large amount of available bandwidth that may be key to meet the rapidly increasing data rate requirements. Before deploying a system in this band, a detailed wireless channel analysis is required as the basis for proper design and testing of system implementations. One of the most important deployment scenarios of this band is the outdoor microcellular environment, where the Transmitter (Tx) and the Receiver (Rx) have a significant height difference (typically ≥ 10 m). In this paper, we present double-directional (i.e., directionally resolved at both link ends) channel measurements in such a microcellular scenario encompassing street canyons and an open square. Measurements are done for a 1 GHz bandwidth between 145-146 GHz and an antenna beamwidth of 13 degree; distances between Tx and Rx are up to 85 m and the Tx is at a height of 11.5 m from the ground. The measurements are analyzed to estimate path loss, shadowing, delay spread, angular spread, and multipath component (MPC) power distribution. These results allow the development of more realistic and detailed THz system performance assessment.

Condensed channel parameters, such as Root Mean Square (RMS) delay spread and angular spread, are essential ways of representing results from the measurement of wireless propagation channels. However, real-world measurements are invariably affected by noise, which is not inherently reduced by the Fourier processing - in contrast to high-resolution parameter estimation. Even when the signal-to-noise ratio is relatively high, e.g., 20 dB, the impact of the noise on the condensed parameters can be significant and lead to erroneous estimates. This can be explained, e.g., for the computation of the RMS delay spread, where long delays (which often carry noise only) are "up-weighted" by the square of the delay. While techniques like noise thresholding are often applied, the reasons for choosing thresholds are usually not described in detail. This paper systematically analyzes noise thresholding for joint delay-angle measurements and derives equations for the impact of thresholds on the computation of delay and angle RMS spreads and window parameters under various measurement circumstances. The paper provides results based on closed-form equations, as well as MonteCarlo (MC) simulations, and application to real-world measurements in the sub-THz band.

The availability of large bandwidths in the terahertz (THz) band will be a crucial enabler of high data rate applications in next-generation wireless communication systems. The urban microcellular scenario is an essential deployment scenario where the base station (BS) is significantly higher than the user equipment (UE). Under practical operating conditions, moving objects (i.e., blockers) can intermittently obstruct various parts of the BS- UE link. Therefore, in the current paper, we analyze the effect of such blockers. We assume a blockage of the strongest beam pair and investigate the availability and extent of angular diversity, i.e., alternative beampairs that can sustain communication when the strongest is blocked. The analysis uses double-directional channel measurements in urban microcellular scenarios for 145– 146 GHz with BS-UE distances between 18 to 83 m. We relate the communication-system quantities of beam diversity and capacity to the wireless propagation conditions. We show that the SNR loss due to blockage depends on the blocked angular range and the specific location, and we find mean blockage loss to be on the order of 10–20 dB in line-of-sight (LOS) and 5–12 dB in NLOS (non-LOS). This analysis can contribute to the design of intelligent algorithms or devices (e.g., beamforming, intelligent reflective surfaces) to overcome the impact of the blockage.

THz band is envisioned to be used in 6G systems to meet the ever-increasing demand for data rate. However, before an eventual system design and deployment can proceed, detailed channel sounding measurements are required to understand key channel characteristics. In this paper, we present a first extensive set of channel measurements for urban outdoor environments that are ultra-wideband, and double-directional where both transmitter and receiver are at the same height. In all, we present measurements at 38 locations, consisting of nearly 50,000 impulse responses, representing both line-of-sight (LoS) and non-line-of-sight (NLoS) cases in the 1-100 m range between 145-146 GHz. We provide modeling for path loss, shadowing, delay spread, angular spread, multipath component (MPC) power distribution and Qtapnumber. We find, among other things, that outdoor communication over tens of meters is feasible in this frequency range even in NLoS scenarios, that omni-directional delay spreads of up to 100 ns, and directional delay spreads of up to 10 ns are observed, while angular spreads are also quite significant, and a surprisingly large number of MPCs are observed for 1 GHz bandwidth and 13° beamwidth. These results constitute an important first step towards better understanding the wireless channel in the THz band.

THz communication has attracted a great deal of attention due to the large bandwidth available in this band. However, system development and deployment requires detailed knowledge of the wireless channel, which must be provided by measurements (channel sounding) and subsequent modeling in key scenarios of interest. One important scenario in this regard is the urban outdoor microcellular scenario where the Transmitter (Tx) and the Receiver (Rx) have a significant height difference. In this paper, we present ultra-wideband double-directional channel measurements in a microcellular scenario for the band between 145-146 GHz in a street canyon with Tx-Rx of distances up to 67 m. The results are analyzed in the delay and angular domain, and the impact of the street canyon on the power delay profiles and angular power spectra is detailed. These measurements thus contribute towards the creation of a more realistic and detailed THz channel model in these scenarios.

Wireless communications in the THz frequency range can allow data rates of hundreds of Gbit/s, and will thus be an important part of 6G. A first important step for system design is an understanding of the underlying propagation channel. In this paper, we present results from one of the first measurement campaigns for medium-distance (up to 35 m) outdoor channels in urban environments where both the directions and delays of multipath are measured with good resolution. The results show a surprisingly rich multipath environment, leading to significant dispersion in both delay and angular domains. We also find that metallic-covered surfaces lead to a considerable enhancement of multipath, which indicates an important impact of building materials. Overall, the results indicate that relying on pronounced sparsity for THz system design might not always be valid in this type of environment.

Delay dispersion is one of the key propagation channel characteristics that impact system design and performance. In particular, for OFDM-based systems such as Wi-Fi, it determines both the amount of available frequency diversity and the minimum required cyclic prefix, which in turn impacts the spectral efficiency. For this reason, delay spread and power delay profiles have been analyzed for a long time. However, recent upgrades in Wi-Fi, in particular the addition of a new frequency range (6-7.1 GHz), and the introduction of adaptive beamforming, require a re-assessment based on new measurements. This paper presents extensive measurement results of RMS delay spread and interference quotient that take these developments into account. Results were measured in the 2.4-2.5, 5-6, and 6-7 GHz bands. Furthermore, we compare the “omni-directional” delay spread and interference quotient (i.e., when measured with omni-antennas at transmitter and receiver), to those that occur when beamformed antennas are used. We found that for both outdoor and indoor environments, beamforming typically improves the interference quotient (for a given window size) by about 3-5 dB. The 2.4 and 5-7 GHz bands show a significant difference, while we could not observe statistically significant differences between the 5-6 and 6-7 GHz bands.

While mm-wave systems are a mainstay for 5G communications, the inexorable increase of data rate requirements and user densities will soon require the exploration of next-generation technologies. Among these, Terahertz (THz) band communication seems to be a promising direction due to availability of large bandwidth in the electromagnetic spectrum in this frequency range, and the ability to exploit its directional nature by directive antennas with small form factors. The first step in the analysis of any communication system is the analysis of the propagation channel, since it determines the fundamental limitations it faces. While THz channels have been explored for indoor, short-distance communications, the channels for wireless access links in outdoor environments are largely unexplored. In this paper, we present the - to our knowledge - first set of double-directional outdoor propagation channel measurements for the THz band. Specifically, the measurements are done in the 141 - 148.5 GHz range, which is one of the frequency bands recently allocated for THz research by the Federal Communication Commission (FCC). We employ double directional channel sounding using a frequency domain sounding setup based on RF-over-Fiber (RFoF) extensions for measurements over 100 m distance in urban scenarios. An important result is the surprisingly large number of directions (i.e., direction-of-arrival and direction-of-departure pairs) that carry significant energy. More generally, our results suggest fundamental parameters that can be used in future THz Band analysis and implementations.

Current and proposed Internet of things (IoT) applications are expected to bring about a major technological revolutions. Next-generation wireless communications in such devices are expected to support high speed data transfers. Among different candidate technologies, terahertz (THz) band communication seems to be a promising direction due to availability of high bandwidth in the electromagnetic spectrum around this frequency range and its directional nature governed by the directive antennas. In this paper, we look into some networking scenarios of full-dimension multiple-input multiple-output (FD-MIMO) based THz Band indoor wireless networks to determine the number of nodes that can be connected to a base station as a function of the antenna characteristics. Furthermore, we analyze the performance of the users and network based on their ergodic capacity. Our results suggest fundamental parameters that can be used in future THz Band analysis and implementations.

Molecular communication (MC) is the most promising communication paradigm for nanonetwork realization since it is a natural phenomenon observed among living entities with nanoscale components. Since MC significantly differs from classical communication systems, it mandates reinvestigation of information and communication theoretical fundamentals. The closest examples of MC architectures are present inside our own body. Therefore, in this paper, we investigate the existing literature on intrabody nanonetworks and different MC paradigms to establish and introduce the fundamentals of molecular information and communication science. We highlight future research directions and open issues that need to be addressed for revealing the fundamental limits of this science. Although the scope of this development encompasses wide range of applications, we particularly emphasize its significance for life sciences by introducing potential diagnosis and treatment techniques for diseases caused by dysfunction of intrabody nanonetworks.