Signal Path Loss Measurement for Future Terahertz Wireless Propagation Links

Terahertz Band (100GHz-10THz) offers larger bandwidth and ultra-higher data rates and is visualized as a key technology to alleviate the capacity limitation and spectrum scarcity of the currents wireless networks. There are some competent development and design challenges in the realization of wireless terahertz network. Signal high path loss is one of the major constraints for enabling wireless communication networks in the terahertz band. Thus for the consummation of wireless propagation links in the THz band an equivalent signal path loss model is designed incorporating the major peculiarities of the wireless channel that accounts for terahertz wave propagation in LoS propagation. The equivalent path loss model for terahertz LoS propagation is developed and simulated in matlabR. The simulation results are compared with the lognormal path loss model results

Performance Analysis of Indoor THz Communications with One-Bit Precoding

In this paper, the performance of indoor Terahertz (THz) communication systems with one-bit digital-to- analog converters (DACs) is investigated. Array-of- subarrays architecture is assumed for the antennas at the access points, where each RF chain uniquely activates a disjoint subset of antennas, each of which is connected to an exclusive phase shifter. Hybrid precoding, including maximum ratio transmission (MRT) and zero-forcing (ZF) precoding, is considered. The best beamsteering direction for the phase shifter in the large subarray antenna regime is first proved to be the direction of the line-of-sight (LoS) path. Subsequently, the closed-form expression of the lower- bound of the achievable rate in the large subarray antenna regime is derived, which is the same for both MRT and ZF and is independent of the transmit power. Numerical results validating the analysis are provided as well

Modeling and Analysis of sub-Terahertz Communication Channel via Mixture of Gamma Distribution

With the recent developments on opening the terahertz (THz) spectrum for experimental purposes by the Federal Communications Commission, transceivers operating in the range of 0.1THz-10THz, which are known as THz bands, will enable ultra-high throughput wireless communications. However, actual implementation of the high-speed and high-reliability THz band communication systems should start with providing extensive knowledge in regards to the propagation channel characteristics. Considering the huge bandwidth and the rapid changes in the characteristics of THz wireless channels, ray tracing and one-shot statistical modeling are not adequate to define an accurate channel model. In this work, we propose Gamma mixture-based channel modeling for the THz band via the expectation-maximization (EM) algorithm. First, maximum likelihood estimation (MLE) is applied to characterize the Gamma mixture model parameters, and then EM algorithm is used to compute MLEs of the unknown parameters of the measurement data. The accuracy of the proposed model is investigated by using the Weighted relative mean difference (WMRD) error metrics, Kullback-Leibler (KL)-divergence, and Kolmogorov-Smirnov test to show the difference between the proposed model and the actual probability density functions (PDFs) that are obtained via the designed test environment. According to WMRD error metrics, KL-divergence, and KS test results, PDFs generated by the mixture of Gamma distributions fit the actual histogram of the measurement data. It is shown that instead of taking pseudo-average characteristics of sub-bands in the wideband, using the mixture models allows for determining channel parameters more precisely.Comment: This paper has been accepted for publication in IEEE Transactions on Vehicular Technolog

Artificial Potential Field Assisted Mirror Reflectors for Terahertz Communications

The expectation for higher capacity wireless communication links is ever increasing due to the demand for high-data intensive applications, such as multimedia streaming, as well as increased number of devices connecting to the Internet. Researchers have now recently explored regions of the spectrum that are under utilized for communications, and this is the Terahertz band (0.1 THz to 10 THz). Unlike wireless technologies today, THz frequencies come with a plethora of challenges, one of which is the requirement of constant LoS. A number of solutions have explored the use of reflectors, or even reflect-arrays, that can help assist in redirecting beams towards the mobile devices in order to avoid blockages. In this paper, we propose the use of the Artificial Potential Field concept to increase the LoS rays in a multi-ray link by controlling antenna strips selection of a base station. Our approach aims to ensure a clear THz signal path from the base station to the reflectors, and to the mobile. We also consider micro-movement events that may result in loss of connectivity, through a concept of Personal Zones that allows multiple THz rays to beam around a user. Simulation results have shown the efficiency of the Artificial Potential Field (APF) in assisting the mirrors to redirect their beams through smaller number of utilized antenna strips, which increases the signal-to-noise ratio of links