Dynamic Blockage in Indoor Reflection-Aided Sub-Terahertz Wireless Communications

The sixth-generation cellular systems are expected to utilize the sub-terahertz frequency band covering 100 − 300-GHz. Due to high path losses, the coverage of such systems will be limited to a few tens of meters making them suitable for indoor environments. As compared to outdoor deployments, indoor usage of sub-terahertz systems is characterized by the need to operate over shorter distances using both line-of-sight (LoS) and in-reflection propagation paths. This potentially results not only in the attenuation of radio signal, but in the appearance of diffraction signatures in its time-related metrics too. We conduct a detailed measurement campaign at the carrier frequency of 156 GHz and report on the dynamics of the reflection and blockage losses as well as signal fall, blockage, and recovery times over various in-reflection paths. We also develop reflection model and use it to extract the complex permittivities of glass, drywall and aerated concrete from their measured reflection spectra. The extracted permittivities of 7.23 + 0.22i, 2.63 + 0.026i, 1.9 + 0.017i are consistent with the material-dependent reflection losses, which are as high as 16 dB for transverse electric (TE)-polarized and 39 dB for transverse magnetic (TM)-polarized signals. Moreover, the asymmetry in the side lobe levels of the transmitting and receiving antenna beams results in the additional losses ranging from 16 to 49 dB as measured for 3.55–4.3-m long non-specular paths with the angles of departure and reception within 30 − 70◦. The blockage losses, in turn, are in the range of 6 − 17 dB. We observe that the presence of a re-directing material does not affect their mean value. However, the acquired blockage duration, signal fall and recovery times are noticeably smaller than in the LoS channels with the same directivity. This implies that the time-budget for blockage detection is much smaller: it reduces to just 20–40 ms as compared to 80–100 ms intrinsic to the LoS propagation paths. © 2023 The Authors. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.