Browsing by Author "de Guzman, Mar Francis"

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An experimentally validated fading model for THz wireless systems
(2021-09-21) Papasotiriou, Evangelos N.; Boulogeorgos, Alexandros Apostolos A.; Haneda, Katsuyuki; de Guzman, Mar Francis; Alexiou, Angeliki
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
As the wireless world moves towards the sixth generation (6G) era, the demand of supporting bandwidth-hungry applications in ultra-dense deployments becomes more and more imperative. Driven by this requirement, both the research and development communities have turned their attention into the tera hertz (THz) band, where more than 20 GHz of contiguous bandwidth can be exploited. As a result, novel wireless system and network architectures have been reported promising excellence in terms of reliability, massive connectivity, and data-rates. To assess their feasibility and efficiency, it is necessary to develop stochastic channel models that account for the small-scale fading. However, to the best of our knowledge, only initial steps have been so far performed. Motivated by this, this contribution is devoted to take a new look to fading in THz wireless systems, based on three sets of experimental measurements. In more detail, measurements, which have been conducted in a shopping mall, an airport check-in area, and an entrance hall of a university towards different time periods, are used to accurately model the fading distribution. Interestingly, our analysis shows that conventional distributions, such as Rayleigh, Rice, and Nakagami-m, lack fitting accuracy, whereas, the more general, yet tractable, alpha-mu distribution has an almost-excellent fit. In order to quantify their fitting efficiency, we used two well-defined and widely-accepted tests, namely the Kolmogorov-Smirnov and the Kullback-Leibler tests. By accurately modeling the THz wireless channel, this work creates the fundamental tools of developing the theoretical and optimization frameworks for such systems and networks.
Uncertainty of millimeter-wave channel sounder due to integration of frequency converters
(2021-09-06) de Guzman, Mar Francis; Hassan, Muhammad; Haneda, Katsuyuki
A4 Artikkeli konferenssijulkaisussa
In this study, we investigate the possible sources of measurement uncertainties with the integration of radio over fiber solution and frequency converters in millimeter-wave sounders. We examined analytically the effect of phase variations due to the disturbance of the optical fiber cable, the limited sideband suppression of the frequency converters, and the influence of the dispersion in rectangular waveguides to the response of the channel sounder. Characterization of the optical fiber cable confirms that disturbance of the cable leads only to phase variation. Back-to-back measurements of Aalto’s sounder operating at V- and D-bands also verify that disturbance of the cable supplying the local (LO) continuous-wave signals are most influential to the stability of frequency- and delay-domain responses of the sounder because the LO signals undergo frequency multiplication. We found that the V-band and D-band channel sounders, with at least 17 dB and 20 dB Image Rejection Ratio, have the maximum gain variation of 0.5 dB and 1.0 dB in the peak of channel impulse responses when subject to different fiber cable positions.