JOURNAL OF COMMUNICATION AND INFORMATION SYSTEMS, VOL. 38, NO.1, 2023. 115 Channel Analysis for 3.5 GHz Frequency in Airport A. S. Macedo, T. A. Costa, E. M. C. Matos, L. E. C. Eras, J. P. L. Araújo, P. V. G. Castellanos and F. J. B. Barros Abstract—This letter presents an analysis of the radio propaga- tion channel based on measurements at the 3.5 GHz frequency. The measurement campaigns were carried out inside the Val- de-Cans airport using line-of-sight (LOS) transmissions. First, the channel small-scale dispersion parameters were extracted through channel probing and the results are similar to those ob- tained by ITU-R P.1238 for the bands below 15 GHz considering commercial indoor environments as well as for those using the 3.5 GHz band in outdoor environments utilizing WiMax OFDM-256 signals. Then, the floating-intercept (FI) and close-in (CI) models are applied and analyzed to evaluate the received signal behavior for co-polarized and cross-polarized antennas. The results show that the CI path loss exponent values are close to the free space propagation loss model, while the FI model provides a lower root mean square error (RMSE) to the measured data. The results show that the FI and CI models are suitable for large-scale indoor propagation loss modeling for 5G networks with a frequency of 3.5 GHz. Index Terms—Frequency of 3.5 GHz, Airport, Channel Sound- ing, Small and Large Scale, Co and Cross Polarized. I. I NTRODUCTION T Here are several studies in the literature on different fre- quency bands as alternatives for the new fifth generation (5G) mobile network [1]–[3]. The 5G will cover the frequency spectrum from around 500 MHz to 100 GHz, with emphasis on frequency bands below 6 GHz or so-called Sub-6 GHz bands [3]. Thus, regulators are moving forward with the process of auctioning the spectrum to be used by 5G. In 2021, the Brazilian regulator, Agência Nacional de Telecomunicações (ANATEL), held the auction of the frequency bands that will be used for the implementation of 5G technology, including the 3.5 GHz band [4]. This increases the expectation that the new technologies will provide telephony services with greater coverage and signal quality, presenting a new scenario in telecommunications, new service experiences and economic impact [5]. The growth of multimedia data stream has created new challenges for the development of wireless access tech- nologies that meet the demands of indoor environments with high traffic, such as bus, rail, port and airport terminals [6]– [9]. In this context, experiments are conducted to characterize A. S. Macedo (orcid: 0009-0007-7856-8842), T. A. Costa (orcid: 0000- 0002-1679-5878), E. M. C. Matos (orcid: 0000-0003-1800-4619), J. P. L. Araújo (orcid: 0000-0003-3514-0401) and F. J. B. Barros (orcid: 0000-0003- 0487-0049) are with the Federal University of Pará, 66075-110 Belém, PA, Brazil. (e-mail: alex.macedo@itec.ufpa.br). L. E. C. Eras (orcid: 0000-0003- 2818-6145) is with the Federal University of the South and Southeast of Pará, PA, Brazil and P. V. G. Castellanos (orcid: 0000-0001-5783-301X) is with the Federal Fluminense University, Rio de Janeiro, RJ, Brazil. This work was supported in partly the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES)- Finance Code 001. Would like to thank the Computation and Telecommunications Laboratory (LCT) and the Electrical Engineering Post-Graduation Program at Federal University of Pará (UFPA-PPGEE) for its financial support. Digital Object Identifier 10.14209/jcis.2023.13. the mobile radio channel to evaluate the signal using predic- tive propagation loss models that support telecommunication systems projects. Research can be found in the literature on evaluating path loss as a function of distance indoors [10]–[12] and outdoors [13]. In this path loss evaluation, it is of interest to quantify the loss and analyze important parameters, such as the Path Loss Expoent (PLE). In [6], the authors performed a mea- surement campaign in a Seoul railroad station and an Incheon international airport at 28 GHz, it was estimated that the PLE was 2.15-2.17 and 2.68-3.03 for LOS and NLOS conditions, respectively. In [7], results of losses in two indoor airports environment in the bands 5 and 31 GHz were reported. The study showed that the PLE has similar characteristics to an internal office environment. Industrial scenarios are also of interest for path loss analysis. In [11] the main Sub-6 GHz bands (3.5, 4.9 and 5.8 GHz) were evaluated, and the obtained PLE was less than 2 (in the case of LOS). Moreover, the loss at 3.5 GHz was lower compared to the other frequencies, suggesting better coverage. In [10], the channel at 4.1 GHz is characterized and parameters such as CI model loss are evaluated (with PLE for LOS and NLOS, 1.96 and 2.72, respectively). Indoor antenna polarization characteristics are studied in various combinations to evaluate the propagation loss behavior through the radiocommunication channel [10], [12], [14]. Such as [10], measurements are reported using directional horn antennas in the same polarization (V-V and H-H) and in cross polarization (V-H) in LOS and NLOS situations for 8-11 GHz indoors environment. In [12], the "n" approach to evaluate path loss with same-polarization and cross-polarization antennas at 11 GHz is considered, where the PLE ranges from 2.0 to 3.0 for the NLOS case and from 0.36 to 1.5 for LOS. Another feature of signal propagation in a channel is the multipath between the transmitter (Tx) and receiver (Rx), which affects the channel and can be represented by dispersion parameters such as mean dispersion, mean delay, coherence bandwidth and others [12]. This paper studies the signal propagation at 3.5 GHz with a bandwidth of 60 MHz at Val de Cans International airport in Belém, Pará, Brazil. Small and large-scale parameters are extracted from the measurements. The main contributions are the more detailed analysis of the propagation losses at different antenna polarizations and the extraction of their dispersion parameters by channel sounding. In the next section, the setup and the measurement campaign are presented. Then, the methodology used to characterize the small and large scale channel and the obtained results are described. Finally, the conclusions are presented.