Path Loss Model at 300 GHz for Indoor Mobile Service Applications

Transcription

1 This article has been accepted and published on J-STAGE in advance of copyediting. Content is final as presented. IEICE Communications Express, Vol.1, 1 6 Path Loss Model at 300 GHz for Indoor Mobile Service Applications Hirokazu Sawada, Katsumi Fujii, Akifumi Kasamatsu, Hiroyo Ogawa, Kentaro Ishizu and Fumihide Kojima National Institute of Information and Communications Technology 3-4, Hikarino-oka, Yokosuka, Kanagawa , Japan sawahiro@m.ieice.org Abstract: Frequency identification for the mobile communication system in GHz was started in the World Radiocommunication Conference Therefore, propagation model is required to enable sharing and compatibility studies between the land-mobile, fixed and passive services. In this study, indoor propagation characteristics at 300 GHz is measured and analyzed to develop path loss models. Measurements have been carried out in office and corridor environments in line-of-sight situation, and the path loss coefficients are extracted. The coefficient of office environment is roughly identical with the free space loss of N=20, and the coefficient of corridor environment was slightly decreased to N=19.5. Keywords: Terahertz wave, Millimeter wave, Indoor radio propagation, Path loss model Classification: Antennas and propagation References IEICE 2016 DOI: /comex.2016XBL0136 Received July 29, 2016 Accepted August 23, 2016 Publicized September 9, 2016 [1] World Radiocommunication Conference 2019 (WRC-19) addenda item 1.15, ITU-R Resolution 767 (WRC-15). [2] ITU-R Study Group 3 (SG3), [3] Recommendation ITU-R P (9/2013). [4] Recommendation ITU-R P (2005). [5] Recommendation ITU-R P (7/2015). [6] Recommendation ITU-R P (7/2015). [7] Recommendation ITU-R P (7/2015). [8] Toshihide Tosaka, Katsumi Fujii, Kaori Fukunaga, and Akifumi Kasamatsu, Evaluation of effect of wall on wave propagation at 300 GHz, 38th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), We P2-06, Sep

2 1 Introduction Frequency identification for the mobile communication system in GHz was started in the World Radiocommunication Conference 2015 [1]. ITU-R Study Group 3 (SG3) [2] is studying to develop propagation models within the frequency range so as to enable sharing and compatibility studies between the land-mobile, fixed and passive services. Furthermore, SG3 established corresponding group 3K-7 in June 2016 to promote this activity. Some useful information exists in ITU-R recommendations to identify the suitable frequency range, ITU-R P [3] and ITU-R P [4] provide methods to estimate the attenuation by atmospheric gases and prediction methods of rain attenuation up to 1 THz, respectively. Also ITU-R P shows that the frequency spectrum around 300 GHz which has no absorption lines is a suitable frequency band for mobile service applications. For the land-mobile and fixed services applications, the path loss model is required in the frequency range GHz, however, the upper frequency ranges in the current ITU-R Recommendations dealing are below 100 GHz [5-7]. Therefore, path loss models above 100 GHz will be required in order to design 300 GHz band telecommunication systems. As a first step, this paper studies pass loss coefficients of office and corridor environments as shown in the Recommendation ITU-R P based on indoor propagation measurement results at 300 GHz. In this letter, we describe the measurement parameters and preliminary results. 2 Measurement instrument and parameters In the first place, propagation loss was measured by using 300 GHz continuous wave in an anechoic chamber [8] as shown in Fig.1 (a) to confirm the transmitter (TX) and receiver (RX). Subsequently propagation loss in office and corridor environments was measured. The maximum transmission distance was a few tens of meters in the line-of-sight situation because the output power was limited to -15 dbm by a used RF device performance. In the measurement, directional antennas as shown in Fig.1(b) were used by considering actual 300 GHz wireless applications. The aperture size of antenna is 6 mm x 8.36 mm and the antenna gain is 25 dbi as shown in Fig.1(c). The antenna polarization was set to the same direction. For path loss measurement, the TX was fixed and RX was moved by using a platform truck. The measuring equipment is validated in the anechoic chamber by comparison with a moment method simulation including an antenna structure because the calibration method of a measuring instrument in 300 GHz band isn't established yet. The relationship between the received power and the transmission distance in the anechoic chamber is shown in Fig.1(d). In this figure, the simulation and theoretical free space loss results are plotted. It was confirmed that the pass loss coefficient is N=20 identical with the free space loss in the far field and also the performance of measurement instrument was validated by simulation and free space loss results.

3 Signal generator External mixer Signal generator Spectrum analyzer Source module (a) Measurement set up (b) Standard gain horn (c) Simulated antenna directivity (d) Received power of measurement and simulation results. Fig. 1. Measurement system evaluation in anechoic chamber. 3 Measurement results in office and corridor environments Fig.2 (a) show the measurement system for indoor environments. The TX and RX were put on the trucks and the RX position was changed in the measurement. The antenna heights of TX and RX were 1.1 m above the floor. The measured polarization was set to vertical. There was no human in the environments during the measurement to keep the static condition. The measured distance was up to 12 m for office and 35 m for corridor environments in the line-of-sight situation.

4 (a) Measurement setup for indoor environments. (b) Office environment (c) Corridor environment Fig. 2. Path loss measurement system for indoor environments The indoor measurement was carried out in the office and corridor environments as shown in Fig.2 (b) and (c), also the snapshots of receiver and transmitter can be seen in the Fig.2 (b) and (c), respectively. TX and RX antenna were aligned by using laser pointing devices. In the office environment, metallic desk and shelf, and partitions were furnished in the room. In the corridor environment, the propagation path was surrounded by metallic walls, plaster board ceiling, and concrete floor. Measured path loss results in the office and corridor environments are shown in Figs.3 (a) and (b), respectively. By simplifying the path loss model of ITU-R P , the following equation is used to develop a path loss model. PL L(d o) N log 10 d d o db (1) where: N : d : do : path loss coefficient separation distance (m) between the base station and portable terminal (where d 1 m) reference distance (m) L(do) : path loss at do (db), for a reference distance do at 1 m, By linear approximations, path loss coefficients were extracted as N=20 and 19.5

5 (a) Office environment (b) Corridor environment Fig. 3. Measurement result and path loss model. for each environment. The coefficient of office environment was roughly identical with the free space loss, because antenna half power beam width was narrow as 10 degrees. The coefficient of corridor environment was slightly decreased from N=20, and it was influence by reflection waves. 4 Conclusion The path loss coefficients of office and corridor environments at 300 GHz have been extracted when directional antennas were used. The coefficient of office environment was roughly identical with the free space loss of N=20, and the coefficient of corridor environment was slightly decreased to N=19.5. These parameters also close in value to the coefficient at 60 and 70 GHz of Recommendation ITU R P These preliminary results is useful for link budget and interference calculations in the design of 300 GHz indoor mobile service applications, and also will be a starting point to discuss the frequency extension of current path loss models [6, 7]. Acknowledgments A part of this study was supported by a project Multi-tens gigabit wireless communication technology at sub-terahertz frequencies under The research and development project for the expansion of radio spectrum resources of the Ministry of Internal Affairs and Communications, Japan.