The Study of Stratospheric Communication 成層圏飛翔体通信に関する研究

1. The Study of Stratospheric Communication成層圏飛翔体通信に関する研究

2. 成層圏飛翔体 (Stratospheric Aircraft) ・Altitude 20km ・Movable Location ・Low Propagation Delay ・Wide Coverage Area ・Low Required Power ・High Elevation Angle ・No Affection by Earthquake

4. 多重波伝搬及びShadowing環境 (Multi-Path Propagation and Shadowing Environment) Direct wave Scattered wave Low Elevation Angle High Elevation Angle Shadowing

5. 合成 (Experiments of Shadowing Environment) 見通し・シャドウイング実験特性測定実験概要 魚眼レンズ 方向別のデータ取得 見通し率 見通し継続距離分布 シャドウイング継続距離分布

6. 相対角度θ r 仰角θ e Visibility Direction θr=0° θr=30° Elevation θr=60° θr=90°

7. 受信局：一定速度 ：仰角 10 °～ 80° 10°刻み 仰角別電波伝搬実験概要 Multi-Path Propagation Experiments Elevation Angle

8. 滑走路 幅　60m 距離　約1km 緑地帯 滑走路脇30m Multi-Path Propagation Experiments using a Balloon 飛翔体、テザー諸元

9. Balloon Station Balloon Control Mobile Station

10. Data Transmission Success Rate Asakusa Shinjyuku Kryuu Shibuya

12. Typical Ray Geometry • In stratospheric platform propagation, the typical ray geometry is depicted by the following figure. multipath ray direct ray single diffraction single building reflection double building to building reflection single street reflection double building to street reflection

13. HAP/Building/Street Model SP (q=600) wb h 1 2 MS 1 2 hb MS dm ws ws ws y z Side view Top view x x z y SP (q=900) SP • Above model representing an urban environment which is characterized by a block of 8 buildings. • We consider in the model that mobile station is situated on a middle between building 1 and 2 with ray from Platform comes from an arbitrary direction

14. Field Strength (1) Receiver Source s2 s1 q q Wall/street Image • Electric field of the ray arriving at the MS is calculated using the following formulas, E0 is the transmit electric field at the transmitter and k is wave number (2p/l). 1. Direct ray distance between transmitter and receiver 2. Reflected ray Reflection coefficient

15. Field Strength (2) Source s a q wall s3 Receiver 3. Diffracted ray Diffraction coefficient

16. Propagation Path Loss • Respective rays for each ray category were added at the MS and expressed as • The total electric field contribution consists of vector summation of 9 ray categories and can be expressed by • Finally, the total path loss formulation is : electric field for jth ray Total electric field for ith categories of ray

17. Result • Propagation path loss vs elevation angle. azimuth 900 azimuth 600

18. K factor • K factor is defined as specular (direct power) to random (multipath power) ratio. azimuth 900 azimuth 600

19. Link Budget Analysis • The required bit energy per noise power spectral density can be given by the simple following expression: L(a,q) : propagation path loss obtained by means of ray tracing. k : boltzmann’s constant (1.23 x 10-23 J/K) T0 : receiver temperature (290 0K) L0 : cable, connector, and combiner loss ML : link margin Rb : transmission rate PT : stratospheric platform power transmit Gt : stratospheric platform antenna gain Gr : mobile station antenna gain

20. Required Transmit Power (1) azimuth 900 azimuth 600 • The required transmitted power at SP for several information rates that applicable to IMT-2000 is as follow.

21. Required Transmit Power (2) Such high power may be impractical • Variation of required transmitted power from 8 kbps to 2 Mbps of information rates. • Azimuth 600 : • - elevation 100 : 0.12 W to 30.2 W • - elevation 200 : 0.013 W to 3.15 W • - elevation 300 : 6.7 mW to 1.68 W • - elevation 600 : 0.15 mW to 0.04 mW • Azimuth 900 : • - elevation 100 : 31.2 W to 7.8 kW • - elevation 200 : 0.05 W to 12.6 W • - elevation 300 : 5.9 mW to 1.48 W • - elevation 600 : 0.15 mW to 0.04 mW

22. Simple PDP Simulation (1) Suburban environment : d=50 km d=40 km d=30 km d=20 km It will be in hundreds of Microsecond 760