1. MICRO AND MACRO SCALE SPATIAL RAIN VARIATION Part 1: Slant path attenuation for EHF systems and considerations for long and medium range diversity gain Part 2: Dynamic millimeter wave communications in the presence of rain Sarah Callaghan University of Portsmouth and Radio Communications Research Unit, RAL S.A.Callaghan@rl.ac.uk Cristina Enjamio University of Portsmouth and University of Vigo cristina@ee.port.ac.uk

2. Macro and Micro Scales

3. Slant path attenuation for EHF systems and considerations for long and medium range diversity gain Sarah Callaghan University of Portsmouth and Radio Communications Research Unit, RAL S.A.Callaghan@rl.ac.uk

4. Introduction Attenuation statistics measured in the South of England for Ku, Ka and V-band Satellite systems operating at EHF frequencies are very affected by the presence of rain, light rain and clouds along the slant path.

5. Attenuation is unlikely to be compensated for by available fade margin alone. Therefore need to design effective fade mitigation techniques Two major techniques are: Time diversity Site diversity To effectively design fade mitigation techniques, it is necessary to accurately model the spatial and temporal structure of rain.

6. STENTOR Experiment Artist's impression of STENTOR Due for launch end 2001. Beacon frequencies 20.7 and 41.4 GHz Schematic map of locations of beacon receivers

7. Chilbolton Advanced Meteorological Radar. 25 m steerable antenna 3 GHz Doppler-Polarization radar operational range of 100 km beam width of 0.25 degrees max angular velocity 1 degree / second CAMRa

8. recorded on the 1 st May 2001 124 near horizontal scans measured over an angle of 80 degrees interpolated onto a square Cartesian grid, with a grid spacing of 300m and a side length of 56.2km data points Storm event: Details

9. Contours of equal (log) rain rate used MATLAB’s predefined contour function at specific values of (log) rain rate to determine contour lines

10. Box counting method: Count number of boxes required to cover length of each contour line. Repeat, using boxes of different side lengths. Plot on graph as ln(1/box size) vs ln(number of boxes). Slope of best fit line is box counting dimension.

11. Box counting results for raster 25 (for each separate contour line having more than 100 vertices) Sample values for different contour values Contour values Box counting (log rain rate) dimension 1 1.12 0.75 1.23 0.5 1.21 0.25 1.15 -0.25 1.21 -0.5 1.15 -0.75 1.18 -1 1.24

12. Box counting results for all contours in raster 25 Contour values Box counting (log rain rate) dimension 1 1.18 0.75 1.23 0.5 1.25 0.25 1.25 -0.25 1.28 -0.5 1.23 -0.75 1.13 -1 1.15

13. Contour values Box counting (log rain rate) dimension 1 1.17 0.75 1.22 0.5 1.25 0.25 1.28 -0.25 1.26 -0.5 1.20 -0.75 1.15 -1 1.17 Box counting dimension for all rasters in storm event.

14. Radar picture from CAMRa taken along slant path to ITALSAT Corresponding attenuation time series experienced by beacon on ITALSAT

15. Concluding remarks Slant path systems operating at EHF suffer from attenuation that cannot be compensated for by available fade margin alone. Need to further understand and accurately model spatial and temporal distribution of rain. Fractal nature of rain rate contours has been established, confirming other work done on the fractal nature of the spatial variation of rain. Work ties in with others working on different scales, working towards a global understanding covering micro and macro scales.

16. References Lovejoy, S., Area-Perimeter Relation for Rain and Cloud Areas, Science, Vol 216, 185- 187, April 1982 Rys, F.S., Waldvogel, A. Fractal Shape of Hail Clouds, Physical Review Letters, Vol. 56, Number 7, 784-787, February 1986 Klinkenberg, B., A fractal analysis of shadowed and sunlit areas, Int. Jnl. Remote Sensing, Vol. 15, No. 5, 967-977, 1994