1. 1 HAP Spectrum Sharing Studies in the 28/31 GHz Band Y.H. Kang

2. 2 Introduction In ITU-R The bands 47.2-47.5GHz and 47.9-48.2GHz were designated within the fixed service(FS) for the use of HAPS before WRC-03. The studies in these bands were completed by WRC-03 and the results are continued in Rec. ITU-R SF. 1481, with the exception of interference to and from FSS spacecraft, and border area coordination matters in the FS. Since 47GHz band is highly susceptible to rain attenuation, studies of the feasibility of identifying suitable frequencies for the use of HAPS of the FS in the range 18-32GHz in Region 3, were requested by several Region 3 countries. In WRC-03 The use of HAPS in the FS within 300MHz of spectrum in the band 27.5-28.35GHz and in the band 31-31.3GHz in certain Region 3 and Region 1 countries on a non-harmful interference, non-protection basis.

3. 3 Introduction(cont.) Resolution 122 (Rev. WRC-2000) urgently requested studies on technical sharing and regulatory issues in order to determine suitable criteria for the operation of HAPS in the 27.5 - 28.35GHz and 31.0 - 31.3GHz bands. Resolution 122 may be considered to extend the timeframe of the ITU-R study on the sharing issues (except compatibility studies with passive services) until WRC 2007. Since the uplink channels of GSO/FSS and FWA systems operate in the same band as the proposed HAPS, the two cases of interference from HAPS into GSO/FSS and FWA systems should be analysed in more detail and more generally. The earlier studies show that whilst the interference into a GSO satellite from the HAP downlink is minimal, an impractical separation distance is required for effective operation of HAPS and FWA systems in the same band. As a result, it is most important to carry out further investigations into the interference from HAPS into FWA systems.

4. 4 Analysis model Since P-MP is a representative FWA model, we focused on the analysis of interference from HAP into P-MP system Four types of sharing scenario can be considered  HAP Airship Station (AS) P-MP Base Station (BS)  HAP Airship Station (AS) P-MP Terminal Station (TS)  HAP Ground Station (GS) P-MP Base Station (BS)  HAP Ground Station (GS) P-MP Terminal Station (TS)

5. 5 System characteristics HAPP-MP Antenna Pattern Airship : Optimized antenna (WP2.3) GS : ITU-R F.1245 BS/TS ETSI EN 301 215-2 Omni antenna Cell Structure Number of cells : 121 cells (3 or 7 Ch. Reuse) Diameter of coverage: 30km Number of sectors : 3 sectors Diameter of coverage : 1km Pathloss Model ITU-R F. 1404 Interference Threshold I/N = -10dB

6. 6 An example of result (Airship->BS) Nadir boresight HAP cellP-MP cell Opposite boresight

7. 7 Conclusion This result shows the possibility of sharing without separation distance between HAP airship and FWA Base Station if we consider the optimized antenna pattern and cell structure. Since the practical antenna pattern and pathloss model have not yet fixed in HAP, we have utilized the general parameters based on ITU-R model for this analysis. In future the practical parameters can be applied to supplement these sharing issues.