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beams, for example, with regard to Kanto Beam 1 beam having power of 72.6 dBW, the C/N0 margin, as shown in Table 1, is 20.8 dB when received by a 1.2 m VSAT on a clear sky. Also, the number of MBA spot beams, although depending on how many service areas the satellite covers, is eight at maximum; this means that, if it is assumed simply that an identical volume of power is supplied to each of the eight beams, the 1.2 m VSAT reception margin on a clear day is 11.3 dB. Also, Table 2 shows another example of downlink satellite link design in an 8-beam operation, where the whole surplus power is allocated to an area under heavy rain and the other areas are under a weather condi-tion that allows applying 6 dB rain margin power.Table 2 is a very simple example because the actual situations, satellite antenna gains are dierent from area to area and also all VSAT do not use over 1.2 m antennas. However, the rain attenuation compensation of about 19 dB is actually applicable to the area under heavy rain. It also should be noted that the compensation 19 dB compensa-tion corresponds to the 13 dB rain attenuation from the C/N0 margin on a clear day of about 6 dB. e downlink required C/N0 and C/N0 margin were veried through the experiments by measuring the packet losses while lowering the reception C/N0 by inserting shield boards. Figure 11 shows the characteristics of reception C/N0 versus packet loss measured using the Kanto MBA with 1.2 m VSAT in Kashima, where at the C/N0 of approximate 95 dB, the packet loss began to increase; the value of 95 dB, having just a dierence of 1 dB compared to the downlink required C/N0 of 93.9 dB, is within the error range.FiF12Characteristics of reception C/N0 versus packet loss (APAA) ClearAreaHeavy RainAreaSatellite TransmissionOutput PowerW10.0210.0Feed LossdB-1.0-1.0Antenna GaindBi49.149.1EIRPdBW58.171.3PropagationFree Space LossdB-208.9-208.9Atmospheric AbsorptiondB-0.2-0.2Rain AttenuationdB0.0-19.0Earth Station ReceptionPointing ErrordB-0.5-0.5G/TdB/K23.123.1Downlink C/NodB100.294.4Modulation SpeedMbps203.5203.5Symbol RateMsps101.75101.75User Data RateMbps155.52155.52Required C/NodB93.993.9C/N MargindB6.30.5Regenerative DownlinkTabT2An example of satellite link design during downlink rain attenuation compensationFiF11　Packet loss rates versus reception C/N0 (MBA)1.5M6M24M51M155MUplink FrequencyGHz28.0528.0528.0528.05Earth Station TransmissionW0.853.3913.1828.18dBm29.335.341.244.5Feed LossdB-1.9-1.9-1.9-1.9Antenna GaindBi47.647.647.647.61.2m ANTEIRPdBW45.051.056.960.2Pointing ErrordB-0.5-0.5-0.5-0.5PropagationFree Space LossdB-212.7-212.7-212.7-212.7Atmospheric AbsorptiondB-0.3-0.3-0.3-0.3 Rain AttenuationdB0.00.00.00.0SatelliteG/TdB/K20.320.320.320.3Uplink C/NodB80.486.492.395.6Output PowerW280.0Feed LossdB-1.0Antenna GaindBi49.1EIRPdBW72.6Downlink FrequencyGHz18.25PropagationFree Space LossdB-208.9Atmospheric AbsorptiondB-0.2 Rain DegradationdB0.0Earth Station ReceptionPointing ErrordB-0.5G/TdB/K23.11.2m ANTDownlink C/NodB114.7Modulation SpeedMbps2.31259.253774.0203.5Symbol RateMsps1.156254.62518.537.0101.75User Data RateMbps1.5366.1442451.8155.52Required C/NodB73.679.785.788.793.9C/N MargindB6.86.76.66.920.8MBA Kantou BeamRemarks Output PowerTabT1Communication link design example (clear day, MBA Kanto Beam)3 Ultra-High-Speed Satellite Communication Technology82　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)