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consequently, as Packet Loss (w/o UPC) indicates, packet losses are inevitable when the C/N0 is below the level of around 105 dB. HPA Output Power (e/w UPC) and HPA Output Power (w/o UPC) are respectively the output power of 1.2 m VSAT HPA output power with UPC and that without UPC. At the C/N0 level below 109 dB, in the case of “with UPC,” the HPA output power goes up as the C/N0 goes down; this indicates that UPC works normally. Figure 5 shows the UPC operation in 51 M using the same parameter settings as mentioned above. Figure 5 shows that, in 51 M mode, VSAT EIRP does not go up in the C/N0 region of the level below 104 dB even with UPC due to the saturation of 40 W SSPA; consequently, even in the case of with UPC, the estimated EIRP shown in Estimated EIRP (e/w UPC) goes down in the C/N0 region below the level of 104 dB, with packet losses occurring.Figures 4 and 5 suggest that the eective work of UPC as designed is well veried.For the validity verication of the assumption that the estimated EIRP uplink attenuation is equivalent to the decrease in the downlink reference burst received signal, the packet loss characteristics are compared with both cases, one uses shield boards to simulate the decrease in VSAT EIRP, and the other lowers the IDU output power to lower the VSAT EIRP. Figure 6 shows the results of the two dierent methods’ measurements.In Figure 6, the cases denoted by “51M,” “24M,” or “6M” are the cases where VSAT EIRP is lowered by adjust-ing IDU output power, and the cases denoted by “51M-P,” “24M-P,” or “6M-P” are the cases where VSAT EIRP is lowered by applying shield boards. e correlation of esti-mated EIRP and packet loss is almost equivalent for dier-ent operation modes; this means that the abovementioned experiment method is veried as appropriate.Note that in this measurement, experiment-dedicated special IDU operation parameters were applied because the amount of attenuation due to the insertion of shield boards is almost equivalent for the reception frequency band and the transmission frequency band. erefore, in the actual situations, because the uplink rain attenuation is approxi-mately twice larger than the attenuation of downlink, THR rain fade (K1/K2), Coecient (K1), and Coecient (K2) shall be determined taking account of such dierence in attenuation amount.2.2Rain attenuation compensation by altering uplink transmission modeIn the WINDS regenerative link, the following uplink transmission modes of TDMA are used: 1.5 M, 6 M, 24 M, and 51 M. According to the communication link critical design review report (CDR) of June 2006, the C/N0 required for the abovementioned modes are respectively 73.6, 79.7, 85.7, and 88.6 dB/Hz. For instance, in the case where 51 M Mode TDMA is used on a clear day, the communication link can be kept available in rain by degrading the trans-mission mode, even if the available transmission speed or quantity can go down. eoretically, the attainable rain attenuation compensation is 15.1 dB—this corresponds to 88.7 dB minus 73.6 dB.Figure 7 shows the earth station estimated EIRP versus packet loss measurements conducted in the Kanto MBA using 1.2 m VSAT, where the earth station estimated EIRP is obtained by conversion using the earth station estimated EIRP diagram.e measurements reveal the following: in 51 M mode, due to less performance of the re-constructer, packet loss FiF6Validity verification of uplink attenuation using shield boardsFiF7Packet loss rates versus earth station estimated EIRP (MBA)3 Ultra-High-Speed Satellite Communication Technology80　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)