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2Uplink rain attenuation compensationUplink rain attenuation compensation is accomplished in the following two dierent ways: controlling the nal stage amplier radiation power of the transmitting earth station, so-called Uplink Power Control (UPC); and con-trolling the required EIRP of the transmitting earth station through alternating the uplink transmission mode.2.1Rain attenuation compensation by uplink power control (UPC)UPC is widely used for rain attenuation compensation in satellite communications; among UPC methods, such a method is well-known that uses, as a standard signal, the beacon signals of a satellite or the pilot signals transmitted from hub stations or standard stations.e regenerative link TDMA reference signal is used as a reference for the UPC in the WINDS regenerative link rain attenuation compensation method, because the regen-erative link TDMA burst signals are radiated with constant power. e regenerative link earth station indoor unit (IDU) estimates the reception C/N0 using the strength of the received reference burst signal and the strength of guard-time noise, calculating the C/N0 margin—dierence between the estimated C/N0 and the predened value of Downlink C/N0 limit. e IDU, when the C/N0 margin is lower than the clear sky margin, raises the transmission power to compensate for the rain attenuation [1]. e IDU has parameters for controlling UPC operations, including THR rain fade (K1/K2), Coecient (K1) and Coecient (K2), raising the transmission power by the rate of those coecients against the loss of C/N0 margin. ose coe-cients are the ratios of 28 GHz band transmission power gains to the losses in 18 GHz reception C/N0, and THR rain fade (K1/K2) species the thresholds for alternating those coecients—for example, under the setting of THR rain fade (K1/K2) to 5, K1 to 1, and K2 to 2, the transmis-sion power is increased as follows: until the C/N0 loss reaches 5 dB, the transmission power is increased by the amount of C/N0 margin loss; when the loss goes beyond 5 dB, the transmission power is increased by twice the amount of C/N0 loss. Figure 2 show such transition in transmission power.Note that the VSAT EIRP will not grow limitlessly along with the increase in the transmission power—the input-output characteristics and saturation output power of the VSAT Final power amplier limit the VSAT EIRP.e abovementioned UPC operation was tested by simulating rain attenuation where shield boards made of FiF2Rain attenuation compensation scheme in WINDS regenerative link IDUATT valueFiF1　Outdoor equipment for experiment of regenerative link rain attenuation compensation 1.2m VSAT 1m Transportable VSAT Large Earth Station (4.8m ANT) 2.4m VSAT3 Ultra-High-Speed Satellite Communication Technology78　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)