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In addition, in Fig. 12 the characteristics of APAA downlink reception C/N0 versus packet loss are shown; the gure shows similar characteristics as the case of MBA.4Rain attenuation compensation by changing throughput and TCP/IP uplink transmission modeTable 3 shows the UDP throughput measured by using iperf which is soware for computing network throughputs in dierent WINDS transmission modes.e throughputs listed in Table 3 are the throughputs in the case where 288 trac slots are used in a super-frame. In the case where a smaller number of slots are allocated to a user, the throughput decreases in proportion to the decrease in the number of allocated slots. In addition, in the case where the transmission mode grade-down is ap-plied for doing rain attenuation compensation, because the uplink transmission speed or information volume de-creases in proportion to the value listed in Table 3, the application side would be required to take measures for adjustment.On the other hand, TCP/IP throughputs, because re-transmissions are done, depend not only on transmission path capacity but also on the packet size, window size and others. With regard to satellite communication systems with larger transmission delays in particular, the transmis-sion capacity varies within a wide rage. Figure 13 shows the estimated EIRP versus throughput or packet loss measured using iperf with the following settings: in order to obtain approximately maximum throughput of the WINDS regenerative link, using TCP/IP, and setting the window size to automatic selection mode within the range from 4 Kbytes to 4 Mbytes for 6 / 24 / 51 M mode and within the range from 4 to 128 Kbytes for 1.5 M mode.Figure 13 shows that TCP/IP throughput drastically decreases on the occurrence of packet loss on satellite links. e gure suggests that the satellite links shall operate with a higher throughput through operating the transmission link under a packet loss condition, by down-stepping the transmission mode on the occasion of packet loss of around 0.2 percent down at 51 M satellite transmission mode and 1 to 2 percent down at 24 M/6 M mode. erefore, for the transmission services by TCP/IP, it will be more eective to immediately shi the transmission mode down to a low-speed mode on the occasion of rain attenuation ex-ceeding the threshold where packet losses begin to occur.5Satellite link unavailability in raine satellite link unavailability due to rain attenuation in the WINDS regenerative link are discussed here, based on the rain attenuation calculated using the UTU-R P.618-8 model. Table 4 lists the uplink rain attenuation versus satellite link unavailability. In addition, the table shows the satellite G/T for the dierent cities estimated using the distance of the city to the MBA beam center and the maximum attainable value of estimated rain attenuation compensation. Such compensation values for dierent cit-ies are obtained by converting the uplink rain attenuation compensation of Kashima 1.2 m VSAT of 26.7 dB—adding or subtracting the dierence of the satellite estimated G/T in a city to the MBA Kanto satellite estimated G/T in Kashima of 20.3 dB/K to or from the compensation in Kashima of 26.7 dB.According to Table 4, the following uplink unavail-ability in dierent districts is expected: in the districts from Hokkaido to Northern Tohoku, 0.01%; in the districts from Sendai to Kanto, 0.03%; in the districts from Chubu to Kyushu, 0.05%; in Okinawa, 0.1%.Table 5 lists the downlink rain degradation against satellite link unavailability—the downlink rain degradation is the sum of rain attenuation and degradation in reception TabT3　UDP throughputs in different uplink transmission modesTransmission Mode1.5M6M24M51MNo of Slot/Super frame288288288288No of Data/Slot283060Data volume incl. All"0" data (Byte)223223223223Data volume excl. All"0" data (Byte)212212212212Data volume excl. ATM header (Byte)192192192192Data rate excl. ATM header (Mbps)1.3825.53020.73641.472Measured Maximum Throughput (Mbps)1.275.119.138.2Note1: In the case where No. of Slot is changed, corresponding throughput can be calculated using proportional distribution.012345678051015202530354035404550556065Packet Loss Rate (%)Throughput (Mbps)Estimated EIRP [dBW]Estimated EIRP vs TCP/IP Throughput & Packet Loss51M24M6M1.5M51M-P/L24M-P/L6M-P/LFiF13　Estimated EIRP versus throughput and packet loss833-2 Experiment Report for Rain Attenuation Compensation