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there is a frequency deviation of about 2 dBp-p in the 550 MHz bandwidth in the signals of the 622 Mbit/s transmission (412 Msymbol/s). In principle, MPA operates in a linear region. It is supposed that the eect from the non-linear characteristics on the 1 wave TDMA signal is not large because of the output back-o by 4 dB in the maximum operation mode. erefore, the main cause of deterioration of the BER characteristic is supposed to be unstable devia-tion of the frequency performance of satellite lines and the received signal level including earth terminals. It is sup-posed that uctuation of the received signal level is af-fected by about 1 dB due to changes in conditions such as clouds or weather even during the short time of measure-ment for the signals in the frequency bands of 28 GHz for up-link and 18 GHz for down-link.(2)Kanto Beam 622 Mbit/s TDMA communication ex-perimente communication experiment of 622 Mbit/s TDMA was performed with the conguration shown in Fig. 1. It was performed between LET and SDR-VSAT1 at Kashima located within the Kanto Beam area. e reference burst (JRB) was transmitted from JAXA station and it was re-ceived at LET via JRB receiver. e modem of LET oper-ated as a master modem. Aer receiving information on satellite positioning, slot allocation and synchronized timing, it transmitted WRB from the high-speed burst modem. Both JRB and WRB carried information on satel-lite positioning, slot allocation and synchronized timing. e SDR-VSAT1 received WRB from WINDS.en, in order to establish TDMA communication, the two modems sent burst signals on the basis of the position-ing, slot allocation and synchronized timing carried by WRB.e transmission timing of the burst signals was deter-mined by calculating the delay time from the positioning of the satellite and earth terminal. e PC1 and the PC2 were connected to modem1 and the modem2, respectively, via LAN.e result of measurement of UDP packet error using iperf which is free soware to measure network throughput and packet error rate is shown in Table 5. is result is for the cases of full slot allocation and half slot allocation. e former case is that transmission signals were allocated continuously to all of the slots in the TDMA frame con-guration shown in Fig. 2. e latter is the case that the data slot columns were divided into two groups with 9 slot columns of TDMA transmission signals for each group. Case (a) achieved a packet error rate of 0% at 100, 400, and 622 Mbit/s for unidirectional continuous wave opera-tion of non-TDMA operation for full slot allocation. Case (b) achieved a packet error rate of 0% at 100, 200, and 300 Mbit/s for bidirectional transmission for half slot alloca-tion.e result of the iperf test for TCP is shown in Table 6. Figure 9 shows the time variation of TCP throughput when FiF9　TCP throughput change for no packet error050100150200250300020406080100Bandwidth (Mbps)Time (sec)hybla-64Mbyteshybla-124Mbytesreno-64Mbytesreno-128MbytesTabT5　Half band UDP iperf test(a) Iperf Test (Full Slot Assign. One Way)Eb/N0100 Mbps400 Mbps622 MbpsSDR-VSAT1⇒LET(Upper Band)14.9 dBLoss 0 %Loss 0 %Loss 0 %SDR-VSAT⇒LET(Lower Band)15.1 dBLoss 0 %Loss 0 %Loss 0 %(b) Iperf Test (Half Slot Assign. TDMA)Eb/N0100 Mbps200 Mbps300 MbpsSDR-VSAT1⇒LET(Upper Band)17.1 dBLoss 0 %Loss 0%Loss 0 %LET⇒SDR-VSAT1(Upper Band)13.8 dBLoss 0 %Loss 0%Loss 0 %TabT6　Half band TCP iperf testtime(sec)Window size(Mbytes)Bandwidth(Mbps)ProtocolLET⇒SDR-VSAT130164256hybla302128293hybla30264257reno301128261renoSDR-VSAT1⇒LET30164200hybla(For UDP packet loss of about 0.002 %)30612857hybla3746436reno4781286reno3 Ultra-High-Speed Satellite Communication Technology106　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)