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by dvdkhlng
1388 days ago
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I'd think that the distance limit for _terrestrial_ mobile networks comes from the guard interval of the OFDM modulation [1]. I.e. on longer distances the time-offset between different different reception paths (due to reflections) of the signal becomes so long that you cannot compensate those with just a complex gain-factor of the OFDM vectors. AFAIR LTE (4G) even uses different guard intervals depending on rural vs. city setting because that time-offset is larger in rural areas (less base station density). I would not expect those problems to be relevant for satellite communication as ground<->satellite does not suffer much of the multi-path signal propagation of terrestrial systems. (IIRC DVB-c sat-TV broadcasts did not even use OFDM, at least not for the older "v1" DVB-c standard). [1] https://en.wikipedia.org/wiki/Orthogonal_frequency-division_... |
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