SpaceX, T-Mobile to connect satellites to cellphones in remote areas

Re:SpaceX, T-Mobile to connect satellites to cellphones in r... by dvdkhlng on Friday August 26, 2022 @02:52AM (#32604077)

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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Re:SpaceX, T-Mobile to connect satellites to cellphones in r... by ahefner on Friday August 26, 2022 @03:19AM (#32604197)

Nitpick: You probably mean DVB-S (and S2, S2X..) rather than DVB-C, and you're correct that they don't employ OFDM (they're just a straightforward single wideband channel mostly employing variations on phase-shift keying), and aren't particularly concerned with multipath interference.

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