4 ms·
Cell phones can supposedly connect to towers up to 25 miles away (presumably at the slowest supported data rate.) Starlink is about 350 miles up. Let's round up
by sgtnoodle 4y ago
Cell phones can supposedly connect to towers up to 25 miles away (presumably at the slowest supported data rate.) Starlink is about 350 miles up. Let's round up to 400 to allow for satellites not being directly overhead. That's 2^4 times farther away, or 24dB of signal difference.
It seems like a sufficiently fancy phased antenna array on the satellite could compensate for that. Also, the atmosphere is 99% gone at 20 miles up, so that probably helps. Also, with the goal of only supporting SMS, a modern software defined radio chipset could probably be made to use an incredibly low data rate that adds more signal margin than currently used by any cell network.
- snovv_crash 4y agoI didn't realise that 4G/5G could connect to receivers that far away. From memory, the maximum Timing Advance in 2G corresponded to ~25km. After that the phones won't get ACKs fast enough due to speed of light and will assume that the response isn't for them. WiFi has similar limits, but much shorter. I know some usecases of WiFi transceivers with longer distances (~5km) which required tweaked firmware that wasn't technically wifi-compliant, to have longer receive windows.
- shenberg 4y agoEven in 2G you have special cells that allocate two+ adjacent time-slots for a channel and so can effectively double the max range at the cost of serving less concurrent clients. This is used in sparsely populated regions (think remote highways etc). It's not a physical, the-signal-can't-reach issue.