bill at herrin.us
Mon Jan 23 17:54:25 UTC 2023
On Sun, Jan 22, 2023 at 8:54 PM Tom Beecher <beecher at beecher.cc> wrote:
> Yes re: Iridium. Contrary to what the Chief Huckster may say, inter-sat comms are not some revolutionary thing that he invented.
1990s Iridium was a modified version of GSM/ATM with the packetization
and routing that implies. I don't know the current constellation's
architecture but I'd be shocked if they had reverted to a bent pipe
For those not in the know, a "bent pipe" communications satellite is
one which accepts a radio signal in one frequency and does an analog
transform to another frequency before sending it back out. Up from the
ground station on one frequency, transform, down to the customer. Up
from the customer on one frequency, transform, down to the ground
station on another.
The nice thing about a bent pipe is that you can upgrade the service
equipment to higher speeds without changing the satellite. The
satellite doesn't care. It doesn't recognize the concept of bits or
packets. The bad thing is that it's straight up and down, so when the
satellite isn't both in range of the customer and a ground station,
you can't use it.
The vast majority of satellite architectures are bent pipe.
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