Link budgeting/Costing of Satellite BW (Bandwidth)

Your will probably need to adjust your design to meet the cost expectations of your customers.

Let us start with the most expensive design, which provides dedicated capacity 24/7 to and from all sites:

Hub to remotes:
1 carrier 5120 Kbit/s
Modulation QPSK (2 bit/symbol)  FEC 3/4 rate
Symbol rate = 5120 / 2 * 4/3 = 3413 ksps
Allocated Bandwidth needed = approx 1.35 x symbol rate = 3413 * 1.35 = 4.6 MHz

Remoted to hub:
10 carriers each 512 kbit/s
Modulation QPSK (2 bit/symbol)  FEC 3/4 rate
Symbol rate per carrier = 512 / 2 * 4/3 = 341 ksps
Allocated Bandwidth needed = 10 x approx 1.35 x symbol rate = 3413 * 1.35 = 4.6 MHz

Now for a cheap shared design:

Hub to remotes:
1 carrier 2048 kbit/s
Modulation QPSK (2 bit/symbol)  FEC 3/4 rate
Symbol rate = 2048 / 2 * 4/3 = 1356 ksps
Allocated Bandwidth needed = approx 1.35 x symbol rate = 1356 * 1.35 = 1.84 MHz

Remotes to hub:
1 TDMA carrier 512 kbit/s
Modulation QPSK (2 bit/symbol)  FEC 3/4 rate
Symbol rate = 512 / 2 * 4/3 = 341 ksps
Allocated Bandwidth needed = approx 1.35 x symbol rate = 0.46 MHz

This gives you "Up to 2048 Mbit/s on the shared outlink and "Up to 512 kbit/s" on the return links. There will be congestion.

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If you modify either of the above by using larger antennas and can get 16QAM with 0.9 FEC to work you will reduce the allocated bandwidth needed and drastically reduce the satellite transponder cost, at some increase in the cost of all 11 antennas.

Modern modems may have better filtering and the factor to get from symbol rate to allocated bandwidth may be less, like 1.2

See: https://www.satsig.net/symbol01.htm

https://www.satsig.net/lnb/ebno-calculator.htm

Get hold of iDirect data sheets and design documents.