O3B Satellite Network

For those that would like to read more about the O3B project go to their web site here: http://www.o3bnetworks.com/

8 satellites are launched simultaneously and then deployed in pairs from the upper stage.  Only two launches will therefore be needed to put up the 16 satellites.  There are 12 spot beam antennas shown on each satellite, presumably each actively steering.

The satellites are all in circular orbit, above the equator, height 8000 km, so will be seen to be moving forwards, eastwards.  Ground users will have to keep switching backwards to more westerly satellites every 15 minutes or so as the satellites march eastwards. This page https://www.satsig.net/O3b/O3b-orbit.htm should give you some idea.

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Assuming use of 500 MHz in each of the bands 19.7-20.2 and 29.5-30.0 GHz and single polarisation, each spot beam could have 500 MHz bandwidth.  If 300 MHz is used for downloads, that could provide 936 Mbit/s using 16APSK DVB-S2.  Times that by 12 beams and you get around 10 Gbit/s which seems reasonable. It might be much more if they use more of the Ka frequency band or dual polarisation.  DVB-S2 has the advantage it can drop back to lower modulation/coding during rain or to cope with beam edge or customer earth station deficiencies.
 
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Strange number that 2133.  My guess is 1 downlink  and I uplink transponder in each of the 10 customer beams.

I believe that two satellite antenna will be used for gateway feeder links and that 10 satellite antennas will be used for 10 customer sites, each covered by a spot beam.

Will it work ?  Much depends in the customer antennas, tracking (1.2m - 7.6m) and working in pairs.  The satellite power (watts) per transponder is also important and again I can find no information.
 
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I am pleased to see someone trying to get the costs down.  The present prices of $4000 to $7000 per month per 1 Mbit/s are too high for most people.  Much will depend on how cheap they can get the satellites manufactured and launched and the financial viability will depend on how quickly they can build up the number of customers paying.  They will be watching the progress of Wildblue, Ka-Sat and ViaSat-1

I hope this O3B project does not go the way of other LEO and MEO satellite projects of the 1990's.

If anyone knows more about the proposed O3B customer antenna, how the satellite antennas will be pointed or the ground infrastructure please say.

Best wishes to all involved.

Best regards, Eric.

That is interesting.  

I was thinking in terms of quite small customer antennas and a 216 MHz wide transponder would need very high watts power on the satellite downlink.  Does anyone make modems that receive at around 200 Msps with 8-PSK?.  I imagined several narrower transponders, each at saturation and with moderate wattage power, and also with bandwidths corresponding to feasible symbol rate for cheap modems.  I can't work out how they get 2133 transponder in total (16 satellites, each with 12 beams).

If they have 1 transponder per 216 MHz I wonder where they are getting the frequency range from to put 2133 transponders in orbit.  Maybe they are using more bandwidth like 2.5 GHz up (25-27.5 GHz) and 1 GHz total down (18.3-18.8 plus 19.7-20.2 GHz). They could fill 1 GHz on the downlink with 8 transponders, each 250 MHz wide and dual polarisation.

It has set me thinking about another matter -  interbeam interference.  12 beams from the same satellite will require some clever interleaving of frequencies and polarisations if the beam coverages are to be adjacent (e.g. 3 beams on A pol F1, 3 beams on A pol F2, 3 beams on B pol F2, 3 beams on B pol F1) ?  Will the customer earth terminals have to switch polarisations ?  Maybe adjacent coverage areas will be covered by the next or previous satellites.

I've had another look at their webiste and I now realise that their market is cell phone companies and town/city ISP phone companies rather than home/small office/ cafe that I was thinking about.  That way the earth stations can be far fewer, may be much larger, with both gateway hub and mesh connectivity, and link/power budgets that all make sense with comfortable margins.

Whetever, it all looks rather clever and I wish them well. It is good news for mid latitudes.

If the new system gets the price down to $500 per 1 Mbits that will be excellent.  I know the typical price now is $4000 - $7000, but this is often based on very conservative assumptions, like small dishes and QPSK 3/4.   If people really want low price per month now they can cut that cost by half if they would only use 16-QAM modems (e.g. CDM570L),  larger antennas and linear BUCs.  In certain rare special conditions (i.e. can see own signal and equal bit rates each way) then carrier on carrier is possible with yet further monthly price reduction - but with more hardware and skill cost.

Best regards, Eric.