Starlink direct to cell (was SpaceX & T-mobile event 25 Aug 2022)

[raptorx2]

Followed by SpaceX's FCC Petition to share the $SATS 2Ghz MSS Spectrum.
https://www.fcc.gov/ecfs/document/1022285915062/1

[OceanCat]

SpaceX and KDDI representatives met with Commission staff on February 20, 2024, to
urge swift action to enable SpaceX to test its direct-to-cellular system with KDDI in Japan in
advance of planned commercial launch later this year, subject to regulatory approvals. SpaceX
and KDDI expect to be ready to begin testing next month. This testing will support the Japanese
Ministry of Internal Affairs and Communications’ ongoing work to license and establish rules for
supplemental coverage from space in the country. Specifically, the companies requested that the
Commission permit SpaceX to conduct international operations subject to local administration
approval similar to the precedent it established in the Lynk Order.

[RedLineTrain]

SpaceX files "Petition for Rulemaking - 1.6 and 2.4 GHz Sharing Framework"
https://www.fcc.gov/ecfs/document/102211948918123/1

So am I getting this correct?  SpaceX has initiated a general scrum for spectrum in the old "Big LEO" frequencies that were last revisited around the 90s to the turn of the millennium.  SpaceX is seeking its own license on the satellite frequencies and supplemental coverage with spectrum owners on the terrestrial frequencies.  So far, SpaceX has not gone after Iridium's Big LEO spectrum.

I am not clear on the allowed power flux densities from space of each piece of spectrum.  That was a big criticism of Iridium in that it didn't have enough power to be used inside buildings.  If Starlink is allowed more power than Iridium on at least some Big LEO frequencies and locations, that could be a big win for satellites in general.

[raptorx2]

SpaceX files "Petition for Rulemaking - 1.6 and 2.4 GHz Sharing Framework"
https://www.fcc.gov/ecfs/document/102211948918123/1

So am I getting this correct?  SpaceX has initiated a general scrum for spectrum in the old "Big LEO" frequencies that were last revisited around the 90s to the turn of the millennium.  SpaceX is seeking its own license on the satellite frequencies and supplemental coverage with spectrum owners on the terrestrial frequencies.  So far, SpaceX has not gone after Iridium's Big LEO spectrum.

I am not clear on the allowed power flux densities from space of each piece of spectrum.  That was a big criticism of Iridium in that it didn't have enough power to be used inside buildings.  If Starlink is allowed more power than Iridium on at least some Big LEO frequencies and locations, that could be a big win for satellites in general.

Actually, the FCC revisited the "Big LEO" Band Plan in both 2004 and 2008.  In the first round.  The FCC Granted Iridium  "shared" use of some of the Globalstar LBand.  ~1618 - 1621Mhz.  In the second round, the FCC Granted Iridium exclusive use of all but a sliver of that previously shared spectrum.  That caused Globalstar to ditch FCC licensing of its "second Generation constellation" in favor of France while refusing to cede the spectrum the FCC required in the 2008 Spectrum Realignment in some markets.  Globalstar's viewpoint was that the FCC lacked authority over the spectrum used in Russia since they would be flagged in France.  The FCC was not too happy with Globalstar's attempt to "end run" around the FCC, and refused to provide Globalstar with "US Market Entry" for the French-flagged Constellation.   Since 90% of Globalstar's revenues came from North America, lack of "US Market Entry" would be fatal.  In the end.  Globalstar elected to give up rights to the spectrum in Russia, agreed that the FCC was it's "global regulatory administrator, and paid a $275,000 fine (Consent Decree). 

Globalstar has largely been a Spectrum Speculator for the past 20 years, attempting to convert the "Big LEO" spectrum into Terrestrial Spectrum. Globalstar main use of this valuable spectrum, IOT, SPT only takes up a few kilohertz.  In 2022, Globalstar agreed to lease 85% of it's spectrum worldwide to Apple, for "future SOS/safety applications" in exchange for about $500MM in financing.  Globalstar publically stated that the remaining 15% of their spectrum would allow them to grow their future business 500%.  SpaceX's opinion is that Globalstar's statements show they have not been using their spectrum to the degree they have explained to the FCC in the past, and that there is room for SpaceX to share some of the L/S Band Big LEO spectrum.  Iridium is left alone as they have only 6 Mhz of LBand (TDD) and they have hundreds of thousands Voice/Data/DoD/IoT. 

Ironically, Apple's agreement with Globalstar has "exit clauses" that state if Globalstar fails to maintain regulatory control over all of it's spectrum, then Apple can bail on the agreement.  A lot has changed in the Direct 2 Cell landscape since 2022, and with the lure of 2-way Text, Voice, Messaging, Data in the works..  Then perhaps Apple no longer see the Globalstar agreement as necessary in the long term.  It should be noted, that in the proceeding where SpaceX has been spearheading their request to share Globalstar's spectrum.  Apple did not comment.

Apple Design Center, in San Diego, was one of the exact GPS locations that SpaceX stated in the D2D  Experimental License Testing Locations.

Even, if successful, SpaceX would need to include the L Band in 3GPP standardization and could be several years for chipset/handset support.

Of course, MSS spectrum provides many advantages, such as Maritime coverage and perhaps more simplified "landing rights".

However, current rules on Power Flux Densities has MSS with lower limits than that of Direct 2 Cell.  Not to mention R.A.S. operating co-primary with priority in the 1610-1614Mhz.  The best option would perhaps be to operate in TD mode in the S Band (3GPP Band n53)

[raptorx2]

MWC2024 Opens tomorrow in Barcelona.  SpaceX is a first-time exhibitor with one of the few outdoor exhibition areas.
The initial 6 D2D Starlinks are expected to make a direct pass over Barcelona around ~17:00 local. Weather forecast for the four days.  Partly Cloudy @~62F

[Nomadd]

 Grandma said that if you can't say anything nice, don't say anything at all. So, as far as Globalstar (the company), both 20 years ago and now.......

[raptorx2]

SpaceX files "Petition for Rulemaking - 1.6 and 2.4 GHz Sharing Framework"
https://www.fcc.gov/ecfs/document/102211948918123/1

 That was a big criticism of Iridium in that it didn't have enough power to be used inside buildings. 

For the developing countries.  A simple outdoor installation cheap ($40) 3G Wifi device with built-in solar cells.

[DanClemmensen]

SpaceX files "Petition for Rulemaking - 1.6 and 2.4 GHz Sharing Framework"
https://www.fcc.gov/ecfs/document/102211948918123/1

 That was a big criticism of Iridium in that it didn't have enough power to be used inside buildings. 

For the developing countries.  A simple outdoor installation cheap ($40) 3G Wifi device with built-in solar cells.

But for that, you use a Starlink terminal, not D2D. Users then connect their smartphones to the Starlink's WIFI. Alternatively, add a nano-cell to the Starlink WIFI and connect the smartphones to the nano-cell using cellphone protocols. A Starlink user terminal has much higher bandwidth than D2D. A single Starlink terminal can support a micro-cell, not just a nano-cell, A microcell can support at least a hundred smartphones in a village.

[catdlr]

https://twitter.com/SpaceX/status/1761994722913198134

This post was sent through a SpaceX Direct to Cell satellite in space 🛰️10:00 PM · Feb 25, 2024

[DigitalMan]

There was also a post showing the tree-covered area where they were texting from

https://twitter.com/longmier/status/1761998954944921955

[gsa]

There was also a post showing the tree-covered area where they were texting from

An interesting followup of this conversation.

Congrats!

https://twitter.com/longmier/status/1762012677961118063

Thank you!

The team is really making progress.

Also interesting that these sats have by far the strongest cell signal at my house, just 15 miles outside the heart of Silicon Valley.

[spacenuance]

The Falcon and Starlink teams are working hard to get the first direct-to-cell constellation up by the end of August.

https://twitter.com/edwards345/status/1762143604276183470

[raptorx2]

SpaceX files "Petition for Rulemaking - 1.6 and 2.4 GHz Sharing Framework"
https://www.fcc.gov/ecfs/document/102211948918123/1

 That was a big criticism of Iridium in that it didn't have enough power to be used inside buildings. 

For the developing countries.  A simple outdoor installation cheap ($40) 3G Wifi device with built-in solar cells.

But for that, you use a Starlink terminal, not D2D. Users then connect their smartphones to the Starlink's WIFI. Alternatively, add a nano-cell to the Starlink WIFI and connect the smartphones to the nano-cell using cellphone protocols. A Starlink user terminal has much higher bandwidth than D2D. A single Starlink terminal can support a micro-cell, not just a nano-cell, A microcell can support at least a hundred smartphones in a village.

Nano-cell?  Why wouldn't you just use something like a cheap 3G/4G Roof Mount Outdoor Mobile Hot Spot for D2D indoor use.  We are talking basically cheap WLL for developing countries.  You have a supercheap 3G UT and use it connected to the Mobile Hotspot when indoors?  Starlink terminal is way too expensive for that market.

[raptorx2]

There was also a post showing the tree-covered area where they were texting from

An interesting followup of this conversation.

Congrats!

https://twitter.com/longmier/status/1762012677961118063

Thank you!

The team is really making progress.

Also interesting that these sats have by far the strongest cell signal at my house, just 15 miles outside the heart of Silicon Valley.

 

Any signal indoors?

[catdlr]

https://twitter.com/elonmusk/status/1764032892663906313

SpaceX just achieved peak download speed of 17Mb/s from satellite direct to unmodified Samsung Android phone

[FutureSpaceTourist]

Rest of the thread:

That’s incredible…. Fixed wireless networks need to be looking over their shoulders?

https://twitter.com/elonmusk/status/1764037779900469312

No, because this is the current peak speed per beam and the beams are large, so this system is only effective where there is no existing cellular service.

This service works in partnership with wireless providers, like what @SpaceX and @TMobile announced.

[abaddon]

Loss rate is pretty high, this looks like UDP, so I would expect sustained throughput of TCP with retransmissions etc would be substantially lower.  QUIC would probably perform better than TCP here.  Still pretty cool.

[raptorx2]

Loss rate is pretty high, this looks like UDP, so I would expect sustained throughput of TCP with retransmissions etc would be substantially lower.  QUIC would probably perform better than TCP here.  Still pretty cool.

LTE Stack development is still in it's infancy. A very steep learning curve. 

Remember, this is running on low-power constrained processing on the satellite.

However, learning Stack development should allow them to deploy other "custom" air interfaces for ultra secure government communications.  IMO

[DanClemmensen]

Loss rate is pretty high, this looks like UDP, so I would expect sustained throughput of TCP with retransmissions etc would be substantially lower.  QUIC would probably perform better than TCP here.  Still pretty cool.

LTE Stack development is still in it's infancy. A very steep learning curve. 

Remember, this is running on low-power constrained processing on the satellite.

However, learning Stack development should allow them to deploy other "custom" air interfaces for ultra secure government communications.  IMO

Not exactly "infancy". LTE is deployed on billions of devices and has been around for a decade, with roots going back at least three decades. Quite a few developers are familiar with it, and several stacks are available for purchase.

What I don't know is how it is being used for satellite. The lower layers are highly optimized for comms between a cell tower and a cell phone. I was very surprised to learn that the basic lower-layer packet error rate is 10%. I'm used to error rates below 0.1%. The LTE trick is fast NAK and retransmit between the phone and cell tower, and since the distance is so low the recovery is instantaneous. The other trick is that the receiver keeps the bad block. The retransmitted packet uses a different FEC than the first one, and is designed so the two packets together form a longer and more robust FEC block.  The problem I have is that this trick won't work nearly as well over a 300 km link, so they will be doing something else.

[cpushack]

Loss rate is pretty high, this looks like UDP, so I would expect sustained throughput of TCP with retransmissions etc would be substantially lower.  QUIC would probably perform better than TCP here.  Still pretty cool.

LTE Stack development is still in it's infancy. A very steep learning curve. 

Remember, this is running on low-power constrained processing on the satellite.

However, learning Stack development should allow them to deploy other "custom" air interfaces for ultra secure government communications.  IMO

Not exactly "infancy". LTE is deployed on billions of devices and has been around for a decade, with roots going back at least three decades. Quite a few developers are familiar with it, and several stacks are available for purchase.

What I don't know is how it is being used for satellite. The lower layers are highly optimized for comms between a cell tower and a cell phone. I was very surprised to learn that the basic lower-layer packet error rate is 10%. I'm used to error rates below 0.1%. The LTE trick is fast NAK and retransmit between the phone and cell tower, and since the distance is so low the recovery is instantaneous. The other trick is that the receiver keeps the bad block. The retransmitted packet uses a different FEC than the first one, and is designed so the two packets together form a longer and more robust FEC block.  The problem I have is that this trick won't work nearly as well over a 300 km link, so they will be doing something else.

I think he meant SpaceX LTE stack is in its infancy, not LTE Stacks in general, but your point remains, Satellite based LTE in general is in its infancy since everything has been optimized for terrestrial usage.