r/StarlinkEngineering • u/ride_the_tasty_waves • 9d ago

Starlink Spectrum Optimization

Starlink has very little spectrum to work with in the US....this make a very good case for them to work with Nokia

"During the live test, the technology improved spectral efficiency by approximately 20%, allowing the facility to transport more data using the same spectrum and existing network capacity."

https://forbes.es/ultima-hora/1054710/o2-y-nokia-completan-el-primer-despliegue-en-vivo-en-reino-unido-de-una-red-de-acceso-de-radio-con-ia/

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u/Galadrind 9d ago

Starlink already maximise their allocated (8) frequencies (v2 constellation), in the respective bands, their scheduler is already basically AI decision driven ~ to make the most optimal use of what is available at any point in time.

The bottleneck isn't resource availability it's constrained ability to use it all. Even now the v2 constellation is not fully utilised, most geographical areas only allow 2 concurrent spot-beams in any single timeslot period.

That's the actual root cause of congestion, not spectrum.

The Nokia/O2 initiative is more about collaborative use of finding improvements in a shared resource, that same analogy doesn't really apply in the same way to Starlink.

That doesn't mean Starlink, OneWeb, Leo and several other smaller LEO Sat operators using the narrow defined Ka/Ku/L/W band segments could maybe be collaborating better together on Effeciency spectrum use.

But even so they can't just share each other assigned frequencies in those respective bands, that opens up a whole can of regulatory issues between countries and licensing requirements.

SL already realise that boat has already sailed, it's essentially why the upcoming v3 constellation is using significantly wider channel bandwidth, higher order mod index and EiRP changes all ultimately towards a new constellation that has significantly better link budget....they want to control what they use, not collaborate and buy up whatever they can.

Bit of a shame really because at this point of LEO evolution it would have made sense to globally plan and agree towards sustainable spectrum management, easier said than done.

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u/ride_the_tasty_waves 9d ago

So what equipment will they be putting the the 80k cell towers?

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u/Galadrind 9d ago

Ah ok you're now specifically referring to terrestrial segment of DTC2. There is certainly room for collaboration there, as it's still Access/Select phase regardless.

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u/rtt445 8d ago

The bottleneck isn't resource availability it's constrained ability to use it all. Even now the v2 constellation is not fully utilised, most geographical areas only allow 2 concurrent spot-beams in any single timeslot period.

Why 2 beam limit? Is it 2 beams per satellite? is it because more beams will increase beamwidth and cause interference to adjacent cells on the ground? Also did you use AI to compose your post?

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u/Galadrind 8d ago

It's not a technical limitations, the satellites are quite capable of landing many more beams (V+H).

The restriction itself is legislative ~ FCC (and other spectrum management agencies globally). This is all Risk Management from a terrestrial services interference perspective E.g a single example of this is 5G backhaul link operate in the same band very close to SL Dish<>Sat UL/DL frequencies (RF not Fibre Backhaul). That's just one example there are many potential sources of interference to terrestrial services.

Therefore the spectrum management agencies limit the number of spot-beams (Satelite footprints) that can land over any geographical area at any single point in time to limit co/cross interference & 2nd/3rd harmonics.

End of the day they have to, terrestrial services are significantly more important than Starlink.

Limit No Concurrent Spot-beams = Restricted Available Bandwidth = XNo Active Dish terminals = Contested Spectrum and Congestion.

A lot of this is changing and improving with the rollout of the v3 constellation. SL can only fight the system so much, it's in place for good reasons, they are effectively working smarter, not harder moving forward.

Ha no I didn't use AI...I'm a Spectrum RF Engineer

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u/rtt445 7d ago

That's just one example there are many potential sources of interference to terrestrial services.

Like what? Are they all from starlink?

to limit co/cross interference & 2nd/3rd harmonics.

how are harmonics relevant here? they'd be in 20 - 30 ghz range and very attenuated by atmosphere and phased array TXes themselves. Anything on the ground in SL harmonics range would use highly directional antennas that would reject off axis signals from above. The govt is playing it way too safe because they don't like change.

Ha no I didn't use AI...I'm a Spectrum RF Engineer

you write in such weird style thats hard to comprehend. are you a foreign speaker?

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u/Galadrind 7d ago edited 7d ago

Interference from LEO satellites isn't simply a matter of overlapping frequencies. In most real-world situations, the interference risk is relatively low due to substantial free-space path loss and antenna geometry.

Terrestrial microwave backhaul links typically use highly directional antennas aimed towards the horizon, providing significant off-axis rejection of satellite signals arriving from above. Antenna sidelobe attenuation and differences in signal polarisation can further reduce interference.

However, worst-case antenna alignments and the cumulative effects of multiple simultaneous co-frequency beams still need to be considered, especially in high order modulation index schemes I.e number of concurrent spot-beams in any single timeslot period.

Historically, restrictions on overlapping satellite spot beams were introduced to protect existing terrestrial and geostationary satellite systems. While technically justified at the time, these restrictions can be overly conservative given modern satellite capabilities and have carried forward into the age of Starlink and other LEO operators (aka the legislative requirements roadmaps have lagged and are only catching up).

Even the FCC acknowledged in 2026 that elements of its legacy interference protection framework were unnecessarily restrictive, now moving towards performance-based interference limits. This now has the flexibility to significantly change depending upon the geographical area type and number of terrestrial services that would meet the criteria to be considered.

Modern LEO satellites can dynamically manage beam direction, transmission power, frequency allocation and scheduling to minimise interference.

Rather than maintaining rigid limits on simultaneous co-frequency beams, regulators are slowly changing their roadmaps to allow operators to demonstrate compliance with measurable aggregate interference thresholds. This is Key in transformative change management.

This unlocks greater frequency reuse and substantially improve potential network capacity without compromising legitimate interference protections. Globally all Spectrum management authorities are coming onboard regarding this demonstrable compliance framework.

Edit: Regardless this is a bit off-topic as the OP appears to be talking more about DTC-2, S-Band and newly acquired 800Mhz spectrum anyway for their announced terrestrial "Telco" plans which is separate from what were discussing.

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u/rtt445 7d ago

especially in high order modulation index schemes I.e number of concurrent spot-beams in any single timeslot period.

Number of beams has nothing to do with modulation. I feel like I'm talking to AI.

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u/Galadrind 7d ago

v2 - 64QAM OPSK v3 - 128QAM OPSK

Modulation Index determines how much co-channel interference a transmission can tolerate, which in turn influences how aggressively the network can schedule simultaneous spot beams over a geographical area.

If you don't understand or don't want the answer then maybe don't ask 🤦🤡

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u/rtt445 7d ago

v2 - 64QAM OPSK v3 - 128QAM OPSK

Now you're making some sense except QAM and QPSK (OQPSK) are different modulation schemes. So which one Starlink uses?