Re: [Starlink] SpaceX/Starlink says it's ready for a fall satellite-to-cell service with T-Mobile

[David Lang <david@lang.hm>]

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Sebastian Moeller wrote:

> Curious, is that doppler correction applied individually per dishy, or per 
> cell? If the latter do cells extend ahead or behind the satellite's projection 
> onto the globe, or is there one or more beams ahead an another one or more 
> behind?

sorry, I was specifically talking about the direct-to-cell capability. In one of 
the early presentations, Elon mentioned that one of the problems was doppler 
shift and the need to correct for it in the satellite so that the phones on the 
ground see the same frequency that they would get from a normal cell tower.

Since normal cell phones depend on timing signals from the tower, I am assuming 
that it's a single correction for the entire cell

David Lang

> On 5 June 2024 06:16:02 CEST, Mike Puchol via Starlink <starlink@lists.bufferbloat.net> wrote:
>> Yes, they correct doppler in a single stream - what I was alluding to is the MIMO advantage of terrestrial networks which cannot be easily replicated from multiple satellites, as the UE cannot correct multiple doppler shifts and timing advances unless it implements an NTN-specific approach.
>>
>> Best,
>>
>> Mike
>> On Jun 4, 2024 at 20:17 -0700, David Lang <david@lang.hm>, wrote:
>>> Mike Puchol wrote:
>>>
>>>> Something else that's much harder to implement is MIMO, as you don't get path
>>>> diversity from a satellite. AST claims they will do this by using more than
>>>> one satellite, however they haven't answered basic questions such as how will
>>>> the UE compensate the huge differences in doppler shift on top of the multiple
>>>> paths.
>>>
>>> for the starlink version, the satellite adjusts it's transmit/receive
>>> frequencies to correct for the doppler shift so that the phones don't need to.
>>>
>>> David Lang
>>>
>
>

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