Re: [6gip] 6G

[Alexandre Petrescu <[e-mail]>]

Le 14/01/2021 à 09:52, Lars Eggert a écrit :
> The limits here are due to physical constraints - the speed of light in vacuum is about 300000 km/sec. An RTT of 1us means that the maximum distance to a base station needs to be below 150m. (Not including coding overheads, etc.)

The distance situation of base stations is not an impediment to achieve 
high bandwidths.

The presence of too many base stations was felt as a drawback also at 
the time prior to existence of mobile telephony.  But nowadays there are 
many base stations in densely populated areas, such as stadiums, markets 
and more.  Some times they might even be at a few hundred meters distance.

The choice of placing base stations is a matter of planning and 
agreements with the local Mayor or administrators of the real estate 
(oftentimes without involving the Citizen, but that's an Ethics issue).

The choice of placing base stations might also have to do with the 
technology used in that base station, and about the form of the 
landscape in the area.  It has to do with how waves propagates and reflects.

Active base stations vs intelligent reflecting surfaces, beam forming, 
and other wave propagation improvement tools will not prevent this 
efficient placement, and thus the obtention of higher bandwidths.

BEsides, there is also the parallelism principle: if 1microsecond cant 
be achieved by one light stream then it might be achieved by two 
simultaneous light streams, or 4, and so on.   If it can be achieved by 
n lighstreams then it can be achieved by m (larger than n) THz streams. 
  It seems light is in the range 400-700 THz.

Or maybe that's where 'fully optical' might join fiber to smartphones...

Alex