SOT: A cellphone tower in space

Jan Panteltje snipped-for-privacy@yahoo.com wrote in news:sj3k3p$aak$ snipped-for-privacy@dont-email.me:

See if I got this right...

SOT means "Semi Off Topic", right?

Or "Sorta On Topic".. Yeah... I like that one better.

On a sunny day (Fri, 1 Oct 2021 00:06:27 -0000 (UTC)) it happened John Doe snipped-for-privacy@message.header wrote in <sj5je3$k4l$ snipped-for-privacy@dont-email.me:

Bingo!

I was taught that maximum distance to GSM tower is about 40km, it is probably shorter for 3,4,5G phones. So, those satellites fly pretty low.

It was originally 35km but is now 120km:

The catch is that the longer range produces a larger cell which limits the number of available cells per given area. So, it only works in lightly populated areas. From a satellite, this wouldn't work until the satellite offers a spot-beam, which should be the same size as the cell. I can't tell if Lynk uses standard cell phone frequencies, but if they do, the satellite will see a huge number of phones as it passes by, which will create impossible levels of RF interference. That's why cell phones are not allowed to be used on airplanes (except for the overpriced airline cellular services such as AeroMobile, Meagafon and OnAir).

lørdag den 2. oktober 2021 kl. 22.42.53 UTC+2 skrev snipped-for-privacy@gmail.com:

GSM is also only rated for 250km/h

If one tries to talk to a base station on the ground from an airplane, the most useful base station connections would be to sites directly below the airplane, where the airplane velocity does not contribute a large component of the Doppler shift. Granted, if one were to try and talk to a longer distance base station further away, the airplane velocity could easily exceed the 250km/hr (135 knot) limit. That would also require a rather large cell size, which isn't going to happen. If anything, the trend in cell sizes is toward small cells.

I didn't want to spoil the discussion, but I don't think anyone is deploying new GSM systems. Most likely, anything new will use LTE. With proposed modifications, it might be possible to make cell phone calls from a supersonic airplane:

"The maximum speed of LTE-R is defined as 500 km/h" "Sequans LTE solutions can be modified to support even ultra high speed (up to MACH 3) profiles." Whether such a system can be made practical or profitable remains to be seen.

søndag den 3. oktober 2021 kl. 03.39.43 UTC+2 skrev snipped-for-privacy@gmail.com:

I'm not sure doppler shift it the issue, but if you a moving at 250km/h and the cells are small the system will have to hand over to the next cell all the time

On Sun, 3 Oct 2021 05:39:51 -0700 (PDT), Lasse Langwadt Christensen snipped-for-privacy@fonz.dk wrote:

Doppler is part of the problem, but timing windows is why there are range limits. The small cell size problem we both mentioned is why I wrote: "That would also require a rather large cell size, which isn't going to happen." It's still possible from the air because from the airplane, one can "see" a huge number of possible (small) cells, any of which are suitable for a handoff. LTE allows multiple simultaneous pre-connections to "neighboring" cell sites where the phone is expected to handoff. My phone shows two neighboring sites using:

(The "Neighbor Cells" section is not shown in the app page sample screen shots shown above). There is a limit to the number of neighboring cells that can be tracked, but I don't know what it might be. It's probably not huge. From the air, I would expect to see large numbers of "neighboring" cells including some from other carriers that demand roaming chargers. That could get messy. Or, if the airplane is flying at a high altitude, it might only see those near the horizon. That's because the vertical beam pattern of most cell site antenna is not very wide. Directly above the cell site antenna, there might not be any signal. We have a local version of the vertical beamwidth problem in my area. As one drives up and down the mountain roads, there are places near the mountain peaks and high roads where I can see the cell site with binoculars, but the signal strength and SNR are terrible.

Typical 2.1GHz cellular antenna spec sheet:

Vertical beamwidth (-3dB) is about 5 degrees. A 700MHz antenna is a bit wider at about 12 degrees: Looks like most or all of the signal goes to the horizon, with nothing overhead. That's not exactly what one might want for a cell phone in an airplane.

Nice idea, but I don't think it's going to work.

Hello, Jeff. That's like trying to pick up a 5 MW TV station at the tower base. The transmitter had a +20dB test port to monitor its output at the site.

VOIP doesn't work on Hughesnet's kA (55 GHz) satellite internet because of both issues. The other end hears a very nasty and choppy message. They brag that their genius engineers can make it work, but of course only at their much higher price. There are many websites that time out, due to the high orbit of these birds.

Same with cell towers. A public exposure calculation UNDER the tower is required for licensing. For example, Pg 14:

Well, they claim they support VoIP:

for $20/month for the first 6 months. I think it goes up to $30/month after that.

I never could get HughesNet to do anything right. I switched my customers to Viasat. I think it's now the same price as HughesNet:

I only have one customer that is using Viasat Voice. I don't know if it's still working as advertised. I haven't heard any complaints in about 18 months, so it either works, or they gave up on it.

I've tried to use other VoIP services on Viasat such as Skype, Future-Nine.com, Google Voice, Zoom (audio only), and some others. In general, they all work reasonably well as long as the upstream bandwidth isn't clogged with traffic. If you're doing Microsoft updates while trying to talk, forget it. The main advantage to paying extra for Viasat's voice service is that voice traffic does not count for the monthly bandwidth limit (FAP). You can exceed your bandwidth limit, find yourself streaming videos VERY slowly, but can still talk on the phone reasonably well. By "reasonably well", I mean both parties can understand each other, but the delay is still there, and there will be some random dropouts and garble.

Note that Viasat has a 6 month contract while Hughesnet demands 24 months.

It also requires extra hardware, so I would have to lose the prepaid VIOP account that I have. I can use it as data from my cell phone, when there is a signal. Hughesnet has horrible rain fade, and a lot of the time I can't get enough bandwidth to stream WSM radio. without long dropouts.

They also scam people by saying that you can rent the equipment rather than buy t. I had an excellent credit rating, and had just paid off my Grand Caravan. I had over $10 in my Direct Express account, but they told me that I was too high risk so I had to fork over $400 for the crap. I'm not adding anything to their crap business. I have nine months left. I am hoping the county has installed Fiber to my subdivision by then. If not, I may just forget about going online.