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Comment by biomcgary | Hacker News Reader

My wife hikes in Western Colorado quite a bit and has helped rescue 3 parties over the past 4 years. In one case, a young woman (an ER nurse) was in dire distress for no apparent reason and fading quickly (in retrospect possibly COVID related sequela). Initially, emergency responders were going the route of a land-based rescue, but the Mini allowed the urgency to be communicated more clearly. The helicopter touched down on a scree field (but couldn't land) while my wife and a couple others helped the EMT load her. Docs said that she had less than an hour or so before long-term consequences or death.

Any emergency beacon is better than none, but two-way communication can be a literal lifesaver. I hope that the Starlink system is eventually linked into our 911 infrastructure and available to anyone with an LTE phone regardless of carrier.

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Two-way communication is important to prevent false positive emergencies, too. There have been several times I've used my inReach to message that I'm going to miss my planned check-in time, but everything is OK - no need to alert SAR.

Also to communicate on-the-fly decision-making to inform potential SAR - "I'm making good time, going to head up this extra peak before continuing the planned route."

I'm happy to have a cell phone backup to the inReach, but I don't see this Starlink offering as a replacement. That goes double if you're out in winter. Phone batteries aren't great in the cold.

Phone batteries are fine down to -20C and usually are functional to about -30C.

You should have no problem with that anywhere in the world as long as you keep it in an inner pocket. Perhaps pack wired earphones just in case you need to make a long call while keeping the phone itself warm.

Notably the battery should not be charged below about 5C. If you do, it will be permanently damaged.

> Notably the battery should not be charged below about 5C. If you do, it will be permanently damaged.

This depends on the specific battery chemistry. The BMS should prevent the charging scenarios which would damage the battery. For some it's 0C not 5C. Some can handle charging below 0C.

I have never seen a phone BMS that prevents charging due to undertemperature

Isn't that a stock feature on pretty much every chip? I mean, if you've got a temperature sensor for overtemperature protection, including undertemperature protection is trivial.

Even the cheapest chips from TI and ST seem to include it. And modern cell phones often advertise extra-fast 20W+ charging, so I doubt they're using the cheapest chips.

I can already imagine freezing to death while my phone refuses to charge because it wants to protect its precious battery

My iPhone refuses to charge when too hot or too cold.

Respectfully, I don't know about that. I wouldn't trust it if my life was on the line. I go for walks and bike rides when it's -25C to -30C air temperature (before windchill) and I've had old samsung galaxies and newer pixels both crash if I take them out to take a photo. I presumable due to voltage dip.

This is exactly the reason why I'm sticking with the CAT S6x series phones and willing to put up with mediocre performance/features, as far as smartphones go.

They've been the only ones that don't just turn off in really cold temperatures, even without babying them in warm pockets.

The general ruggedness is also pretty good to amazing, depending on how fragile your previous phones were. For example: it survived a ~10 meter (32ft) drop on rocks, whereas everyone was convinced it was done for.

Do you have one of the newer models with the thermal camera? I was very interested in seeing how well that works.

Yes, currently the S62 Pro. What would you be interested in knowing?

To be honest I first thought it would be a gimmick, but being able to see heat / rough temperature degrees has proven itself quite useful.

But you don't really realize it until you have it available. It's kind of like having another sense available to you.

Random examples of where it was useful:

- finding shitty chargers/electronics which were really hot while doing nothing -> wasted power

- spotting a water leak before it was visible (think cold spot in the middle of the ceiling)

- checking car tire alignment (one side hotter than the other)

- finding buried hot water pipes

- finding where cold air is leaking in during winter

- spotting damp areas

and probably others that I'm forgetting right now

Thank you for tkaing the time to repsond to me and giving me a good breakdown!

Do people in those areas need phone cases that are insulated to retain heat?

I don't know if those exist. I imagine if you are a linemans or working in the oil field you might have a rugged phone/radio or leave it in the truck cab.

To someone that lives in a place where we just had an entire summer of 40°C and higher, -25°C sounds like Antarctica, or Mars. And you do that on a bicycle? Clearly, you must be an alien!

Actually, an Italian guy is about to start a bike hike to the South Pole. This is the first link I found to a page in English about it https://aminhacorrida.com/en/omar-di-felice-comes-back-to-at...

Thanks for the laugh. I send my australian friends photos of snowbanks and iced up hair. The hardest part if having a plan if something goes wrong, e.g. I'm not changing a tire or fixing a chain at that temperature. I've been tempted to wait on a bus at a slow train crossing. At least cold I can layer up with and move. I'd die at +40C.

> -25°C sounds like Antarctica, or Mars

I had that in my hometown in eastern France at 800m altitude, a town a few km away has a record of -41. -15/-20c was almost a yearly occurance when I was a kid

Yeah having a newer phone helps.

Once I was stuck with a ridesharing car opened and off in -20C because my old samsung s8 throttled so bad I couldn't even reboot it. It was completely unresponive with the flashlight still on discharging it even faster.

I couldn't leave the car too, being responsible for damages during the rent.

After a bit of time I remembered that to force shut down newer androids you have to hold volume down and power. Why would they not keep it as a long press is beyond me.

my iphone 6s and 12 pro beg to differ. both saw serious drops in battery in pretty normal 10-15F chicago winters while I was outdoor ice skating or even just going for a long walk with the phone in my pocket.

iPhones often turn off around -20c with a warning about temperature, it happens to me every time I travel to Lapland in the Winter.

My last two phones (Xiaomi 9T and Pixel 7) have struggled below about -5C. They still work but the battery drops very quickly so you can't rely upon them. Keeping them in an inner pocket works but I then take them out and see the battery drop. The sudden temperature change might not help there.

Samsung Galaxy XCovers have user replaceable batteries, so can atleast keep spare(s) warm.

> I hope that the Starlink system is eventually linked into our 911 infrastructure and available to anyone with an LTE phone regardless of carrier.

If Starlink's solution is really completely unmodified LTE, I'd expect 911 calls to work regardless of being a T-Mobile subscriber, just like for existing terrestrial networks (where you can dial 911 even if your carrier does not have signal in a given location, or even entirely without a SIM card).

I don't think LTE can cope with the extreme doppler shift present when the other end is a satellite in LEO

I don't know how much I'm allowed to say, but at least part of what they're doing is normal Cat-1 LTE that any modem that supports it will be able to pick up

How are they accounting for the presumably very high timing advance?

As far as I understand, the timing advance only matters to compensate for differences in distance/latency between different devices (i.e. to avoid uplink transmissions to talk over each other on the same frequency).

The satellites can correct for "global" latency themselves (unless there are higher-level parts of the LTE/E-UTRA radio protocol that can't tolerate such long latencies, e.g. ARQ timers).

For GSM as a half-duplex technology, there's also the matter of devices not being able to transmit and receive at the same time, but I believe the same principle applies: As long as the timing differences between different devices in the same spot beam isn't too large, that's something the satellites could globally correct for.

The same probably applies for doppler corrections.

The shift is actually not that extreme in LEO (a few KHz at most).

And couldn’t the satellites mostly adjust for that, given that the relative doppler shift should be pretty constant between mobiles in the same spot beam?

LTE can't even handle a high speed train. 1 kHz causes significant degradation

https://eudl.eu/pdf/10.1007/978-3-319-66628-0_41

doppler shift is not a constant for a stationary observer from Earth.

Obviously it's not constant, but if it's uniform (enough) within the footprint of a single spot beam, the satellites can adjust for the global component both in their transmitter and receiver, and the mobile devices only have to compensate for (or tolerate) their local difference from that.

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