What’s the fundamental reason why SOTA modems are more challenging than microprocessors for Apple? Intuitively I would’ve guessed the opposite was true.
A long time ago i used to work at a company that made mobile phones. This was in the days before smartphones, and 3G was a shiny new toy. Back then, many companies would implement the protocols in the phone firmware, as opposed to today where chips usually offload a large part of this.
Despite doing our best to implement the GSM Standards[1], the thing at the time was 19,000 pages long, and one of our biggest issues was that our protocol stack would work well with most cell towers, there would always be some carriers that had configured their network just a tiny bit different, and we had to tweak our software to match that.
At the time, there were 5 major vendors of GSM cells, and none of them had intepreted the standards identically, so we would also have tweaks to allow for different vendors.
I don't remember exactly how many people we employed in our protocol division, but it was more than 100.
I do remember that implementing the first version of bluetooth took 19 people almost 2 years, and that, at the time, was a much simpler protocol (it probably still is). I can only imagine the "horrors" that have gone into 4G and 5G since then.
These days, all of the above problems are "solved" by simply installing a chip. Qualcomm handles any vendor hardware communication issues, and they're probably "big enough" to also have an impact in the opposite direction, making for a more streamlined protocol landscape.
This. The standard is also truly horrible to read. It's not really designed to be read, as much as it is an after-the-fact description of what somebody has already done.
To the point that testing against a very wide variety of base-stations (and the multitudinous variety of configuration options in those base-stations) is mandatory.
If I ran a company where someone tried to release a 19K page spec I'd keep firing people until someone could produce a spec that I could actually review and sign off on, that could also still be reproduced in working technology. How does this kind of thing fly at all?
Analog is hard, and quite different from digital.* And then you have to work around the patent thicket in an already difficult domain.
* Nowadays clock speeds are so fast that you have a lot of analog things to worry about with all these high speed serial lines and on the chips themselves. But the domain constraints are in general simpler, with recovery and reconstruction opportunities available due to things like how you structure your protocols. The same is true in radio (came from radio, actually) but when you have a device operating at arbitrary and continually changing orientations, with all sorts of unknown environments outside you get all sorts of unpredictable multipath, loss, ringing and innumerable other problems to deal with.
> Modem chips are trickier to make than processing chips because they must work seamlessly with 5G wireless networks, as well as the 2G, 3G and 4G networks used in countries around the world, each with its own technological quirks. Apple microprocessors run software programs designed solely for its iPhones and laptops.
I would guess lack of expertise? Apple purchased PA Semi a while ago and the team went on to work on their processors. Have they purchased a company specialized in mixed-signal circuit design? That's one of the key differences, a modem contains a lot of analog circuitry and analog is very different from digital.
> Have they purchased a company specialized in mixed-signal circuit design?
They bought Intel's modem business, which was originally part of Infineon.
Intel had working 4G modems which were only a year or two behind Qualcomm to the point where most users wouldn't notice. But they never seemed to manage to make the jump to 5G.
PA Semi was 2008 or so, and Intrinsity in 2009-10. In both cases they came with (more or less) working products, an existing relationship, and coherent engineering teams with an active development pipeline. Its fair to say the intel modem folks have a lot of that individually, but Im not clear how much of the whole transferred over.
Edit: and the HwEng org already had established VLSI, SoC, and PCB groups shipping products before those acquisitions happened.
IMO cellular network protocols are remarkably challenging to understand. Then you add to that various quirks of certain network operators, optimal power consumption and throughput, security.
They probably want their design to work as well as the baseline one, and globally.
From the article: "Modem chips are trickier to make than processing chips because they must work seamlessly with 5G wireless networks, as well as the 2G, 3G and 4G networks used in countries around the world, each with its own technological quirks. Apple microprocessors run software programs designed solely for its iPhones and laptops."
Also: "[Apple's modem] chips were essentially three years behind Qualcomm’s best modem chip. Using them threatened to make iPhone wireless speeds slower than its competitors."
I wonder what some of the regional quirks are, instances where the implementation strays from the standard, but if you don’t do it in quirks mode, you can’t connect to the cellular connection or calls will not go through etc.
A sort of woops, non-strict YAML moment, but in telecommunications.
The Apple CPU's architecture is already known (ARM). To iterate from there is probably easier than designing a modem without the basics already designed and ready to go.
Apple also has a pretty robust ability to dictate to their developers how and what they must do to run on MacOS, and they produce the compiler and toolchain as well. They seem to do a lot less shimming and other compatibility work on behalf of developers. Modem doesn't work that way, there's tons of existing, immutable hardware across the world with its own quirks and edge cases, all of which you have to support seamlessly.
>Intuitively I would’ve guessed the opposite was true.
It wouldn't be intuitive if people actually have some basic understanding of how modern wireless network works. Unfortunately even those who work on Hardware, CPU design and embedding programming dont understand that. Let alone 99.99999999% of HN.
8fingerlouie|2 years ago
Despite doing our best to implement the GSM Standards[1], the thing at the time was 19,000 pages long, and one of our biggest issues was that our protocol stack would work well with most cell towers, there would always be some carriers that had configured their network just a tiny bit different, and we had to tweak our software to match that.
At the time, there were 5 major vendors of GSM cells, and none of them had intepreted the standards identically, so we would also have tweaks to allow for different vendors.
I don't remember exactly how many people we employed in our protocol division, but it was more than 100.
I do remember that implementing the first version of bluetooth took 19 people almost 2 years, and that, at the time, was a much simpler protocol (it probably still is). I can only imagine the "horrors" that have gone into 4G and 5G since then.
These days, all of the above problems are "solved" by simply installing a chip. Qualcomm handles any vendor hardware communication issues, and they're probably "big enough" to also have an impact in the opposite direction, making for a more streamlined protocol landscape.
[1]: https://www.etsi.org/standards/get-standards#page=1&search=&...
grandinj|2 years ago
To the point that testing against a very wide variety of base-stations (and the multitudinous variety of configuration options in those base-stations) is mandatory.
sixstringtheory|2 years ago
gumby|2 years ago
* Nowadays clock speeds are so fast that you have a lot of analog things to worry about with all these high speed serial lines and on the chips themselves. But the domain constraints are in general simpler, with recovery and reconstruction opportunities available due to things like how you structure your protocols. The same is true in radio (came from radio, actually) but when you have a device operating at arbitrary and continually changing orientations, with all sorts of unknown environments outside you get all sorts of unpredictable multipath, loss, ringing and innumerable other problems to deal with.
scrlk|2 years ago
In the infamous words of Bob Widlar [0]: "Every idiot can count to one."
[0] For those who don't recognise the name, Widlar was a legendary analog designer - along with Jim Williams and Bob Pease.
https://en.wikipedia.org/wiki/Bob_Widlar
vdfs|2 years ago
kylehotchkiss|2 years ago
lbourdages|2 years ago
kalleboo|2 years ago
They bought Intel's modem business, which was originally part of Infineon.
Intel had working 4G modems which were only a year or two behind Qualcomm to the point where most users wouldn't notice. But they never seemed to manage to make the jump to 5G.
donavanm|2 years ago
Edit: and the HwEng org already had established VLSI, SoC, and PCB groups shipping products before those acquisitions happened.
wyldfire|2 years ago
They probably want their design to work as well as the baseline one, and globally.
staticautomatic|2 years ago
tech-historian|2 years ago
Also: "[Apple's modem] chips were essentially three years behind Qualcomm’s best modem chip. Using them threatened to make iPhone wireless speeds slower than its competitors."
justusw|2 years ago
A sort of woops, non-strict YAML moment, but in telecommunications.
bsder|2 years ago
Getting your modem "certified" with a carrier network requires an absolutely Byzantine set of testing that would stagger your imagination.
And the carriers all like it very much since it enforces their monopoly position just like the old "You must use Ma Bell phones on the Ma Bell lines."
testrun|2 years ago
secabeen|2 years ago
ksec|2 years ago
It wouldn't be intuitive if people actually have some basic understanding of how modern wireless network works. Unfortunately even those who work on Hardware, CPU design and embedding programming dont understand that. Let alone 99.99999999% of HN.
Sporktacular|2 years ago
unknown|2 years ago
[deleted]
ReptileMan|2 years ago
CamperBob2|2 years ago