Linked by Thom Holwerda on Tue 12th Nov 2013 23:06 UTC
PDAs, Cellphones, Wireless

I've always known this, and I'm sure most of you do too, but we never really talk about it. Every smartphone or other device with mobile communications capability (e.g. 3G or LTE) actually runs not one, but two operating systems. Aside from the operating system that we as end-users see (Android, iOS, PalmOS), it also runs a small operating system that manages everything related to radio. Since this functionality is highly timing-dependent, a real-time operating system is required.

This operating system is stored in firmware, and runs on the baseband processor. As far as I know, this baseband RTOS is always entirely proprietary. For instance, the RTOS inside Qualcomm baseband processors (in this specific case, the MSM6280) is called AMSS, built upon their own proprietary REX kernel, and is made up of 69 concurrent tasks, handling everything from USB to GPS. It runs on an ARMv5 processor.

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RE[5]: But not in Symbian
by fuckregistration on Thu 14th Nov 2013 08:54 UTC in reply to "RE[4]: But not in Symbian"
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"But anyway, how does that matter? One processor or two, the baseband firmware is closed.

How does it matter is in fact the critical question. If everything is in the one processor and their is a breach in any part the complete system could be breached.

Now some phones will be more safe than others.

The application part is completely irrelevant when it comes to the telephony functionality.
The microphone and speaker are connected to the BB processor.
A breached BB has the effect of somebody else listening to your calls, reading your SMS.
Nobody cares about the appliation side.
The stuff on the application processor is just a PDA, if you have a modem in the same case does not matter.

Like baseband and gps can be sharing same processor/memory for their baseband operations. Great for emergency services and person tracking.

Symbian 8 loads the baseband firmware. So the baseband firmware is a driver under Symbian 8.

That's just your definition, nothing accepted by the general public.

So the old Symbian 8 was a Application Processor with a Software-defined radio connected. Basically a PC does not cease to be a PC because you connect a Software defined radio or win-modem either.

Those phones do the demodulation in a DSP which is connected to the (BB-) processor.
The modulation is even done without the DSP involved.
Your definition of a SDR is different than the definition of the rest of the world.

What defines if it a baseband processor or an application processor is what starts first. Symbian 8 devices it is Symbian 8.

Again, just your gentleman definition.

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