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[4]: But not in Symbian
by oiaohm on Thu 14th Nov 2013 00:16 UTC in reply to "RE[3]: 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.

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.

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.

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

Yes this did disappear in Symbian 9. Also you would not get what was Symbian 8 style past FCC any more. You might be able to get single processor past using arm trusted extensions but the baseband would have to be starting first. Over all it simple to get past regulators with decanted baseband processor with decanted ram. There have been issues with phones sharing baseband and application space.

Yes there is a open source baseband firmware issue is legally using it.

Yes FCC and other regulator approvals are required to transmit to your standard telephone carriers.

Of course this is not a issue when you are your own carrier out side the normal phone network. Understanding baseband to make sim cards is in fact critical to open source GSM stations like openbts.

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