[Battlemesh] IEEE magazine on FCC lockdown

Jonathan Morton chromatix99 at gmail.com
Wed Apr 20 17:13:04 CEST 2016

> On 20 Apr, 2016, at 17:36, Simon Wunderlich <sw at simonwunderlich.de> wrote:
> Personally, I wouldn't mind a firmware which just locks the radio stuff (and 
> ONLY the radio) so we can get some peace in this discussion. But from the past 
> experience, vendors tend to put all kind of things into the firmware instead 
> of making it small.

I’ve said this before: we need a clean separation of Layer 1 and Layer 2 in wifi.

Layer 1, as everyone here *should* know, is the physical layer.  I place the radio itself here, and in modern wifi chipsets that’s a software-defined radio.  There are some gnarly DSP routines involved here, and I imagine vendors consider those to be sensitive IP.  But that’s fine - once they’re working right, we don’t need to touch them again.  Bundle it in a crypto-signed package with a regulatory database, burn it (or the verification key) into the chipset and lock it down hard.

Job done, the FCC et al should be satisfied; the only people who lose out are the amateur-band folks who want to go beyond the licence-free frequencies.

Layer 2 is the MAC - media-access controller.  This is where rate selection, negotiation for airtime, framing, aggregation, retries, etc happen.  It’s entirely possible to leave much of this up to the host CPU, with just a few specialised buffers and helper functions implemented on the wifi chipset.  It’s also entirely possible to do it all on the chipset, relieving the host of some timing constraints but reducing flexibility for experimentation.

But the MAC functions have nothing to do with the frequency-power emissions of the radio, from a regulatory standpoint.  We need to be able to change the MAC to make wifi better.  With separated layers 1 & 2, we can do that without having to re-certify the radio.

Layers 3 and 4, for completeness’ sake, are where IPv{4,6} and TCP/UDP live respectively.  They are not directly relevant to anything the chipset does; at this level, they are payloads.

 - Jonathan Morton

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