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Subject: Re: [Make-wifi-fast] [PATCH v3 3/6] mac80211: Add airtimeaccounting
 and scheduling to TXQs
To:     "David P. Reed" <dpreed@deepplum.com>, David Lang <david@lang.hm>
Cc:     Dave Taht <dave.taht@gmail.com>,
        Rajkumar Manoharan <rmanohar@codeaurora.org>,
        Make-Wifi-fast <make-wifi-fast@lists.bufferbloat.net>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        ath10k <ath10k@lists.infradead.org>,
        Ben Greear <greearb@candelatech.com>,
        Felix Fietkau <nbd@nbd.name>
References: <1542814135.446217011@apps.rackspace.com>
From:   Sebastian Gottschall <s.gottschall@newmedia-net.de>
Message-ID: <eb65f613-23b0-737f-fabe-851e6c1abbdd@newmedia-net.de>
Date:   Wed, 21 Nov 2018 21:58:52 +0100
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its not bluetooth. active tire pressure control systems are based on 433 
mhz in most countries. in the usa its 315 mhz

Sebastian

Am 21.11.2018 um 16:28 schrieb David P. Reed:
> Really? Tires are Bluetooth? I don't think mine are, but now I want to figure out how that works. 1600Chips/sec is 600 microseconds per chip. They spin at up to, say, radial rates that are a 100 revs/sec and thus take maybe 10 msec. to travel 30 cm. How much warble in a chip frequency is there?
>
> Ok, maybe they only need to work when the car is stopped.
>
> I would design a tire pressure system that sends, maybe, 10 bits per second, at most. Or calibrate the sensor to produce 1 bit, and use the car metal frame to carry the signal to the computer as a single bit. A very slowly varying sensor can be sensed without needing a battery, by using some passive, tuned circuit.
>
> Bluetooth is way overkill, but cheap. I doubt it works well in the application, though.
>
> -----Original
> From: "David Lang" <david@lang.hm>
> Sent: Mon, Nov 19, 2018 at 9:12 pm
> To: "Dave Taht" <dave.taht@gmail.com>
> Cc: "Dave Taht" <dave.taht@gmail.com>, "Rajkumar Manoharan" <rmanohar@codeaurora.org>, "Make-Wifi-fast" <make-wifi-fast@lists.bufferbloat.net>, "linux-wireless" <linux-wireless@vger.kernel.org>, "ath10k" <ath10k@lists.infradead.org>, "Ben Greear" <greearb@candelatech.com>, "Felix Fietkau" <nbd@nbd.name>
> Subject: Re: [Make-wifi-fast] [PATCH v3 3/6] mac80211: Add airtimeaccounting and scheduling to TXQs
>
> On Mon, 19 Nov 2018, Dave Taht wrote:
>
>>> I'm not sure if this was a fluke or not, but at Starbucks recently I sat outside,
>>> right next to their window, and could not scan their AP at all.  Previously, I sat
>>> inside, 3 feet away through the glass, and got great signal.  I wonder what that was
>>> all about!  Maybe special tinting that blocks RF?  Or just dumb luck of some sort.
>> Ya know, I could definitely see a market for a material like that! I'd
>> like it for my car, so bluetooth wouldn't escape.
> That would break your tire pressure sensors (each car is rolling around
> broadcasting 4 unique bluetooth IDs, not hard to track)
>
> David Lang
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