From owner-freebsd-wireless@FreeBSD.ORG Wed Aug 27 23:47:04 2014 Return-Path: Delivered-To: freebsd-wireless@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 3632D25D for ; Wed, 27 Aug 2014 23:47:04 +0000 (UTC) Received: from mail-qg0-x230.google.com (mail-qg0-x230.google.com [IPv6:2607:f8b0:400d:c04::230]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id E9F303C0E for ; Wed, 27 Aug 2014 23:47:03 +0000 (UTC) Received: by mail-qg0-f48.google.com with SMTP id z107so21572qgd.7 for ; Wed, 27 Aug 2014 16:47:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=9Wfi26d0CJ+k+XQFLSFYkIbFaRt757HnBqxgGZCXS1E=; b=Gx6orIcIHs5qHzXDJ2Ca53082cXdsN6p7PAgVfl6hIVP/lBhyyGx42Xr2dyU8pQ1KD 1JVdKYCITnhauowKVtm+71T1vwMvgax5/zgcIv89ELi/zrQIjyy5jBzVxAR172Gq1foE B5ghv0O4a/kNhlbEI+M+YVboE6l12XjjyweEkviw0vO0z3KWKi5PLt6p7egFJaY5w0VB gg7vpojPPSNE6ma4WeHt6cEL6eqK2tNGhLqcqYJT7OxYr3T9qx2TYCYNBjmN88wcblqj 8OAXf4TgRtyAZazohH9EswtoJ2ieTrlshr3KySgHjq8533Kl0lWuk9tAhxVzfxUfm+qj WrdQ== MIME-Version: 1.0 X-Received: by 10.224.86.5 with SMTP id q5mr794078qal.36.1409183222516; Wed, 27 Aug 2014 16:47:02 -0700 (PDT) Sender: adrian.chadd@gmail.com Received: by 10.224.39.139 with HTTP; Wed, 27 Aug 2014 16:47:02 -0700 (PDT) In-Reply-To: <53FE6BDC.5030306@bartk.us> References: <53FE5CF4.1000901@bartk.us> <53FE6513.8040107@bartk.us> <53FE6BDC.5030306@bartk.us> Date: Wed, 27 Aug 2014 16:47:02 -0700 X-Google-Sender-Auth: 7lqAVdUe13XedzS-Q7uel_yJqZs Message-ID: Subject: Re: FreeBSD TDMA: Legalizing 440MHz 802.11 modems From: Adrian Chadd To: Bart Kus Content-Type: text/plain; charset=UTF-8 Cc: "freebsd-wireless@freebsd.org" X-BeenThere: freebsd-wireless@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: "Discussions of 802.11 stack, tools device driver development." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 27 Aug 2014 23:47:04 -0000 On 27 August 2014 16:38, Bart Kus wrote: > I'm guessing the chip generates its own internal clocks from an external > reference. Can that PLL be slowed down ahead of timers overflowing? > Hopefully the PCI clock is generated independently. Yeah, that's what you're slowing down - you program the PLL. The PCI clock is generated separately. > Also, I think Mikrotik implements narrower bands by dropping subcarriers > instead of slowing down their symbol rates. I'll try to get a good spectrum > picture of their 5MHz mode tonight. Keeping the subcarrier symbol rates > relatively higher might offset some analog droops, at the cost of OFDM skirt > sharpness. Hey cool, if they're doing that then I should likely go digging for the PHY documentation for the AR5414 and find out. > Also, a slight correction. I think you meant the subs are 312.5kHz wide, > which would result in a 200kHz emission having 3.125kHz wide subs. Or, > perhaps more realistically, running at 1/128th the speed, 2.44140625kHz > wide. How can you not love a number like that? :) Someone else can do better math, I'm busy doing non-wifi at the moment. :) But, it really is 20MHz / 64 carriers == each subcarrier width. > Does the project have a map of all these clocks + timers which might need > tweaking for spectrum reduction? I know you can't cite original Atheros > docs, but perhaps there's been derivative documentation works created? Not at the moment I'm afraid. I haven't really dug into that level of detail. I documented what's needed for 5 and 10MHz modes. However - there's an analog filter that I don't know if it's programmable or not. It's used for both transmit and receive filtering. I know on these chips it can do 5/10/20/40 but I don't know if it's an arbitrary width. -a