Return-path: Received: from mail2.candelatech.com ([208.74.158.173]:52402 "EHLO mail2.candelatech.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750815AbdBKR5c (ORCPT ); Sat, 11 Feb 2017 12:57:32 -0500 Message-ID: <589F50B8.4020609@candelatech.com> (sfid-20170211_185739_161817_D8F1FA52) Date: Sat, 11 Feb 2017 09:58:16 -0800 From: Ben Greear MIME-Version: 1.0 To: Adrian Chadd , Sebastian Gottschall CC: "linux-wireless@vger.kernel.org" , ath10k Subject: Re: VHT 160Mhz and nss related config. References: <0082a9e3-83f3-9bc3-af43-b890b91cfd93@candelatech.com> In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 02/10/2017 08:37 PM, Adrian Chadd wrote: > On 10 February 2017 at 20:22, Sebastian Gottschall > wrote: >> i really can't believe this. if this is true the 160 mhz mode would not >> make any sense. >> the maximum tx / rx rate for 4x4 vht80 and 2x2 vht160 is identical. so >> vht160 would not increase performance in any way > > Well, if it can also do 2x2 MU-MIMO at 160MHz then it can be a > perfectly fine STA to a 4x4 160MHz MU-MIMO chip that can actually > transmit 2x2 rates to different MU-MIMO peers. > > That's the outstanding question I have - is it like, 2x2 MU only, or > is it say, 2 concurrently different spatial stream 2x2 MU? Ie, can you > have 2 peers, different VHT spatial groups (or 4 peers, 1 spatial > group each) all going at the same time? > > I'm .. not even sure how you're supposed to cleanly negotiate that you > can do 4NSS in VHT80 but 2NSS in VHT160 to a peer... that only makes > sense if you're doing lots of 1NSS and 2NSS MU-MIMO peers.. I think using the max-rx-rate logic might could imply this, but I am not sure many drivers fill this out properly. Looks like a mess waiting to happen to me. Even if you can do 1x1 160Mhz MU-MIMO to two stations, and I am not certain you can since in 80Mhz you can only do a 1x1 and a 2x2 (not two 2x2). So, from what I know currently, 80+80 is not that useful on the 9984 NIC... Thanks, Ben > > > -adrian > >> >> Am 10.02.2017 um 23:58 schrieb Ben Greear: >>> >>> So, it appears that the ath10k QCA9984 4x4 160Mhz chip can do 4x4 MIMO at >>> VHT80, but >>> it can do only 2x2 MIMO at VHT160/80+80. >>> >>> When configuring a peer, we need to tell the firmware the number of >>> spatial streams >>> of the peer at VHT160 and at VHT80 and lower. They are not the same >>> value. >>> >>> I cannot think of any standard way to get this information based on VHT >>> capabilities >>> and such. Currently, one could just assume VHT160 NSS is 1/2 of the VHT80 >>> NSS, >>> but that is unlikely to be true for all vendors. >>> >>> Any ideas? >>> >>> Thanks, >>> Ben >>> >> >> >> -- >> Mit freundlichen Grüssen / Regards >> >> Sebastian Gottschall / CTO >> >> NewMedia-NET GmbH - DD-WRT >> Firmensitz: Berliner Ring 101, 64625 Bensheim >> Registergericht: Amtsgericht Darmstadt, HRB 25473 >> Geschäftsführer: Peter Steinhäuser, Christian Scheele >> http://www.dd-wrt.com >> email: s.gottschall@dd-wrt.com >> Tel.: +496251-582650 / Fax: +496251-5826565 >> >> >> _______________________________________________ >> ath10k mailing list >> ath10k@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/ath10k > -- Ben Greear Candela Technologies Inc http://www.candelatech.com