From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bifrost.lang.hm (lang.hm [66.167.227.134]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 3005B3B25E; Mon, 27 Jun 2016 16:09:47 -0400 (EDT) Received: from asgard.lang.hm (asgard.lang.hm [10.0.0.100]) by bifrost.lang.hm (8.13.4/8.13.4/Debian-3) with ESMTP id u5RK9gmj003482; Mon, 27 Jun 2016 13:09:42 -0700 Date: Mon, 27 Jun 2016 13:09:42 -0700 (PDT) From: David Lang X-X-Sender: dlang@asgard.lang.hm To: Bob McMahon cc: Dave Taht , make-wifi-fast@lists.bufferbloat.net, "cerowrt-devel@lists.bufferbloat.net" In-Reply-To: Message-ID: References: <1466803464.927322699@mobile.rackspace.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII Subject: Re: [Cerowrt-devel] [Make-wifi-fast] more well funded attempts showing market demandfor better wifi X-BeenThere: cerowrt-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Development issues regarding the cerowrt test router project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Jun 2016 20:09:47 -0000 On Mon, 27 Jun 2016, Bob McMahon wrote: > The ~10K is coming from empirical measurements where all aggregation > technologies are disabled, i.e. only one small IP packet per medium > arbitration/access and where there is only one transmitter and one > receiver. 900Mb/sec is typically a peak-average throughput measurement > where max (or near max) aggregation occurs, amortizing the access overhead > across multiple packets. so 10K is minimum size packets being transmitted?or around 200 transmissions/sec (plus 200 ack transmissions/sec)? > Yes, devices can be hidden from each other but not from the AP (hence the > use of RTS/CTS per hidden node mitigation.) Isn't it the AP's view of the > "carrier state" that matters (at least in infrastructure mode?) If that's > the case, what about a different band (and different radio) such that the > strong signal carrying the data could be separated from the the BSSID's > "carrier/energy state" signal? how do you solve the interference problem on this other band/radio? When you have other APs in the area operating, you will have the same problem there. David Lang > Bob > > On Mon, Jun 27, 2016 at 12:40 PM, David Lang wrote: > >> On Mon, 27 Jun 2016, Bob McMahon wrote: >> >> Hi All, >>> >>> This is a very interesting thread - thanks to all for taking the time to >>> respond. (Personally, I now have better understanding of the >>> difficulties >>> associated with a PHY subsystem that supports a wide 1GHz.) >>> >>> Not to derail the current discussion, but I am curious to ideas on >>> addressing the overhead associated with media access per collision >>> avoidance. This overhead seems to be limiting transmits to about 10K per >>> second (even when a link has no competition for access.) >>> >> >> I'm not sure where you're getting 10K/second from. We do need to limit the >> amount of data transmitted in one session to give other stations a chance >> to talk, but if the AP replies immediatly to ack the traffic, and the >> airwaves are idle, you can transmit again pretty quickly. >> >> people using -ac equipment with a single station are getting 900Mb/sec >> today. >> >> Is there a way, >>> maybe using another dedicated radio, to achieve near instantaneous >>> collision detect (where the CD is driven by the receiver state) such that >>> mobile devices can sample RF energy to get theses states and state changes >>> much more quickly? >>> >> >> This gets back to the same problems (hidden transmitter , and the >> simultanious reception of wildly different signal strengths) >> >> When you are sending, you will hear yourself as a VERY strong signal, >> trying to hear if someone else is transmitting at the same time is almost >> impossible (100 ft to 1 ft is 4 orders of magnatude, 1 ft to 1 inch is >> another 2 orders of magnatude) >> >> And it's very possible that the station that you are colliding with isn't >> one you can hear at all. >> >> Any AP is going to have a better antenna than any phone. (sometimes >> several orders of magnatude better), so even if you were located at the >> same place as the AP, the AP is going to hear signals that you don't. >> >> Then consider the case where you and the other station are on opposite >> sides of the AP at max range. >> >> and then add cases where there is a wall between you and the other >> station, but the AP can hear both of you. >> >> David Lang >> >