From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bk0-f43.google.com (mail-bk0-f43.google.com [209.85.214.43]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id C338921F1CB for ; Wed, 9 Jan 2013 23:38:03 -0800 (PST) Received: by mail-bk0-f43.google.com with SMTP id jf20so93010bkc.16 for ; Wed, 09 Jan 2013 23:38:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:from:date :x-google-sender-auth:message-id:subject:to:cc:content-type; bh=zgTTHGwpbXTdSWiASrGkTiTYUhLxB2TobsJXPt94cU0=; b=D1GtRVKHmpVZK40XU5YsEdTTVm38T8tVAipRsVlbvlHXhA7iAlXsuvsGy64W7xb0b8 jtdsg9L+z3HEZmt/BtF8qi+xzJAd+xt91Pre6Ne+AXEztgNEf6D+X2v9ftraCM90edLB tARC3lvZAkrtCkk7b3cpaehFs03dpTwI/sF499Suk1em2MgxUmrjC3M+R2t12IEVDQfi AJj0J9EEywfK3otxPGojpMxv2iU33fd/Np/oS8i1zzi1NuTWHN/RsAceC3hFrlGBE6Pr yMBwkEN0LWCJza92T5CHSWOusp9bcj7cSBhHMG9kZeSH3fn+tWLpvDKt4789/z2eZkAU //mQ== Received: by 10.204.147.79 with SMTP id k15mr33693588bkv.55.1357803481407; Wed, 09 Jan 2013 23:38:01 -0800 (PST) MIME-Version: 1.0 Sender: winstein@gmail.com Received: by 10.204.17.146 with HTTP; Wed, 9 Jan 2013 23:37:41 -0800 (PST) In-Reply-To: <1354.1357740450@sandelman.ca> References: <81564C0D7D4D2A4B9A86C8C7404A13DA0801AF@ESESSMB205.ericsson.se> <1354.1357740450@sandelman.ca> From: Keith Winstein Date: Thu, 10 Jan 2013 02:37:41 -0500 X-Google-Sender-Auth: C89EwKCwrTJ3C0KaQUHaTN006BQ Message-ID: To: Michael Richardson Content-Type: text/plain; charset=ISO-8859-1 Cc: "bloat@lists.bufferbloat.net" , "end2end-interest@postel.org" Subject: Re: [Bloat] [e2e] bufferbloat paper X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 10 Jan 2013 07:38:04 -0000 Hello Michael, On Wed, Jan 9, 2013 at 9:07 AM, Michael Richardson wrote: > Have you considered repeating your test with two phones? Yes, we have tried up to four phones at the same time. > Can the download on phone1 affect the latency seen by a second phone? In our experience, a download on phone1 will not affect the unloaded latency seen by phone2. The cell towers appear to use a per-UE (per-phone) queue on uplink and downlink. (This is similar to what a commodity cable modem user sees -- I don't get long delays just because my neighbor is saturating his uplink or downlink and causing a standing queue for himself.) However, a download on phone1 can affect the average throughput seen by phone2 when it is saturating its link, suggesting that the two phones are contending for the same limited resource (timeslices and OFDM resource blocks, or possibly just backhaul throughput). > Obviously the phones should be located right next to each other, with > some verification that they are actually associated to the same tower. This is harder than we thought it would be -- the phones have a tendency to wander around rapidly among cell IDs (sometimes switching several times in a minute). We're not sure if the different cell IDs really represent different towers (we doubt it) or maybe just different LTE channels or logical channels. I understand in LTE it is possible for multiple towers to cooperate to receive one packet, so the story may be more complicated. In practice it is possible to get four phones to "hold still" on the same cell ID for five minutes to do a test, but it is a bit like herding cats and requires some careful placement and luck. Best regards, Keith