From owner-freebsd-wireless@FreeBSD.ORG Thu Dec 1 07:15:59 2011 Return-Path: Delivered-To: freebsd-wireless@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 433E51065673 for ; Thu, 1 Dec 2011 07:15:59 +0000 (UTC) (envelope-from hapvbk@yahoo.co.uk) Received: from nm8.bullet.mail.ukl.yahoo.com (nm8.bullet.mail.ukl.yahoo.com [217.146.182.249]) by mx1.freebsd.org (Postfix) with SMTP id 85B5E8FC14 for ; Thu, 1 Dec 2011 07:15:58 +0000 (UTC) Received: from [217.146.183.182] by nm8.bullet.mail.ukl.yahoo.com with NNFMP; 01 Dec 2011 07:01:33 -0000 Received: from [77.238.184.67] by tm13.bullet.mail.ukl.yahoo.com with NNFMP; 01 Dec 2011 07:01:33 -0000 Received: from [127.0.0.1] by smtp136.mail.ukl.yahoo.com with NNFMP; 01 Dec 2011 07:01:33 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.co.uk; s=s1024; t=1322722893; bh=N9SqNvW0vQ5hif7iOeaHH2jIuC8EU9tTddxiq/+jKLg=; h=X-Yahoo-Newman-Id:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Message-ID:From:To:Cc:Subject:Date:MIME-Version:Content-Type:X-Priority:X-MSMail-Priority:Importance:X-Mailer:X-MIMEOLE; b=Ah2kA4LWalAYJW+3xLS2WMq4mhwbsDLg9GYFIvljQ57Sf5UebkzEc4Z/qRaXeACErJNj2bcN4jS/1zGd8tKG+MX3yoE+am3xTrgr/hGTe1lm2FS+HgnJeJcMQqK0+Zo/xCjWlWHDBzyQJ9k72/vidoXrx1ReuwKUhpj7VhlNJDQ= X-Yahoo-Newman-Id: 598653.56199.bm@smtp136.mail.ukl.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: HdAK7D0VM1nju30lXuU9AuKM8Fv7BjEvffKkPt6YiFWtlNF tpG3jaNIY_QvJ3gg4ZF6yXfuywBEPv5Eow2Cq0yRaM3ZN0XYJZw.u_30tdZ8 WEqx0l4vdLpOGHi7kklSNzKLDuxRNC.D5ZJ1pmIPUP8bQAEOFdnyeWFRPQU5 XjIjjQCXwR15C9LGraPdr0i9_46Q2vlW7ksTmI8npGraIp19ps8187cMq7nA 7xCBfjaDAS6d4psEBMxqJauBIvbWSVxU2zmE06Ujpj1sYtLPVHdWIWjjL00h .8XJ0nUMe2zmhWlCbtTld2q7a_njoR1xsnVPJVXS.rc309wbe1_wqzltqgii 35H01CDuIGdNW4ZOgJ85cpP0rgW5QeHLjFzjjJINVrZhfm.2BskwPtPdmoZx cgv3_.7TTQAkLI2s4bhgDJqQ4WuWrfuyJwgSmd_kZgC9B X-Yahoo-SMTP: xBpCc9iswBApASleyiIs9lcZMA-- Received: from PC (hapvbk@66.11.191.2 with login) by smtp136.mail.ukl.yahoo.com with SMTP; 01 Dec 2011 07:01:33 +0000 GMT Message-ID: <214354BF8661405A81ABD036DEB3D0A2@PC> From: "Viet-Ha Pham" To: Date: Thu, 1 Dec 2011 02:01:30 -0500 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 15.4.3538.513 X-MIMEOLE: Produced By Microsoft MimeOLE V15.4.3538.513 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: Subject: Wifi througput test issue X-BeenThere: freebsd-wireless@freebsd.org X-Mailman-Version: 2.1.5 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: Thu, 01 Dec 2011 07:15:59 -0000 I have posted this to freebsd-net mailing list. I repost it here. Thanks = for your attention.=20 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D Hello, I am doing some throughput measurement for Wifi network. I am using = jperf/iperf to generate traffic (at the transmitter) and measure the = throughput (at the receiver). The transmitter and receiver are running = FreeBSD 8.2, using CM9-GP as the Wifi NIC. We are testing AWGN channel. = So, the transmitter and receiver are connected by cables, txpower on = both sides is set lower than the max (ranging from 0 to 10), AWGN noise = is injected in the middle of the cable.=20 We measure the maximum throughput at each transmission rate. Transmitter = is a STA, receiver is an AP. We fix the unicast rate at the transmitter = to 54 Mbps (using "ifconfig ... ucastrate" command). The packet size is = set to 400 Bytes, UDP protocol is used and the transmit bandwidth is set = to 30 Mbps in order to flood the transmission channel (to push it to its = limit). At first, at the receiver (AP) the measured throughput is about = 12 Mbps. Then I fix the unicast rate at the receiver (using ifconfig = again) to 54 Mbps. The measured throughput increases to 20 Mbps. I set = the unicast rate at the receiver to autoselect again, the throughput is = still 20 Mbps.=20 When I switch the rate at the receiver, there are multiple message = displayed on the screen of the transmitter: "wlan0: = ieee80211_new_state_locked: pending RUN -> AUTH transition lost". This = message is repeated for many times (at least 20).=20 I repeated the test with all transmission rates, change the packet size = and still observe the same thing: a throughput improvement of about 30% = is observed when I switch the unicast rate at the receiver and the = improvement is still there when I switch the unicast rate back to = autoselect. The same thing is observed in modes a and g. The same thing = is observed if the unicast rate at the receiver is set different from = the unicast rate at the transmitter.=20 This issue happened even when no noise is added. The objective of this = test is to measure the maximum throughput at each noise level for each = transmission rate. So we fix the rate, vary the noise and repeat the = procedure for all transmission rates.=20 I spent time to look at the kernel source codes but I did not find a = solid answer for this. Please help me to identify the problem and the = answer.=20 My question is:=20 1. Why do I have that throughput improvement when I switch the rate like = that?=20 2. Is it a bug in the driver?=20 3. What does the error/infor message on the transmitter mean?=20 Thank you so much.=20 HAPV