From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-x52a.google.com (mail-ed1-x52a.google.com [IPv6:2a00:1450:4864:20::52a]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 94EE53B29E for ; Thu, 14 May 2020 17:38:36 -0400 (EDT) Received: by mail-ed1-x52a.google.com with SMTP id w2so194383edx.4 for ; Thu, 14 May 2020 14:38:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=43EF+byZN3OfR4OHtES936SURekdmatdYUr0Y2suOdg=; b=EiLEiW6Ewx9d0IEnFYrKJsHH5hZ8riuq+PPpVKQqcjyU10g1+EbbqLCin1B190593T +xoStA+EcwpoKi2aq90reXJLugDPAHcsQU+FdlfEGy0FboKTX3TE3TfVW9AP2Xq++A/L H6Fj9wEJg+I6Q7jR/93vDnWPsvF9KKtZiwLyM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=43EF+byZN3OfR4OHtES936SURekdmatdYUr0Y2suOdg=; b=J3XjMbRwmGO3rzJ15Nr3l81bhg3p/nozAUH5DNXfKVjZRl3t0KgJbebDsAbXVhLbEV B9NYVdjExAzuwQAV8ORbCqj2UXnZTNsWrl375SascFzjnrNXjuRd4MmmumIsn38ZLtC9 31H9Ck0FvBq960SH3GDakoPJpYc1tyosOyMmzykZqWFz8CAYGoIAIt2TsXLx9OTU3SNk GmICPXVo3lsXLp3U2I2SNggVHAC82rBOZGq6nAnKa3xwitWpciiGJULnobtfBAHyZRas 1t3RMBsyX2f3RJ31GMLFWTqh41KNApZ66zh9X1L4hv2o7PUk/cYJ79K5J4joKpdgk3qS 0vVQ== X-Gm-Message-State: AOAM532EixGRWHe8PmoHjwySwe0mzdFxq9xn9M+1/rgonibo4XRCnr+U 3R2xhPJvpTjAW2hGbzvSCLTuL3bhmSPmsocw6OQaOw== X-Google-Smtp-Source: ABdhPJxeFEXWS83xS449EVM8qOMgGosyeotY2WDNS9uPvNM/4BpwHoZOoZrRSo/XbukzQAAp0rrebuUhtW3QRRnc/eA= X-Received: by 2002:aa7:daca:: with SMTP id x10mr100830eds.59.1589492315430; Thu, 14 May 2020 14:38:35 -0700 (PDT) MIME-Version: 1.0 References: <56a03e99-3337-bf4a-4743-deb93abb9592@smallnetbuilder.com> In-Reply-To: <56a03e99-3337-bf4a-4743-deb93abb9592@smallnetbuilder.com> From: Bob McMahon Date: Thu, 14 May 2020 14:38:24 -0700 Message-ID: Subject: Re: [Make-wifi-fast] SmallNetBuilder article: Does OFDMA Really Work? To: Tim Higgins Cc: Make-Wifi-fast Content-Type: multipart/alternative; boundary="000000000000d60f3d05a5a284b7" X-List-Received-Date: Thu, 14 May 2020 21:38:36 -0000 --000000000000d60f3d05a5a284b7 Content-Type: text/plain; charset="UTF-8" I haven't looked closely at OFDMA but these latency numbers seem way too high for it to matter. Why is the latency so high? It suggests there may be queueing delay (bloat) unrelated to media access. Also, one aspect is that OFDMA is replacing EDCA with AP scheduling per trigger frame. EDCA kinda sucks per listen before talk which is about 100 microseconds on average which has to be paid even when no energy detect. This limits the transmits per second performance to 10K (1/0.0001.). Also remember that WiFi aggregates so transmissions have multiple packets and long transmits will consume those 10K tx ops. One way to get around aggregation is to use voice (VO) access class which many devices won't aggregate (mileage will vary.). Then take a packets per second measurement with small packets. This would give an idea on the frame scheduling being AP based vs EDCA. Also, measuring ping time as a proxy for latency isn't ideal. Better to measure trip times of the actual traffic. This requires clock sync to a common reference. GPS atomic clocks are available but it does take some setup work. I haven't thought about RU optimizations and that testing so can't really comment there. Also, I'd consider replacing the mechanical turn table with variable phase shifters and set them in the MIMO (or H-Matrix) path. I use model 8421 from Aeroflex . Others make them too. Bob On Thu, May 14, 2020 at 9:43 AM Tim Higgins wrote: > Hi folks, > > I decided to publish some details of the hoops I've been jumping through > to try to find benefit from OFDMA. > It's proving very hard to do. > > > https://www.smallnetbuilder.com/wireless/wireless-features/33222-does-ofdma-really-work-part-1 > > I'll publish results from real devices next. But I'm still trying > different things to get SOMETHING to show an improvement from OFDMA. > > Suggestions are welcome. > =========== > Tim > _______________________________________________ > Make-wifi-fast mailing list > Make-wifi-fast@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/make-wifi-fast --000000000000d60f3d05a5a284b7 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I haven't looked closely at OFDMA but these latency nu= mbers seem way too high for it to matter.=C2=A0 Why is the latency so high?= =C2=A0 It suggests there may be queueing delay (bloat) unrelated to media a= ccess.

Also, one aspect is that OFDMA is replacing EDCA with AP sche= duling per trigger frame.=C2=A0 EDCA kinda sucks per listen before talk whi= ch is about 100 microseconds on average which has to be paid even when no e= nergy detect.=C2=A0 This limits the transmits per second performance to 10K= (1/0.0001.). Also remember that WiFi aggregates so transmissions have mult= iple packets and long=C2=A0transmits will consume those 10K tx ops. One way= to get around aggregation is to use voice (VO) access class which many dev= ices won't aggregate (mileage will vary.). Then take a packets per seco= nd measurement=C2=A0with small packets.=C2=A0 This would give an idea on th= e frame scheduling being AP based vs EDCA.=C2=A0=C2=A0

Also, measuri= ng ping time as a proxy for latency isn't ideal. Better to measure trip= times of the actual traffic.=C2=A0 This requires clock sync to a common re= ference. GPS atomic clocks are available but it does take some setup work.<= br>
I haven't thought about RU optimizations and that testing so can= 't really comment there.=C2=A0

Also, I'd consider replacing = the mechanical turn table=C2=A0with variable phase shifters and set them in= the MIMO (or H-Matrix) path.=C2=A0 I use model 8421 fro= m Aeroflex. Others make them too.

Bob

On Thu, May 14, 2020 at 9:4= 3 AM Tim Higgins <tim@smallne= tbuilder.com> wrote:
=20 =20 =20
Hi folks,

I decided to publish some details of the hoops I've been jumping through to try to find benefit from OFDMA.
It's proving very hard to do.

https://www.smallnetbuild= er.com/wireless/wireless-features/33222-does-ofdma-really-work-part-1
I'll publish results from real devices next. But I'm still tr= ying different things to get SOMETHING to show an improvement from OFDMA.

Suggestions are welcome.
=20
=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D
Tim
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