From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi1-x22f.google.com (mail-oi1-x22f.google.com [IPv6:2607:f8b0:4864:20::22f]) (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 A05513BA8E for ; Mon, 8 Oct 2018 16:18:51 -0400 (EDT) Received: by mail-oi1-x22f.google.com with SMTP id p125-v6so16500445oic.3 for ; Mon, 08 Oct 2018 13:18:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to :content-transfer-encoding; bh=ZS7NEALPk0ap2CG5gu5TZa1fnxMy5P/6M+KMvdp1fLA=; b=h09pZExUNetMnPaTScuu9v/q9rqWa69krvPjtMPRahhVCjnLpUjNCnoM+U5n9tHn9q NaVRi1wVGhDAr+js1h+8yPBPJdKbOf04UoCJObgkYPL09zw9LoKcmkp2adnkTEXGjqtl /wCmbEpDs4iUDxD4+oN+m3ieQdAdXO0IfAOa14hh+i34w4uN2mGOelPlkm0UFrZZfekh aRXqcyWo9BQ0Sge9ZpzOJ1EdUE2JaMVrG1zrQSO0I68RI+6y+IB+X01V8WhB30MTldd9 1WVS4nONUth+xnof0X7FrGGXFm6TZJKGtW+99w4FSNFGWpYcLaLEWvjrHotc863oUlkQ UGKg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to :content-transfer-encoding; bh=ZS7NEALPk0ap2CG5gu5TZa1fnxMy5P/6M+KMvdp1fLA=; b=t1HiY1cxiTu4yodEA0NnYNwzWmmLC4wbOUsKmBdGYNxmFChRwWM7cNjGMdRqaLtzaz 6e2Wv+YuuW+yZxpoDgQ6+54Jjx1pIfqIzwrwQ1To9Y3dS7LUawFyWCiHKw17aysASfKl 9843MYxk7c2JyjPN3uaVFMNzt7pUIkVfpNsJ79eDRVA+oRxKcB7ORIEgHbxCBaAbGF3n x8sX7epM/Hm+uAEPnyNTEb/qPA8tEHcul/cB34ObOJa+OoYchLEYgHCSVecRle9LI+Bp 041bGPlWupXPrLm5Dkk/XT9N3apcc4ZCF7U6x0AoB0YgC0In1ZHRzjnriEXIOzdmOzIK N1yQ== X-Gm-Message-State: ABuFfogAv5Y7Qijc6pAbOeoCnaQhTb7o/AzsY6lSwywG0xOaLO9Kd4cY S7mA304nCO/geLzP2YEkKvHlORhh9B/d0n600K0im8hZ X-Google-Smtp-Source: ACcGV62qJsInoZOGpmO5PhdtpkicfkAXnzNpMv5IXWkg1MWWivRQg/FbiDk7g67yI4xA3DFzsnuS7Yei2TLqU4RMKxc= X-Received: by 2002:aca:1018:: with SMTP id 24-v6mr5287705oiq.303.1539029930564; Mon, 08 Oct 2018 13:18:50 -0700 (PDT) MIME-Version: 1.0 From: bkil Date: Mon, 8 Oct 2018 22:18:39 +0200 Message-ID: To: bloat Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Subject: [Bloat] Is 5/10MHz wifi bandwidth legal in 2.4GHz (half/quarter-clocking)? X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Oct 2018 20:18:51 -0000 If this is not the right forum to discuss, could you please point me in the right direction? After all, channel spacing is indeed 5MHz here. Although using a new raster instead of the 20MHz channel center frequencies would allow full utilization of the band (16 or 8 channels respectively), using the standard set of 11 (13) channels is better than nothing. Is it a good idea to use HT instead of g for such links? =3D Some background and links for those who do not know this mode: "the 2007 version of the IEEE 802.11 standard [1] specifies 5 and 10 MHz wide channels for use in the 4.9 GHz public safety bands" Although according to my reading of section 17.1, it applies to the 5GHz bands as well: >> 17. Orthogonal frequency division multiplexing (OFDM) PHY specification for the 5 GHz band [...] The OFDM system also provides a =E2=80=9Chalf-clocked=E2=80=9D operation us= ing 10 MHz channel spacings with data communications capabilities of 3, 4.5, 6, 9, 12, 18, 24, and 27 Mb/s. The support of transmitting and receiving at data rates of 3, 6, and 12 Mb/s is mandatory when using 10 MHz channel spacing. The half- clocked operation doubles symbol times and clear channel assessment (CCA) times when using 10 MHz channel spacing. The regulatory requirements and information regarding use of this OFDM system in 4.9 GHz and 5 GHz bands is in Annex I and Annex J.<< They probably did not highlight 2.4GHz usage because of mixed-mode (non-OFDM) crowding, although nowadays we could actually move this band to OFDM-only as well. It is unfortunate that this allowance has disappeared in newer versions of the standard. Was that intentional? Reasons why downclocking is advantageous (up to +9dB link budget): * longer GI =3D better protection against multipath fading; * higher power density allowed (2x here) =3D better SNR; * less chance for (adjacent-channel) interference; * reduced TX & RX power consumption for idling and low load. I know that 802.11ah/af are here, but there exist literally millions of devices potentially supporting this old and trusty mode, software permit. Many Atheros chipsets support it, both old and new. OpenWrt has debugfs patches applied to enable this, while Linux has some other patches as well, although it is not user visible. If this is a legal and preferred mode, it would be nice if we could unify access. https://openwrt.org/docs/guide-user/network/wifi/basic?s[]=3Dchanbw http://ccr.sigcomm.org/online/files/p135-chandra.pdf https://kabru.eecs.umich.edu/papers/publications/2011/xyzhang_kgshin_mobico= m11.pdf https://www.etsi.org/deliver/etsi_en/300300_300399/300328/01.08.01_60/en_30= 0328v010801p.pdf https://www.cwnp.com/forums/posts?postNum=3D305220 https://forum.archive.openwrt.org/viewtopic.php?id=3D38590 https://forum.openwrt.org/t/5-mhz-bandwith-option/3615