Return-path: Received: from vps.qorvus.com ([67.213.217.156]:35062 "EHLO vps.qorvus.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753650AbZKQXjP (ORCPT ); Tue, 17 Nov 2009 18:39:15 -0500 Message-ID: <7C9BF2FB3F6D47238EB6BC9B4441A996@qlaptop2> Reply-To: "Tom Sharples" From: "Tom Sharples" To: "Luis R. Rodriguez" , "David Acker" Cc: "linux-wireless" , , "Andrey Yurovsky" , References: <2205.95.222.251.107.1258282369.squirrel@webmail.otaku42.de> <43e72e890911161701p61d0db5ag25a1459f900b3ab7@mail.gmail.com> <4B02DFF4.1060509@roinet.com><45e8e6c40911171257m7c687380k6e6e2677fd11f851@mail.gmail.com> <43e72e890911171337p4b0d97fcp844266137bb51b56@mail.gmail.com> <4B03193E.2080304@roinet.com><43e72e890911171345q2dc59d66g6ac2a9eec04c577c@mail.gmail.com> <4B031B48.1090105@roinet.com><43e72e890911171404x1a46d07alb54946768d0f9cf5@mail.gmail.com> <4B032390.3080501@roinet.com> <43e72e890911171439q74f30bc2t3e6f4ada19a85594@mail.gmail.com> Subject: Re: [Madwifi-devel] Survey: What are you using MadWifi for, and why? Date: Tue, 17 Nov 2009 15:39:14 -0800 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="utf-8"; reply-type=original Sender: linux-wireless-owner@vger.kernel.org List-ID: > >> There are several miniPCI >> based radios that require half or quarter width channels on some >> channels. > > That *require* this? > >> For example, the Ubiquiti XR7 requires quarter width channels on two of >> its >> four available channels. > > Regulatory wise? What's the restriction based on? > >> The XR9 requires half width channels on two if its >> four available channels. > > Same here, what's the restriction based on? > On 900 and the 4.9 Ghz public safety bands, the half or quarter channels are required if you want to: (a) Support multiple non-overlapping links within the legally allocated bandwidth. For example, within 900 Mhz there is only 25 Mhz total available, and only two 20-mhz channels defined (which, of course, overlap) so really you've only got one. With 5 Mhz channels, you can operate legally near the edge of the band without interfering with other 900 Mhz links, or transmitting outside of the FCC allocated band. (b) Operate legally and efficiently in the 4.9 Ghz public-safety band. The upper and lower three channels defined by the FCC are 5Mhz and 10Mhz. 20 Mhz operation there would violate the allocated band edges. (b) Be compatible with other company's products that use these channels, e.g. Proxim, Cisco, Ubiquiti, etc. On 2.4 and 5.8 half and quarter aren't a legal requirement, but they certainly are necessary for efficient operation! Tom S.