On 17 December 2013 15:44, Simon Wunderlich <sw@xxxxxxxxxxxxxxxxxx> wrote: > Sorry for answering after so many revisions, but ... why do you think this is > required? Many APs first do a CAC on all available channels, but then pick one > channel and use that, while being able to switch to another channel > immediately. > > WIth this patch (if I understand that correctly), this is not possible > anymore. Why do you think it is required? I can not find this requirement in > ETSI, at least. > > To quote from ETSI 301.893: > > Once the RLAN has started operations on an Available Channel, then that > channel becomes an Operating Channel. During normal operation, the master > device shall monitor all Operating Channels (In-Service Monitoring) to ensure > that there is no radar operating within these channel(s). If no radar was > detected on an Operating Channel but the RLAN stops operating on that channel, > then the channel becomes an Available Channel. > > I think this patch is wrong and should not be applied. > > Thanks, > Simon I also have doubts when reading this specification: ETSI 301.893 v1.7.0: "A master device shall only start operations on Available Channels. At installation (or reinstallation) of the equipment, the RLAN is assumed to have no Available Channels within the band 5 250 MHz to 5 350 MHz and/or 5 470 MHz to 5 725 MHz. In such a case, before starting operations on one or more of these channels, the master device shall perform either a Channel Availability Check or an Off-Channel CAC to ensure that there are no radars operating on any selected channel. If no radar has been detected, the channel(s) becomes an Available Channel(s) and remains as such until a radar signal is detected during the In-Service Monitoring. The Channel Availability Check or the Off-Channel CAC may be performed over a wider bandwidth such that all channels within the tested bandwidth become Available Channels." First thing: how to interpret words installation and reinstallation? If we include stating hostapd in installation process then we should have no available channels when starting hostapd. Second thing: How to interpret this sentence: "If no radar has been detected, the channel(s) becomes an Available Channel(s) and remains as such until a radar signal is detected during the In-Service Monitoring." As I understand this sentence channel can be available as long as radar detection works, so called In-Service Monitoring. When in service monitoring is off then channel can not be available. Of course this is my interpretation. So if there are APs than can monitor one channel after switch to new channel then I agree that both channels can be available. In hostapd when last AP interface is stopped then it is no longer monitoring current channel, so starting AP after some time can not happened without CAC. Simple case: we have our AP on mobile device, it was stopped in one place where was no radars and after moving to new place we start AP again. But this new place is in radar range. So we should start beaconig or start CAC first? Marek -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
