> Hi, > FIRST, Will there be any difference in duration of PHY header for 20MHz and > 40Mhz. > Do u think 40Mhz header will take lesser time?
Which bits of the header are you talking about? Just the initial PLCP bits? I'm not sure how HT40 PLCP works. I am not talking about the training (preamble) part. I was asking about MAC header. So, you can do some tricks by watching the success rate of HT40 transmissions and the primary/extension MIB channel busy counters and determine what's going on. Instead of monitoring MIB counters. If some controllers tells me its better to switch to 20MHz do u have any idea what will be the delay and what rate would be picked. On Wed, Sep 24, 2014 at 9:52 PM, Adrian Chadd <adrian.ch...@gmail.com> wrote: > On 22 September 2014 14:14, Kamran Nishat <kamran.nis...@gmail.com> wrote: > > Hi, > > FIRST, Will there be any difference in duration of PHY header for 20MHz > and > > 40Mhz. > > Do u think 40Mhz header will take lesser time? > > Which bits of the header are you talking about? Just the initial PLCP > bits? I'm not sure how HT40 PLCP works. > > > Second, if my AP is connected to a client on 40MHz (Channel Bonding). > During > > Carrier Sense (CS) it sense ext channel of 20MHz is busy will it > > automatically switch to 20MHz and start sending on primary channel. If > yes > > will it take some time to shift from 40MHz to 20MHz? > > THat depends upon the AP model. > > It can for sure just decide to monitor the air and if i's busy > downgrade to selecting HT20 rates to transmit on. There's also the > channel width update stuff that an AP can use to migrate a BSS between > 20MHz and 40MHz. > > Now, as for chip support with Atheros 11n parts - no, it doesn't > auto-detect 20 or 40MHz wide CCA/CS and select a rate. The 11ac chips > started doing that. > > What they _do_ however is detect CCA/CS on both halves of the channel > and you can select whether to treat them separately or joint. (Ie, > whether to bother doing CCA on the full 40MHz for all transmissions or > just when it wants to do a HT40 transmission.) > > So, you can do some tricks by watching the success rate of HT40 > transmissions and the primary/extension MIB channel busy counters and > determine what's going on. > -a >
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