On 27 March 2016 at 09:43, sandeep suresh <sandeep.suresh@xxxxxxxxxxx> wrote: > Dear Experts, > > WiFi-BT Coexistence: > To let wireless LAN systems coexist with Bluetooth system, a hardware Packet > Traffic Arbiter (PTA) scheme is used. Here PTA is based on 2-wire > coexistence , BT_ACTIVE and WL_ACTIVE. When BT wants to use the medium, it > will assert the BT_ACTIVE line, during which WLAN cannot perform any > transactions. When WLAN is in client mode, during this assertion period > waiting for a packet from WLAN router (AP) to be received , WLAN packet will > be lost !!! Let us call this window during which WiFi being stomped by BT > as stomping window. WLAN device in client mode considered here is based on > AR9287 chipset and let us call this as Apple accessory > > Bonjour discovery: > Apple devices connect to the same WiFi router to which the Apple accessory > is also connected. Apple device is also connected in WiFi client mode. In > order to determine other clients (Apple compatible) in the same network, it > performs Bonjour discovery which is based on mDNS broadcast. > > Concern/Query:- > The mDNS query is a broadcast query received from Apple device and sent by > the WiFi AP to the WiFi network (to which the apple accessory is also > connected) only once. The period of reception of this broadcast query can > coincide with the stomping window. Hence the broadcast query can be lost by > Apple accessory. This might result in discovery, pair verify (later) from > apple devices to fail. Apple devices implement a back-off strategy and as > per this the next discovery will be after 10s of minutes. During this long > period the WiFi client based apple accessory will be offline!!!! > Is the understanding and concern correct? If so, how can this be solved via > ath9k drivers and/or settings in WiFi AP? Well, sure. I mean, the bluetooth coexistence code is just designed to ensure that they stomp predictably and can be controlled. I didn't think the pair/discovery would take so long though, so I'd go and figure out what's going on there. You can set up the weights and stomping preference for controlling bluetooth and wifi. I think at the moment ath9k (and freebsd) just use a static weight matrix and prefer bt? I forget. There's some extensions to 802.11 (802.11aa, at least) which allows for reliable multicast. That means it gets replicated to each device that asks for it, and it gets ACKed/retransmitted/etc. I don't know of anything open source that implements all of that. -adrian -- 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
