I am trying to achieve periodic multicast with WAP (Wireless Access Point) [basically trying to stream real time audio data to multiple devices]. The regularity in the interval between successive UDP audio data packets matter in my application. Currently that interval is 16 ms and need to be kept lower to have lower latency.
From some resources I came to know that multicast does not employ random back-off mechanism (as no ACK is involved). But still, if channel is busy then WAP should logically postpone the transmission of multicast packets. My questions are :
- How fast(i.e. reducing interval between successive multicast packets) multi-casting can be done with present 802.11 b/g/n systems.
- Multicast packets have more priority than unicast packets, how is this priority implemented in WAP functioning ? ( By 'priority' I mean, as ACK not involved and reliable multicast packet delievery is still desired, does WAP tries to reserve the channel prior to sending multicast packets by some means or what? )
- What's the size of the contention window in this case? What will happen if channel is busy for sufficiently long time and AP has multicast packets to send ?
- Is there anything like post back-off period (the period in which WAP should not send any multicast packets)?