Hello, everyone!
Today, I would like to continue on the novel features ot the IEEE 802.11aa amendment.
Figure 1: Various retransmission strategies for the GCR service
The Access point can preemptively rebroadcast every groupcast frames a couple of times when employing GCR-UR to alleviate the effect of channel faults (Figure 1 - a), and receivers are not required to submit acknowledgements. Although this strategy appears to increase transmission reliability, it still has scaling concerns.
When GCR-BA is utilized, the Access point delivers a burst of successive groupcast frames and demands a Block ACK message from receivers, which provides a bitmap to negatively or positively acknowledge delivered frames (Figure 1 - b).
Because Block ACK frames can be sought instantly after a transmission burst or after a randomized back-off period, the Block ACK methodology developed for the GCR-BA service is extremely flexible.
To decrease overheads and delays, the Access point can send the Block ACK frame to every groupcast recipients or just a subset of those. In the research, the benefits of GCR approaches over broadcast and DMS were substantially shown.
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