transmission. The number of clients depends on the type of stream, for example one client can receive 1SS while another is
receiving 2SS.
•
Wi-Fi alliance certification for Wave-2 includes MU-MIMO.
•
Take-away: MU-MIMO is designed to maximize downlink capacity by overlapping clients in space (multiplexing). Best
performance occurs with high client counts and high AP densities.
Challenges of Multi-User MIMO
•
Requires precise (CSI) channel state information to maintain deep nulls so that each MU-MIMO client can properly decode its
data without too much interference from the other clients.
•
MU-MIMO CSI, pre-coding group data adds overhead as does their acknowledgments and so on.
• Rate adaptation is slow – Wave-2 clients to be integrated into new laptops, tablets, and phones but this moves slowly.
•
MU-MIMO is a new technology and needs to develop and mature. So, issues such as lower end clients may be sensitive to MU
grouping overhead and client driver version issues.
Figure 47: Example of a MU-MIMO protocol advertisement
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