The Xiaomi 15 supports 2×2 MIMO (Multiple Input Multiple Output) and 8×8 Sounding for MU-MIMO (Multiple User-Multiple Input Multiple Output).
For your reference, here are more details about MIMO and MU-MIMO:
1. MIMO allows a Wi-Fi router to use multiple antennas to send and receive more than one data stream at the same time, which can provide faster speeds, better range and coverage, and stronger and more stable connection;
2. MU-MIMO takes MIMO to the next level. With MU-MIMO, the router can send multiple streams to multiple devices at the same time, which can reduce lag when lots of devices are connected, provide better performance in busy homes or offices, and ensure everyone gets fair share of Wi-Fi.