MIMO (Multiple-Input Multiple-Output) uses multiple antennas at both the transmitter and receiver to send multiple data streams simultaneously over the same frequency. It's like having multiple parallel pipes instead of one. 2x2 MIMO: 2 transmit, 2 receive antennas — up to 2x throughput 4x4 MIMO: 4 transmit, 4 receive — up to 4x throughput 8x8 MIMO: Used in LTE-Advanced Massive MIMO (64T64R): Used in 5G — up to 64 transmit antennas!