Compare SU-MIMO and MU-MIMO and their impact on capacity.

• A. MU-MIMO serves multiple clients at once, but reduces throughput.
• B. SU-MIMO serves a single client at a time; MU-MIMO serves multiple clients simultaneously, increasing aggregate throughput.
• C. SU-MIMO serves a single client at a time; MU-MIMO serves multiple clients simultaneously, increasing aggregate throughput.
• D. MU-MIMO serves no clients; it's only for downlink.

Answer: (B)

The idea is that multiple antennas let a wireless link send several data streams at once. In single-user MIMO, the system focuses on boosting the data rate to one client, using the antenna array to send parallel streams to that single user. In multi-user MIMO, the access point can deliver separate streams to several clients at the same time, using spatial separation to keep those streams distinct. This simultaneous transmission to multiple clients increases the total amount of data the network can carry at once, which is why this option best describes the impact on capacity—aggregate throughput goes up when you serve multiple users simultaneously. Keep in mind that real-world gains depend on having enough clients with data to receive, good channel state information, and effective beamforming to avoid interference.