The Medium Access Control (MAC) layer in 5G acts as the traffic conductor for the radio spectrum. It efficiently manages shared access to the wireless channel, ensuring smooth data flow between user equipment (UE) and the network. Here are its key responsibilities:

1. Channel Access Control: MAC regulates how UEs access the channels, preventing collisions and ensuring efficient utilization of the shared spectrum.
2. Scheduling: MAC intelligently schedules data transmissions for different UEs, considering factors like channel quality, traffic demands, and QoS requirements.
3. Multiplexing and Demultiplexing: MAC combines (multiplexing) data streams from different logical channels (control signaling, user data) onto transport channels for transmission and separates (demultiplexing) them at the receiving end.
4. Error Correction (HARQ): While not its primary function, MAC can participate in error correction through Hybrid Automatic Repeat Request (HARQ) by requesting retransmission of corrupted data packets.
5. Logical Channel Mapping: MAC maps logical channels, which define the type of information carried (control signaling, voice, video), onto transport channels, which represent the actual wireless resources used for transmission.