This technical module offers a comprehensive exploration of the 5G Radio Access Network (RAN) protocol stack, dissecting the layers and channels that govern how data is transmitted and controlled.

We begin at the foundation with the Physical Layer (Layer 1), providing a detailed overview of the critical downlink and uplink channels: the Physical Downlink Shared Channel (PDSCH) for user data, the Physical Downlink Control Channel (PDCCH) for scheduling, and their uplink counterparts, PUSCH and PUCCH. This theory is reinforced with practical simulations, illustrating the function and interaction of these channels.

The journey continues upward through Layer 2, where we examine the key functions and data flow handled by each sublayer: the SDAP for QoS mapping, PDCP for ciphering and integrity protection, RLC for reliable segmentation, and the MAC for scheduling and multiplexing.

Finally, we conclude at Layer 3 with the Radio Resource Control (RRC) protocol, understanding its role in connection management and the critical distinction between its different states (e.g., RRC_IDLE and RRC_CONNECTED) that optimize device power consumption and network resource allocation.