Definition: PDCP is a protocol layer in the Radio Protocol Stack responsible for the convergence of various data streams into a single format suitable for transmission over the radio interface.
Objective: PDCP ensures the efficient and reliable transfer of data between the Radio Access Network (RAN) and the core network in 5G.
2. Functions of PDCP in 5G:
Header Compression: PDCP compresses the headers of IP packets to reduce the overhead, making more efficient use of the available bandwidth.
Ciphering and Integrity Protection: PDCP provides security features like encryption and integrity protection for user data.
Robust Header Compression (RoHC): In 5G, PDCP uses the Robust Header Compression algorithm to minimize the header size, especially for Voice over IP (VoIP) and other real-time services.
3. Protocol Stack Position:
PDCP is situated above the Radio Link Control (RLC) layer and below the Radio Resource Control (RRC) layer in the 5G protocol stack.
It receives service data units (SDUs) from higher layers, performs necessary functions, and passes the PDUs (Protocol Data Units) to the RLC layer.
4. Header Format:
PDCP introduces its own header, including information for header compression, security, and other control parameters.
The header structure may include fields like the PDCP PDU Number, SN (Sequence Number), and various control flags.
5. Security in PDCP:
Ciphering: PDCP encrypts user data to ensure its confidentiality during transmission over the air interface.
Integrity Protection: PDCP provides integrity protection to detect and discard any tampered or corrupted data.
6. Reordering and Duplication Detection:
PDCP manages the reordering of out-of-sequence packets and detects duplicate packets to ensure the correct delivery of data to higher layers.
7. Support for Different Radio Bearers:
PDCP supports multiple Radio Bearers, each optimized for specific types of traffic (e.g., conversational voice, streaming, or best effort data).
8. Handover Support:
During handovers between different cells or even different types of networks (e.g., LTE to 5G), PDCP plays a crucial role in ensuring continuity of data transmission.
9. Interworking with Previous Technologies:
PDCP is designed to interwork with LTE (Long-Term Evolution) technology, allowing for seamless mobility and backward compatibility.
10. Signaling and Control:
PDCP exchanges control and signaling information with the RRC layer to manage the configuration and operation of the PDCP layer.
