5G • RAN
SDAP
Service Data Adaptation Protocol
The 5G NR Layer 2 protocol that maps 5G QoS Flows from the 5G Core to Data Radio Bearers (DRBs) over the air interface.
Technical Explanation
SDAP is a new protocol introduced in 5G NR, located above PDCP in the radio protocol stack. In the 5G Core, user traffic is categorized into QoS Flows identified by a 5G QoS Identifier (5QI). The gNodeB SDAP entity maps one or more 5G QoS Flows onto appropriate Data Radio Bearers (DRB) over the Uu interface. SDAP also marks the QoS Flow ID (QFI) in downlink and uplink packets and performs reflective QoS mapping.
Key Functions
- Mapping between 5G Core QoS Flows and Access Stratum Data Radio Bearers (DRBs)
- Marking QoS Flow ID (QFI) in downlink and uplink data packets
- Reflective QoS mapping (UE learns uplink flow-to-DRB mapping from downlink headers)
Specifications
3GPP TS 37.324, TS 38.300
Interfaces
Uu Interface Layer 2 (Above PDCP)
Related 5G Concepts
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