Tech Junction Answered question August 1, 2023
- Service Data Adaptation Protocol (SDAP): – is responsible for mapping QoS bearers to radio bearers according to their quality-of-service requirements. This protocol layer is not present in LTE but introduced in NR when connecting to the 5G core network due to the new quality-of-service handling.
- Packet Data Convergence Protocol (PDCP): – performs IP header compression, ciphering, and integrity protection. It also handles retransmissions, in-sequence delivery, and duplicate removal3 in the case of handover. For dual connectivity with split bearers, PDCP can provide routing and duplication. There is one PDCP entity per radio bearer configured for a device.
- Radio-Link Control (RLC): – is responsible for segmentation and retransmission handling. The RLC provides services to the PDCP in the form of RLC channels. There is one RLC entity per RLC channel (and hence per radio bearer) configured for a device. Compared to LTE, the NR RLC does not support in-sequence delivery of data to higher protocol layers, a change motivated by the reduced delays as discussed below.
- Medium-Access Control (MAC): – handles multiplexing of logical channels, hybrid-ARQ retransmissions, and scheduling and scheduling-related functions. The scheduling functionality is located in the gNB for both uplink and downlink. The MAC provides services to the RLC in the form of logical channels. The header structure in the MAC layer has been changed in NR to allow for more efficient support of low-latency processing than in LTE.
- Physical Layer (PHY): – handles coding/decoding, modulation/demodulation, multiantenna mapping, and other typical physical-layer functions. The physical layer offers services to the MAC layer in the form of transport channels.
Tech Junction Answered question August 1, 2023