The Radio Link Control (RLC) protocol provides the following services:
- Segmentation of SDU according to the size
- Re-Segmentation of PDU
- Radio Bearer to logical channel mapping
Transfer of data in 3 modes:
- TM Transparent Mode
Without retransmission. For real-time service. - UM Unacknowledged Mode
Without retransmission, but error statistics (BLER)
It can be used for the signaling. - AM Acknowledged Mode
With retransmission. For non real-time services, like internet.
The main services and functions of the RLC sublayer include:
- Transfer of upper layer PDUs;
- Error Correction through ARQ (only for AM data transfer);
- Concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer);
- Re-segmentation of RLC data PDUs (only for AM data transfer);
- In sequence delivery of upper layer PDUs (only for UM and AM data transfer);
- Protocol error detection and recovery;
- RLC SDU discard (only for UM and AM data transfer);
Introduction to RLC in LTE
The RLC (Radio Link Control) protocol in LTE is responsible for ensuring reliable communication between the user equipment (UE) and the evolved NodeB (eNB). It handles segmentation, reassembly, and retransmission of data to ensure no data is lost during transmission.
RLC Modes in LTE
RLC operates in three modes: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM). In TM, data is transmitted without error correction. In UM, error correction is handled, but there is no retransmission. AM ensures both retransmission and error correction, providing the most reliable service.
RLC’s Role in Data Integrity
RLC ensures data integrity by detecting errors and correcting them when necessary. If a packet is lost or corrupted, RLC in AM mode will request a retransmission, ensuring reliable delivery of data.