Radio Link Control
Radio link control (RLC) is a layer 2 protocol used in mobile radio on the air interface . The protocol is specified by 3GPP for UMTS in TS 25.322, for LTE in TS 36.322 and for 5G New Radio (NR) in TS 38.322. RLC is in the protocol stack above the MAC layer and below the PDCP layer.
The most important functions of the RLC protocol are:
- Transfer of data from higher protocol layers. Three types of transmission are offered: Acknowledged Mode (AM), Unacknowledged Mode (UM) and Transparent Mode (TM)
- Error correction using ARQ (only in AM transmission mode)
- Segmentation and assembly of information (only for UM and AM)
- Sorting the data in the correct order (only for UM and AM);
- Detection and rejection of data received twice (only for UM and AM);
- Detecting and handling protocol errors