ABSTRACT
Radio Link Control (RLC) is an important sublayer in the LTETM Narrowband Internet of Things (NB-IoT) protocol stack. RLC entity can be one of the three modes: Transparent Mode (TM), Unacknowledgment Mode (UM), or Acknowledgement Mode (AM). RLC entity of TM is a unidirectional entity which means that the entity is for one direction only, either transmitting or receiving. RLC mode UM is used only to receive multicast traffic. RLC entity of an AM mode is bidirectional which means that the RLC entity is used for both transmitting and receiving. Radio Resource Control (RRC) sublayer configures each RLC entity as a transmitting TM, receiving TM, receiving UM, or AM. RRC also associates each RLC entity with its signalling or radio bearer. RLC Protocol Data Units received by User Equipment in this mode can contain one of the three Service Data Unit (SDU): a single RLC SDU, concatenated RLC SDU, or a segment of an RLC SDU.
