What are RLC modes?
The main tasks of the RLC protocol are: Transfer of upper layer Protocol Data Units (PDUs) in one of three modes: Acknowledged Mode (AM), Unacknowledged Mode (UM) and Transparent Mode (TM) Error correction through ARQ (only for AM data transfer) Concatenation, segmentation and reassembly of RLC SDUs (UM and AM)
What is RLC retransmission in LTE?
After RLC transmitter do the segmentation/concatenation process, it adds RLC header and then it creates two identical copies and transmit the one copy of the data out to lower layer (MAC) and send another copy to Retransmission buffer. ii) The RLC layer removes the RLC header from the PDU.
What is RLC PDU?
An RLC PDU (Protocol Data Unit) consists of an RLC header and data. From an upper layer, RLC receives an RLC SDU (Service Data Unit). The data part of an RLC PDU is either a complete RLC SDU or an SDU segment. A single RLC PDU maps to a single MAC SDU . RLC has three transmission modes: TM , UM and AM .
What is polling in RLC?
The ARQ procedure in LTE RLC is initiated when the transmitting side RLC entity starts the polling procedure. Polling procedure triggers STATUS reporting from receiving side AM RLC entity. Both transmission and retransmission buffers become empty. No new RLC data PDU can be transmitted (e.g., due to window stalling)
What is RLC transparent mode?
Transparent Mode Data PDU (TMD PDU) As the name suggests the Transparent mode entity in RLC does not add any overhead to the upper layer SDUs. RLC TM is used for transmission of paging messages on PCCH, system informations transmitted on BCCH and SRB0 messages transmitted on CCCH.
What is the difference between SDU and PDU?
It differs from a PDU in that the PDU specifies the data that will be sent to the peer protocol layer at the receiving end, as opposed to being sent to a lower layer. The SDU accepted by any given layer (n) from layer (n+1) above, is a PDU of the layer (n+1) above. In effect the SDU is the ‘payload’ of a given PDU.
What is RLC SAP?
RLC – Radio Link Control protocol is a data link layer protocol. RRC (Radio Resource Control) is generally controls RLC configuration via RRC-RLC SAP. A RLC entity receives/delivers RLC SDUs from/to upper layer and ends/receives RLC PDUs to/from its peer RLC entity via lower layers.
What is RLC entity?
An RLC entity is established when a radio bearer is set up, and removed when the associated radio bearer is released. When established, the RLC entity is configured in one of three operating modes: Transparent Mode (TM), Unacknowledged Mode (UM), and Acknowledged Mode (AM).
What is PDCP and RLC?
PDCP is located in the Radio Protocol Stack in the UMTS/LTE/5G Air interface on top of the RLC layer. PDCP provides its services to the RRC and user plane upper layers, e.g. IP at the UE or to the relay at the base station.
What is 5G PDCP?
Packet Data Convergence Protocol (PDCP) is specified by 3GPP in TS 25.323 for UMTS, TS 36.323 for LTE and TS 38.323 for 5G New Radio (NR). PDCP provides its services to the RRC and user plane upper layers, e.g. IP at the UE or to the relay at the base station.
What is the difference between PDU and SDU?
What is PDU in LTE?
Packets received by a layer are called Service Data Unit (SDU) while the packet output of a layer is referred to by Protocol Data Unit (PDU).