ARQ: Automatic Repeat Request In this procedure, RLC re-transmits RLC PDU or RLC PDU segment according to RLC status report. RLC sending entity can request RLC status report as needed. The AM RLC entity provides ACK/NACK to the peer M RLC entity through the STATUS PDU. …
AM stands for “Acknowledge Mode”. In AM mode, RLC adds protocol header to the RLC SDU and if necessary, the RLC SDU can be segmented and then protocol header is updated. AM mode expects ACK/NACK from the other party. AM supports ARQ transmission. When the size …
UM stands for “Unacknowledged Mode”. In UM mode, RLC adds protocol header to RLC SDU and if required SDU can be segmented. The transmitting entity performs the below operation: 1. Buffering of the data and generate RLC header. 2. Segmentation and modify RLC header 3. Add …
In TM mode, RLC does not perform any operations on the SDU and it is transmitted transparently. It will only buffer data on Tx side. No RLC header, No reordering, No segmentation, no ressembly is done. The PDU that is transmitted is called as TMD PDU. …
In this chapter we shall see how an RLC entity is established, re-established and released. RLC entity establishment procedure When any upper layer request an RLC entity establishment, the UE will: 1. Establish a RLC entity. 2. Set the state variables of the RLC entity to …
RLC layer is located between PDCP (or RRC layer) and MAC Layer. It communicates with the PDCP layer (or RRC layer) through the RLC channel, and communicates with the MAC layer through logical channels. Data received by RLC layer from PDCP layer is called as RLC …
Below shows a schematic diagram of PDCP duplication: If PDCP duplication is not enabled, a PDCP packet will be transmitted to an RLC entity and RLC entity will send to MAC layer. If PDCP duplication is enabled, PDCP packet will be transmitted to 2 RLC entities, …
SDU discard For DRB, When the discardTimer expires for a PDCP SDU, or the successful delivery of a PDCP SDU is confirmed by PDCP status report, the transmitting PDCP entity shall discard the PDCP SDU along with the corresponding PDCP Data PDU. For SRBs, when upper …
In this section, we shall learn about Transmit and Receive operation along with related state variables. Constants and timers: Window_Size: his constant indicates the size of the reordering window. The value equals to 2 – 1. Timers: discardTimer: This is transmitter timer, it is started upon …
