What is BSR (buffer status report)?

BSR is the Buffer status report is a kind of MAC CE (Control Element) from UE to the Network carrying the information on how much data is in UE buffer to be sent out. There are several types of BSR and they can be classified in terms of data structure and BSR timing. In terms of the data structure of BSR, there are two types: one is short BSR and the other is long BSR. The BSR reporting procedure is used to provide the serving eNB with information about the amount of data available for transmission in the UL buffers of the UE. Regular BSR, Periodic BSR, and Padding BSR are the three types of BSR that are available. BSR will carry the information on the amount of data available for each logical channel group from UE to eNB.