BSR(Buffer Status Report)

BSR(Buffer Status Report)

BSR is a MAC CE which carries information on how much data is in UE buffer to be sent to the network.

Types of BSR (Based on Data Structure):

1. Short BSR : UE can inform the amount of data in UL buffer for one LCID.

2. Long BSR: UE can inform UL buffer information for all LCID

There are three BSR Types:

1. Regular BSR: Regular BSR is sent when a New data arrives in UL buffer and the new data has higher priority than the one already waiting in the buffer.

2. Periodic BSR: Periodic BSR is sent with the predefined periodicity. The periodicity is defined by Network and get informed to UE by RRC message (e.g, radioResourceConfigDedicated IE in RRC Connection Reconfiguration)

3. Padding BSR : Padding BSR is sent when the number of padding bits in a data message is larger than the size of BSR, so that the padding bit space can be used to send the BSR.


Short BSR Vses Long BSR:

1.for Regular and periodic BSR
if the numbar of LCG with allocated data are more than 1 than Long BSR is used else short BSR is used

2. for padding BSR if the number of padding bits are more than size of short BSR plus its subheader and less than size of long BSR and its subheader, also LCID used are more than 1 than truncated BSR is used.
for padding BSR if the number of padding bits are more than size of short BSR plus its subheader and less than size of long BSR and its subheader, also LCID used is 1 than short BSR is used.