LTE MAC CE - BSR
BSR - Buffer status report is used by UE to indicate the eNodeB about the pending data at higher layers in UE to send it to eNodeB, so that eNodeB will allocate the grants accordingly. This is sent by the UE in UL_SCH channels. to eNodeB.
Types:
3 types of BSR's available. Long BSR, Short BSR & Truncated BSR. Long BSR will generally carry the actual data. Short & Truncated BSR are used for carrying padding data's.
Short & Truncated BSR:
Length is of 1 byte. It comprises of LCG ID & Buffer Size elements in it.
LCG ID: The Logical Channel Group ID field identifies the group of logical channel(s) which buffer status is being reported. The length of the field is 2 bits
Buffer Size: The Buffer Size field identifies the total amount of data available across all logical channels of a logical channel group after all MAC PDUs for the TTI have been built. The amount of data is indicated in number of bytes. It shall include all data that is available for transmission in the RLC layer and in the PDCP layer. The size of the RLC and MAC headers are not considered in the buffer size computation. The length of this field is 6 bits.
If extendedBSR-Sizes is not configured, the values taken by the Buffer Size field will be lesser compared to the extendedBSR-Sizes configured at eNodeB. Refer the BSR buffer size index to Data avialable in the UE mapping table below.
Long BSR:
It carries 3 bytes of UE's actual data available to send to eNodeB from each Logical channel group ID (LCG-ID) So explicit lcg-id mapping is not required to inform the eNodeB about which lcgid is having the data to send.
Note: LCID & LCGID are different. LCID for MAC CE for BSR is given below. This will be present in the MAC-CE to inform what type of MAC-CE is sent by the UE.
BSR - Buffer status report is used by UE to indicate the eNodeB about the pending data at higher layers in UE to send it to eNodeB, so that eNodeB will allocate the grants accordingly. This is sent by the UE in UL_SCH channels. to eNodeB.
Types:
3 types of BSR's available. Long BSR, Short BSR & Truncated BSR. Long BSR will generally carry the actual data. Short & Truncated BSR are used for carrying padding data's.
Short & Truncated BSR:
Length is of 1 byte. It comprises of LCG ID & Buffer Size elements in it.
LCG ID: The Logical Channel Group ID field identifies the group of logical channel(s) which buffer status is being reported. The length of the field is 2 bits
Buffer Size: The Buffer Size field identifies the total amount of data available across all logical channels of a logical channel group after all MAC PDUs for the TTI have been built. The amount of data is indicated in number of bytes. It shall include all data that is available for transmission in the RLC layer and in the PDCP layer. The size of the RLC and MAC headers are not considered in the buffer size computation. The length of this field is 6 bits.
If extendedBSR-Sizes is not configured, the values taken by the Buffer Size field will be lesser compared to the extendedBSR-Sizes configured at eNodeB. Refer the BSR buffer size index to Data avialable in the UE mapping table below.
Long BSR:
It carries 3 bytes of UE's actual data available to send to eNodeB from each Logical channel group ID (LCG-ID) So explicit lcg-id mapping is not required to inform the eNodeB about which lcgid is having the data to send.
Note: LCID & LCGID are different. LCID for MAC CE for BSR is given below. This will be present in the MAC-CE to inform what type of MAC-CE is sent by the UE.
can any1 please help me, if some data is pending on UE side ,then what basis MAC will decide the LCID, which need to be used between 1 to 16.
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