Buffer Status Reporting

1. BSR上报机制

对于常规和周期BSR：

如果大于1个LCG有可用数据传输，上报需要传输数据的所有LCGs;

否则上报shortBSR

对于Padding BSR

如果padding bit数等于或大于一个Short  BSR加上头且小于Long BSR加上头

 ----如果超过一个LCG有数据需要传输

 --------如果padding数等于Short  BSR加上头

-------------则上报 Short Truncated BSR ，选择有数据需要传输且最高优先级逻辑信道对应的LCG。

---------否则上报Long Truncated BSR ，选择有数据需要传输且优先级从高到底逻辑信道对应的LCG，对于相同优先级，按照LCGID升序来选择。

-----否则上报Short BSR

否则

     上报 Long BSR，选择有数据需要传输的所有LCGs

2. BSR MAC CE填写

    Short BSR format 和 Short Truncated BSR format 为固定长度

LCG_i: For the Long BSR format, this field indicates the presence of the Buffer Size field for the logical channel group i. The LCG_i field set to 1 indicates that the Buffer Size field for the logical channel group i is reported. The LCG_i field set to 0 indicates that the Buffer Size field for the logical channel group i is not reported. For the Long Truncated BSR format, this field indicates whether logical channel group i has data available. The LCG_i field set to 1 indicates that logical channel group i has data available. The LCG_i field set to 0 indicates that logical channel group i does not have data available;

此段说明，对于 Long BSR format，LCG_i 为0说明没有数据需要上报，Buffer Size field to zero,LCG_i 为1说明有数据需要上报，具体有多少可看Buffer Size fields。

对于Long Truncated BSR format，LCG_i 为0说明可用的数据需要传输，LCG_i 为1说明有可用的数据需要传输，但是Buffer Size fields根据Pading的大小填写，按照优先级高低填写，对于没填写的LCGi，如果LCGi为0说明，没有数据需要传输，如果LCGi为1说明有数据需要传输，具体有多少，可能知道也可能不知道。Buffer Size fields按照优先级从高到低排序。

对于 Long BSR format和Long Truncated BSR format可以没有Buffer Size fields，当Long BSR format没有Buffer Size fields，说明所有LCGi可以清空，对于Long Truncated BSR format标注为0的可以清空，标注为1的不清空，保持现状。

疑问：Buffer size怎么排列

Buffer Size: The Buffer Size field identifies the total amount of data available according to the data volume calculation procedure in TSs 38.322 [3] and 38.323 [4] across all logical channels of a logical channel group after the MAC PDU has been built (i.e. after the logical channel prioritization procedure, which may result the value of the Buffer Size field to zero). The amount of data is indicated in number of bytes. The size of the RLC headers and MAC subheaders are not considered in the buffer size computation. The length of this field for the Short BSR format and the Short Truncated BSR format is 5 bits. The length of this field for the Long BSR format and the Long Truncated BSR format is 8 bits. The values for the 5-bit and 8-bit Buffer Size fields are shown in Tables 6.1.3.1-1 and 6.1.3.1-2, respectively. For the Long BSR format and the Long Truncated BSR format, the Buffer Size fields are included in ascending order based on the LCG_i. For the Long Truncated BSR format the number of Buffer Size fields included is maximised, while not exceeding the number of padding bits