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LTE-NB : TBS / MCS

 

In legacy LTE, a single rule (table) determine transport block size for both downlink and uplink and it applies in the same way regardless of whether the data is SIB or other data (i.e, signaling data or user data).  However in LTE-NB, a few different tables are used depending on situations (e.g, UL vs DL, SI data or signaling/User data)

 

 

How to determine TBS (Transport Block Size)

 

As mentioned above, LTE-NB TBS table are different depending on UL vs DL, SI data or Control/User data as follows.

 

 

TBS for SIB1-NB

 

 

< 36.213 Table 16.4.1.5.2-1:Transport block size (TBS) table for NPDSCH carrying SystemInformationBlockType1-NB >

 

 

 

TBS for NPDSCH (Signaling Message / User Data)

 

 

< 36.213 : Table 16.4.1.5.1-1: Transport block size (TBS) table.>  

 

 

 

TBS for NPUSCH (Signaling Message / User Data)

 

 

< 36.213 Table 16.5.1.2-2: Transport block size (TBS) table for NPUSCH >

 

 

Maximum MCS for Downlink

 

Maximum MCS for Downlink is determined by two major factors as follows.

 

 

Maximum MCS for Uplink

 

Maximum MCS for Uplink is 12, but the max value varies depending on I_RU according to 36.213-Table 16.5.1.2-2.