5G • RAN
TBS Determination
Transport Block Size Determination
Mathematical algorithm calculating exact transport block bit size based on allocated PRBs, symbols, and MCS.
Technical Explanation
Unlike LTE which used fixed lookup tables, 5G NR determines Transport Block Size (TBS) algorithmically: (1) calculate unpunctured REs per PRB, (2) multiply by allocated PRBs and target code rate to get intermediate bits, (3) round to standardized byte-aligned quantization steps, (4) map to LDPC base graph 1 or 2.
Key Functions
- Dynamically calculates bit capacity from PRBs, symbols, and MCS index
- Adapts continuously to flexible symbol allocations and DMRS overheads
- Directs transport blocks to optimal LDPC Base Graph 1 or 2
Specifications
3GPP TS 38.214
Interfaces
Uu
Related 5G Concepts
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