5G NR TBS Calculation: Transport Block Size

This page explains the 5G NR TBS (Transport Block Size) determination procedure. The TBS calculation relies on factors like Qm, R, v, and the number of REs (Resource Elements) as outlined in the 5G NR 38.214 standard.

This document provides the formulas and equations used in 5G NR TBS calculation.

5G NR Transport Block Size (TBS) Calculation | 5G NR TBS Determination Procedure

The following sections describe the 5G NR TBS determination procedure, including the formulas and equations used in the TBS calculation.

** Step-1:**

In the 5G NR standard, three tables (5.1.3.1-1, 5.1.3.1-2, and 5.1.3.1-3) specify the modulation order (Qm) and target code rate (R) based on the MCS Index (I_MCS). For this calculator, we’ll directly input Qm and R for the TBS calculation.

** Step-2:**

N_RE (Number of Resource Elements) is determined based on N’_RE and n_PRB. Here, N’_RE represents the number of REs allocated for PDSCH (Physical Downlink Shared Channel) within a PRB (Physical Resource Block). We will directly use N_RE as an input for the TBS calculator.

** Step-3:**

First, calculate N_info from N_RE, R, Qm, and v using the following procedure for TBS (Transport Block Size) determination:

• For N_info <= 3824: Follow procedure-1 (Step-3 in the PDF document).
• For N_info > 3824: Follow procedure-2 (Step-4 in the PDF document).

** Refer to the PDF below for a complete understanding of 5G NR TBS determination or calculation:**