What is 5G NR Transport Block Calculation

The technical details of 5G NR Transport Block Calculation.

The Transport Block Size (TBS) in 5G NR refers to the amount of data that can be transmitted in a single transmission time interval (TTI). It depends on various parameters, including modulation, coding rate, and the number of allocated physical resource blocks (PRBs). Here’s how you can calculate it:

1. Modulation Order (Qm): The modulation order determines how many bits can be transmitted per symbol. Common modulation schemes include QPSK, 16-QAM, and 64-QAM. The modulation order is specified by the MCS (Modulation and Coding Scheme) index.
2. Code Rate ®: The code rate represents the efficiency of error correction coding. It is typically expressed as a fraction (e.g., 1/3, 1/2). Higher code rates provide better error protection but reduce the effective throughput.
3. Number of Allocated PRBs (Nprb): PRBs are the basic frequency resource units in 5G NR. The TBS calculation considers the number of PRBs allocated for the user equipment (UE).
4. Number of Information Bits (Ninfo): This is the actual payload data size in bits.

The formula for calculating TBS is based on 3GPP 38.214 standards and involves the following steps:

1. Calculate the reference number of resource elements (REs) per RB:
   • (N_{\text{RE}} = \min(156, N’{\text{RE}}) \cdot n{\text{RB}})
   • (N’_{\text{RE}}) is the reference number of REs per RB (specified in the standard).
2. Determine the number of information bits:
   • (N_{\text{info}} = N_{\text{RE}} \cdot \text{Qm} \cdot R \cdot 1024)
3. Calculate the TBS:
   • (TBS = \frac{N_{\text{info}}}{8}) (in bytes)
4. Finally, you can convert TBS to throughput (in Mbps):
   • (\text{Throughput (Mbps)} = \frac{\text{Bandwidth (MHz)} \cdot \text{MIMO Layers} \cdot \log_2(\text{Modulation Order}) \cdot \text{Scaling Factor} \cdot \left(\frac{\text{Coding Rate}}{1024/948}\right) \cdot \text{Resource Blocks} \cdot 12 \cdot 14 \cdot 10 \cdot \frac{1000}{10} \cdot (1 – 0.14)}{1 \times 10^6})