RF5G NR: FFT Size, Sampling Time, and Subcarrier Parameters
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subcarrier spacing
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This page details the 5G NR (New Radio) FFT Size, Sampling time, Effective Subcarriers, symbol length, subcarrier spacing, and other related parameters as defined in the 3GPP 5G NR standard.
Introduction
5G NR (New Radio) is the latest cellular wireless technology following 3GPP specifications, similar to LTE, and defined in the 38 series of documents. The various physical layer parameters are outlined in Table 1.
Table 1
| Parameters | Description/value |
|---|---|
| FFT Size | 4096 |
| Effective Subcarriers | 3300 for maximum bandwidth of 400 MHz |
| Sampling time |  It is 0.509 ns for subcarrier spacing of 480 KHz. |
| Subcarrier spacing | Supports different subcarrier spacings such as 15 KHz, 30 KHz, 60 KHz, 120 KHz, 240 KHz and 480 KHz. |
| Symbol length | The symbol lengths vary as per subcarrier spacings. It is 66.7 µs (for 15 KHz), 33.3 (for 30 KHz), 16.7 (for 60 KHz), 8.33 (for 120 KHz), 4.17 (for 240 KHz) and so on. |
Other 5G NR physical layer parameters are mentioned in Table 2.
Table 2: Subcarrier spacing, Number of OFDM symbols and slots
| Subcarrier spacing (KHz) | 15 | 30 | 60 | 120 | 240 |
|---|---|---|---|---|---|
| Symbol duration (µs) | 66.7 | 33.3 | 16.7 | 8.33 | 4.17 |
| CP duration (µS) | 4.7 | 2.3 | 1.2 (Normal CP), 4.13 (Extended CP) | 0.59 | 0.29 |
| Max. nominal system BW (MHz) | 50 | 100 | 100 (sub-6 GHz), 200 (mmwave) | 400 | 400 |
| FFT size (max.) | 4096 | 4096 | 4096 | 4096 | 4096 |
| Symbols per slot | 14 | 14 | 14 (normal CP), 12 (extended CP) | 14 | 14 |
| Slots per subframe | 1 | 2 | 4 | 8 | 16 |
| Slots per frame | 10 | 20 | 40 | 80 | 160 |
References
- 3GPP TS 38.214, V15.2.0 (June, 2018), NR; Physical layer procedures for data
