5G NR numerology

The 5G NR numerology for the carrier is similar to LTE includes subcarrier spacing (SCS) and CP.

15 kHz Subcarrier Spacing (SCS) is not enough and multiple larger SCS values with 2^μ × 15 kHz, where μ = 0, 1, 2, 3, 4 were introduced for the mobility requirement supporting up to 500 km/h.

The CP length is defined to well mitigate the impact of the delay spread, and have a reasonable overhead. 

In the case 15 kHz SCS of LTE, the ratio of CP length over the duration of one OFDM symbol is  7.03%, Which is reused for 5G NR in the case of 15 kHz SCS and normal CP.

 As the duration of one OFDM symbol is equal to the reciprocal of SCS, the CP length for other SCS will be proportionally reduced by 2μ, μ = 0, 1, 2, 3, 4 which keeps the same ratio of CP overhead as 15 kHz.

Supported transmission numerologies
  • Δ is the oversampling factor over 2048.
  • 240 KHz is defined in the numerology, but not used for FR1 and FR2 currently in Rel-15

NR supports multiple numerologies on the same carrier and, consequently, there are multiple resource sets of resource grids, one for each numerology Since a resource block is 12 subcarriers.

Resource grids for two different subcarrier spacing.

The resource block boundaries are aligned across numerologies such that two resource blocks at a subcarrier spacing of Δf occupy the same frequency range as one resource block at a subcarrier spacing of 2Δf.