In 5G, 1 PRB (Physical Resource Block) is equivalent to 12 subcarriers.
Understanding the 5G NR Physical Resource Block (PRB)
The Physical Resource Block (PRB) is a fundamental unit used in 5G New Radio (NR) for allocating frequency resources to users. Unlike its predecessor in LTE, where the PRB defined both frequency and time dimensions, the 5G NR PRB specifically defines resource allocation in the frequency domain only.
Based on the provided reference, the core definition remains consistent:
- 1 PRB = 12 consecutive subcarriers
The total bandwidth available in 5G is divided into these PRBs, which are then allocated to different users or services based on their needs and scheduling decisions by the network.
PRB Components: Subcarriers and Numerology
While a PRB always contains 12 subcarriers, the actual frequency width covered by a single PRB is not fixed. This is because the spacing between the subcarriers can vary in 5G NR.
- Subcarriers: These are individual, narrow frequency bands that together make up the wider channel used for communication. A PRB bundles 12 of these together.
- Numerology: In 5G NR, different 'numerologies' are defined, primarily corresponding to different subcarrier spacings. Common numerologies include 15 kHz, 30 kHz, 60 kHz, etc.
The subcarrier spacing is based on the chosen Numerology. This means:
- A PRB with 15 kHz subcarrier spacing covers 12 * 15 kHz = 180 kHz.
- A PRB with 30 kHz subcarrier spacing covers 12 * 30 kHz = 360 kHz.
- And so on...
This flexibility in numerology allows 5G networks to efficiently support a wide range of services, from low-latency applications requiring smaller subcarrier spacing to wideband applications benefiting from larger spacing.
Key Points about 5G PRBs
- A 5G NR PRB defines resources in the frequency domain only.
- It consists of exactly 12 subcarriers.
- The frequency width of a PRB depends on the chosen numerology (subcarrier spacing).
- PRBs are the basic units for frequency resource allocation in 5G scheduling.
