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5G NR Resource Block Definition and RB calculations

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5G NR Resource Block Definition:

In 5G NR, a resource block is the smallest unit of resource allocation. It is a time-frequency resource that can be allocated to a user or a service. Resource blocks are used for both downlink (DL) and uplink (UL) transmissions.

Frequency Domain:

In the frequency domain, a resource block is defined as a set of consecutive subcarriers. The basic resource block in 5G NR is 12 subcarriers wide. The subcarrier spacing can be either 15 kHz or 30 kHz, depending on the numerology used (e.g., normal or extended CP - cyclic prefix, and different subcarrier spacings for different frequency ranges).

  • For example, with a 15 kHz subcarrier spacing, a basic resource block would span 180 kHz (12 subcarriers * 15 kHz).

Time Domain:

In the time domain, a resource block corresponds to a slot in the time domain. A slot is a unit of time that consists of a certain number of symbols, and the number of symbols per slot depends on the subcarrier spacing and the chosen numerology.

  • For example, in a normal CP scenario with a 15 kHz subcarrier spacing, a slot might consist of 14 symbols, and a resource block would occupy one slot.

Resource Block Calculations:

Frequency Domain Calculations:

  1. Carrier Bandwidth (B): The carrier bandwidth is determined by the subcarrier spacing (Δf) and the number of subcarriers in a resource block (N).�=�×Δ�B=N×ΔfWhere �B is the carrier bandwidth, �N is the number of subcarriers in a resource block, and Δ�Δf is the subcarrier spacing.
  2. Frequency Range:The frequency range covered by a resource block can be calculated based on the carrier frequency (f) and the carrier bandwidth (B).Frequency Range=[�−�/2,�+�/2]Frequency Range=[f−B/2,f+B/2]

Time Domain Calculations:

  1. Slot Duration (T_slot): The slot duration is determined by the symbol duration (T_symbol) and the number of symbols per slot (NS).�slot=�S×�symbolTslot​=NS​×Tsymbol​Where �slotTslot​ is the slot duration, �SNS​ is the number of symbols per slot, and �symbolTsymbol​ is the symbol duration.
  2. Slot Structure:The slot structure depends on the chosen numerology and whether normal or extended cyclic prefix is used. For example, a slot might consist of different numbers of symbols and be divided into different parts (e.g., control region and data region).

These calculations may vary based on the specific 5G NR parameters chosen, so it's important to refer to the 3GPP specifications for the exact details and formulas based on the deployment scenario.