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RG vs RB vs RE | Difference between RG RB RE in 5G NR

This page compares Resource Grid (RG) vs Resource Block (RB) vs Resource element (RE) and mentions difference between Resource Grid (RG), Resource Block (RB) and Resource element (RE) in 5G NR system.

As shown in the figure-1, a frame in 5G NR consists of 10 ms duration. A frame consists of 10 subframes with each having 1ms duration similar to LTE. Each subframe consists of 2μ slots. Each slot can have either 14 (normal CP) or 12 (extended CP) OFDM symbols. All the subcarrier spacing options have 14 OFDM symbols. 60 KHz spacing supports both normal and extended CP types.

5G NR Frame Structure-slot,mini-slot

For μ = 0 there are 1 slots per subframe , for μ = 1 there are 2 slots per subframe, for μ = 2 there are 4 slots per subframe and so on. Number of slots per frame is ten times of number of slots per sub frame. Hence for μ = 2, there are 40 slots/frame. 5G NR uses 4096 FFT points which consists of 3300 data subcarriers.

5G NR Numerology

Like OFDMA used in mobile wimax and LTE, the resources are mapped across time and frequency grid in the 5G NR too. This is shown in the figure-1.


Resource Grid

• The resource grid which consists of number of subcarriers in frequency axis and number of OFDM symbols in time axis is known as resource grid.
• There is one set of resource grids assigned per transmission direction("x") (uplink and downlink).
• There is one set of resource grid assigned for each of the antenna ports ("p") as per subcarrier spacing configuration ("μ").
• 5G NR supports (Ngrid,x)size,μ X (NSC)RB subcarriers and (Nsymb)subframe,μ OFDM symbols.

➤Carrier bandwidth (Ngrid)size,μ for "μ" is given by higher layer parameters viz. "carrierBandwidth" in the "SCS-SpecificCarrier IE".
➤Starting position (Ngrid)start,μ for "μ" is given by higher layer parameters viz. "offsetToCarrier" in the "SCS-SpecificCarrier IE".

Resource Block

• RB (Resource Block) consists of total 12 consecutive subcarriers in frequency domain.
• (NSC)RB = 12
• Following table mentions (NRB)μ for each of the subcarrier spacing configurations ("μ").
• There are more than one RBs in a resource grid.
• Resource elements are grouped into PRB (Physical Resource Blocks). Each PRB consists of 12 subcarriers as mentioned.
• For each numerology and carrier, a resource grid of (NRB)max,μ subcarriers and (Nsymb)subframe,μ OFDM symbols are defined. Resource grids for all subcarrier spacing are overlapped.

5G NR Resource Blocks

Resource Element

• Each element in resource grid for antenna port ("p") and subcarrier spacing configuration ("μ") is known as Resource Element.
• It is uniquely identified by (k,l)p,μ, where
k = index in the frequency domain.
l = symbol position in time domain.

• Resource element (k,l)p,μ corresponds to a physical resource and the complex value (ak,l)p,μ.

5G NR Numerology | 5G NR Terminology

5G NR Control channels | 5G NR Traffic Channels | 5G NR Reference Signals and sequences


This 5G tutorial also covers following sub topics on the 5G technology:
5G basic tutorial
5G Frequency Bands
5G millimeter wave tutorial
5G mm wave frame
5G millimeter wave channel sounding
Difference between 4G and 5G
5G testing and test equipments
5G network architecture
5G NR Physical layer
5G NR MAC layer
5G NR RLC layer
5G NR PDCP layer

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