5G Resource Grid:
A 5G Resource Grid is defined by one subframe (1ms) in time domain and full carrier bandwidth in frequency domain.
Example:
Consider below parameters:
Channel Bandwidth = 50MHz
Sub Carrier Spacing = 30MHz
Guard Band = 692.5KHz.
First we will calculate number of OFDM symbols in time domain:
For a SCS of 30MHz, the slot duration is 0.5ms. Each slot will hold 14 symbols, so in 1ms, it will hold 28 symbols.
Next we will calculate number of Sub Carriers:
Guard Band = 692.5 KHz. So it means, we need to remove from both sides. So we need to remove 692.5 KHz twice.
Effective Bandwidth = 500000Khz – 2(692.5)KHz = 48.615 MHz.
Number of Sub Carriers = Now divide by 30 KHz = 46.615MHz/30KHz = 1620 SC.
So total of 1620 SC in frequency domain.
Resource Grid will be as below:
It is important to note that, there can be a part of the Resource Grid can be allocated to different users.
There will be different resource grid for both uplink and downlink.
Resource Element: It is the smallest unit in resource grid that is made up of one subcarrier and one OFDM symbol.
The block in red color represents one resource element.
Resource Block: Resource Block is defined only for frequency domain. According to 38.211-4.4.4.1 ‘A resource block is defined as 12(N_RB_sc) consecutive subcarriers in the frequency domain’.
3GPP TS 38.211