| Overview of 5G/NR frame format |
Numerology parameter set introduction is
different from the LTE frame structure design. The frame structure in NR has different structures according to different values of the parameter set.
Sub-carrier spacing The
sub-carrier spacing is not static, but determined by the parameter u. From the following table, we can see that when u=0, it is equivalent to LTE.
Note : As the subcarrier spacing in the frequency domain becomes larger, the corresponding time slot length in the time domain becomes smaller. As shown below.
In the frequency domain, an RB is 12 sub-carrier spacing widths. The sub-carrier spacing values are different. The size of the RB is the purple value in the figure.
Although 5G supports multiple subcarrier intervals, under different subcarrier interval configurations, their radio frame and subframe lengths are fixed, that is, the frame length is 10ms and the subframe length is 1ms. The difference is: the slot contained in each subframe The numbers are different.
Physical channel OFDM symbol length supported by different subcarrier spacing parameter sets
Slot length
LTE is based on subframe SF as the basic unit for scheduling. Each frame of LTE has 10 subframes, each subframe is 1ms, contains 2 slots, and each slot has 7 symbols (ncp). However, 5G uses slot as the scheduling unit. Each frame is also 10ms, and the subframe is 1ms, but the relationship between the subframe and the number of slots is not fixed, and it changes with the change of the subcarrier interval. But each slot is determined to have 14 symbols (ncp). As shown below.
Frame structure In the
case of normal CP in the time domain, the frame structure is as follows:
1. The subcarrier spacing is 15KHz, and 1 slot=1ms, that is, 1 subframe=1 slot length.
2. The subcarrier spacing is 30KHz, 1 slot=0.5ms, that is, 1 subframe=2 slot length.
3. The subcarrier interval is 60KHz, and 1 slot=0.25ms, that is, 1 subframe=4 slot length.
4. The subcarrier spacing is 120KHz, 1 slot=0.125ms, that is, 1 subframe=8 slot length.
5. The subcarrier spacing is 240KHz, 1 slot=0.0625ms, that is, 1 subframe=16 slot length.
The composition of the radio frame in NR can be obtained from the above 5 parameter sets, which are summarized as shown in the following table.
Slot Format
NR uses slot as the basic unit of scheduling (subframes in LTE). Under normal CP, each slot contains 14 symbols fixedly. Then in each slot, which symbols are used for downlink transmission of DL and which symbols Is it used for uplink transmission UL? 14 symbols, if you use DL, UL, Flexible (upper and lower optional), you can combine a large number of scheduling methods, but 3GPP provides 61 combinations, this combination is called Slot Format. As given in the table below.
Resource Grid
The resource grid of NR is defined as shown in the figure below. The difference from LTE is that its sub-carrier spacing and the number of symbols in a frame take different values as u changes.
The definition of min\max bandwidth required for uplink and downlink transmission in NR is as follows. As can be seen from the table, 5g supports a minimum transmission bandwidth of 4.32MHz and a maximum bandwidth of 397.44MHz. Of course, this is in FR2 (millimeter wave above 24GHz) Only frequency segmentation is possible. 
The introduction to the NR frame structure is here first, and there is a need to continue to add it later.
Reference