Understanding 5G Frame and Subframe Structure

This article describes the 5G frame structure used in the 5G air interface. It explains the possible combinations of the 5G subframe structure employed in the 5G downlink and uplink. We’ll also cover the mapping of 5G channels (xPDCCH, xPDSCH, xPUCCH, xPUSCH) and 5G signals (DMRS, SRS) within each of these subframes.

5G Frame Structure

Figure 1 illustrates the 5G frame structure. A single radio frame has a duration of 10ms, containing 100 slots. Each slot lasts for 0.1 ms. Two consecutive slots form one subframe, with a total duration of 0.2 ms.

There are four primary types of 5G subframes, divided into downlink and uplink subframes. Possible combinations of these are detailed below.

5G Subframe Structure: Possible Combinations

Figure 2 depicts the possible combinations of the 5G subframe structure as used in the downlink and uplink.

The following combinations are typically found within a 5G subframe:

a.) DL Control Channel, DL Data Channel b.) DL Control Channel, DL Data Channel, UL Control Channel c.) DL Control Channel, UL Data Channel d.) DL Control Channel, UL Data Channel, UL Control Channel

Both the uplink and downlink share the same basic slot structure. Each slot is composed of 7 OFDM symbols in the time domain and 100 PRBs (Physical Resource Blocks) in the frequency domain. Each PRB contains 12 subcarriers, spaced at 75 KHz.

As shown in Figure 2, each of these combinations carries the following 5G channels and 5G signals within a single subframe (i.e., in two slots):

• Combination #1: {xPDCCH, xPDSCH, xPDSCH/DMRS, xPDSCH (11 times)} OR {xPDCCH (2 times), xPDSCH/DMRS, xPDSCH (11 times)}
• Combination #2: {xPDCCH, xPDSCH, xPDSCH/DMRS, xPDSCH (9 times), Guard, xPUCCH/SRS} OR {xPDCCH (2 times), xPDSCH/DMRS, xPDSCH (9 times), Guard, xPUCCH/SRS}
• Combination #3: {xPDCCH, Guard, xPUSCH/DMRS, xPUSCH (9 times), xPUCCH/SRS (2 times)} OR {xPDCCH, Guard, xPUSCH/DMRS, xPUSCH (10 times), xPUCCH/SRS}
• Combination #4: { xPDCCH, Guard, xPUSCH/DMRS, xPUSCH (11 times) }

References

• TS V5G.201 V1.0
• Verizon 5G TF (Test Plan for Air Interface)