In 5G (Fifth Generation) wireless communication, a subframe is a fundamental time unit used in the frame structure of the air interface. The frame structure in 5G is designed to accommodate the transmission of data, control information, and various signals between the base station (gNB) and user devices (UEs). The length of a subframe in 5G depends on the specific numerology used, which defines the time and frequency configurations.
The key concept related to the length of a subframe in 5G is the slot duration. A subframe is typically divided into one or more slots, and the duration of a slot is determined by the chosen subcarrier spacing. The subcarrier spacing, measured in hertz, represents the frequency separation between individual subcarriers within a subframe.
The two primary numerology options in 5G are:
- Normal cyclic prefix (CP): In this case, the subframe duration is 1 millisecond (ms), and it is divided into 14 slots. The duration of each slot is 0.0714 ms (71.4 microseconds). The subcarrier spacing for normal CP can be either 15 kHz or 30 kHz, affecting the number of subcarriers within each slot.
- Extended cyclic prefix (CP): With an extended CP, the subframe duration remains 1 ms, but it is divided into a different number of slots. The duration of each slot is still 0.0714 ms. The subcarrier spacing for extended CP can be 60 kHz or 120 kHz.
In addition to the slot duration, it’s important to consider the number of symbols within a slot. The duration of a symbol depends on the specific subcarrier spacing and the chosen modulation scheme.
In summary, the length of a 5G subframe is 1 millisecond, and it is divided into slots, with the duration of each slot determined by the chosen subcarrier spacing and cyclic prefix configuration. The specific numerology chosen for a 5G deployment will impact the detailed characteristics of the subframe, including the number of slots and subcarriers within each slot.