Subframes in 5G New Radio (NR) and 4G LTE differ significantly in terms of flexibility, configuration, and purpose, reflecting the advancements in technology and the broader range of use cases that 5G aims to support.
These differences highlight how 5G NR's frame and subframe structures have been designed to provide the flexibility and efficiency needed to accommodate a much wider range of use cases than 4G LTE, including those requiring high data rates, low latency, and massive connectivity.
Flexibility and Numerology:
- In 5G NR, subframes offer much greater flexibility due to the concept of numerology, which allows for different subcarrier spacings. This flexibility enables 5G to efficiently support a wide range of applications, from ultra-reliable low-latency communications (URLLC) to massive machine-type communications (mMTC), by adjusting the subcarrier spacing and, consequently, the structure and duration of slots within a subframe.
- 4G LTE uses a fixed subcarrier spacing of 15 kHz, and each subframe is rigidly defined as 1 ms in duration, divided into two slots of 0.5 ms each.
Slot Configuration:
- 5G NR's use of different numerologies allows for a dynamic number of slots within each subframe, with the potential for mini-slots that further increase scheduling flexibility and support for low-latency applications.
- In contrast, 4G LTE's subframe structure is static, with each 1 ms subframe containing exactly two slots, limiting its flexibility in supporting different latency and bandwidth requirements.
Dynamic TDD Configuration:
- 5G NR supports a more dynamic and flexible TDD (Time Division Duplex) configuration, allowing the downlink and uplink patterns within a frame to be adjusted more readily to meet varying traffic demands.
- LTE also supports TDD, but with less flexibility in dynamically adjusting the downlink and uplink configuration within the frame structure.