The impact of NR Scheduling Timings on End-to-End Delay for Uplink Traffic

One of the main design targets of New Radio (NR) is to support multiple applications, including low-latency data transmissions. To achieve that, multiple features have been introduced, among which dynamic scheduling timings (denoted by K0, K1, K2) is the one which determines the delay between the different paired control and data transmissions. For example, K2 is the delay (in unit of slots) between an uplink grant reception and the corresponding uplink data transmission. The End-to-End (E2E) latency would be highly impacted by these scheduling timings. Based on the common observation, lower scheduling timings would lead to low E2E latency. However, in this paper, especially for uplink traffic, we show that this is not always true, and there are cases in which increasing the scheduling timings provides better E2E delay performance. This is due to the interplay between traffic patterns, gNB-UE process, and the NR numerology. To show such impact of scheduling timings on E2E latency with different uplink traffic patterns and NR numerologies, we implement an E2E ns-3 based NR simulator.