Self-Contained Slot in 5G NR

What is a Self-Contained Slot?

The Self-Contained Slot can be defined as a slot that contains the Downlink part, Uplink part, and a Guard Period.

• It was introduced in 5G-NR and this design system was not available in LTE.
• This provides flexibility in NR which delivers significantly lower latency when compared to LTE.

Time Slots in 5G NR

In 5G New Radio (NR), a "time slot" refers to a discrete unit of time within the radio frame structure used for the transmission and reception of data. Time slots are an essential concept in wireless communication systems, managing the flow of data between the base station (gNB) and user devices (UEs).

• Frame Structure: The radio frame is divided into subframes, and each subframe contains a fixed number of time slots depending on the numerology (SCS).
  • Example: For 30 kHz SCS, there are 2 slots in a subframe.
• Scheduling: Time slots can be allocated for both Uplink (UL) and Downlink (DL). The gNB dynamically schedules these based on communication needs.

Industry Definition

Although 3GPP has not defined any term "Self-Contained" type Slot, it is commonly referred to in the industry.

Structure of a Self-Contained Slot:

1. The downlink and uplink are separated by a Guard Period.
2. There can be Downlink Self-Contained Slots and Uplink Self-Contained Slots.

• Downlink Self-Contained Slot: Consists of Downlink Data + Guard Period + Uplink HARQ Feedback.
• Uplink Self-Contained Slot: Consists of Downlink Scheduling Information + Guard Period + Uplink Data.