16 4.2.2 self-contained integrated subframe the

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16 4.2.2 Self-contained integrated subframe The self-contained integrated subframe is another key enabler for lower latency, forward compatibility, and many new 5G NR features. The lower latency is achieved by having the data transmission and its acknowledgement all contained in the same subframe. Figure 16 shows an example of a TDD downlink-centric subframe, where data transmission is from the network to the device and the acknowledgement is sent by the device back to the network in the same subframe. With the 5G NR self-contained integrated subframe, each TTI is now a modular transaction (e.g., DL grant DL data Guard Period UL ACK) that gets completed within that time period. Figure 16: Self-contained integrated subframe design (e.g., TDD downlink) The modular aspect of the self-contained integrated subframe design also allows for different types of subframes to be multiplexed for new services that are introduced in the future. This, along with the ability for the 5G NR framework to support blank subframes and blank frequency resources, enables a forward-compatible 5G NR design for easily adding future features/services to be deployed in the same frequency in a synchronous and asynchronous manner. The subframe can also contain additional headers that can be used to provide additional information for the transmission. For example, operating in unlicensed spectrum requires typically requires the support LBT46to ensure fair sharing across different users. These LBT headers, sent by the network, are used by downlink devices to assess channel availability for data transmission. And when used in device-to-device communications, these headers can indicate the link direction and provide scheduling information for the directly connected devices. The self-contained subframe also plays an integral role in enabling advanced 5G NR antenna techniques, such as massive MIMO. In the downlink, in order for a transmitting cell to more efficiently direct RF energy to a device, it needs to continuously evaluate link quality and make necessary beamforming adjustments. The feedback mechanism is provided by the transmission of common uplink burst, which carries uplink control information (e.g., the ACK) and the uplink sounding reference signals. More accurate and timely knowledge of downlink channel can be obtained at the base stations thanks to the channel reciprocity, which enables the use of uplink sounding reference signal for downlink channel estimate in a TDD 46Listen-Before-Talk
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  • Fall '19
  • Mobile network operator, NR, WiMAX, 3GPP Long Term Evolution, 5G NR

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