Implicit Beam Switch via CSI Report in 5G NR
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Solution Overview
Problem
Current 5G NR technology faces challenges in optimizing beam switching processes for user equipment (UE) and base stations, particularly in reducing latency and signaling overhead, especially when transitioning between different beams for communication.
Innovation Solution
The implementation of a method where user equipment (UE) and base stations can perform beam switches based on channel state information (CSI) reports, either without waiting for a transmission configuration indicator (TCI) or after receiving confirmation through a DCI, allowing for more efficient and autonomous beam management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE waits for TCI indication from base station before beam switching, then beam switching reliability is improved, but beam switching latency increases
Solution Approach 1:
The base station pre-configures multiple TCI states and indicates them to the UE in advance through RRC signaling. The UE stores these pre-configured TCI states and can immediately switch beams by selecting from the pre-configured states without waiting for real-time TCI indications, thus reducing beam switching latency while maintaining reliability through the pre-established configuration.
2Loss of time
If the UE performs implicit beam switching without TCI indication, then beam switching latency is reduced, but beam switching reliability deteriorates
Solution Approach 1:
The UE performs implicit beam switching by selecting beams based on CSI reports and feeds back the selected TCI state index to the base station. The base station receives this feedback and confirms or adjusts the beam switching decision, providing a feedback loop that ensures beam switching reliability is maintained while enabling low-latency implicit switching without waiting for explicit TCI indications.
3Ease of operation
If the base station transmits TCI indication for every beam switch, then beam switching control is improved, but signaling overhead increases
Solution Approach 1:
The base station performs preliminary configuration of multiple TCI states and indicates them to the UE in advance through RRC signaling. This pre-configuration reduces the need for frequent TCI indication transmissions during actual beam switching operations, as the UE can select from pre-configured states, thereby reducing signaling overhead while maintaining effective beam switching control.
Solution Approach 2:
The base station uses the TCI state index from CSI reports as a reference to determine beam switching decisions. By copying the TCI state indication from the UE's CSI report feedback, the base station can confirm beam switching without transmitting entirely new TCI indications, reducing signaling overhead while maintaining control over the beam switching process.
4Productivity
If the UE uses autonomous beam selection based on CSI reports, then beam switching efficiency is improved, but beam switching accuracy deteriorates
Solution Approach 1:
The UE autonomously selects beams based on CSI reports and feeds back the selected TCI state index to the base station. The base station uses this feedback to verify the UE's autonomous selection and make final beam switching decisions. This feedback mechanism ensures that autonomous beam selection efficiency is maintained while beam switching accuracy is preserved through base station verification and adjustment.
Solution Approach 2:
The base station pre-configures multiple TCI states with specific parameters and characteristics. When the UE performs autonomous beam selection based on CSI reports, it selects from this pre-configured set of states. The preliminary configuration ensures that the autonomous selection process operates within a controlled framework, maintaining accuracy while improving efficiency by eliminating the need for real-time base station intervention in every selection decision.
Data Source
AI summary
Methods, apparatuses, and computer readable medium for beam switch are provided. An example method may include transmitting, to a base station, a channel state information (CSI) report associated with a beam switch. The example method may further include performing the beam switch based on the CSI report and an absence, for a period of time after transmission of the CSI report, of a downlink control information (DCI) including a transmission configuration indicator (TCI) indication.