Cellular Beam Switching With Buffered Feedback During Uplink TCI
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Solution Overview
Problem
Existing beam management techniques in cellular communication networks, particularly in 5G NR, face inefficiencies due to unequal delays in uplink and downlink TCI state switching, leading to prolonged periods where devices cannot be scheduled for data reception or transmission during beam switching, which is comparable to handover delays.
Innovation Solution
Implementing a method where devices receive downlink transmissions before completing uplink TCI state switching by utilizing a unified or separate TCI state switch command, allowing devices to buffer feedback information and schedule downlink transmissions during the uplink switch period, thereby reducing the unscheduled time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If devices wait to complete uplink TCI state switching before receiving downlink transmissions, then uplink beam switching reliability is improved, but downlink scheduling productivity deteriorates due to prolonged unscheduled periods
Solution Approach 1:
The network node transmits downlink transmissions to the device before the uplink TCI state switching is completed. The device receives and buffers these transmissions during the switching period, then transmits feedback after switching completes. This preliminary action allows downlink scheduling to proceed without waiting for uplink switching to finish, resolving the contradiction between maintaining reliable uplink switching and maintaining productive downlink scheduling.
2Reliability
If devices complete both uplink and downlink TCI state switching before scheduling, then beam switching reliability is improved, but network performance productivity deteriorates due to extended unscheduled time
Solution Approach 1:
The system allows downlink transmissions to be scheduled and transmitted before the uplink TCI state switching completes. The device buffers these preliminary downlink transmissions and transmits feedback after uplink switching completes. This separates the scheduling decision from the feedback transmission timing, allowing the network to maintain productive scheduling while ensuring reliable feedback delivery after beam switching completes.
3Speed
If devices transmit feedback information immediately after receiving downlink transmissions, then communication speed is improved, but feedback reliability deteriorates due to TCI state mismatch
Solution Approach 1:
The device receives downlink transmissions and buffers them during the uplink TCI state switching period. Instead of transmitting feedback immediately (which would cause TCI state mismatch), the device waits until uplink switching completes, then transmits the buffered feedback. This preliminary buffering action maintains communication speed by keeping data ready while ensuring feedback reliability by transmitting only after the correct uplink beam state is established.
4Adaptability or versatility
If devices use separate TCI state switch commands for uplink only, then scheduling flexibility is improved, but device complexity increases due to independent switching management
Solution Approach 1:
The TCI state switching is segmented into independent uplink and downlink components. The network can send separate TCI state switch commands for uplink only, allowing independent control of uplink beam switching without affecting downlink scheduling. This segmentation provides scheduling flexibility while the device manages each direction independently, reducing the complexity of coordinated switching while maintaining adaptability.
Data Source
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Figure 3(a)~3(b)
AI summary
According to an example aspect of the present disclosure, there is provided an apparatus comprising means for receiving, from a wireless network node, a Transmission Coordination Indication, TCI, state switch command, the TCI state switch command commanding the apparatus to perform at least an uplink TCI state switch, means for receiving, from the wireless network node, at least one downlink transmission before the uplink TCI state switch is required to be completed and means for transmitting, to the wireless network node, feedback information related to the at least one downlink transmission after completing the uplink TCI state switch.