Multi-TAG Uplink Time Alignment Across Asynchronous TRPs
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Solution Overview
Problem
Existing wireless communication systems face challenges in achieving time alignment for uplink transmissions from wireless devices (WDs) with multiple timing advance groups (TAGs), particularly in scenarios with large time differences between transmission and reception points (TRPs), leading to interference and demodulation difficulties.
Innovation Solution
A method for acquiring and maintaining timing advances (TAs) for multiple TAGs by using PDCCH orders, PRACH transmissions, and MAC CEs to associate TAs with specific TAGs, allowing flexible and efficient time alignment without requiring message exchanges between TRPs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple timing advance groups (TAGs) are used for uplink transmissions from wireless devices, then time alignment flexibility is improved, but system complexity increases due to multiple time alignment timers and TAG associations
Solution Approach 1:
The system divides the uplink transmission timing management into multiple independent Timing Advance Groups (TAGs), where each TAG is associated with a specific Transmission Reception Point (TRP) and has its own time alignment timer. This segmentation allows independent timing control for different TRPs, enabling flexible time alignment without requiring complex coordinated control across all TRPs.
Solution Approach 2:
The network node pre-configures the wireless device with multiple time alignment timers and TAG associations before uplink transmissions begin. This preliminary configuration establishes the timing management framework in advance, allowing the device to autonomously manage timing for different TRPs without real-time intervention, thereby reducing operational complexity.
2Reliability
If time alignment is maintained for multiple TAGs with large time differences, then uplink transmission synchronization is improved, but interference increases between transmissions from different TRPs
Solution Approach 1:
Each TAG is configured with a specific time alignment timer that is independently managed according to the local timing requirements of its associated TRP. This allows the system to maintain appropriate time alignment for each TRP based on its specific characteristics, preventing interference from mismatched timing while ensuring synchronization where needed.
Solution Approach 2:
The time alignment timers for different TAGs can be independently activated, deactivated, or adjusted based on the actual transmission requirements of each TRP. This dynamic management allows the system to adapt timing configurations in real-time, maintaining synchronization for active TRPs while avoiding interference from inactive or differently-timed TRPs.
3Measurement precision
If message exchanges between TRPs are required for TA association, then timing accuracy is improved, but communication overhead and latency increase
Solution Approach 1:
The network node autonomously determines and configures the association between Timing Advances (TAs) and TAGs without requiring message exchanges between TRPs. Each TRP independently provides timing information to the network node, which then configures the appropriate TAG associations. This self-service approach maintains timing accuracy while eliminating the latency and overhead associated with inter-TRP communication.
Data Source
AI summary
A method, network node and WD for time alignment enhancements for a serving cell with multiple timing advance groups (TAGs) are disclosed. According to one aspect, a method in a wireless device (WD) includes stopping first uplink transmissions associated with a first time alignment timer for a first TAG in a serving cell when the first time alignment timer expires. The method also includes continuing second uplink transmissions associated with a second time alignment timer for a second TAG in the same serving cell after the first time alignment timer has expired but before the second time alignment timer expires.