Uplink Timing Advance Update via Transmission Gaps in NTN
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Solution Overview
Problem
In Non-Terrestrial Networks (NTN), the timing advance (TA) during uplink transmission in NB-IoT is not updated effectively due to long round-trip delays and large cell ranges, leading to potential orthogonality destruction of OFDM signals, especially in satellite communications where the satellite's movement causes significant propagation delay changes.
Innovation Solution
The proposed solution involves inserting transmission gaps of specific durations during uplink data transmission to update the timing advance, either by dropping data periodically or puncturing symbols, ensuring that the TA is updated frequently enough to maintain orthogonality and frequency synchronization, using transmission gaps of configurable lengths (X and Y) within or after each data transmission period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uplink data transmission continues without interruption in NTN, then transmission continuity is maintained, but timing advance becomes outdated causing orthogonality destruction
Solution Approach 1:
The patent implements periodic transmission gaps at predetermined intervals during uplink data transmission. These periodic gaps allow the UE to update timing advance values by receiving downlink signals and calculating round-trip delays, ensuring timing synchronization is maintained without completely interrupting the data transmission flow.
Solution Approach 2:
The continuous uplink transmission is segmented into multiple transmission blocks separated by periodic gaps. Each transmission block can be independently handled, and the gaps provide opportunities for timing advance updates. This segmentation allows the system to maintain overall transmission continuity while periodically refreshing synchronization information.
2Measurement precision
If transmission gaps are inserted frequently to update TA, then timing synchronization is improved, but data transmission efficiency deteriorates
Solution Approach 1:
Instead of continuously updating timing advance, the patent applies partial action by updating TA only at predetermined periodic intervals. This reduces the number of gaps inserted into the transmission stream, thereby maintaining timing synchronization accuracy while minimizing the impact on data transmission efficiency. The periodic update frequency is optimized to balance synchronization needs with throughput requirements.
3Reliability
If uplink data is dropped periodically to update TA, then frequency synchronization is maintained, but data loss increases
Solution Approach 1:
The patent uses downlink signals as an intermediary to indirectly update the uplink timing advance. Instead of directly measuring uplink timing, the UE receives downlink signals during transmission gaps, calculates the round-trip delay, and derives the timing advance value. This intermediary approach allows synchronization updates without requiring direct uplink measurement opportunities.
Solution Approach 2:
The patent discards (drops) specific uplink data transmissions at predetermined gaps to allow timing advance updates, with the expectation that the overall data can be recovered through retransmission or alternative paths. The periodic discarding of minimal data segments enables synchronization maintenance while the system recovers throughput through the continued transmission of remaining data blocks and potential retransmission mechanisms.
Data Source
AI summary
Methods and apparatuses for updating TA during uplink transmission are disclosed. A method comprises transmitting uplink data on a physical resource, wherein, the uplink data is dropped in a first time duration (Y) every a time period (X), the first time duration (Y) is in a first part and/or an end part of the time period (X).