NTN Uplink Synchronization Using Joint Timing and Doppler Updates
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Solution Overview
Problem
Existing satellite communication systems face challenges in managing rapid frequency and timing variations due to high-speed satellite motion, leading to substantial frequency offsets and timing drifts that require excessive signaling overhead and inefficient UE adjustments.
Innovation Solution
Implementing dynamic frequency and timing adjustment methods using MAC Control Elements (CE) and Downlink Control Information (DCI) for UEs in non-terrestrial networks, with configurable MAC-CE designs and DCI signaling to manage delay and Doppler variations, allowing UEs to self-adjust their timing and frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If timing advance and frequency offset adjustments are made separately, then control precision is improved, but signaling overhead increases
Solution Approach 1:
The patent combines timing advance adjustment and frequency offset adjustment into a single MAC CE message format. The MAC CE contains both a timing adjustment field (5 bits) and a frequency offset adjustment field (6 bits) that are transmitted together in one signaling message, thereby reducing the number of separate signaling operations while maintaining the ability to precisely control both parameters independently.
Solution Approach 2:
The MAC CE message structure is designed to serve multiple functions simultaneously: it can indicate timing advance adjustments, frequency offset adjustments, or both together. The message format includes fields that can be independently configured and interpreted by the UE, allowing a single signaling mechanism to handle multiple types of uplink synchronization adjustments.
2Adaptability or versatility
If separate MAC-CE designs are used for timing and frequency adjustments, then control flexibility is improved, but device complexity increases
Solution Approach 1:
The patent merges the functionality of separate timing adjustment MAC CE and frequency offset adjustment MAC CE into a single unified MAC CE structure. This unified message contains all necessary fields for both types of adjustments, reducing the number of different message formats the UE must handle and process, thereby simplifying device complexity while preserving control flexibility.
Solution Approach 2:
The MAC CE message structure is designed to be dynamically configurable, where the presence and interpretation of timing adjustment fields and frequency offset adjustment fields can vary based on network configuration and current synchronization needs. This dynamic structure allows the system to adapt to different scenarios without requiring multiple fixed-format messages.
3Ease of manufacture
If existing RACH-based methods are used for timing adjustment, then implementation simplicity is improved, but adaptability to Doppler variations deteriorates
Solution Approach 1:
The patent segments the uplink synchronization adjustment into two distinct components: timing advance adjustment (addressing propagation delay) and frequency offset adjustment (addressing Doppler shift). By separating these functions into distinct adjustable parameters within the MAC CE, the system maintains the simplicity of RACH-based timing acquisition while adding the capability to independently correct frequency offsets caused by Doppler effects in NTN scenarios.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances synchronization accuracy and reduces signaling overhead by enabling efficient and dynamic adjustments to frequency and timing changes in satellite communications, improving network performance.
Implementation Method 1
Methods for dynamic update for delay and doppler variations in non-terrestrial networks. Techniques for dynamic adjustment of the frequency offset and timing advance for a UE in a non-terrestrial (NTN) are described.
Data Source
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AI summary
Techniques for dynamic adjustment of the frequency offset and timing advance for a UE in a non-terrestrial (NTN) are described. Details of Medium Access Control (MAC) Control Element (CE) and Downlink Control Information (DCI) based methods for indicating the timing and/or frequency adjustment commands either separately or jointly in the presence of delay and/or Doppler variations in NTN are provided. A terminal, also known as a user equipment (UE), can use DCI or MAC signaling to update the timing and frequency adjustment in presence of delay and Doppler variations in NTN. Further, a configurable MAC-CE design is provided for indicating commands related to timing and/or frequency adjustment. Procedures are also provided to report, during a random access procedure, the timing and frequency adjustment applied in preamble transmission.