Rx-Tx Time Difference Mapping for TDD Timing Advance
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Solution Overview
Problem
The disparity in reporting timing advance (TA) between Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD) systems in cellular networks leads to differences in maximum cell coverage, particularly when UEs are close to the eNB, affecting positioning accuracy and cell identification.
Innovation Solution
A new Rx-Tx time difference mapping table is introduced for TDD UEs, allowing for finer granularity in reporting and compensating for the TA offset, enabling similar coverage and accuracy as FDD systems, and an Enhanced Cell Identification (ECID) mechanism is defined to consider the TA offset in position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If TDD systems use the same TA reporting mechanism as FDD systems, then implementation simplicity is maintained, but cell coverage and positioning accuracy deteriorate due to TA offset disparities
Solution Approach 1:
The patent changes the reporting parameters for TA in TDD systems by introducing a new reporting format that includes the TA offset value. This allows TDD UEs to report their timing advance information in a way that accounts for the dual-directional timing characteristics of TDD, thereby improving positioning accuracy without significantly increasing system complexity
Solution Approach 2:
The patent segments the TA reporting mechanism into different formats: one for FDD systems and a modified version for TDD systems. This segmentation allows each system type to use the reporting format optimized for its specific characteristics, resolving the contradiction between maintaining simplicity and achieving accurate positioning
2Ease of operation
If TDD UEs report TA with the same granularity as FDD UEs, then reporting simplicity is maintained, but cell coverage capability deteriorates due to insufficient resolution for close-range positioning
Solution Approach 1:
The patent introduces dynamic reporting granularity for TDD UEs, where the reporting resolution adapts based on the UE's distance from the eNB. For UEs within a threshold distance, finer granularity is used to improve positioning accuracy, while for distant UEs, the standard granularity applies, maintaining reporting simplicity across different scenarios
3Device complexity
If TA offset is not compensated in TDD systems, then system complexity is reduced, but positioning accuracy and cell identification performance deteriorate
Solution Approach 1:
The patent applies preliminary compensation for the TA offset by having the UE calculate and report the offset value in advance. The eNB uses this pre-reported offset information to correctly interpret the TA measurements, thereby improving positioning reliability without requiring complex real-time compensation mechanisms
Data Source
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AI summary
Devices and methods of determining TA for a TDD UE are generally described. A UE measures a Rx-Tx time difference (TD) of a CRS from a PCell. The Rx-Tx TD is mapped to a Rx-Tx TD value based on tables having a mapping that is dependent on whether the UE is a TDD UE or FDD UE. The Rx-Tx TD value is reported to the eNB, and, if appropriate, a timing advance (TA) command to adjust the TA received in response. The TDD table includes an offset to account switching of the UE between transmit and receive chains. Independent of which table is used, the Rx-Tx TD value range remains the same. The offset is taken into account when determining the TA and a location of the TDD UE.