Timing Advance Validity Detection via TDOA Measurements
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Solution Overview
Problem
In cellular communications systems, particularly in NB-IoT and LTE-M, devices face challenges in maintaining a valid Timing Advance (TA) configuration during idle mode, leading to potential intra-cell interference due to incorrect TA values during uplink transmissions.
Innovation Solution
A method for determining the validity of a TA value by measuring Time Difference of Arrival (TDOA) between reference and neighbor base stations at two different times, allowing devices to assess whether their stored TA configuration remains valid for idle mode transmissions, and updating it if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a device uses a stored TA configuration during idle mode without validation, then power consumption is reduced and transmission efficiency is improved, but intra-cell interference increases due to potential TA invalidity
Solution Approach 1:
The device performs preliminary TDOA measurements and TA validity checks during idle mode before actual uplink transmission. By validating the TA configuration in advance using TDOA comparisons between reference and neighbor base stations, the device ensures transmission accuracy without requiring continuous network connection, thus improving power efficiency while preventing interference from invalid TA values.
Solution Approach 2:
The system implements a feedback mechanism where the device continuously monitors TDOA values and compares them against stored reference values to determine TA validity. When TDOA changes exceed a threshold indicating device movement, the device receives feedback to update its TA configuration through random access procedure, ensuring ongoing transmission accuracy while maintaining idle mode power savings.
2Reliability
If a device continuously updates TA configuration during idle mode, then TA validity is maintained, but power consumption increases
Solution Approach 1:
Instead of continuous TA updates, the device performs periodic TDOA measurements and validity checks only when needed during idle mode. The device monitors TDOA changes over time and triggers TA updates only when changes exceed a predetermined threshold, thereby maintaining reliability while minimizing unnecessary power consumption associated with continuous monitoring and updating.
Solution Approach 2:
The device performs partial validation by measuring TDOA to a subset of neighbor base stations rather than all possible base stations. This selective measurement approach provides sufficient confidence in TA validity for most scenarios while reducing the computational and energy overhead compared to exhaustive validation, achieving an optimal balance between reliability and power consumption.
3Measurement precision
If a device performs TDOA measurements to validate TA configuration, then TA validity is determined accurately, but device complexity increases
Solution Approach 1:
The device uses the same TDOA measurement capability that is already required for other cellular functions (such as positioning and neighbor cell measurement) to also validate TA configuration. By making the TDOA measurement mechanism multi-functional, the patent avoids adding dedicated hardware or complex specialized processing circuits, thereby achieving accurate TA validity determination without proportionally increasing device complexity.
Solution Approach 2:
The device autonomously performs TDOA measurements, compares measured values with stored reference values, and determines TA validity without requiring complex network assistance or external validation infrastructure. The device self-manages the entire validation process including measurement, comparison, and decision-making, which simplifies the overall system architecture while maintaining high measurement precision through sophisticated signal processing algorithms.
Data Source
AI summary
Systems and methods are disclosed herein that relate to determining Timing Advance (TA) value validity in a cellular communications system. In some embodiments, a method performed by a wireless device comprises measuring a reference time of arrival (TOA) value for a reference base station (BS) for a time T0 at which the wireless device has a valid timing advance, TA(T0), value, measuring TOA values for a set of other BSs for T0, and computing and storing time difference of arrival, TDOAX(T0), values for the other BSs for T0. The method further comprises measuring a reference TOA value for the reference BS for a time T1, measuring TOA values for the other BSs for T1, and computing time difference of arrival, TDOAX(T1), values for the other BSs for T1. The method further comprises determining whether the TA(T0) value is valid at T1 based on the TDOAX(T0) and TDOAX(T1) values.