Idle-State SRS Transmission Using Timing Advance Synchronization
Solution Overview
Problem
In New Radio (NR) systems, terminal devices face challenges in transmitting Sounding Reference Signals (SRS) in idle or inactive states due to synchronization issues, as they cannot receive configurations from the network side.
Innovation Solution
The terminal device determines a first Timing Advance (TA) based on a second TA or a TA timer to transmit SRS in idle or inactive states, ensuring uplink synchronization and enabling SRS transmission without entering a connected state, thereby achieving energy savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a terminal device camps on a cell with a larger reference signal received power (RSRP) threshold, then the terminal device can wake up earlier andCamp on the cell earlier, but the terminal device may camp on a cell with poor signal quality, leading to frequent handovers and increased power consumption
Solution Approach 1:
The cell selection process is segmented into multiple stages: initial cell search using RSRP threshold for quick identification, followed by detailed evaluation using signal quality metrics (RSRQ, SINR) and cell reselection criteria. This segmentation allows the terminal to wake up early based on RSRP while ensuring final camping decision considers signal quality, preventing premature camping on poor-quality cells.
Solution Approach 2:
The terminal device performs preliminary cell measurement and identification using RSRP threshold before final camping decision. By conducting preliminary action (initial cell search) with relaxed criteria, the terminal can wake up earlier and identify candidate cells. Subsequent detailed measurement and evaluation then ensure the final camping choice meets quality requirements, resolving the contradiction between early waking and signal quality assurance.
2Reliability
If the terminal device frequently measures signal quality and performs handovers, then the signal quality can be maintained, but the power consumption increases significantly
Solution Approach 1:
The terminal device performs signal quality measurements and handovers periodically based on predefined criteria and thresholds rather than continuously. Cell reselection evaluations are triggered periodically when specific conditions are met (e.g., signal quality degrades below threshold, timer expires), reducing measurement frequency while maintaining acceptable signal quality. This periodic action significantly reduces power consumption compared to continuous monitoring.
Solution Approach 2:
The system implements feedback mechanisms where measurement results and signal quality assessments feed into subsequent decision-making. The terminal monitors signal quality metrics (RSRQ, SINR) and compares them against thresholds, triggering handovers or reselection only when feedback indicates degradation. This feedback-based approach maintains signal quality by acting only when necessary, avoiding unnecessary measurements and power consumption.
3Productivity
If the terminal device uses simplified cell selection criteria, then the cell selection process is faster and power consumption is lower, but the cell selection accuracy decreases
Solution Approach 1:
The cell selection process is segmented into two phases: initial cell identification using simplified RSRP threshold comparison for fast selection, followed by detailed cell evaluation using comprehensive metrics (signal quality, load conditions, reselection criteria). This segmentation enables fast initial selection while ensuring accurate final decision through multi-criteria evaluation, resolving the contradiction between speed and accuracy.
Solution Approach 2:
The terminal performs preliminary cell identification using simplified criteria (RSRP threshold) to quickly narrow down candidate cells. This preliminary action filters the cell list to a manageable set of candidates, after which more accurate but computationally intensive evaluation metrics are applied. The preliminary simplified selection maintains speed while the subsequent detailed evaluation ensures accuracy.
Data Source
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AI summary
Embodiments of the present disclosure provide a wireless communication method, a terminal device, and a network device, enabling the terminal device to achieve uplink synchronization in an idle state or an inactive state, thereby allowing SRS transmission. The wireless communication method includes: determining, by the terminal device, a first Timing Advance (TA); and transmitting, by the terminal device, a Sounding Reference Signal (SRS) according to the first TA. The terminal device is in an idle state, or the terminal device is in an inactive state.