Uplink Synchronization Timer Management for SDT
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The management of uplink synchronization for Small Data Transmission (SDT) procedures in wireless communication systems, particularly in the context of a user equipment (UE) transitioning between connected and inactive states, is not clearly defined, leading to potential data communication latency and network inefficiencies.
Innovation Solution
The UE maintains a single time alignment timer and manages it accordingly based on transitions between connected and inactive states, specifically starting or restarting it when configured for CG-SDT operation, and stopping it when transitioning back to the connected state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE maintains separate time alignment timers for connected and inactive states, then uplink synchronization can be maintained independently in each state, but the device complexity and management overhead increase
Solution Approach 1:
The patent merges the time alignment timer management for connected and inactive states into a single unified timer (TAT). Instead of maintaining separate timers for different RRC states, the same TAT is used across both states, simplifying the timer management mechanism while ensuring consistent uplink synchronization control throughout state transitions.
Solution Approach 2:
The time alignment timer is designed to serve multiple functions across different RRC states. The same TAT operates during both RRC_CONNECTED and RRC_INACTIVE states, providing universal timing management for uplink synchronization regardless of the current state, thereby reducing complexity while maintaining reliability.
2Reliability
If the UE transitions to connected state for data transmission, then data communication reliability is improved, but the transition latency and network inefficiency increase
Solution Approach 1:
The network performs preliminary actions by configuring the UE with SDT resources and parameters while the UE is still in the inactive state. This includes providing configured grant resources, path loss reference signals, and other transmission parameters in advance, so that the UE can immediately resume data transmission without requiring a full state transition to connected mode.
Solution Approach 2:
The patent enables dynamic operation where the UE can flexibly switch between inactive state with SDT and connected state based on data transmission needs. The UE maintains the ability to perform uplink transmissions in inactive state when data volume is small, and only transitions to connected state when necessary, optimizing the balance between latency and resource utilization.
3Measurement precision
If the UE performs random access procedure for uplink synchronization, then timing alignment accuracy is improved, but the access latency and network overhead increase
Solution Approach 1:
The UE performs self-service for uplink synchronization by autonomously determining timing alignment based on downlink reference signals and path loss measurements. The UE calculates the timing advance offset using the configured path loss reference signal and applies it to maintain uplink synchronization without requiring network intervention through random access procedures.
Solution Approach 2:
The patent replaces the traditional mechanical random access procedure with a calculated timing advance mechanism. Instead of using the random access preamble exchange to obtain timing alignment, the UE substitutes this with a direct calculation based on downlink path loss measurements and configured offset parameters, eliminating the need for the multi-step random access protocol.
4Productivity
If the UE maintains configured grant resources in inactive state, then data transmission efficiency is improved, but the risk of uplink desynchronization and network inefficiency increases
Solution Approach 1:
The network provides feedback mechanisms to monitor and maintain uplink synchronization while the UE operates in inactive state with configured grant resources. The network can detect uplink desynchronization conditions and trigger synchronization procedures or state transitions, ensuring that the configured grant resources remain effective and synchronized with network expectations.
Data Source
AI summary
A method, performed by a UE, of managing time alignment includes receiving a timing advance command from a RAN, starting or restarting a first time alignment timer that indicates validity of a CG configuration when the UE is in an RRC connected state with the RAN, and then receiving a first message from the RAN. The method also includes, in response to the first message, transitioning from the RRC connected state to an RRC inactive state, stopping the first time alignment timer, and starting or restarting a second time alignment timer that indicates validity of a CG-SDT configuration when the UE is in the RRC inactive state, and then receiving a second message from the RAN. The method also includes, in response transitioning to the RRC connected state, again starting the first time alignment timer, and communicating data with the RAN.