L1/L2 Triggered Mobility Random Access Preamble Power Ramping
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Solution Overview
Problem
Current 5G mobile communication systems face challenges in providing low latency and low complexity while avoiding user plane data loss, especially in scenarios requiring rapid mobility and efficient resource utilization across broad frequency bands.
Innovation Solution
The implementation of Layer 1 (L1)/Layer 2 (L2)-triggered mobility (LTM) in telecommunication networks, which involves a method for UE to initiate and manage random access procedures, perform cell switches, and maintain data transmission without resetting user plane data, using RRC signaling to configure LTM candidate cells and indicators for MAC, RLC, and PDCP re-establishment or recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional random access procedures are used for cell switching in 5G networks, then user plane data loss can be avoided through proper re-establishment, but latency increases and complexity increases due to multiple re-transmission attempts and power ramping counter management
Solution Approach 1:
The patent applies preliminary action by pre-configuring uplink data resources and configuring the UE with LTM candidate cell configurations including PDCCH monitoring configurations before mobility execution is needed. This allows the UE to quickly switch cells without waiting for random access procedures, thereby reducing latency while maintaining reliability through pre-established data transmission paths.
Solution Approach 2:
The patent extracts the random access procedure from the mobility execution path for LTM candidate cells. By removing the mandatory random access step and allowing direct data transmission on pre-configured resources, the system achieves lower latency while maintaining user plane data integrity through proper MAC and RLC re-establishment procedures.
2Reliability
If traditional random access procedures with power ramping are implemented for LTM, then connection reliability is maintained through re-transmission attempts, but device complexity increases due to counter management and power adjustment logic
Solution Approach 1:
The patent removes the power ramping counter management logic from the LTM execution procedure. By extracting this complex logic and replacing it with pre-configured uplink resources and simplified transmission procedures, the device complexity is reduced while connection reliability is maintained through alternative mechanisms such as pre-configured redundancy and proper MAC/RLC re-establishment.
Solution Approach 2:
The system uses self-service by pre-configuring all necessary parameters, resources, and configurations for LTM candidate cells before mobility is needed. This eliminates the need for complex real-time decision-making and counter management during execution, as the UE simply follows the pre-configured instructions, thereby reducing device complexity while maintaining reliability.
3Loss of time
If LTM with pre-configured resources is used, then latency is reduced and complexity is lowered, but adaptability decreases due to fixed resource allocations
Solution Approach 1:
The patent applies dynamics by configuring multiple LTM candidate cells with different PDCCH monitoring configurations and uplink resource settings. The UE can dynamically select among these pre-configured options based on current channel conditions and network instructions, thereby maintaining adaptability while benefiting from the low-latency LTM mechanism. The system remains flexible as configurations can be updated through RRC signaling when needed.
Data Source
AI summary
A method of transmitting a random access preamble in a telecommunication system is provided. The method includes, if the random access procedure is initiated by a physical downlink control channel (PDCCH) ordering for a layer 1 (L1)/layer 2 (L2)-triggered mobility (LTM) candidate cell as preamble re-transmission, and incrementing a variable, PREAMBLE_POWER_RAMPING_COUNTER, by 1.