L1/L2 Triggered Mobility with Preassigned PRACH for Fast Cell Switch
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently managing mobility and resource allocation for user equipment (UE) in heterogeneous networks, particularly in scenarios involving layer 1 or layer 2 triggered mobility, leading to suboptimal performance and increased latency.
Innovation Solution
Implementing layer 1/L2 triggered mobility mechanisms, including early TA acquisition and resource allocation strategies, to enhance UE mobility management and reduce latency in heterogeneous networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional mobility management methods are used, then system complexity is reduced, but mobility management efficiency deteriorates and latency increases
Solution Approach 1:
The patent implements early timing advance (TA) acquisition where the UE obtains TA values from candidate target cells before actual handover occurs. This preliminary action allows the UE to be pre-synchronized with the target cell, eliminating synchronization delays during handover and improving mobility management efficiency without significantly increasing system complexity
Solution Approach 2:
The patent segments the mobility management process into distinct phases: measurement phase, TA acquisition phase, and execution phase. By dividing the handover process into manageable segments with specific resources allocated to each phase, the system achieves more efficient mobility management while maintaining manageable complexity through structured resource allocation
2Loss of time
If layer 1/L2 triggered mobility mechanisms are implemented, then latency is reduced, but resource allocation complexity increases
Solution Approach 1:
The network configures and allocates dedicated physical random access channel (PRACH) resources and TA values to the UE in advance, before handover is triggered. This preliminary resource allocation eliminates the need for resource negotiation during handover execution, reducing latency while the structured configuration approach keeps resource allocation complexity manageable
Solution Approach 2:
The patent introduces a configured list of candidate target cells with pre-assigned PRACH resources and TA values as an intermediary structure. This pre-configured resource pool acts as a mediator between the network and UE during handover, enabling fast access without real-time resource allocation complexity
3Speed
If early TA acquisition is implemented, then handover speed is improved, but resource requirements increase
Solution Approach 1:
The patent segments PRACH resources into cell-specific dedicated resources for each candidate target cell in the configured list. This segmentation allows efficient reuse of resources across different cells and UEs, enabling fast handover through dedicated resources without proportionally increasing total resource requirements
Solution Approach 2:
The patent allocates specific PRACH resources and TA values locally to each candidate target cell based on its characteristics and the UE's measured conditions. This localized resource allocation optimizes handover speed for each specific target cell while avoiding unnecessary resource allocation to all possible cells, thereby controlling overall resource requirements
Data Source
AI summary
A wireless device receives, from a base station, a medium access control (MAC) control element (CE) indicating a layer 1 or layer 2 triggered mobility (LTM) cell switch from a first cell to a second cell and a resource of the second cell for a transmission, by the wireless device, of a random access preamble.