NTN Handover RACH Timing to Reduce UE Access Contention
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Solution Overview
Problem
Current wireless communication systems face challenges in managing mobility and access control, particularly in Non-Terrestrial Networks (NTN) where satellite movement leads to simultaneous handovers of multiple User Equipments (UEs), resulting in increased RACH contention and access delays.
Innovation Solution
The proposed solution involves configuring wireless devices with a randomly generated time delay for initiating Random Access Channel (RACH) procedures, as well as methods for UE assistance information reporting to verify the accuracy of reported locations, thereby enhancing mobility management and access control efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If satellite movement enables continuous coverage in NTN, then network coverage is improved, but simultaneous handovers of multiple UEs cause increased RACH contention and access delays
Solution Approach 1:
The network device pre-configures handover parameters and RACH resources to UEs before handover execution. This preliminary configuration includes providing multiple RACH occasion candidates and associated parameters, allowing UEs to quickly initiate handover without extensive real-time negotiation, thereby reducing access delays while maintaining continuous coverage
Solution Approach 2:
The RACH procedure is segmented into multiple independent RACH occasions with different time offsets. Instead of a single centralized RACH process, the system divides the random access opportunities into multiple segments (different RACH occasions), allowing UEs to distribute their access attempts across different time slots, thereby reducing contention and delays
2Stability of the object's composition
If multiple UEs perform handover simultaneously due to satellite movement, then mobility continuity is improved, but RACH contention increases
Solution Approach 1:
The system dynamically adjusts RACH occasion assignments based on UE characteristics and channel conditions. Different UEs are assigned different RACH occasions with varying time offsets, creating a dynamic distribution pattern that adapts to changing mobility patterns and reduces simultaneous contention while maintaining seamless handover
Solution Approach 2:
The network device pre-assigns different RACH occasion parameters to different UEs before handover execution. This preliminary differentiation of RACH resources ensures that even when multiple UEs handover simultaneously, they access the network through different time-spread RACH occasions, reducing contention while preserving mobility continuity
3Speed
If UEs initiate RACH immediately upon handover decision, then handover speed is improved, but access failure rate increases due to contention
Solution Approach 1:
The network device provides UEs with pre-configured RACH parameters including multiple occasion candidates and selection criteria before handover. UEs can immediately select and initiate RACH based on pre-provided guidance, maintaining fast handover speed while the diversified occasion selection reduces contention-induced failures
Solution Approach 2:
The system changes RACH parameter values (time offsets, frequency resources) across different RACH occasions. By providing UEs with multiple parameter sets and enabling selection based on current conditions, the system maintains fast access initiation while parameter diversity reduces the probability of collision and failure
Data Source
AI summary
This document discloses methods, apparatus, and systems that conduct mobility management and access control in wireless communication systems. In one example aspect, a method for wireless communication includes receiving, by a wireless device, from a network device, a configuration information comprising handover configuration information; and initiating, by the wireless device, a handover process based on the configuration information.