RAR Window Start Position in Non-Terrestrial Networks
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Solution Overview
Problem
In non-terrestrial network communications, the extended and varying propagation delays cause synchronization issues between user equipment (UE) and the network regarding when to start monitoring for a random access response (RAR) within the RAR window.
Innovation Solution
The techniques involve determining the start position of the RAR window based on the random access occasion, round trip time parameters for non-terrestrial network communications, and one or more timing offset parameters, ensuring that the UE and network are synchronized despite varying propagation delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the RAR window start position is determined using conventional timing parameters, then the system works for terrestrial networks, but synchronization fails in non-terrestrial networks due to extended and varying propagation delays
Solution Approach 1:
The patent changes the timing parameters used to determine the RAR window start position. Specifically, it introduces new parameters (k_mac and offset_X) that account for non-terrestrial network propagation characteristics, replacing or supplementing conventional terrestrial network timing parameters. This allows the system to adapt to extended and varying propagation delays in satellite and other non-terrestrial networks.
Solution Approach 2:
The patent makes the RAR window start position dynamic by allowing it to be adjusted based on the actual propagation delay characteristics of the non-terrestrial network. The timing parameters are no longer fixed but are dynamically determined based on network-specific conditions, enabling the system to adapt to varying propagation delays differentially across the coverage area.
2Device complexity
If the RAR window start position is fixed relative to the RA occasion, then the timing is simple to calculate, but the UE and network become desynchronized due to varying propagation delays in non-terrestrial networks
Solution Approach 1:
The patent introduces additional parameters (k_mac representing portion of round trip time and offset_X) that modify the timing calculation. While this increases the number of parameters, it maintains a systematic approach where the RAR window start is still calculated relative to the RA occasion, just with adjusted timing values that account for non-terrestrial propagation delays.
Solution Approach 2:
The patent applies preliminary timing adjustments by pre-calculating the appropriate offset based on the non-terrestrial network propagation characteristics before the random access procedure begins. The network configures the UE with the appropriate timing parameters in advance, allowing the UE to correctly determine the RAR window start position without real-time adjustments during the access procedure.
3Ease of manufacture
If conventional timing parameters are used for RAR window determination, then the system is simple to implement, but downlink performance and RAR reception latency are degraded in non-terrestrial networks
Solution Approach 1:
The patent modifies the timing parameters (introducing k_mac and offset_X) to optimize RAR window positioning for non-terrestrial networks. This ensures that the RAR window starts at the correct time accounting for extended propagation delays, thereby improving RAR reception efficiency and reducing latency while maintaining a relatively simple implementation approach.
Solution Approach 2:
The patent adapts the terrestrial network timing mechanism by creating a modified version that incorporates non-terrestrial propagation characteristics. Rather than creating an entirely new mechanism, it copies the existing RAR window determination approach and adjusts the timing parameters to suit non-terrestrial networks, preserving implementation simplicity while improving performance.
Data Source
AI summary
Certain aspects of the present disclosure provide techniques and apparatus for random access channel communications in non-terrestrial networks. A method that may be performed by a user equipment (UE) includes transmitting a physical random access channel (PRACH) preamble to the network entity in a random access (RA) occasion; and monitoring for a random access response (RAR) within a RAR window with a start position determined based at least in part on the RA occasion, round trip time parameters for non-terrestrial network communications, and one or more timing offset parameters.