Adaptive RAR Window Definition for NTN Timing
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Solution Overview
Problem
Current Random Access Response (RAR) window definitions are inadequate for Non-Terrestrial Networks (NTN) due to excessive round-trip times, which are beyond what user equipment (UE) can handle in terrestrial networks, leading to inefficiencies in random access procedures.
Innovation Solution
The proposed solution involves defining a method for a User Equipment (UE) to determine a reference symbol for the start of a response window, such as a RAR window or MsgB response window, based on an uplink symbol related to the Physical Random Access Channel (PRACH) occasion, with considerations for timing advances and subcarrier spacings, ensuring proper monitoring for responses within the NTN context.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current RAR window definitions are used in NTN, then the random access procedure can be initiated, but the excessive round-trip times cause the RAR window to expire before the response is received
Solution Approach 1:
The patent applies dynamics by making the RAR window length adaptive rather than fixed. The window length is dynamically determined based on the PRACH occasion index and subcarrier spacing, allowing the system to adjust the monitoring window duration to match the actual round-trip time conditions in NTN environments. This resolves the contradiction by enabling the RAR window to be sufficiently long to accommodate excessive round-trip times while maintaining proper timing alignment.
2Adaptability or versatility
If the RAR window start time is aligned with terrestrial network standards, then compatibility is maintained, but NTN-specific timing challenges are not addressed
Solution Approach 1:
The patent applies parameter changes by modifying the RAR window start time calculation based on NTN-specific parameters. Instead of using a fixed offset from the end of the PRACH occasion as in terrestrial networks, the patent introduces a new calculation that incorporates the PRACH occasion index and subcarrier spacing to determine an adjusted start time. This allows the system to adapt to NTN timing characteristics while using standard procedures once the window is properly defined.
3Reliability
If a longer RAR window is used to accommodate NTN round-trip times, then response reception is possible, but UE power consumption and processing complexity increase
Solution Approach 1:
The patent applies dynamics by making the RAR window length adaptive rather than uniformly long. Instead of extending the window indefinitely to cover maximum round-trip times, the window length is dynamically calculated based on the specific PRACH occasion index and subcarrier spacing configuration. This allows the UE to monitor for responses during the actual expected response period without unnecessarily extending the monitoring window, thereby reducing power consumption while maintaining reliable response reception.
Data Source
AI summary
Systems and methods for defining a Random Access Response (RAR) window for a Non-Terrestrial Network (NTN) are provided. In some embodiments, a method performed by a User Equipment (UE) comprises transmitting a first random access transmission in a Physical Random Access Channel (PRACH) occasion, the first random access transmission being either a random access preamble or a Msg A; determining a reference symbol for a start of a response window, the response window being either a RAR window or a MsgB response window; and monitoring for a response during the response window, the start of the monitoring response window being defined relative to the reference symbol. In this way, some embodiments herein eliminate the problems associated with the current RAR window timing definition, when applied in an NTN.