Timing Advance Resolution for Higher Band Random Access
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Solution Overview
Problem
In wireless communication systems, particularly in higher frequency bands, the existing random access channel (RACH) procedures face challenges in resolving timing advance wrap-around issues due to the cyclic prefix exceeding a full symbol duration, which limits the supportable cell size and causes ambiguity in timing advances.
Innovation Solution
The proposed method involves a four-step RACH procedure where initial timing advance information is received and updated based on multiple hypotheses to resolve timing advance wrap-around, allowing the cyclic prefix to exceed a full symbol duration, and using different PRACH numerologies for two-step and four-step RACH procedures to manage timing advances effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the cyclic prefix duration is extended to exceed a full symbol duration to support larger cell sizes in higher frequency bands, then the supportable cell size is improved, but timing advance wrap-around ambiguity occurs
Solution Approach 1:
The timing advance information is segmented into two parts: a first timing advance value transmitted in msg2 for initial uplink synchronization, and a second timing advance value transmitted in msg4 for resolving wrap-around ambiguity. This segmentation allows the system to handle both initial synchronization and precise timing correction separately, enabling accurate timing measurement even when cyclic prefix exceeds symbol duration.
Solution Approach 2:
The base station performs preliminary timing advance estimation and transmits the first timing advance value in msg2 before the UE completes the random access procedure. This preliminary action enables the UE to transmit msg3 with approximate timing alignment, allowing the base station to then accurately measure the actual timing advance and resolve any wrap-around ambiguity in the subsequent msg4 transmission.
2Measurement precision
If different PRACH numerologies are used for two-step and four-step RACH procedures to manage timing advances, then timing advance resolution is improved, but procedure complexity increases
Solution Approach 1:
Different PRACH numerologies are applied locally to different RACH procedure types: two-step RACH uses one numerology configuration while four-step RACH uses another. This local quality differentiation allows each procedure type to be optimized for its specific timing requirements, improving timing advance resolution for each procedure while maintaining clear procedural distinctions that manage overall system complexity.
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a base station may transmit, and a user equipment (UE) may receive, initial timing advance information in a msg2 communication of a four-step random access channel procedure based at least in part on a subcarrier spacing in a cell associated with the base station. The UE may transmit, and the base station may receive, a msg3 communication with an initial timing advance that is based at least in part on the initial timing advance information. The base station may transmit, and the UE may receive, updated timing advance information resolving a timing advance wrap-around between the UE and the base station based at least in part on the base station detecting the msg3 communication. Numerous other aspects are provided.