PTRS in Downlink RACH for Phase Error Correction
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Solution Overview
Problem
Existing wireless communication systems face challenges in accurately maintaining phase continuity during downlink random access channel (RACH) communications, leading to phase drift and noise, especially in initial access scenarios where radio resource control (RRC) signaling is not available.
Innovation Solution
Incorporating a phase tracking reference signal (PTRS) within downlink RACH messages, such as RACH Message B of a two-step RACH procedure or RACH Message 4 of a four-step RACH procedure, to enable phase error correction and frequency error correction, thereby improving channel estimation and communication reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If downlink RACH messages are transmitted without PTRS, then device complexity is reduced, but phase continuity is lost causing phase drift and noise
Solution Approach 1:
The patent introduces PTRS as an intermediary reference signal embedded within downlink RACH messages to enable phase tracking. This mediator signal provides the necessary phase information for the UE to correct phase drift and maintain continuity, resolving the contradiction by adding a targeted reference component without fundamentally redesigning the entire RACH message structure.
Solution Approach 2:
The patent modifies the parameter structure of downlink RACH messages by adding PTRS configuration parameters (such as ptrs-Config, ptrs-DMRS-AssociationIndicator, and density parameters) to control the insertion and characteristics of PTRS. This allows flexible adjustment of the reference signal properties to balance between phase tracking accuracy and overall message complexity.
2Measurement precision
If PTRS is added to downlink RACH messages, then phase error correction is enabled, but message complexity increases
Solution Approach 1:
The patent segments the downlink RACH message into distinct components: the original RACH message payload and the separately inserted PTRS reference signal. This segmentation allows the PTRS to be added as a modular reference component that operates independently from the main message content, enabling precise phase measurement without redesigning the entire message structure.
Solution Approach 2:
The patent performs preliminary configuration of PTRS parameters before the actual RACH message transmission. Configuration parameters such as PTRS density, association indicators, and resource allocation are pre-established through higher-layer signaling, allowing the PTRS to be automatically inserted at predetermined locations without adding complexity during the time-critical RACH transmission process.
3Measurement precision
If PTRS is transmitted in downlink RACH messages, then frequency error correction is improved, but transmission time increases
Solution Approach 1:
The patent implements PTRS transmission in a periodic manner within the RACH message structure, where PTRS resources are allocated at specific intervals rather than continuously. This periodic insertion of reference signals enables frequency error correction through multiple measurement points while minimizing the overall time overhead compared to continuous reference signal transmission.
Solution Approach 2:
The patent applies partial action by transmitting PTRS only at strategically selected positions within the RACH message rather than throughout the entire transmission. The density and distribution of PTRS are optimized to provide sufficient frequency error correction capability while using minimal reference signal resources, thereby reducing the time penalty associated with adding PTRS to RACH messages.
Data Source
AI summary
This disclosure provides systems, methods, and apparatuses for a wireless node to receive a phase tracking reference signal (PTRS) transmitted inside a downlink random access channel (RACH) message. The wireless node may receive a downlink RACH message that includes a PTRS based on an indication received in a downlink RACH message or a physical downlink control channel (PDCCH) associated with a downlink RACH message. In some aspects, the wireless node may utilize the PTRS for phase error correction or frequency error correction (such as frequency error caused by Doppler effects). This disclosure also provides systems, methods, and apparatuses for a component of a base station to provide an indication that a PTRS is included in a downlink RACH message. The indication may be provided in a downlink RACH message or a PDCCH associated with a downlink RACH message.