Coherence Indication for DMRS Bundling in PUSCH
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Solution Overview
Problem
In wireless communication systems, especially in LTE and NR technologies, the base station struggles to unambiguously determine whether physical uplink shared channel (PUSCH) transmissions are phase coherent, leading to communication errors and inaccurate channel estimation due to uncertainties in phase continuity across multiple PUSCH transmissions.
Innovation Solution
User equipment (UE) transmits a coherence indication in uplink control information (UCI) multiplexed with PUSCH transmissions, indicating whether the transmissions are phase coherent, allowing the base station to determine when to perform joint channel estimation using demodulation reference signal (DMRS) bundling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the base station performs joint channel estimation across multiple PUSCH transmissions, then the spectral efficiency is improved, but the reliability deteriorates when phase coherence cannot be unambiguously determined
Solution Approach 1:
The base station transmits a coherence indication to the UE, and the UE provides feedback in the form of a coherence indicator included in UCI. This feedback mechanism allows the base station to reliably determine whether phase coherence conditions are met before performing joint channel estimation, resolving the contradiction between improving spectral efficiency through joint estimation and maintaining reliability when coherence is uncertain
Solution Approach 2:
The base station performs preliminary determination of phase coherence conditions by transmitting coherence indications to the UE before performing joint channel estimation. The UE prepares coherence indicators in advance based on these indications. This preliminary action ensures that joint channel estimation is only performed when coherence conditions are confirmed, preventing estimation errors while maintaining the opportunity for spectral efficiency improvements
2Measurement precision
If the base station transmits coherence indication to UE, then the channel estimation accuracy is improved, but the use of energy increases due to additional signaling
Solution Approach 1:
The base station transmits coherence indications selectively rather than continuously - only when needed to resolve ambiguity about phase coherence conditions. The UE similarly provides coherence indicators only when relevant. This partial action approach maintains channel estimation accuracy while minimizing the additional energy consumption from signaling overhead
Solution Approach 2:
The UE autonomously determines phase coherence conditions based on its transmission parameters (frequency resource allocation, transmit power, beam, time continuity) and provides coherence indicators in UCI without requiring continuous base station intervention. This self-service mechanism reduces the signaling overhead and energy consumption compared to a system where the base station must continuously query or dictate coherence status
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive a configuration that indicates to the UE to apply demodulation reference signal (DMRS) bundling to physical uplink shared channel (PUSCH) transmissions. The UE may maintain phase coherence across multiple PUSCH transmissions, to which the DMRS bundling is applied, to enable joint channel estimation across the multiple PUSCH transmissions. The UE may transmit, based at least in part on the configuration, uplink control information (UCI) that includes a coherence indication. The UE may multiplex the UCI with a PUSCH transmission of the multiple PUSCH transmissions to which the DMRS bundling is applied. The coherence indication may indicate whether the PUSCH transmission is coherent with one or more other PUSCH transmissions, of the multiple PUSCH transmissions, transmitted by the UE. Numerous other aspects are described.