DMRS Sequence Signaling for Bandwidth-Agnostic Channel Estimation
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Solution Overview
Problem
In LTE networks, the always-on Cell-specific Reference Signals (CRS) lead to high network energy consumption and unnecessary interference, while the Demodulation Reference Signals (DMRS) in NR networks pose challenges due to varying system bandwidths and terminal capabilities, requiring terminals to know their scheduled bandwidth within the system bandwidth.
Innovation Solution
The use of DMRS sequences numbered relative to the overall system bandwidth, allowing wireless communication devices to determine the overlaying portion of the sequence elements within their scheduled bandwidth without needing to know the system bandwidth, through signaling of sequence offsets or seed values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CRS are transmitted always-on across the system bandwidth, then UEs can reliably perform channel estimation and interference measurement, but network energy consumption increases and unnecessary interference is created
Solution Approach 1:
The patent applies periodic action by transmitting reference signals only during scheduled data transmissions rather than continuously. DMRS are transmitted periodically when needed for specific UE data transmissions, replacing the always-on CRS approach. This reduces network energy consumption while maintaining reliable channel estimation for active transmissions.
Solution Approach 2:
The patent extracts the reference signal transmission from the always-on CRS system and creates a separate, on-demand DMRS transmission mechanism. By taking out the reference signal function from continuous transmission and implementing it as a scheduled, data-linked transmission, the system eliminates unnecessary energy consumption while preserving estimation reliability for active data channels.
2Device complexity
If DMRS sequences are numbered globally relative to system bandwidth, then sequence alignment across different bandwidths is simplified, but terminals cannot determine their local sequence portion without knowing system bandwidth
Solution Approach 1:
The patent applies segmentation by dividing the global reference signal sequence into local segments that correspond to each UE's scheduled bandwidth. Each terminal receives only the portion of the sequence relevant to its allocated resources, determined through signaling of the first sequence number. This segmentation allows global numbering simplicity while providing local relevance without requiring terminals to know the full system bandwidth.
Solution Approach 2:
The patent introduces an intermediary signaling mechanism that provides the first sequence number to terminals. This intermediary information acts as a bridge between the global sequence numbering system and the terminal's local bandwidth, allowing terminals to identify their specific sequence portion without direct knowledge of the overall system bandwidth configuration.
3Measurement precision
If CRS are transmitted across the complete system bandwidth, then interference measurement is reliable across all bandwidths, but signaling overhead and bandwidth management complexity increase for NR with varying terminal capabilities
Solution Approach 1:
The patent applies dynamics by making the reference signal transmission adaptive to each terminal's scheduled bandwidth rather than static across the full system bandwidth. The network dynamically determines and signals the appropriate sequence portion for each terminal based on its current resource allocation. This dynamic approach maintains measurement precision for active terminals while reducing bandwidth management complexity compared to always-on full-bandwidth CRS.
Data Source
AI summary
Methods and apparatuses disclosed herein enable the use of Demodulation Reference Signal (DMRS) sequences that are numbered relative to an overall system bandwidth, while simultaneously enabling wireless communication devices to determine the DRMS sequence elements mapped to their scheduled bandwidths within the system bandwidth. Advantageously, the wireless communication devices need not know the system bandwidth, or even be aware of where their scheduled bandwidths reside within the system bandwidth.