Separate DMRS for LTE e-PDCCH Detection
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Solution Overview
Problem
In LTE cellular communication systems, the existing methods for detecting time-frequency resources allocated to UE-specific control channels, such as e-PDCCH, are inefficient due to high implementation complexity and inability to adapt to fast-varying channels, especially when relying on blind decoding or semi-static configuration.
Innovation Solution
The introduction of separate demodulation reference signals (DMRS) for data and control channels, where the e-PDCCH-DMRS uses a distinct modulation sequence different from PDSCH-DMRS, allowing unambiguous identification of allocated PRBs and reducing search complexity by using UE-specific e-PDCCH signature sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If blind decoding or semi-static configuration is used for detecting e-PDCCH resources, then the system can operate with existing reference signals, but the implementation complexity is high and adaptability to fast-varying channels is poor
Solution Approach 1:
The patent segments the reference signal into two distinct types: cell-specific reference signals (CRS) and UE-specific reference signals (DMRS). This segmentation allows the e-PDCCH to use DMRS which is specifically designed for UE-specific control channels, providing better adaptability to fast-varying channels while reducing implementation complexity through dedicated signal design
Solution Approach 2:
The patent introduces dynamic reference signal configuration where the e-PDCCH can be dynamically scheduled and detected using DMRS with UE-specific signature sequences. This dynamic approach allows the system to adapt to fast-varying channels by using UE-specific reference signals that change with the UE's channel conditions, rather than relying on static cell-specific reference signals
2Device complexity
If a single DMRS is used for both data and control channels, then the reference signal structure is simplified, but unambiguous identification of allocated PRBs becomes difficult
Solution Approach 1:
The patent segments the DMRS into two distinct types: PDSCH-DMRS for data channels and e-PDCCH-DMRS for control channels. Each type uses a different modulation sequence, enabling unambiguous identification of allocated PRBs. The e-PDCCH-DMRS uses a distinct modulation sequence that allows the UE to specifically identify and detect control channel resources without confusion with data channel resources
Solution Approach 2:
The patent applies local quality by assigning different modulation sequences to different channel types within the same reference signal framework. The e-PDCCH-DMRS uses a specific modulation sequence different from PDSCH-DMRS, creating local differentiation that enables clear identification of control channel PRBs while maintaining overall reference signal structure
3Difficulty of detecting and measuring
If UE-specific signature sequences are introduced for e-PDCCH-DMRS, then detection complexity is reduced and adaptability is enhanced, but the reference signal configuration becomes more complex
Solution Approach 1:
The patent makes the reference signal configuration universal by defining UE-specific signature sequences that can be applied across multiple e-PDCCH transmissions. The same signature sequence mechanism works for different UEs and different scheduling scenarios, reducing detection complexity through a unified approach while the configuration complexity is managed through standardized sequence definitions
Data Source
AI summary
The present disclosure provides a solution which solves the problem of demodulation reference signal (DMRS) ambiguity by introducing separate, i.e. different DMRSs. This is especially the case for systems employing dynamic allocation of control and data signals to different PRBs.