DMRS Structure for E-PDCCH Channel Estimation
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Solution Overview
Problem
In LTE Rel-11 wireless communication systems, the existing DMRS structure for receiving Enhanced PDCCH (E-PDCCH) in a subset of resource blocks with limited frequency domain bandwidth leads to degraded channel estimation and decoding performance due to insufficient DMRS resources, particularly when early decoding is required for DL control information.
Innovation Solution
The proposed solution modifies the DMRS structure by allocating 12 DMRS resource elements per antenna port in the first slot and maintaining 12 DMRS resource elements in the second slot for improved channel estimation, allowing for better decoding performance of E-PDCCH while supporting up to 2 DL E-PDCCHs in the first slot and UL E-PDCCHs in the second slot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DMRS structure is modified to allocate 12 DMRS resource elements per antenna port in the first slot, then channel estimation performance is improved, but the number of multiplexed DL E-PDCCHs is reduced
Solution Approach 1:
The patent applies local quality by differentiating DMRS resource element allocation between the first slot (for E-PDCCH reception with enhanced channel estimation) and the second slot (for data reception with standard channel estimation). This allows optimized performance for each specific function without compromising the other, resolving the contradiction between channel estimation quality and multiplexing capacity.
2Reliability
If DMRS resource elements are increased in the first slot for better channel estimation, then decoding performance of E-PDCCH is improved, but spectral efficiency is reduced
Solution Approach 1:
The patent segments the subframe into two slots with different DMRS allocation strategies. The first slot receives enhanced DMRS resources (12 REs per antenna port) for reliable E-PDCCH decoding, while the second slot uses standard DMRS allocation for data transmission. This segmentation allows the system to optimize for reliability where needed without permanently sacrificing spectral efficiency across the entire subframe.
3Loss of time
If DMRS structure is modified to support early decoding of DL control information, then HARQ-ACK preparation time is improved, but the complexity of DMRS structure increases
Solution Approach 1:
The patent implements preliminary action by allocating additional DMRS resource elements in the first slot before data transmission occurs. This enables the UE to perform channel estimation and decode E-PDCCH information earlier than traditional methods, allowing timely HARQ-ACK preparation without requiring complex structural changes to the overall system architecture.
Data Source
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Figure 1C
AI summary
A wireless communication terminal receives a first set of pilot signal resource elements and control information in one or more spatial layers in a first resource block in a sub-frame and a second set of pilot signal resource elements and data in one or more spatial layers in a second resource block in the sub-frame, wherein the first and second resource blocks span a set of time symbols in a sub-frame, the first resource blocks span a first set of frequency carriers in the sub-frame, and the second resource blocks span a second set of frequency carriers in the sub-frame. The terminal decodes the one or more spatial layers in which the control information is received using the first set of pilot signal resource elements, wherein the first set of pilot signal resource elements comprises a first number of pilot signal resource elements per layer. The terminal also decodes the one or more spatial layers in which the data is received in the second resource block using the second set of pilot signal resource elements, wherein the second set of pilot signal resource elements comprises a second number of pilot signal resource elements, per layer, present in the second resource block, wherein the first number is greater than the second number.