EPDCCH Candidate Assignment for LTE Blind Detection Optimization
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Solution Overview
Problem
In LTE Rel-11, the utilization of EPDCCH candidates and blind detection times is limited due to unbalanced sizes of control channel elements and unsupported aggregation levels, leading to decreased efficiency in data transmission, especially when using DCI format series 2X, which may result in skipped detection and reduced resource utilization.
Innovation Solution
The method involves reassessing and reassigning the number of EPDCCH candidates and blind detection times across aggregation levels, ensuring that each level supports the required transmission code rate, particularly by determining subsets of aggregation levels and redistributing candidates and detection times based on DCI formats and available resource units, thereby optimizing resource allocation and utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of CCEs in the PDCCH region is increased to support more users, then the scheduling capacity is improved, but the number of blind detection times increases linearly, leading to increased complexity
Solution Approach 1:
The patent divides the PDCCH region into multiple search spaces (common search space and UE-specific search space) with different aggregation levels. Each search space contains a limited number of PDCCH candidates, segmenting the overall blind detection process into manageable parts. This segmentation allows the system to support more users (increased scheduling capacity) while limiting the number of blind detection times per UE (controlled complexity).
Solution Approach 2:
The patent introduces aggregation levels (L=1, 2, 4, 8) as a parameter to vary the number of CCEs per PDCCH candidate. By changing the aggregation level parameter, the system can adjust the number of blind detection times without linearly increasing the total number of CCEs. Higher aggregation levels provide more robust detection for edge users while requiring fewer candidates, thus managing complexity while maintaining scheduling capacity.
2Device complexity
If aggregation levels are limited to reduce blind detection times, then detection complexity is reduced, but transmission code rate requirements cannot be met for some DCI formats
Solution Approach 1:
The patent makes the aggregation level selection dynamic based on the DCI format being transmitted. For DCI format 1A (compact format), aggregation levels 1, 2, 4, 8, and 16 are supported, while for DCI format 2X (non-compact format), aggregation levels 2, 4, 8, and 16 are supported. This dynamic adaptation allows the system to meet transmission code rate requirements for different DCI formats while managing detection complexity through the aggregation level framework.
Solution Approach 2:
The patent changes the available aggregation level parameter based on the DCI format type. By adjusting which aggregation levels are permitted for each DCI format, the system ensures that transmission code rate requirements are met (higher aggregation levels provide better code rate performance) while maintaining reasonable detection complexity (through the maximum blind detection times limit).
3Productivity
If EPDCCH resources are allocated flexibly across resource blocks, then resource utilization is improved, but the number of blind detection times increases due to additional aggregation levels
Solution Approach 1:
The patent segments the EPDCCH search space into multiple aggregation levels (1, 2, 4, 8, 16) with different candidate numbers. This segmentation allows flexible resource allocation across resource blocks while limiting the total number of blind detection times to 32. The segmentation enables the system to utilize EPDCCH resources flexibly (improved resource utilization) while maintaining controlled detection complexity through the structured search space design.
4Reliability
If the number of PDCCH candidates is increased to improve reliability, then transmission reliability is improved, but the number of blind detection times increases, reducing system efficiency
Solution Approach 1:
The patent introduces asymmetric aggregation levels where different numbers of CCEs are aggregated (L=1, 2, 4, 8) to create PDCCH candidates with different reliability characteristics. Higher aggregation levels (more CCEs) provide better reliability for edge users, while lower aggregation levels provide faster detection for near users. This asymmetric design improves overall transmission reliability without requiring all users to perform the maximum number of blind detections, thus maintaining system efficiency.
Solution Approach 2:
The patent changes the aggregation level parameter based on user equipment conditions (channel quality). Users with poor channel conditions are assigned higher aggregation levels for improved reliability, while users with good channel conditions use lower aggregation levels for faster detection. This parameter adaptation improves transmission reliability for those who need it while maintaining system efficiency through reduced blind detection times for others.
Data Source
AI summary
The present invention provides a method for assigning the number of control channel candidates and the number of blind detection times, a base station, and a user equipment. The method includes determining a first aggregation level set {L1i} and determining the number of EPDCCH candidates corresponding to each aggregation level in the {L1i}. {L1i} is formed by N aggregation levels supported by an EPDCCH. A second aggregation level set {L2j} is determined along with the number of EPDCCH candidates corresponding to each aggregation level in the {L2j}. {L2j} is formed by M aggregation levels supported by an EPDCCH to be detected, {L2j} is a subset of {L1i}, and the number of EPDCCH candidates corresponding to L2j in {L2j} is greater than or equal to the number of EPDCCH candidates corresponding to L2j in {L1i}.