PDCCH Blind Decoding Search Space Optimization
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Solution Overview
Problem
The processing overhead for blind decoding of the Physical Downlink Control Channel (PDCCH) in user equipment exceeds practical hardware limitations, leading to increased costs and reduced performance due to the need to decode from multiple possible formats and associated Control Channel Elements (CCEs).
Innovation Solution
A method is provided to reduce processing overhead by estimating a suitable sized CCE segment, generating a tree structure with contiguous CCE aggregation levels, arranging them in a hierarchical order, and using boundaries defined by the tree structure to form a search path for reduced blind decoding, thereby simplifying the search process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE blindly decodes PDCCH from several possible formats and associated CCEs, then the PDCCH can be reliably received, but the processing overhead exceeds practical hardware limitations
Solution Approach 1:
The patent segments the blind decoding process into two stages: first decoding only the first downlink control information (DCI) with a first search space, then decoding the second DCI with a second search space that has a narrower range. This segmentation reduces the total number of blind decoding attempts while maintaining reliable PDCCH reception.
Solution Approach 2:
The patent performs preliminary decoding of the first DCI before decoding the second DCI. By first identifying and decoding the first downlink control information, the system prepares the UE in advance with initial scheduling information, which then enables more efficient decoding of the second DCI with reduced search space.
2Loss of information
If the UE decodes multiple PDCCH formats to ensure complete control information reception, then all control information is captured, but hardware costs increase and performance decreases
Solution Approach 1:
The patent divides control information into two segments: first downlink control information decoded with a first search space, and second downlink control information decoded with a second search space. This ensures complete control information reception while reducing the computational burden on UE hardware.
Solution Approach 2:
The patent applies partial action by decoding only the necessary portion of control information in each stage. The first DCI decoding handles initial control information, and the second DCI decoding handles additional control information with a narrowed search space, avoiding excessive blind decoding attempts.
3Device complexity
If the search space for blind decoding is reduced, then processing overhead decreases, but the ability to detect all PDCCH formats is compromised
Solution Approach 1:
The patent segments the search space into a first search space for decoding first DCI and a second search space for decoding second DCI. The second search space has a narrower range than the first, reducing processing overhead while maintaining detection capability through the two-stage approach.
Solution Approach 2:
The patent performs preliminary decoding of the first DCI to establish initial control information and scheduling parameters. This preliminary action enables the subsequent decoding of the second DCI with a narrowed search space, as the first decoding provides context that reduces the complexity of the second decoding operation.
Data Source
AI summary
Various methods and systems for efficiently performing the blind decoding of downlink signals is described. Several forms of arranging possible CCE combinations are examined and investigated. Based on PDCCH size estimation/information, CCE concatenations that are most likely (of limited sets) can be arrived at. Tree-based concatenations are also devised using largest CCE ordering to align smaller CCE sizes to similar boundaries. By such ordering, the search space for all possible CCE ordering and sizes can be reduced to an efficient tree. Set mapping between possible lnposelstartCCElnposelend/REs are also described using a first set to secondary and tertiary sets. Various other ordering and sorting schemes are also detailed that enable a blind decode of a PDCCH channel to be efficiently performed.