PDCCH Search Window Scheduling Under Terminal Processing Limits
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Solution Overview
Problem
Terminal devices in cellular communication systems face challenges in processing a high number of downlink control channel candidates due to limited processing capabilities, particularly at higher numerologies where time slots are shorter, leading to uncontrolled dropping of PDCCH candidates that may carry DCI.
Innovation Solution
The solution involves determining first and second search space configurations with varying starting positions and durations, forming a sequence of search spans, and creating a virtual search window with changing duration to determine a maximum number of downlink control information candidates the terminal device can process, allowing for efficient search and omission of unnecessary searches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal device scans through a high number of search spaces to detect PDCCH, then the coverage and reliability of control channel detection is improved, but the terminal device processing capability is exceeded leading to uncontrolled dropping of candidates
Solution Approach 1:
The patent segments the search space candidates into multiple groups based on aggregation levels and search space sets. The terminal device processes candidates in a controlled sequence through multiple passes, dividing the overwhelming number of candidates into manageable portions that respect the device's processing capabilities while maintaining comprehensive detection coverage.
Solution Approach 2:
The patent introduces dynamic processing where the terminal device adapts its search behavior based on detected candidates. After detecting a PDCCH in an earlier search space set, the device dynamically adjusts by skipping or reducing processing of subsequent candidates in later sets, optimizing resource usage while maintaining detection reliability.
2Loss of information
If the terminal device processes all downlink control channel candidates, then complete DCI detection is achieved, but the processing time exceeds the available time slot duration at higher numerologies
Solution Approach 1:
The patent implements preliminary action by processing search space candidates with lower aggregation levels first, which are more likely to contain DCI and require less processing time. This preliminary processing allows the terminal to detect common DCI formats quickly, reducing the overall processing time while maintaining detection completeness for critical information.
Solution Approach 2:
The patent changes the processing parameters dynamically based on the detected aggregation levels and search space configurations. By adjusting the number of blind decoding attempts and the depth of candidate processing based on observed patterns, the system optimizes the balance between detection completeness and processing time constraints.
3Measurement precision
If the terminal device increases the number of blind decoding attempts to detect PDCCH, then the detection accuracy is improved, but the processing load and energy consumption increase beyond device capabilities
Solution Approach 1:
The patent applies partial action by limiting the number of blind decoding attempts to a reasonable threshold that achieves sufficient detection accuracy without exhausting device resources. Instead of attempting to decode all possible candidates with equal effort, the system performs partial processing on candidates beyond the threshold, maintaining acceptable detection accuracy while controlling energy consumption within device capabilities.
Data Source
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AI summary
This document discloses a solution for searching a downlink control channel by a terminal device. According to an aspect, a method performed by the terminal device comprises: determining at least a first search space configuration and a second search space configuration for searching for a downlink control channel from a received signal, wherein the first search space configuration defines first starting positions and first durations for a first set of periodic search windows and the second search space configuration defines second starting positions and second durations for a second set of periodic search windows different from the first set of periodic search windows; determining a first set of periodic search spans formed by a first subset of time-domain symbols of each search window in the first set of periodic search windows and further determining a second set of periodic search spans formed by a second subset of time-domain symbols of each search window in the second set of periodic search windows; forming a sequence of search spans from the first set of periodic search spans and the second set of periodic search spans and determining a virtual search window changing in duration as dependent on a time interval between consecutive search spans in the sequence of search spans; determining, on the basis of a duration of the virtual search window, a maximum number of downlink control information candidates the terminal device is capable of processing within the virtual search window, wherein the maximum number of downlink control information candidates is configured to change together with the changing duration of the virtual search window; searching the received signal within the virtual search window for up to the maximum number of downlink control channel candidates and omitting the searching for remaining downlink control channel candidates and, upon detecting the downlink control channel, extracting downlink control information on the downlink control channel.