Wireless Control Channel Tree Search for Lower UE Complexity
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Solution Overview
Problem
Existing LTE communication systems face high decoding complexity and power consumption due to the need for numerous decoding attempts of aggregated control channels, which is inefficient and suboptimal for user equipment (UE) performance.
Innovation Solution
Implementing a tree search method that limits the tree structure by applying frequency diversity and power balancing to reduce the number of decoding attempts, thereby reducing UE complexity and power consumption while maintaining scheduling flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a full tree search is performed for aggregated control channels, then complete scheduling flexibility is maintained, but decoding complexity and power consumption increase significantly
Solution Approach 1:
The patent segments the control channel elements (CCEs) into different aggregation levels (AL1, AL2, AL4, AL8) organized in a tree structure. By dividing the search space into hierarchical segments, the UE can perform decoding attempts at coarser aggregation levels first, reducing the total number of decoding operations needed while maintaining the ability to access finer granularity when required.
Solution Approach 2:
The patent implements preliminary decoding attempts at higher aggregation levels (AL8, AL4) before proceeding to lower aggregation levels (AL2, AL1). This preliminary action allows the UE to potentially find its control channel information earlier in the decoding process, avoiding unnecessary decoding attempts at finer aggregation levels and thus reducing overall decoding complexity and power consumption.
2Adaptability or versatility
If multiple aggregation levels are supported for control channels, then scheduling flexibility is improved, but the number of decoding attempts required increases
Solution Approach 1:
The patent implements a periodic hierarchical decoding approach where the UE systematically attempts decoding at aggregation levels in a predetermined sequence (AL8, AL4, AL2, AL1). This periodic structure allows the system to exploit frequency diversity across different aggregation levels while establishing an energy-efficient search pattern that stops early when control information is found, reducing average power consumption compared to exhaustive searching.
Solution Approach 2:
The patent applies local quality by allowing different aggregation levels to be used in different frequency resources and time slots based on channel conditions and scheduling requirements. The eNB can select appropriate aggregation levels locally for different UEs and different control channels, optimizing the balance between scheduling flexibility and UE power consumption for each specific transmission scenario.
3Productivity
If control channels are separately coded for downlink and uplink, then channel allocation efficiency is improved, but control channel decoding complexity increases
Solution Approach 1:
The patent implements a universal tree search structure that can be applied to both downlink (PDCCH) and uplink (PUCCH) control channels. The same hierarchical aggregation level structure and decoding approach are used for both directions, allowing the UE to handle different control channel types with a unified decoding methodology. This universality maintains channel allocation efficiency through separate coding while managing decoding complexity through a standardized search procedure.
Data Source
AI summary
A user equipment (UE) may receive an OFDM signal having control channel elements (CCEs). The CCEs may be arranged in levels where a first level aggregates less CCEs than a second level. A processor may search for a control channel from control channel candidates that is comprised of the CCEs. A limited number of CCEs may be searched on the first level.