Nested Search Space Block Allocation for PDCCH
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Solution Overview
Problem
The use of cell-specific reference signals in LTE systems limits advanced techniques to increase cell capacity, as it does not account for the increased complexities of these systems, thereby affecting channel estimation performance.
Innovation Solution
A network node and user device configuration that allocates control channel elements (CCEs) in a nested structure for the physical downlink control channel (PDCCH), using hashing functions and bit-maps to determine start positions and locations of search space blocks, allowing for flexible mapping onto time and frequency resources to balance channel estimation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cell-specific reference signals are used for PDCCH demodulation, then system compatibility is maintained, but channel estimation performance deteriorates and cell capacity increases are limited
Solution Approach 1:
The search space is segmented into multiple search space blocks, each containing CCEs of different aggregation levels. This segmentation allows independent channel estimation for each block, improving estimation accuracy while enabling flexible resource allocation to increase cell capacity.
Solution Approach 2:
The patent implements a nested structure where search space blocks contain CCEs with different aggregation levels (ALs) within the same block. This nesting enables reuse of channel estimation across multiple PDCCH candidates with different ALs, improving reliability while reducing resource overhead and supporting higher cell capacity.
2Reliability
If multiple PDCCH candidates with different CCE aggregation levels are allocated, then user device reliability is improved, but resource collision increases
Solution Approach 1:
Different search space blocks are assigned to different user devices with localized resource allocations. Each user device receives search space blocks with specific CCE aggregation levels tailored to its channel conditions, reducing resource collisions while maintaining reliability through appropriate AL selection.
Solution Approach 2:
The patent introduces a new dimension in resource allocation by organizing CCEs into search space blocks with nested aggregation levels. This dimensional organization allows multiple users to share resources more efficiently by allocating different ALs within the same block, reducing collisions while maintaining reliability.
3Ease of manufacture
If CCEs are allocated without nested structure, then allocation simplicity is maintained, but channel estimation reuse is limited
Solution Approach 1:
The patent implements a nested structure within search space blocks where CCEs of different aggregation levels are organized hierarchically. This nesting enables channel estimation results from one CCE to be reused across multiple PDCCH candidates with different aggregation levels, improving reliability while maintaining relatively simple allocation procedures.
Solution Approach 2:
The search space block structure provides multi-functionality by accommodating multiple CCE aggregation levels within a single block. This universal structure allows the same block to serve multiple purposes: supporting different ALs, enabling channel estimation reuse, and maintaining allocation simplicity through standardized block-based management.
Data Source
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AI summary
A network node, a user device, and a method for a wireless communication system are provided. The network node includes a processor and a transceiver. The processor is configured to allocate a plurality of control channel elements (CCEs) for a physical downlink control channel (PDCCH) having PDCCH candidates defined for a plurality of different CCE aggregation levels (ALs). The processor is configured to form at least one search space block containing the CCEs of different CCE ALs, the at least one search space block is in a nested structure to carry PDCCH candidates with the different CCE ALs, and the processor is configured to determine start positions of the at least one search space block. The processor is configured to determine locations of the PDCCH candidates of the different CCE ALs within the at least one search space block.