Shuffled Cyclic Layer Selection for 5G PDCCH Beamforming
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Solution Overview
Problem
Existing wireless communication systems face challenges in implementing user-specific PDCCH beamforming due to limitations in hardware memory and the complexity of layer selection algorithms, particularly when dealing with multi-layer transmissions, which affects coverage and capacity in 5G NR systems.
Innovation Solution
A shuffled cyclic truncated layer selection algorithm is introduced, which restricts the number of layers to two, randomly shuffles and cyclically assigns indices to bundles, ensuring directional and phase diversity while reducing memory requirements and algorithm complexity, suitable for both 3GPP and generic codebooks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PMI-based beamforming is implemented for user-specific PDCCH, then coverage and capacity are improved, but hardware memory requirements increase due to needing to store additional PMI codebooks
Solution Approach 1:
The patent reuses the existing PMI codebooks that are already stored for PDSCH operations to also serve PDCCH beamforming. Instead of creating and storing separate duplicate codebooks for PDCCH, the system copies/reuses the existing PMI structures, thereby avoiding additional hardware memory requirements while still enabling user-specific PDCCH beamforming
Solution Approach 2:
The existing PMI codebooks are made multi-functional by using them for both PDSCH and PDCCH operations. The same codebook structures serve dual purposes: for data transmission (PDSCH) and for control channel beamforming (PDCCH), eliminating the need for separate dedicated codebooks for PDCCH and reducing overall memory requirements
2Reliability
If layer selection algorithms are made more sophisticated to identify the strongest layer, then PDCCH beamforming performance is improved, but algorithm complexity increases
Solution Approach 1:
The patent performs layer selection in advance by utilizing the RI (Rank Indicator) and layer indexing information that is already available from the WD's CSI report. The strongest layer is identified beforehand based on the layer indexing convention, avoiding the need for complex real-time analysis algorithms during PDCCH transmission
Solution Approach 2:
The system uses the existing layer indexing information and RI reports that the WD generates for PDSCH purposes to automatically identify the strongest layer for PDCCH beamforming. The layer selection process serves itself by reusing the WD's own feedback information without requiring additional complex processing or external assistance
3Device complexity
If the number of layers is restricted to two, then memory requirements and algorithm complexity are reduced, but the ability to utilize multi-layer feedback for PDCCH is limited
Solution Approach 1:
The patent extracts and utilizes the essential diversity information from multi-layer feedback by selecting and using the strongest layer (or top two layers) for PDCCH beamforming. Instead of attempting to process all layers, the system extracts the most critical layer information that provides the necessary spatial and polarization diversity for robust control channel transmission
Solution Approach 2:
The system changes the parameter of layer count from the original multi-layer configuration to a restricted two-layer configuration for PDCCH. This parameter change is achieved by mapping the selected layers to two PDCCH layers using cyclic shifting, thereby simplifying the system while maintaining the essential diversity benefits through the cyclic layer assignment mechanism
Data Source
AI summary
A method and network node for diversity-aware truncated layer selection for low complexity beamforming are provided. According to one aspect, a method in a network node includes receiving a precoder rank indication, and selecting one of two precoders of different ranks one of cyclically and randomly when the indicated precoder rank is greater than 1.