Two-Stage DCI Signaling to Reduce UE Blind Decoding
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Solution Overview
Problem
The increasing number of DCI formats and sizes in wireless communication systems, particularly in 3GPP NR Release-16 and beyond, leads to higher UE implementation complexity due to blind decoding requirements, especially with carrier aggregation and dual connectivity, which is not forward compatible and burdens the UE with excessive blind decodings.
Innovation Solution
A two-stage DCI framework is introduced, where a first stage DCI explicitly indicates the presence or absence of a second stage DCI, reducing the need for blind decoding of the second stage and allowing for a compact first stage DCI design with flexible size and content, and optionally including partial retransmission information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple DCI formats and sizes are supported for different communication scenarios, then the system's adaptability and versatility are improved, but the UE implementation complexity and blind decoding burden increase significantly
Solution Approach 1:
The DCI transmission is divided into two stages: first stage DCI in PDCCH providing basic scheduling information, and second stage DCI in PDSCH providing additional information. This segmentation allows the UE to first decode the compact first stage DCI to determine if a second stage DCI is present, reducing the need for extensive blind decoding across multiple DCI formats while maintaining support for diverse communication scenarios through the flexible second stage
Solution Approach 2:
The first stage DCI acts as an intermediary that indicates the presence or absence of the second stage DCI. This intermediary structure allows the system to maintain adaptability for different scenarios without requiring the UE to perform blind decoding on all possible DCI formats, as the first stage DCI provides the necessary information to determine whether further decoding is needed
2Reliability
If the first stage DCI is made compact to improve decoding reliability, then the decoding success probability increases, but the amount of scheduling information that can be conveyed is reduced
Solution Approach 1:
Scheduling information is segmented into two parts: essential scheduling information is conveyed in the compact first stage DCI to ensure reliable decoding, while additional scheduling information is transmitted in the second stage DCI within the PDSCH. This segmentation allows the first stage DCI to remain compact and reliable while still providing complete scheduling information across both stages
Solution Approach 2:
The first stage DCI performs preliminary scheduling by providing basic scheduling information that is sufficient for initial decoding and resource allocation. Additional scheduling details are then provided in the second stage DCI, allowing the system to maintain reliability at the critical first decoding stage while still conveying complete scheduling information
Data Source
AI summary
A two-stage DCI framework is provided in which the first stage DCI is carried by PDCCH, second stage DCI is carried by PDSCH. The first stage DCI is blind decoded. The second stage DCI is indicated by the first stage DCI and therefor no blind decoding is necessary. The size of the second stage DCI can be very flexible, can indicate scheduling information for one carrier, multiple carriers, multi transmission for one carrier. The first stage DCI can be compact in size to enhance reliability.