DCI Repetition Decoding in NR PDCCH
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Solution Overview
Problem
The decoding performance of Downlink Control Information (DCI) in New Radio (NR) networks is limited by code rate, making it impossible to decode DCI below a certain signal-to-noise ratio, resulting in a Block Error Rate of 0.1 at approximately −11 dB with existing solutions.
Innovation Solution
Implementing multiple repetitions of DCI in the Physical Downlink Control Channel (PDCCH) and configuring user equipment (UE) to decode these repetitions, which can be transmitted within a span, across spans in the same slot, or across consecutive slots, improving the observed signal-to-noise ratio and decoding capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DCI is transmitted using conventional PDCCH with single transmission, then transmission complexity is low, but decoding performance is limited and cannot achieve reliable decoding below −11 dB
Solution Approach 1:
The DCI transmission is segmented into multiple repetitions transmitted separately through PDCCH candidates. Each repetition contains the same DCI information but is transmitted independently, allowing the UE to combine multiple segments to achieve reliable decoding at lower signal-to-noise ratios
Solution Approach 2:
Multiple PDCCH candidates containing repetitions of the same DCI are merged at the UE side through combining operations. The UE collects soft bits from multiple PDCCH candidates and combines them to improve the effective signal-to-noise ratio, enabling successful decoding below the conventional −11 dB threshold
2Reliability
If multiple repetitions of DCI are transmitted in PDCCH, then decoding capability at low signal-to-noise ratio is improved, but transmission complexity and resource overhead increase
Solution Approach 1:
Instead of transmitting full redundant copies of DCI multiple times, the system uses partial repetitions where multiple PDCCH candidates transmit the same DCI information. This allows the UE to accumulate sufficient signal energy through combining without requiring complete independent transmissions, reducing overall resource overhead while maintaining decoding reliability
Solution Approach 2:
The system changes the transmission parameter by configuring multiple PDCCH candidates with different aggregation levels and monitoring occasions. By adjusting these parameters, the network can control the number of repetitions and resource allocation dynamically, optimizing the balance between decoding reliability and resource overhead
Data Source
AI summary
A user equipment (UE) is configured to receive physical downlink control channel (PDCCH) configuration information comprising repetitions for PDCCH candidates that comprise Downlink Control Information (DCI), receive PDCCH candidates and decode the PDCCH candidates based on the PDCCH configuration information. A UE is configured to receive semi-persistent scheduling (SPS) configuration information for a physical downlink shared channel (PDSCH), receive a PDSCH comprising Downlink Control Information (DCI) and decode the PDSCH comprising the DCI based on the SPS configuration information.