PDCCH Repetition for 5G Control Channel Robustness
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Solution Overview
Problem
The existing control channel implementations in 5G wireless communication systems face challenges in ensuring robustness and meeting reliability and latency requirements, particularly due to the self-contained and one-shot nature of PDCCH transmissions, which can lead to issues in ultra-reliable and low-latency communications.
Innovation Solution
The solution involves repeating the PDCCH transmission multiple times without affecting the start and stop times of PDSCH, with at least two repetitions having different source RS for QCL assumptions, enabling spatial multiplexing diversity through multiple physically separated transmission points, and allowing for spatial processing across different signal types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PDCCH transmission is repeated multiple times to improve robustness, then reliability is improved, but latency increases
Solution Approach 1:
The patent applies preliminary action by transmitting multiple PDCCH repetitions in advance before the scheduled PDSCH reception time. The network node sends the same control information through multiple PDCCH candidates across different time slots, allowing the wireless device to decode the control channel earlier and more reliably, thus reducing the effective latency for control channel detection while improving reliability through redundant transmissions.
Solution Approach 2:
The patent implements periodic action by transmitting PDCCH repetitions at periodic intervals with different aggregation levels and search space configurations. The control information is repeated across multiple monitoring occasions with periodic timing, enabling the wireless device to attempt decoding at multiple periodic points, thereby improving detection reliability without significantly increasing the overall latency budget.
2Reliability
If multiple PDCCH repetitions with different QCL assumptions are transmitted, then robustness against fading is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by configuring different QCL (Quasi-Co-Location) assumptions for different PDCCH repetition instances. Each PDCCH candidate is associated with specific reference signals and QCL types that are locally optimized for that transmission instance. This allows the network to tailor the channel estimation and demodulation parameters locally for each repetition, improving robustness against frequency-selective fading and spatial interference while keeping the overall system manageable.
Solution Approach 2:
The patent segments the control channel transmission into multiple PDCCH candidates with different aggregation levels and search space configurations. Each segment (PDCCH candidate) is independently decodable and associated with specific QCL assumptions. The wireless device processes each segment separately through blind decoding attempts, which divides the complex task of reliable control channel detection into manageable segments, reducing overall device complexity while maintaining robustness.
3Reliability
If PDCCH monitoring is performed across multiple search spaces with repetition, then detection reliability is improved, but processing overhead increases
Solution Approach 1:
The patent applies partial action by configuring the wireless device to monitor a subset of PDCCH candidates across multiple search spaces rather than all possible candidates. The network node transmits PDCCH repetitions with different aggregation levels, and the device performs blind decoding on a selective basis based on configured search space sets. This partial monitoring approach improves detection reliability through multiple opportunities while reducing the excessive processing overhead by not requiring exhaustive decoding of all possible candidates.
Data Source
AI summary
A method, network node and wireless device for transmitting and decoding repeated physical downlink control channel (PDCCH) messages are disclosed. According to one embodiment a method implemented in a wireless device (WD) includes receiving multiple transmissions of a PDCCH message, each of the multiple transmissions of the PDDCH message being repeated in a repetition set. The method further includes monitoring the multiple received PDCCH transmissions to obtain scheduling information for a physical uplink shared channel (PUSCH) transmission or a physical downlink shared channel (PDSCH) reception.