Slow DCI Reliability via Indication Element in LTE-Advanced Pro
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Solution Overview
Problem
The reliability of slow Downlink Control Information (DCI) in LTE-Advanced Pro systems is compromised due to dependency between slow and fast DCI, leading to potential failure in receiving resources for short Transmission Time Intervals (TTIs) if the slow DCI is not received correctly.
Innovation Solution
A method and apparatus that transmit a separate indication element with the slow DCI to indicate its validity, allowing user equipment to determine if the slow DCI content is the same as in the previous subframe, thereby improving reliability and enabling continued operation even if the slow DCI is not decoded correctly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If slow DCI is transmitted in legacy PDCCH once per subframe to determine resources for short TTI operation, then latency is reduced and short TTI operation is enabled, but reliability of DCI reception deteriorates because UE cannot receive any sTTI if slow DCI is not received correctly
Solution Approach 1:
The DCI transmission is segmented into two independent parts: slow DCI transmitted in legacy PDCCH for resource determination, and fast DCI transmitted in sPDCCH for actual sTTI scheduling. This segmentation allows the system to maintain low latency through fast DCI while improving reliability through the redundancy of having multiple DCI components that can be independently received and processed.
Solution Approach 2:
The slow DCI is transmitted in advance in the legacy PDCCH to pre-determine the resources for short TTI operation and sPDCCH transmission. This preliminary action enables the UE to prepare for receiving fast DCI in subsequent sTTIs, reducing overall latency while maintaining reliability through the advance resource allocation.
2Reliability
If separate indication element is transmitted with slow DCI to indicate validity, then reliability of slow DCI reception is improved, but device complexity increases due to additional signaling
Solution Approach 1:
A separate indication element is introduced as an intermediary signal transmitted together with slow DCI to indicate whether the slow DCI content is valid or unchanged from previous subframes. This intermediary element improves reliability by allowing UE to verify DCI validity without requiring complex retransmission protocols, while the indication itself remains a simple binary signal that minimizes added complexity.
Solution Approach 2:
Instead of retransmitting the entire slow DCI when content remains unchanged, the system uses a compact indication element that copies or references the validity status of previous DCI content. This copying approach significantly reduces the amount of data that needs to be transmitted and processed compared to full retransmission, thereby improving reliability while minimizing the increase in device complexity.
Data Source
AI summary
The present invention addresses a method, apparatus and computer program product for improving slow DCI reliability. Thereby, with regard to a subframe including slow downlink control information, an indication element indicating that the slow downlink control information transmitted in this subframe has the same content as slow downlink control information in the previous subframe or one of the past subframes is generated, and the indication element is transmitted in the same subframe and the same downlink control channel candidate as the slow downlink control information to a user equipment.