Flexible Subframe Uplink Downlink Configuration via DCI
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Solution Overview
Problem
Current 3GPP LTE-Advanced systems do not support dynamic adjustment of uplink and downlink ratio configurations, leading to inefficiencies when transmission loads are mismatched, with a minimum latency of 640 ms for configuration changes and potential differences in comprehension between eNodeB and UE regarding DCI formats.
Innovation Solution
A new radio frame structure with flexible subframes that can be dynamically switched between uplink and downlink, using a configuration indication field (CIF) in the DCI format transmitted over the PDCCH, allowing for dynamic re-configuration of uplink-downlink ratios without modifying System Information Block Type 1 (SIB1), supporting both homogeneous and heterogeneous network deployments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If uplink-downlink configuration is changed using SIB1 modification, then configuration can be updated, but latency is at least 640 ms
Solution Approach 1:
The patent segments the configuration update process into two parts: legacy UEs continue using SIB1-based configurations while new UEs receive dynamic configurations via DCI messages. This allows simultaneous support of both static and dynamic configuration methods, reducing overall system latency without forcing legacy UEs into the new mechanism.
Solution Approach 2:
The patent introduces dynamic uplink-downlink configuration adjustment for new UEs using DCI format 5/6 messages that can be updated in real-time based on traffic conditions. The eNodeB can dynamically switch between different UL/DL configurations (0-6) for new UEs without the 640ms latency constraint, enabling adaptive response to changing traffic patterns.
2Productivity
If dynamic adjustment of uplink-downlink configuration is implemented, then traffic handling efficiency improves, but system complexity increases
Solution Approach 1:
The patent applies different configuration management approaches to different UE groups: legacy UEs (Release 8-10) continue using the simple SIB1-based static configuration, while new UEs (Release 11+) receive dynamic configurations via DCI messages. This localized differentiation allows dynamic adjustment benefits to be applied only where needed without complicating the entire system.
Solution Approach 2:
The DCI format 5/6 messages serve multiple functions: they provide dynamic UL/DL configuration indication, carrier indicator field (CIF) information, and scheduling assignments. This multi-functionality reduces the need for separate signaling mechanisms, thereby limiting the increase in system complexity while achieving dynamic configuration adjustment.
3Adaptability or versatility
If flexible subframes are switched dynamically, then uplink-downlink ratio adapts to traffic conditions, but interpretation differences between eNodeB and UE may occur
Solution Approach 1:
The patent implements feedback mechanisms where the eNodeB transmits DCI format 5/6 messages to new UEs indicating the current UL/DL configuration. The UE acknowledges and follows the eNodeB's configuration indications, ensuring both sides have consistent understanding. The eNodeB monitors UE responses and can re-transmit or adjust configurations if mismatches are detected.
Solution Approach 2:
Before dynamically switching flexible subframes, the eNodeB pre-configures new UEs with the available UL/DL configuration options (0-6) and their corresponding flexible subframe patterns through RRC signaling. This preliminary configuration ensures that when dynamic switching occurs, both eNodeB and UE have pre-established understanding of what each configuration means, preventing interpretation differences.
Data Source
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AI summary
An apparatus and method for dynamically changing an uplink and downlink ratio configuration is disclosed herein. An evolved Node B (eNodeB) operating in a wireless communications network transmits a System Information Block Type 1 (SIB1) including first uplink and downlink ratio configuration information. The eNodeB also transmits in at least one downlink subframe of a radio frame configured in the first uplink and downlink ratio configuration second uplink and downlink ratio configuration information. The second uplink and downlink ratio configuration information is included in a downlink control information (DCI) message. The DCI message is included in the at least one downlink subframe of the radio frame.