Uplink 256QAM MCS Configuration Across Different Subframe Sets
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Solution Overview
Problem
In LTE systems, the limited soft buffer size in user equipment (UE) restricts the effectiveness of incremental redundancy retransmissions, especially in dual-codeword MIMO operations, and varying interference conditions across uplink subframe sets hinder the utilization of 256QAM, leading to suboptimal data rates.
Innovation Solution
Configuring the Modulation and Coding Scheme (MCS) table for uplink 256QAM separately per uplink subframe set, allowing for optimized power control and interference management, and employing techniques like soft demodulation to handle high interference by setting low reliability soft bits to zero, thereby increasing the use of 256QAM in more subframes and enhancing uplink data rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single MCS table is used for all uplink subframes, then device complexity is reduced, but adaptability to varying interference conditions deteriorates
Solution Approach 1:
The patent divides the uplink subframes into multiple subframe sets (first uplink subframe set and second uplink subframe set) and assigns different MCS tables to each set. This segmentation allows the system to adapt to varying interference conditions in different subframes without requiring the UE to handle a single complex configuration for all subframes, thereby resolving the contradiction between device complexity and adaptability.
Solution Approach 2:
The patent applies different MCS table configurations to different subframe sets based on their specific interference characteristics. The first MCS table is used for subframes with certain interference levels while the second MCS table is used for subframes with different interference levels. This local quality approach enables optimized performance for each subframe set while maintaining manageable device complexity through clear configuration rules.
2Productivity
If 256QAM is used in all uplink subframes, then uplink data rate is increased, but reliability under varying interference conditions deteriorates
Solution Approach 1:
The patent dynamically selects which MCS table to use based on the specific uplink subframe set and its interference conditions. Rather than statically using 256QAM in all subframes, the system adapts the modulation scheme to match current channel conditions, thereby maintaining high data rates when conditions permit while ensuring reliability when interference is high. This dynamic approach resolves the contradiction between productivity and reliability.
3Adaptability or versatility
If separate power control is applied to all uplink subframe sets, then adaptability to interference conditions is improved, but device complexity increases
Solution Approach 1:
The patent segments uplink subframes into distinct sets and applies separate power control configurations to each set. This segmentation allows the UE to implement adapted power control for each subframe set based on their specific interference characteristics, improving overall system adaptability while maintaining manageable device complexity through structured configuration management.
4Reliability
If incremental redundancy retransmissions are used with limited soft buffer, then retransmission effectiveness is improved, but device complexity is reduced
Solution Approach 1:
The patent changes the MCS table parameter based on the uplink subframe set, which directly impacts the modulation and coding schemes used in transmissions and retransmissions. By selecting appropriate MCS tables for different subframe sets, the system optimizes the balance between retransmission effectiveness and buffer management complexity, allowing incremental redundancy to work more effectively within the limited soft buffer constraints without requiring complex buffer management strategies.
Data Source
AI summary
Systems and methods are disclosed herein for configuring a wireless device individually (i.e., separately) per uplink subframe set as to whether or not the wireless device can use uplink 256 Quadrature Amplitude Modulation (256QAM). In some embodiments, a method of operation of a network node comprises configuring a wireless device for use of a Modulation and Coding Scheme (MCS) table for uplink 256QAM separately per uplink subframe set for two or more uplink subframe sets. In some embodiments, the two or more uplink subframe sets are two or more uplink subframe sets for separate uplink power control. In this manner, 256QAM can be utilized in more subframes and, as a result, uplink data rate can be increased.