Terminal Device MCS Table Switching for 256 QAM
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Solution Overview
Problem
Current LTE systems face challenges in efficiently supporting 256 QAM mode due to increased control information, leading to decreased throughput when switching between modulation modes, especially with abrupt changes in channel states.
Innovation Solution
The system employs a method to change modulation modes at high speed without increasing the number of bits in the PDCCH by using a CSI request field with two-bit configurations and RRC signaling, allowing for flexible modulation mode selection based on channel conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If 256 QAM mode is supported with increased control information, then modulation capability is improved, but throughput decreases due to increased control overhead
Solution Approach 1:
The patent dynamically switches between 64 QAM and 256 QAM modes based on channel conditions (ABS subframes vs. non-ABS subframes). The terminal device determines channel quality and selects appropriate MCS tables accordingly, enabling adaptive modulation that optimizes throughput while supporting 256 QAM capability when conditions permit
Solution Approach 2:
Different MCS tables are applied to different subframe types. The 256 QAM MCS table is used specifically for non-ABS subframes where channel conditions are favorable, while the 64 QAM MCS table is used for ABS subframes. This localized application of different modulation schemes optimizes performance for each subframe type without requiring increased control overhead across all subframes
2Adaptability or versatility
If modulation mode switching is performed rapidly, then adaptability to channel changes is improved, but control information complexity increases
Solution Approach 1:
The patent extracts and utilizes the existing CSI request field in downlink control information to implicitly indicate MCS table selection. By repurposing this existing field rather than adding new control elements, the system achieves rapid modulation mode switching without increasing overall control information complexity
Solution Approach 2:
The CSI request field serves multiple functions: it triggers channel state information reporting and simultaneously indicates which MCS table (64 QAM or 256 QAM) should be used for PDSCH decoding. This multi-functionality enables rapid adaptation to channel changes while avoiding additional control overhead
Data Source
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AI summary
Disclosed is a terminal apparatus configured to communicate with a base station apparatus, where the terminal apparatus comprises: a DL reception unit configured to receive, from the base station apparatus, a RRC signaling which includes a setting information indicating the applicability of an alternative CQI (Channel Quality Information) table of a CQI table and the alternative CQI table, and PDSCH (Physical Downlink Shared CHannel), and a UL transmission unit configured to report CQI according to the alternative CQI table for a corresponding CSI subframe set configured by the setting information, in a case that the setting information indicates a first CSI subframe set of the first CSI subframe set and a second CSI subframe set.