Dual Table Modulation Scheme Selection for LTE Signaling Overhead
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Solution Overview
Problem
Current LTE systems are limited to 64 QAM modulation schemes, and extending existing CQI and MCS tables to support 256 QAM requires additional signaling bits, which can lead to increased overhead and potential uplink coverage issues, necessitating a new approach for efficient modulation and coding scheme configuration.
Innovation Solution
The implementation of dual tables for modulation and coding schemes, where a default table and a secondary table with additional entries for 256 QAM are maintained, allowing seamless switching between legacy and higher-order modulation schemes without altering existing signaling formats, and enabling efficient differential CQI reporting and soft buffer management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing CQI and MCS tables are extended to support 256 QAM, then higher-order modulation capability is improved, but signaling overhead increases and uplink coverage deteriorates
Solution Approach 1:
The patent segments the modulation scheme support by maintaining separate default and secondary tables. The default table supports legacy modulation schemes (QPSK, 16QAM, 64QAM) while the secondary table supports higher-order schemes (256QAM, 1024QAM). This segmentation allows the system to support extended modulation capabilities without requiring all signaling bits to be present in every transmission, thereby reducing signaling overhead while maintaining adaptability.
Solution Approach 2:
The patent implements dynamic table selection where the UE and eNB can switch between default and secondary tables based on channel conditions and configured modulation schemes. The secondary table is activated only when higher-order modulation is needed, making the system dynamic rather than static. This dynamic approach allows the signaling format to adapt to actual network conditions without permanently increasing overhead.
2Adaptability or versatility
If dual tables for modulation schemes are implemented, then flexibility and backward compatibility are improved, but device complexity increases
Solution Approach 1:
The patent makes the table selection mechanism universal by designing it to work across different UE capabilities and network configurations. The same dual-table structure and selection logic apply whether the UE supports only legacy modulation or also supports 256QAM/1024QAM. This multi-functionality allows the system to handle various scenarios (legacy mode, enhanced mode, ambiguous period) with a unified approach, reducing the perceived complexity despite the dual-table implementation.
Solution Approach 2:
The patent introduces an intermediary mechanism - the ambiguity period table - that mediates between the default and secondary tables during transition periods. When the eNB configures the secondary table but the UE hasn't fully processed the configuration, the ambiguity period table serves as a safe intermediary that ensures both sides use consistent tables, preventing mismatches while managing the complexity of table transitions.
3Productivity
If secondary table with 256 QAM entries is used, then throughput is improved, but reliability during ambiguity period deteriorates
Solution Approach 1:
The patent prepares for potential reliability issues by establishing the ambiguity period table in advance. Before the UE fully switches to using the secondary table for 256QAM operations, the ambiguity period table is configured as a cushioning mechanism. This pre-prepared table ensures that if any configuration issues arise during the transition, there is a fallback option that maintains reliability while allowing the system to eventually achieve higher throughput with the secondary table.
Data Source
AI summary
A mobile communication device includes a table component, a table selection component, a control information component, and a communication component. The table component is configured to maintain two or more tables each having entries for a plurality of available modulation schemes. The table selection component is configured to select a selected table from one of the default table and the secondary table based on one or more of RRC layer signaling and MAC layer signaling and further based based on a control information format for control information received from the eNB. The control information component is configured to receive control information indicating a modulation and coding scheme from the selected table, and the communication component is configured to receive and process a communication from the eNB based on the modulation and coding scheme from the selected table.