Downlink MCS Table Configuration for 256 QAM Support
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Solution Overview
Problem
The existing LTE system only supports three modulation modes: QPSK, 16 QAM, and 64 QAM, limiting peak downlink transmission rates and failing to adapt to varying channel conditions, especially in situations with high SINR where 256 QAM is needed.
Innovation Solution
The method involves configuring User Equipment (UE) to use either the existing LTE MCS and CQI tables or newly defined tables that support 256 QAM, by adjusting the number of MCS and CQI indexes and adding or removing items from the existing tables to optimize modulation modes based on channel conditions, allowing for switching between 256 QAM, 64 QAM, 16 QAM, and QPSK.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the LTE system uses only QPSK, 16 QAM, and 64 QAM modulation modes, then the system maintains backward compatibility and reliable transmission, but the peak downlink transmission rate is limited and cannot adapt to high SINR channel conditions
Solution Approach 1:
The patent implements dynamic modulation mode selection by enabling the system to switch between multiple modulation schemes (QPSK, 16 QAM, 64 QAM, and 256 QAM) based on real-time channel conditions. The base station determines the appropriate modulation mode for each UE according to channel quality indicators, allowing the system to adapt dynamically rather than being fixed to limited modulation options.
Solution Approach 2:
The patent changes the modulation order parameter from a fixed set (QPSK, 16 QAM, 64 QAM) to include variable modulation orders up to 256 QAM. By modifying the modulation scheme parameter based on channel SINR conditions, the system can achieve higher transmission rates when channel quality permits while maintaining compatibility with existing devices.
2Productivity
If the system configures multiple MCS tables to support 256 QAM, then downlink peak rates are enhanced, but the complexity of MCS configuration and table management increases
Solution Approach 1:
The patent segments the MCS table into multiple versions (first MCS table without 256 QAM, second MCS table with 256 QAM). Each table is optimized for specific channel conditions, allowing the system to select the appropriate table based on current requirements. This segmentation reduces the complexity of managing a single large table by dividing it into manageable, purpose-specific subsets.
Solution Approach 2:
The patent creates a universal MCS configuration framework that can operate with or without 256 QAM support. The system maintains compatibility with existing LTE devices using the first MCS table while enabling enhanced performance with the second MCS table when needed. This multi-functionality allows the same system to serve both legacy and advanced requirements without increasing overall complexity.
3Productivity
If the system dynamically switches between different MCS tables based on channel conditions, then transmission efficiency is improved, but the overhead for signaling and coordination increases
Solution Approach 1:
The patent performs preliminary configuration by pre-defining multiple MCS tables with different modulation capabilities. The base station and UE are pre-configured with knowledge of available MCS tables, so when channel conditions change, the system can quickly switch between pre-prepared tables without extensive real-time negotiation, reducing signaling overhead during dynamic adaptation.
Data Source
AI summary
Disclosed is a method for communication by a base station in a wireless communication system, including transmitting, to a user equipment (UE), downlink control information (DCI) including information on a modulation and coding scheme (MCS) for processing downlink data using an MCS table among a plurality of tables, and transmitting, to the UE, the downlink data, wherein each of the plurality of MCS tables indicates modulation orders and code rates, wherein the plurality of MCS tables comprises a first MCS table which supports 256 quadrature amplitude modulation (QAM) and a second MCS table which does not support 256 QAM, and wherein a number of MCS indexes in the first MCS table is equal to a number of MCS indexes in the second MCS table.