Adaptive Modulation and Coding for High-Order Schemes
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Solution Overview
Problem
Future radio communication systems, such as LTE-Advanced, require support for high-order modulation schemes like 256 QAM to improve spectral efficiency, but existing adaptive modulation and coding methods only support up to 64 QAM.
Innovation Solution
The method involves a user terminal that measures channel quality, acquires a channel quality indicator (CQI) from a table associating CQIs with modulation schemes and coding rates, and transmits this to a radio base station, which determines the applicable modulation scheme and coding rate, including support for modulation schemes higher than 64 QAM by using expanded CQI bits, sub-tables, or sampled tables without increasing the number of bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing adaptive modulation and coding methods are used, then the system is simple to operate, but the spectral efficiency is limited because modulation schemes higher than 64 QAM are not supported
Solution Approach 1:
The CQI table is divided into multiple sub-tables, where each sub-table corresponds to a specific modulation scheme (e.g., one sub-table for 64 QAM, another for 256 QAM). This segmentation allows the system to support multiple modulation schemes without creating a single overly complex table, enabling high-order modulation while maintaining manageable system complexity.
Solution Approach 2:
The patent introduces a new dimension to the CQI reporting mechanism by adding a sub-table indication bit. This additional dimension allows the system to select between multiple CQI sub-tables, each optimized for different modulation schemes. The extra bit provides a simple way to extend capability without significantly increasing overall system complexity.
2Adaptability or versatility
If the CQI table is expanded to include modulation schemes higher than 64 QAM, then high-order modulation is supported, but the number of bits required for CQI reporting increases
Solution Approach 1:
The CQI table is segmented into multiple sub-tables, each handling a specific modulation scheme. This segmentation allows the system to support high-order modulation schemes like 256 QAM while keeping each individual sub-table manageable in size, thereby avoiding the need for a single large CQI table that would require excessive bits for reporting.
Solution Approach 2:
The patent adds a new dimension to the CQI reporting structure by introducing a sub-table indication mechanism. This additional dimension allows the system to select between multiple pre-defined CQI sub-tables, enabling support for high-order modulation schemes without proportionally increasing the number of bits required for CQI reporting.
3Adaptability or versatility
If a single large CQI table is used to support all modulation schemes, then all modulation schemes are supported in one table, but the table size and complexity increase significantly
Solution Approach 1:
The CQI table is divided into multiple smaller sub-tables, with each sub-table dedicated to a specific modulation scheme (e.g., one sub-table for 64 QAM, another for 256 QAM). This segmentation reduces the size and complexity of each individual table while collectively supporting a wide range of modulation schemes, making the system more manageable and efficient.
Solution Approach 2:
The patent creates a universal CQI reporting mechanism that can handle multiple modulation schemes through the use of multiple sub-tables. Each sub-table is specialized for a particular modulation scheme, but together they provide universal support for various modulation types, allowing the system to adapt to different channel conditions and requirements without being limited to a single large table.
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AI summary
The present invention is designed to make possible adaptive modulation and coding (AMC) that supports high-order modulation schemes. The adaptive modulation and coding method of the present invention is an adaptive modulation and coding method for a downlink shared channel, and includes, in a user terminal, the steps of measuring channel quality based on a reference signal from the radio base station, acquiring a channel quality indicator to indicate the modulation scheme and the coding rate that are applicable to the downlink shared channel in the channel quality, from a table in which channel quality indicators, modulation schemes and coding rates are associated with each other, and transmitting the channel quality indicator to the radio base station, and the modulation schemes include a modulation scheme of a higher order than 64 QAM.