CSI Feedback for 256QAM in Wireless Access Systems
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Solution Overview
Problem
Current Long Term Evolution (LTE)/LTE-Advanced systems only support Quadrature Phase Shift Keying (QPSK), 16-ary Quadrature Amplitude Modulation (16QAM), and 64QAM, and require new transport block size and Modulation and Coding Scheme (MCS) signaling to support 256QAM for efficient data transmission and CSI feedback.
Innovation Solution
Methods and apparatuses for transmitting and receiving Channel State Information (CSI) to support 256-ary Quadrature Amplitude Modulation (256QAM) by defining new transport block sizes and MCS signaling, and developing a new CSI feedback method suitable for 256QAM, including specific embodiments for channel coding and modulation schemes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If 256QAM modulation scheme is adopted to transmit more data, then data capacity increases, but new transport block size and MCS signaling definitions are required increasing system complexity
Solution Approach 1:
The patent extends the existing MCS signaling mechanism to support 256QAM by defining new MCS indices (29-31) that can indicate both 64QAM and 256QAM modulation schemes. This allows the same signaling framework to serve multiple modulation orders, reducing the need for entirely separate signaling structures while enabling higher data capacity.
Solution Approach 2:
The patent introduces new transport block size definitions and MCS index ranges (29-31) specifically for 256QAM operation. By changing the parameter space of existing signaling structures rather than creating new ones, the system accommodates higher modulation orders while maintaining backward compatibility and minimizing overall complexity.
2Measurement precision
If new CSI feedback method is defined for 256QAM, then CSI accuracy for high modulation order improves, but feedback overhead and processing complexity increase
Solution Approach 1:
The patent enables dynamic selection between 64QAM and 256QAM based on channel conditions and CSI feedback. The eNodeB can adaptively choose the modulation scheme by interpreting MCS indices, allowing the system to optimize for 256QAM when channel quality supports it while falling back to 64QAM when conditions are poorer, thus achieving high CSI accuracy without permanently increasing complexity.
Solution Approach 2:
The patent extends existing CQI tables to include 256QAM support by defining new CQI index ranges and corresponding transport block sizes. This parameter extension allows accurate CSI feedback for 256QAM while reusing the existing CQI feedback structure, avoiding the need for completely new feedback mechanisms and minimizing processing complexity overhead.
Data Source
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AI summary
The present invention relates to a wireless access system, more particularly, to methods for transceiving channel state information (CSI) for supporting 256 quadrature amplitude modulation (QAM) scheme and apparatuses for supporting the methods. A method by which a terminal capable of supporting 256QAM in a wireless access system reports CSI, according to one embodiment of the present invention, comprises the steps of: receiving a higher-layer signal for configuring a first rank indicator (RI) reference process in the terminal; measuring a channel quality for one or more CSI processes associated with the first RI reference process configured in the terminal; selecting a channel quality indication (CQI) index by using only a first CQI table or a second CQI table for the one or more CSI processes; and reporting the CSI including the CQI index. Here, the first CQI table can support up to 64 QAM and the second CQI table can support up to 256 QAM, and only the same CQI table can be applied to the one or more CSI processes associated with the first RI reference process.