FD-MIMO Channel Quality Information Grouping for MU Scheduling
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Solution Overview
Problem
Current LTE/LTE-A MIMO systems primarily support implicit feedback-based SU MIMO due to limited base station antenna ports, inaccurate multi-user CQI, and feedback costs, restricting MU scheduling gain, while FD-MIMO systems require more advanced feedback schemes to maximize MU scheduling gain.
Innovation Solution
A method and apparatus for a terminal to measure and transmit channel state information efficiently in FD-MIMO systems by determining a most favored direction and transmitting channel quality information groups to the base station, allowing for precise beamforming and enhanced MU scheduling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If implicit feedback-based SU MIMO is used, then feedback cost is reduced and compatibility with legacy terminals is maintained, but multi-user scheduling gain is limited and CQI accuracy for MU is poor
Solution Approach 1:
The patent segments CQI feedback into multiple groups corresponding to different channel directions. Each group contains CQI values for specific spatial layers, allowing the system to provide accurate CQI for selected MU pairs while maintaining manageable feedback overhead. This segmentation enables the base station to identify suitable MU pairs with orthogonal channel directions based on the grouped CQI information.
Solution Approach 2:
The patent introduces a new dimension to CQI feedback by organizing it according to channel directions rather than just spatial layers. This directional grouping adds a spatial dimension to the feedback structure, enabling the system to evaluate and select MU pairs based on their channel direction orthogonality, thereby improving MU scheduling gain without proportionally increasing feedback overhead.
2Adaptability or versatility
If explicit feedback is used, then base station transmission scheme freedom is increased and MU scheduling gain is improved, but CQI link adaptation accuracy deteriorates
Solution Approach 1:
The patent segments explicit feedback into directional groups where each group contains CQI information for specific channel directions. This segmentation allows the base station to maintain transmission scheme freedom by receiving comprehensive channel information while improving link adaptation accuracy by selecting CQI values from groups corresponding to the actual scheduled MU pairs, rather than using a single aggregate explicit feedback value.
3Measurement precision
If FD-MIMO with 32 or more transmit antennas is deployed, then beamforming precision and beamforming freedom are significantly improved, but feedback overhead and system complexity increase
Solution Approach 1:
The patent segments the large-scale antenna array into multiple channel directions, with each direction group containing CQI information for a subset of spatial layers. This segmentation reduces feedback overhead by only transmitting CQI for selected directional groups rather than all possible layers, while maintaining beamforming precision through the use of FD-MIMO's inherent spatial resolution.
Solution Approach 2:
The patent extracts and transmits only the essential CQI information for selected channel directions rather than complete channel state information for all 32 or more antennas. This extraction approach reduces feedback overhead by focusing on the most relevant directional information needed for MU scheduling, thereby reducing system complexity while preserving beamforming precision.
Data Source
AI summary
A method for reporting channel state information by a terminal in a multiple access based communication system is provided. The method includes determining a most favored direction with a highest signal quality with respect to a reference signal received from a base station and determining, as a reported object, some channel directions including the most favored direction among channel directions formed together with the base station, identifying a channel quality information group including channel quality information corresponding to the some channel directions among channel quality information groups classified according to a distance measured with respect to the most favored direction, and transmitting the identified channel quality information group to the base station.