MIMO Sub-stream Allocation for Feedback Overhead Reduction
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Solution Overview
Problem
In MIMO communication systems, data transmission efficiency and system performance degrade when the number of users within a cell is variable, and channel states between antennas are uneven, leading to increased overhead and reduced multiuser diversity gain.
Innovation Solution
A method and system that set the number of sub-streams for precoding matrices based on channel states, measure and transmit data using optimal sub-stream and antenna combinations, and compute data transmission rates to maximize efficiency, reducing feedback overhead and improving system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If receivers feed back CQI for all precoding matrices and sub-stream combinations, then multiuser diversity gain is maximized, but feedback overhead increases significantly
Solution Approach 1:
The patent segments the feedback process into two stages: first, the receiver identifies and reports only the best precoding matrix index (PMI) and corresponding sub-stream combination; second, the transmitter uses this segmented feedback to efficiently select users and allocate resources. This segmentation reduces feedback overhead while preserving the essential information needed for multiuser diversity.
Solution Approach 2:
The patent extracts only the most critical information (best PMI and sub-stream combination) from the complete set of possible precoding matrices and sub-stream combinations. Instead of feeding back CQI for all possible combinations, the system extracts and reports only the optimal configuration, significantly reducing feedback overhead while maintaining multiuser diversity performance.
2Device complexity
If the number of users in a cell is small, then system complexity is reduced, but data transmission efficiency degrades
Solution Approach 1:
The patent implements dynamic adaptation of the number of sub-streams based on the actual number of active users in the cell. When few users are present, the system dynamically reduces the number of sub-streams to match user demand, maintaining transmission efficiency without unnecessary complexity. When more users are present, the system can utilize more sub-streams to maintain high data transmission efficiency.
Solution Approach 2:
The patent changes the parameter of sub-stream number adaptively based on user count and channel conditions. By adjusting this parameter dynamically, the system optimizes the balance between complexity and transmission efficiency - using fewer sub-streams when users are scarce to reduce complexity, and more sub-streams when users are abundant to maintain efficiency.
3Reliability
If channel states between antennas are uneven, then antenna diversity gain is improved, but data transmission efficiency degrades due to closed-loop control requirements
Solution Approach 1:
The patent implements a closed-loop feedback mechanism where receivers measure channel states and feed back CQI, PMI, and sub-stream combination information to transmitters. This feedback enables the system to adapt to uneven channel states between antennas, selecting the best precoding matrices and sub-stream combinations to maximize data transmission efficiency while maintaining antenna diversity gain.
Solution Approach 2:
The patent performs preliminary computation of SINR for all possible sub-stream combinations and precoding matrices before actual data transmission. By pre-calculating and identifying the optimal configurations, the system prepares in advance for uneven channel conditions, enabling efficient data transmission without real-time computation delays during actual transmission.
Data Source
AI summary
A method and system are provided for transmitting data in a multiple-input multiple-output (MIMO) communication system. A receiver sets the number of sub-streams of each column of a preceding matrix with respect to all precoding matrices of channels formed between the receiver and a transmitter and measures channel states with respect to sub-stream combinations whose number is equivalent to the number of set sub-streams. The receiver transmits data according to channel states to the transmitter after measuring the channel states with respect to the sub-stream combinations and antenna combinations representing sub-streams used upon data transmission of all the precoding matrices.