SDMA User Selection and Stream Allocation in Multi-User MIMO
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Solution Overview
Problem
Multi-user multi-antenna systems face complexity in selecting users and determining transmission streams for Spatial Division Multiple Access (SDMA) due to exponential system complexity with the number of users and streams, leading to suboptimal performance and diversity effects.
Innovation Solution
A method and apparatus that select SDMA users based on channel state information and determine the number of transmission streams using a tree search method, specifically employing a transmitter with a user selector and stream decider to allocate streams efficiently, reducing complexity and enhancing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all possible user combinations and stream combinations are compared to optimize SDMA performance, then system capacity and performance are improved, but system complexity increases exponentially
Solution Approach 1:
The patent segments the user selection process into multiple stages: first selecting a subset of candidate users based on channel state information, then determining stream allocation for these candidates. This segmentation avoids evaluating all possible user combinations, reducing complexity from exponential to polynomial while maintaining performance.
Solution Approach 2:
The patent performs preliminary user selection based on channel state information before determining stream allocation. By pre-selecting candidate users with good channel conditions, the system narrows down the search space early, avoiding the need to evaluate all possible combinations and thus reducing computational complexity.
2Device complexity
If the number of transmission streams per user is fixed, then implementation complexity is reduced, but diversity effect is not achieved
Solution Approach 1:
The patent makes the number of transmission streams dynamic by determining it based on channel state information and user selection, rather than fixing it beforehand. This dynamic adaptation allows the system to achieve diversity effects by allocating different numbers of streams to different users based on their channel conditions, while keeping implementation complexity manageable through the staged selection approach.
3Device complexity
If SDMA user groups are fixed, then system complexity is reduced, but multi-user diversity is not achieved
Solution Approach 1:
The patent performs preliminary selection of SDMA users based on channel state information before forming user groups. This preliminary action ensures that users with good channel conditions are selected, enabling multi-user diversity while avoiding the need to evaluate all possible user group combinations, thus keeping system complexity manageable.
Solution Approach 2:
The patent changes the parameter of user group composition dynamically based on channel state information. By selecting users whose channel states meet certain criteria, the system adapts user groups to current channel conditions, achieving multi-user diversity without requiring exhaustive search of all possible group configurations.
Data Source
AI summary
An apparatus and method for implementing SDMA in a multi-user multi-antenna system are provided, in which SDMA users are selected from among total users according to channel state information of the total users, and the number of transmission streams to be allocated to each of the SDMA users is determined by a tree search method.