User Selection in MIMO Systems via Channel Orthogonality
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Solution Overview
Problem
The complexity of selecting users in a multiuser multiple-input multiple-output (MIMO) communication system increases exponentially with the number of users, making it difficult to maximize multiuser diversity efficiently.
Innovation Solution
A method that calculates and selects users based on channel orthogonality, excluding users with orthogonality below a predefined threshold, and iteratively refining the user groups to maximize data throughput, using equations to determine the optimal user groups for data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all user combinations are searched to maximize multiuser diversity, then user selection optimality is improved, but computational complexity increases exponentially
Solution Approach 1:
The patent segments the user selection process into two phases: first selecting users based on channel gain criteria, then selecting remaining users based on orthogonality criteria. This segmentation avoids exhaustive search of all user combinations while still achieving near-optimal multiuser diversity, thereby reducing computational complexity from exponential to polynomial order.
Solution Approach 2:
The patent performs preliminary user selection based on channel gain before performing orthogonality-based selection. By pre-selecting users with strong channel conditions, the system reduces the search space for subsequent orthogonality evaluation, avoiding the need to evaluate all possible user combinations and thus reducing computational complexity.
2Reliability
If the number of users K is larger than the number of antennas M, then multiuser diversity gain is improved, but the number of combinations to be searched increases
Solution Approach 1:
The patent applies partial action by selecting only M users out of K available users through a two-stage process rather than evaluating all C(K,M) combinations. The first stage selects users based on channel gain, and the second stage selects remaining users based on orthogonality, thereby achieving sufficient multiuser diversity gain without exhaustive search.
Solution Approach 2:
The patent changes the selection criterion parameter from exhaustive combination evaluation to a two-stage criterion based on channel gain and orthogonality. This parameter change transforms the complexity from exponential (evaluating all combinations) to polynomial (evaluating users twice with different criteria), while still achieving good multiuser diversity when K > M.
Data Source
AI summary
Disclosed herein is a method for selecting a user. A method for selecting a user in a communication system including a base station having M antennas and K users having one receive antenna includes: (a) calculating channel orthogonality between each of the possible users and previously selected users; and (b) selecting users having the largest channel orthogonality calculated at the step (a) among the possible users.