Virtual MIMO Power Control via Successive Interference Cancellation
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Solution Overview
Problem
The performance of virtual MIMO systems is hindered by unbalanced arrival power and signal-to-noise ratios (SNRs) among user terminals due to varying path losses, leading to inefficient power control methods that either increase interference or limit system capacity.
Innovation Solution
A power control method that determines the minimum total transmission power for each user terminal by setting specific indices such as bit error rate or SNR to threshold values, using successive interference cancellation and considering interference as additive white Gaussian noise, to optimize power distribution and minimize overall power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmission power of user terminals with larger path loss is increased to balance arrival power, then arrival power balance is improved, but overall system capacity deteriorates due to interference with adjacent cells
Solution Approach 1:
The patent changes the power control parameter from equalizing arrival power to minimizing total transmission power subject to SNR constraints. This fundamental parameter change allows the system to operate with unbalanced arrival powers while maintaining performance through optimized power allocation that respects water-filling theory and reduces adjacent cell interference.
Solution Approach 2:
Instead of increasing power to achieve balance, the patent inverts the approach by allowing unbalanced arrival powers and using successive interference cancellation to detect users in descending order of arrival SNR. This inversion transforms the problem from power equalization to interference management through detection ordering.
2Reliability
If transmission power of user terminals with larger path loss is increased to balance arrival power, then arrival power balance is improved, but power efficiency deteriorates
Solution Approach 1:
The patent fundamentally changes the power control objective from power balance to total power minimization subject to SNR constraints. This parameter change aligns with water-filling theory, which optimizes power allocation by allocating more power to channels with better conditions, thereby improving overall power efficiency while maintaining reliable communication.
Solution Approach 2:
The patent converts the previously harmful unbalanced arrival power condition into a beneficial feature by using successive interference cancellation that exploits the unbalanced structure. Users with higher arrival SNRs are detected first and their signals are subtracted, making the unbalanced power distribution advantageous for sequential detection and improving power efficiency.
3Reliability
If user terminals are carefully paired through scheduling to balance arrival power, then arrival power balance is improved, but system capacity is limited
Solution Approach 1:
The patent changes the pairing criterion from arrival power balance to maximizing the number of simultaneously served users. By using successive interference cancellation and optimizing power allocation subject to SNR constraints, the system can support more users in virtual MIMO without requiring careful pairing for power balance, thereby increasing system capacity.
Solution Approach 2:
The patent inverts the scheduling approach by not requiring careful pairing for power balance. Instead, it allows any users to be paired and uses successive interference cancellation to handle the unbalanced arrival powers, thereby maximizing the number of users that can be served simultaneously and increasing system capacity.
4Ease of operation
If conventional detection techniques are used with unbalanced arrival power, then detection simplicity is maintained, but detection performance deteriorates
Solution Approach 1:
The patent inverts the conventional approach by not trying to equalize arrival powers through power control, but instead using successive interference cancellation that exploits the unbalanced structure. Users are detected in descending order of arrival SNR, with each detected user's signal being subtracted before detecting the next user. This inversion transforms the detection problem into a sequential process that handles unbalanced powers effectively.
Solution Approach 2:
The patent segments the detection process into sequential steps, detecting users one by one in descending order of arrival SNR. Each detection step handles one user at a time by treating other users' signals as interference, then subtracting the detected user's signal before proceeding to the next user. This segmentation makes the detection process manageable and effective for unbalanced arrival powers.
Data Source
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AI summary
A power controlling method and corresponding base station for controlling the transmission power of each user terminal are disclosed, in which, each user terminal is paired into virtual MIMO transmission. In the solution, first, determining the transmission power of each user terminal that makes the sum of the transmission power of each user terminal minimum under the case that the specific index for each user terminal meets a required threshold value; then, feed backing the determined transmission power of each user terminal to each user terminal. Compared with the prior art, the solution can achieve a preferable power efficiency.