Power Control in Distributed MIMO Systems
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Solution Overview
Problem
In distributed MIMO wireless communication systems, existing power control techniques fail to ensure minimum Signal-to-Noise Ratio (SNR) and transmission rate requirements, leading to transmission-not-allowed states due to limited transmission power conditions and high noise interference.
Innovation Solution
A method and apparatus for power control in a distributed MIMO system that determines optimal power values for each terminal by considering the limit transmission power of each antenna, using beamforming matrices and Lagrangian multipliers to maximize transmission efficiency and meet minimum transmission rate requirements, while minimizing the probability of transmission-not-allowed states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If water-filling based power control is used to allocate high power when channel gain is large, then transmission efficiency is improved, but minimum SNR level and transmission rate requirements may not be met leading to transmission-not-allowed states
Solution Approach 1:
The patent modifies the water-filling power control parameters by introducing minimum power constraints (P_min) and maximum power constraints (P_max) for each terminal. The power allocation formula is changed from pure water-filling P_k = [μ|H_k|^2 - σ^2/|H_k|^2]^+ to a constrained version that ensures P_k ≥ P_min and P_k ≤ P_max, thereby guaranteeing minimum transmission rates while maintaining transmission efficiency through optimized power distribution.
Solution Approach 2:
The patent applies different power allocation strategies to different terminals based on their individual channel conditions, minimum power requirements, and maximum power constraints. Each terminal receives customized power allocation rather than uniform treatment, with the power control parameter μ adjusted locally for each terminal to satisfy both minimum SNR requirements and maximum power limits, thus resolving the contradiction between overall efficiency and individual rate guarantees.
2Reliability
If power is allocated to meet minimum transmission rate requirements for all terminals, then transmission reliability is improved, but total transmission power exceeds the limit power of the base station
Solution Approach 1:
The patent introduces a power control parameter μ that scales the water-filling power allocation to fit within the total power constraint. The modified power allocation formula P_k = min(P_max, max(P_min, [μ|H_k|^2 - σ^2/|H_k|^2]^+)) allows dynamic adjustment of μ to ensure that the sum of allocated powers ΣP_k ≤ P_total, while still maintaining minimum power guarantees for each terminal. This parameter adjustment resolves the contradiction between reliability and power consumption.
3Measurement precision
If ZF beamforming is used to cancel interference between terminals, then signal quality is improved, but power allocation becomes limited by power gain and individual terminal power limits
Solution Approach 1:
The patent applies local quality optimization by determining power allocations individually for each terminal based on their specific channel conditions, minimum power requirements, and maximum power constraints. The power control parameter μ is adjusted locally for each terminal to satisfy both the ZF beamforming power gain constraints and the individual terminal power limits, thereby maintaining signal quality while managing power allocation complexity through localized optimization.
Data Source
AI summary
An apparatus is operable to control power of a base station in a distributed Multiple Input Multiple Output (MIMO) wireless communication system. At least one beamforming matrix is used for processing transmission signals to terminals included in a terminal set for a multiple access is determined. Minimum power values required for satisfying a minimum transmission rate of the terminals are determined. Whether optimum power values exist is determined using the minimum power values, the beamforming matrix, and a limit transmission power of the base station. When the optimum power values exist, transmission power values for respective terminals are determined in a range meeting the limit transmission power of the base station.