Uplink Power Control in Heterogeneous Wireless Networks
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Solution Overview
Problem
In heterogeneous wireless communication systems, inter-cell uplink interference occurs due to differing cell coverage sizes and transmission powers, which affects the transmission performance of pico cells and femto cells.
Innovation Solution
A method and apparatus for controlling uplink power by measuring received signal strengths from both upper-layer and lower-layer base stations, determining a transmission power ratio, and selecting a serving base station to minimize inter-cell interference, using a power control equation based on signal-to-interference ratios to adjust transmission power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a common power control equation is used for all cells in heterogeneous network, then the uplink transmission capacity is maintained, but inter-cell interference increases significantly
Solution Approach 1:
The patent applies local quality by deriving separate power control equations for different cell types (macro cell and pico cell) based on their specific transmission characteristics. The macro cell uses Equation (3) while the pico cell uses Equation (4), allowing each cell to have optimized power control parameters that account for their specific coverage areas and interference levels, thereby reducing inter-cell interference while maintaining transmission capacity.
Solution Approach 2:
The patent changes the power control parameters by introducing cell-specific variables such as PLmacro and PLpico for path loss, and PTXmacro and PTXpico for transmission power. By adjusting these parameters differently for macro and pico cells, the system achieves optimal power control that reduces interference between cells while maintaining overall system productivity.
2Length of stationary object
If macro mobile station transmits uplink signals with high power to compensate for large path loss, then the transmission distance is extended, but interference to pico cell increases
Solution Approach 1:
The patent resolves this contradiction by applying different power control strategies to different cell types. The macro mobile station uses Equation (3) with parameters optimized for macro cell coverage, while the pico mobile station uses Equation (4) with parameters optimized for pico cell coverage. This local optimization ensures that each station transmits at the appropriate power level for its cell type, extending transmission distance where needed without causing excessive interference to neighboring cells.
3Object-affected harmful factors
If pico cell uses narrow cell coverage to reduce interference, then inter-cell interference is reduced, but system capacity is limited
Solution Approach 1:
The patent applies dynamics by enabling flexible cell coverage configuration where pico cells can dynamically adjust their coverage areas based on traffic conditions and interference levels. The separate power control equations allow the system to optimize coverage dynamically, expanding pico cell coverage when interference is low and contracting it when interference is high, thereby balancing interference reduction with system capacity maximization.
Data Source
AI summary
A method is provided for controlling an uplink (UL) power by a Mobile Station (MS) in a wireless communication system including an upper-layer Base Station (BS) and a lower-layer BS whose cell coverage is narrower than that of the upper-layer BS. The method also includes measuring a first received signal strength indicating a received signal strength of a first reference signal received from the upper-layer BS, and a second received signal strength indicating a received signal strength of a second reference signal received from the lower-layer BS, acquiring a transmission (TX) power ratio representative of a ratio of a first TX power indicating a TX power of the upper-layer BS to a second TX power indicating a TX power of the lower-layer BS, selecting a first serving BS indicating a UL serving BS to which the MS will transmit a UL signal, from among the upper-layer BS and the lower-layer BS, and determining a UL TX power, based on the first received signal strength, the second received signal strength, and the TX power ratio, and transmitting the UL signal to the first serving BS using the UL TX power.