Macrocell Pico-cell Interference Control via Almost Blank Subframes
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Solution Overview
Problem
In HetNet environments, 'Range Expansion' methods to reduce macrocell base station load lead to increased interference between macrocell and pico-cell, necessitating interference control measures like 'Almost Blank Subframe', which have limited effectiveness.
Innovation Solution
Implementing interference control through 'Almost Blank Subframe' and using specific subframe timing shared between macrocell and pico-cell base stations, where the macrocell base station reduces or omits signals except control signals, and the pico-cell base station adjusts reception quality measurement timing to minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Range Expansion is used to distribute load from macrocell to pico-cell, then macrocell load is reduced, but interference between macrocell and pico-cell increases
Solution Approach 1:
The patent implements Almost Blank Subframes where the macrocell base station periodically transmits only control signals and reference signals while omitting data transmissions in specific subframes. This periodic action creates interference-free time windows that allow pico-cell users to communicate without macrocell interference, thus enabling load distribution without the harmful interference effect
Solution Approach 2:
The patent ensures continuous load distribution by configuring multiple Almost Blank Subframes across different time periods, allowing pico-cell users to continuously access the network during these protected subframes. This maintains the load distribution benefit while eliminating interference through the continuous provision of interference-free transmission opportunities
2Object-affected harmful factors
If Almost Blank Subframe is used to control interference, then interference between cells is reduced, but throughput is degraded
Solution Approach 1:
The patent applies different transmission qualities to different time resources: during Almost Blank Subframes, the macrocell provides high-quality interference-free transmission for pico-cell users, while during normal subframes, the macrocell provides full-capacity transmission. This local differentiation in transmission quality allows the system to optimize for interference reduction when needed while maintaining high throughput during normal operation
Solution Approach 2:
The patent uses partial action by transmitting only essential control signals and reference signals during Almost Blank Subframes rather than completely silencing the macrocell. This partial transmission maintains necessary network functions and provides interference protection for pico-cell users, while the limited transmission reduces but does not eliminate macrocell throughput, achieving a balanced compromise
Data Source
AI summary
A macrocell base station controls to reduce interference between cells by a downlink signal of the macrocell base station with specific timing, the interference which a downlink signal of a low transmission power cell suffers for a wireless terminal. A low transmission power cell base station decides measurement timing with which the wireless terminal measures reception quality of the low transmission power cell based on information about the specific timing, and sends a setting message including a parameter according to the measurement timing to the wireless terminal. The wireless terminal measures reception quality with the measurement timing indicated by the parameter, and when the wireless terminal satisfies a condition for executing an event based on the measured result, the wireless terminal sends a reception quality measurement message including information indicating that the measurement is made with the measurement timing to the low transmission power cell base station.