Femto Cell Power Reduction for Macro Access in Heterogeneous Networks
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Solution Overview
Problem
In heterogeneous networks, user equipment (UE) near a Femto cell base station may fail to access the macro cell base station due to stronger synchronous signals from the Femto cell, leading to increased interference and reduced data transmission efficiency.
Innovation Solution
An initial access method where the UE transmits a power reduction request message to the Femto cell base station, allowing it to reduce its transmission power, thereby controlling interference and enabling successful macro cell ID search and maintaining data transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the Femto cell base station transmits synchronous signals at high power to provide service to allowed terminals, then the coverage and service quality of the Femto cell is improved, but the interference to macro cell terminals attempting to access the macro cell base station increases
Solution Approach 1:
The Femto cell base station dynamically adjusts its transmission power based on the presence of macro cell terminals in the vicinity. When a macro cell terminal is detected (through detection messages or access attempts), the Femto cell reduces its synchronous signal transmission power to minimize interference, and restores normal power when no macro cell terminals are present. This dynamic power adjustment resolves the contradiction between providing strong coverage for Femto cell users and minimizing interference to macro cell users.
Solution Approach 2:
The system implements a feedback mechanism where macro cell terminals send detection messages to the Femto cell base station when they detect strong synchronous signals. The Femto cell base station uses this feedback information to adjust its transmission power accordingly. This feedback loop enables the Femto cell to be aware of macro cell terminal presence and adjust power to prevent interference, resolving the contradiction between strong Femto cell coverage and minimal macro cell interference.
2Ease of operation
If the UE searches for macro cell ID from synchronous signals in the presence of strong Femto cell synchronous signals, then the UE attempts to access the macro cell, but the probability of failure to search the macro cell ID increases due to interference
Solution Approach 1:
The system performs preliminary detection and power adjustment before the macro cell terminal attempts to access the macro cell. When a macro cell terminal sends a detection message, the Femto cell base station proactively reduces its synchronous signal power before the terminal's access attempt, ensuring that the terminal can successfully search for and identify the macro cell ID without interference. This preliminary action prevents access failures before they occur.
Solution Approach 2:
The Femto cell base station applies preliminary anti-action by reducing its transmission power in advance when it detects the presence of a macro cell terminal. This preemptive power reduction counteracts the potential interference that would otherwise prevent the macro cell terminal from successfully searching for the macro cell ID, thereby ensuring reliable macro cell access.
3Reliability
If the UE transmits a power reduction request message to the Femto cell base station, then the interference from the Femto cell is reduced enabling successful macro cell access, but the data transmission amount for the UE accessing the Femto cell may be affected
Solution Approach 1:
The Femto cell base station uses periodic transmission power timers to temporarily reduce transmission power only during periods when macro cell terminals need to access the macro cell. The timer is set for a specific duration (e.g., 10 seconds) during which power is reduced, after which normal power levels are restored. This periodic action ensures that macro cell access succeeds during critical periods while minimizing the impact on Femto cell data transmission during non-critical periods.
Solution Approach 2:
The system applies partial power reduction rather than complete power shutdown during macro cell access periods. The Femto cell base station reduces power to a level that is sufficient to eliminate interference with macro cell access while maintaining minimal service for Femto cell users. This partial action balances the need for reliable macro cell access with the need to maintain Femto cell data transmission productivity.
Data Source
AI summary
An initial access method of a user equipment (UE) and an apparatus performing the same are provided. The initial access method of a user equipment attempting access a macro cell base station in a network with which the macro cell base station and at least one Femto cell base station share, includes: receiving a cell ID from the macro cell base station or the Femto cell base station; transmitting an interference control request message to the Femto call base station when the received cell ID is a Femto cell ID; and receiving a macro cell ID provided from the macro cell base station when an interference control response message is received from the Femto cell base station to attempt an initial access. When a macro UE near to a Femto cell base station attempts to access a macro cell, it searches an ID of the macro cell through interference control from the Femto call base station to achieve initial access.