Uplink Interference Control in Heterogeneous Wireless Networks
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Solution Overview
Problem
In heterogeneous wireless cellular networks, neighboring cells using the same frequency band experience uplink interference due to independent power control, leading to a 'wind-up' effect and signal-to-noise ratio degradation, especially between macro-cells and small-cells, where implementing full soft handover is complex.
Innovation Solution
Establishing a set-up parameter exchange interface between macro and small-cell radio network subsystems to transmit radio link set-up information, decode E-DCH control channel information, estimate uplink interference, and send requests to reduce the uplink power level of user equipment when interference thresholds are reached, using Iur interfaces and RNSAP radio link set-up information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If full soft handover mechanism is implemented between macro-cell and small-cell, then uplink interference control is improved, but device complexity and implementation difficulty increase significantly
Solution Approach 1:
The patent extracts only the essential power control functionality from the full soft handover mechanism. The small-cell base station router receives only the minimum necessary information (physical layer parameters) from the macro base station to decode E-DCH control channels and estimate interference, without implementing the complete soft handover protocol stack. This selective extraction reduces complexity while maintaining interference control effectiveness.
Solution Approach 2:
The patent applies partial action by implementing only the specific subset of soft handover functions needed for interference control (information exchange and power adjustment), rather than the complete soft handover mechanism. The small-cell router performs partial decoding of control channels and partial interference estimation, which is sufficient to control uplink interference without the overhead of full soft handover implementation.
2Ease of operation
If independent power control is used in each cell, then device operation simplicity is improved, but uplink interference increases due to wind-up effect
Solution Approach 1:
The patent establishes a feedback mechanism where the small-cell base station router monitors uplink interference by decoding E-DCH control channels from user equipment and estimates interference levels. When interference exceeds a threshold, the small-cell router sends power reduction commands back to the user equipment through the macro base station. This feedback loop enables coordinated power control while maintaining the operational simplicity of independent cell management.
Solution Approach 2:
The patent introduces an intermediary information exchange interface between the macro base station and small-cell base station router. The macro base station acts as an intermediary that receives physical layer parameters from the small-cell router and transmits power control commands to user equipment. This intermediary mechanism enables coordinated interference control without requiring direct complex interaction between independent cells.
3Reliability
If power level instructions are sent from macro base station to small-cell base station as in prior art, then uplink interference control is improved, but information loss occurs due to insufficient physical layer parameters
Solution Approach 1:
The patent applies preliminary action by having the small-cell base station router pre-process and decode E-DCH control channel information from user equipment before sending interference estimates to the macro base station. By performing this preliminary decoding and extraction of physical layer parameters in advance, the system ensures that all necessary information is available for accurate interference control decisions, preventing information loss that would occur with simpler prior art approaches.
Data Source
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AI summary
The present invention refers to a method for reducing the uplink interferences produced by non-serving user equipments (23) using an enhanced-dedicated channel "E-DCH" in a wireless cellular communication network comprising radio network subsystems (1, 15) that are independent and that present coverage areas that are at least partially overlapping wherein it comprises the following steps: - the establishment of a set up parameter exchange interface (7) between the first (1, 15) and the second (1, 15) radio network subsystem, - when a user equipment attached to a first radio network subsystem (1, 15) is located in the coverage area of a second radio network subsystem (1, 15) independent from the first radio network subsystem, the transmission, through the said established interface (7), of radio link set up information including physical layer parameters information from the first radio network subsystem to the second, - the reception by the second radio network subsystem (1, 15) of uplink coded E-DCH control channel information sent from the user equipment, - the configuration of the second radio network subsystem (1, 15) based on the transmitted radio link set up information in order to decode the received E-DCH control channel information, - the estimation of the uplink interference level produced by the user equipment (23) in the second radio network subsystem based on the decoded E-DCH control channel information, if the estimated uplink interference level in the second radio network subsystem meets a predetermined criterion, - the establishment of a downlink connection between the second radio subsystem and the user equipment (23) based on the transmitted radio link set up information and the sending through the established downlink connection of a request to reduce the uplink power level of the user equipment (23).