Femtocell Carrier Selection via RSS Interference Measurement
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Solution Overview
Problem
Femto cells in wireless communication systems cause interference due to ad-hoc deployment, leading to coverage holes and performance degradation in macro cellular networks, as they are not optimized by mobile operators and can interfere with each other and macro cells.
Innovation Solution
Femto nodes are enabled to autonomously select carrier frequencies from a set of available carriers based on received signal strength and interference levels, using a preference order to minimize interference and optimize coverage, allowing them to concentrate on preferred carriers while adjusting for tradeoffs between interference and coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If femto base stations are deployed in an ad-hoc manner by subscribers, then ease of deployment is improved, but interference to macro cells and other femto cells increases
Solution Approach 1:
The femto base station autonomously performs carrier selection by measuring interference levels on different carriers and automatically selecting the carrier with lowest interference, eliminating the need for operator-configured restrictions while reducing harmful interference to macro cells
Solution Approach 2:
The system changes the operating carrier parameter dynamically by measuring interference levels on multiple carriers and selecting the optimal carrier, allowing the femto base station to adapt to different deployment scenarios and reduce interference without operator intervention
2Object-generated harmful factors
If femto base stations use restricted association policies, then interference to other femto cells is reduced, but coverage holes increase
Solution Approach 1:
Instead of restricting association, the system changes the operating carrier parameter to achieve interference avoidance, allowing unrestricted association while maintaining low interference through autonomous carrier selection based on measured interference levels
Solution Approach 2:
The femto base station autonomously measures interference from neighboring femto cells on different carriers and self-selects the optimal carrier, eliminating the need for restricted association policies while preventing interference to other femto cells
3Adaptability or versatility
If femto base stations are not optimized by mobile operators, then deployment flexibility is improved, but interference management performance deteriorates
Solution Approach 1:
The femto base station autonomously performs interference measurement and carrier selection without operator optimization, maintaining deployment flexibility while achieving good interference management through self-configuration based on measured interference levels
Solution Approach 2:
The system uses feedback from interference measurements on different carriers to automatically adjust carrier selection, enabling flexible deployment without operator intervention while achieving effective interference management through continuous monitoring and adaptation
Data Source
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AI summary
A carrier for a femtocell is selected from a set of carriers available to femtocells. The femto node determines a preference order for the set and measures received signal strength (RSS) for each carrier. The femto node determines a least interference carrier from the set based on the RSS for each carrier, then defines a selected carrier for the femtocell by comparing the RSS of the least interference carrier to the RSS of other carriers in the set. The selected carrier may have a RSS larger than or equal to the RSS of the least interference carrier offset by a predefined margin. The comparisons may be performed in the preference order. The set available to femto nodes may be a subset of all carriers available to a combination of femtocells and macrocells and one or more of the carriers available to femtocells also may be a carrier available to macrocells.