Fractional Frequency Reuse Scheduling for Macro-Femto Interference
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Solution Overview
Problem
Inter-cell interference in heterogeneous cellular networks, particularly between macro and femto cells, due to overlapping coverage areas and varying population density, leads to reduced effectiveness and inefficient resource allocation.
Innovation Solution
A centralized scheduler coordinates with individual base stations using fractional frequency reuse (FFR) and inter-cell interference coordination (ICIC) to allocate resources dynamically, minimizing interference by reserving specific frequency bands for cell edge users and restricting their use in neighboring cells, facilitated by a coordinating node that communicates with eNodeBs via X2 protocol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple cell sizes are deployed in heterogeneous networks to handle varying population density, then coverage effectiveness is improved, but inter-cell interference increases
Solution Approach 1:
The patent applies local quality by assigning different frequency resources to different spatial locations within cells. Specifically, cell-center users are allocated frequency band 1 while cell-edge users are allocated frequency band 2. This spatial differentiation of frequency resources allows small cells to provide enhanced coverage in high-density areas without causing harmful interference to macro cell users, as each spatial region uses dedicated frequency bands.
Solution Approach 2:
The patent segments the frequency spectrum into multiple bands (frequency band 1 for cell-center, frequency band 2 for cell-edge) and assigns them to different user groups. This segmentation enables independent resource management where cell-edge users in small cells can use frequency band 2 without interfering with macro cell users who primarily use frequency band 1, thereby resolving the interference issue while maintaining coverage adaptability.
2Productivity
If frequency resources are shared between macro and femto cells, then resource utilization is improved, but interference and throughput performance deteriorate
Solution Approach 1:
The patent changes the frequency resource allocation parameters dynamically based on user location. Cell-center users are assigned frequency band 1 while cell-edge users are assigned frequency band 2. This parameter change ensures that when small cells are deployed, they can utilize frequency band 2 for edge users without degrading the throughput performance of macro cell users who remain on frequency band 1, thus maintaining both high resource utilization and reliable throughput performance.
3Reliability
If centralized coordination is used for resource allocation, then interference coordination is improved, but system complexity increases
Solution Approach 1:
The patent implements self-service by enabling base stations to autonomously identify cell-edge users and allocate appropriate frequency resources without requiring complex centralized coordination. Each base station independently determines which users are at the cell edge and assigns them frequency band 2, while cell-center users receive frequency band 1. This self-service approach achieves effective interference coordination while minimizing system complexity.
Data Source
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AI summary
Systems and methods are disclosed to address inter-cell interference in a heterogeneous network. In one embodiment, a system is disclosed, comprising: a coordinating node situated between a radio access network and a core network; and a first base station in the radio access network in communication with the coordinating node, wherein: the coordinating node has a coordinating scheduler with a first scheduling period; the first base station has a first base station scheduler with a second scheduling period shorter than the first scheduling period; the coordinating scheduler is configured to send a resource reservation list and a resource restriction list to the first base station scheduler once during each first scheduling period; and the first base station is configured to receive the resource reservation list and the resource restriction list and to use the resource reservation list and the resource restriction list when performing mobile device resource scheduling.