Interference Mitigation in Heterogeneous Wireless Networks
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Solution Overview
Problem
In heterogeneous wireless communication networks, interference between macro-cells and home-base stations (HeNBs) leads to degraded quality of service, particularly due to overlapping bandwidth deployments, where downlink and uplink transmissions from HeNBs can interfere with macro-cell users, and existing methods like blanking subframes are inefficient and incompatible with LTE Rel-8 standards.
Innovation Solution
A method that involves using a mapping function to determine the time-frequency resources used by HeNBs based on their cell identifier and load status, allowing macro-cells to avoid interfering resources and minimize interference by configuring DL scheduling resources to be orthogonal to HeNB patterns, and incorporating load indicators and SIR metrics for improved resource allocation and interference mitigation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If HeNBs deploy overlapping bandwidth with macro-cells to increase network capacity and coverage, then spectral efficiency and network flexibility improve, but interference between macro-cell users and HeNB transmissions increases
Solution Approach 1:
The patent segments the time-frequency resources by dividing the uplink bandwidth into different regions (first uplink region for macro-cell, second uplink region for HeNB) and time periods (first and second time periods with different cyclic prefix lengths). This segmentation allows HeNBs and macro-cells to operate on the same frequency band simultaneously without interfering with each other, thus increasing network capacity while controlling interference.
Solution Approach 2:
The patent applies local quality by configuring different uplink transmission parameters (cyclic prefix length, resource allocation) for different spatial locations and cell types. Macro-cell users and HeNB users receive tailored resource configurations based on their specific deployment scenarios, allowing optimal performance for each local context while coexisting in the same network.
2Adaptability or versatility
If HeNBs use normal cyclic prefix to maintain compatibility with LTE Rel-8 standards, then standard compliance improves, but uplink interference with macro-cell users increases
Solution Approach 1:
The patent segments time resources by assigning different cyclic prefix configurations to different time periods. During the first time period, macro-cell users use normal cyclic prefix while HeNB users use extended cyclic prefix, and vice versa during the second time period. This time-domain segmentation allows both cell types to operate with appropriate CP lengths without mutual interference, maintaining standard compatibility while reducing interference.
Solution Approach 2:
The patent implements periodic switching of cyclic prefix configurations between macro-cell and HeNB users across different time periods. This periodic action allows the system to alternate resource allocation patterns, ensuring that each cell type has dedicated time periods with optimized CP lengths, thereby reducing interference while maintaining overall standard compliance.
3Object-affected harmful factors
If macro-cells blank subframes to reduce interference with HeNBs, then interference mitigation improves, but network resource utilization and spectral efficiency deteriorate
Solution Approach 1:
The patent employs dynamic resource allocation where the network controller adaptively assigns time-frequency resources to macro-cell and HeNB users based on current network conditions, traffic demand, and interference levels. This dynamic approach replaces static blanking with flexible resource scheduling that optimizes spectral efficiency while maintaining interference mitigation, allowing resources to be utilized whenever possible rather than being permanently blanked.
Solution Approach 2:
The patent enables self-service by allowing HeNBs to autonomously select uplink resources from the second uplink region configured by the network controller, without requiring macro-cell intervention or subframe blanking. This self-organized resource allocation eliminates the need for macro-cells to sacrifice spectral efficiency through blanking, as HeNBs independently manage their own resource usage within the allocated region.
4Area of stationary object
If HeNBs are deployed in coverage areas of macro-cells to extend network reach, then coverage and capacity improve, but service quality for macro-cell users near HeNBs deteriorates
Solution Approach 1:
The patent segments the uplink resource space into distinct regions (first uplink region for macro-cell, second uplink region for HeNB) that are orthogonal in the time-frequency domain. This segmentation ensures that signals from macro-cell users and HeNB users do not overlap or interfere with each other, allowing HeNBs to extend coverage into macro-cell areas without degrading service quality for macro-cell users.
Solution Approach 2:
The patent resolves spatial interference by introducing time and frequency dimensions as additional separation mechanisms. Instead of relying solely on spatial distance, the system uses time-domain separation (different time periods with different CP lengths) and frequency-domain separation (different uplink regions) to orthogonally allocate resources, thereby extending coverage while maintaining service quality.
Data Source
AI summary
A method in a wireless terminal transceiver includes receiving a sequence of frames from a first base station, wherein each frame in the sequence contains a first set of time-frequency resources which may be used for scheduling data and a second set of time-frequency resources not used for scheduling data. The transceiver also receives a message from the first base station identifying a third set of time-frequency resources that is a subset of the first set of time-frequency resources, and estimates the channel state based on the transmission received in the third set of time-frequency resources.