Beamforming for Cell Edge Capacity in Heterogeneous Networks
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Solution Overview
Problem
Heterogeneous networks face challenges in providing dense coverage and reducing interference, especially for cell-edge UEs in macro cells and neighboring cells, due to limitations in deploying small base stations and obstacles that affect coverage.
Innovation Solution
The method involves forming a list of non-targeted UEs and generating candidate precoding matrices to communicate with a selected UE, discarding those that may cause interference, and selecting an available precoding matrix for communication using remote radio heads (RRHs) to mitigate interference and enhance coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If small base stations are deployed to improve network capacity and coverage, then network capacity and coverage are improved, but deployment cost and complexity increase
Solution Approach 1:
The patent embeds remote radio heads (RRHs) within the existing macro base station infrastructure. The RRHs are deployed at remote locations but are logically nested under the macro base station's control and resource management, allowing small cell functionality to be integrated without requiring completely separate deployment infrastructure.
Solution Approach 2:
The patent introduces remote radio heads as intermediary devices between macro base stations and user equipment. These RRHs act as mediators that extend coverage to cell-edge users and provide additional capacity without requiring direct deployment of full base stations at every location, thereby reducing overall deployment complexity.
2Area of stationary object
If transmission power of low power nodes is increased to extend coverage, then coverage is improved, but interference to other UEs increases
Solution Approach 1:
The patent applies precoding matrices to create spatially selective transmission. Different precoding matrices are applied to different user equipment based on their specific channel conditions and locations. This allows the system to concentrate transmission energy toward intended recipients while minimizing interference to other users, effectively providing localized quality optimization for each user.
Solution Approach 2:
The patent dynamically changes transmission parameters including precoding matrix selection, rank indication, and modulation and coding scheme based on channel conditions. By adjusting these parameters in response to changing channel states, the system can optimize coverage extension while controlling interference levels to other users.
3Speed
If precoding matrices are selected to improve data rate for selected UE, then data rate is improved, but interference to non-targeted UEs increases
Solution Approach 1:
The patent implements user-specific precoding matrix selection where each targeted UE receives a precoding matrix optimized for its specific channel characteristics. This localized optimization maximizes data rate for each user while the spatial selectivity of precoding inherently limits interference to non-targeted users by directing energy beams toward intended recipients only.
Solution Approach 2:
The patent employs partial precoding where not all available precoding matrices are utilized, but only those that provide beneficial signal-to-interference-plus-noise ratio improvement for targeted users. This selective application of precoding achieves sufficient data rate improvement without the excessive interference that would result from using all possible precoding options.
4Area of stationary object
If macro base stations are deployed to provide coverage, then coverage area is improved, but cost and deployment time increase significantly
Solution Approach 1:
The patent segments the base station functionality into two parts: the macro base station providing core control and resource management, and remote radio heads providing distributed transmission and reception. This segmentation allows the expensive macro base station infrastructure to be shared across multiple geographic locations through the use of remotely deployed, lower-cost radio head units, thereby reducing overall deployment cost while maintaining extensive coverage.
Solution Approach 2:
The patent nests remote radio heads within the macro base station's network infrastructure. The RRHs are deployed at remote locations but are logically nested under the macro base station's control, allowing the system to achieve extended coverage without requiring proportional increases in expensive macro base station deployments.
Data Source
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Figure 3A~3B
Figure 4A
AI summary
Methods of communicating with a selected user equipment terminal (UE) in a first cell served by a base station and a remote radio head include forming a list of non-targeted UEs including other UEs in the first cell and cell edge UEs in a neighboring cell that borders the first cell that are located near a border of the first cell and the neighboring cell, generating a list of candidate precoding matrices that can be used to communicate with the selected UE from the base station and/or from the remote radio head, generating a list of available precoding matrices by discarding from the list of candidate precoding matrices those precoding matrices that may cause interference to at least one non-targeted UE, selecting a precoding matrix from the list of available precoding matrices, and communicating with the selected UE using the selected precoding matrix.