Linear Precoder Design for Multi-Cell Downlink Interference
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Solution Overview
Problem
Existing wireless communication networks face challenges in optimizing signal quality due to increasing user demand, with existing methods failing to effectively account for inter-cell and intra-cell interference, and assuming perfect channel state information which is not practical.
Innovation Solution
The design of precoders that account for inter-cell and intra-cell interference, considering channel states and uncertainty regions, to optimize user utilities by maximizing minimum receiver rates or weighted-sum rates within bounded channel estimation errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmit precoding is employed to mitigate interference in downlink transmissions, then signal quality for multiple users is improved, but the system complexity increases due to the need for channel state information acquisition and coordination among base stations
Solution Approach 1:
The patent segments the precoding design into independent per-base-station optimizations rather than requiring global coordination. Each base station independently determines its precoding matrix by maximizing a utility function that accounts for local and neighboring cell interference, eliminating the need for complex centralized coordination while maintaining signal quality improvements
Solution Approach 2:
The patent employs preliminary actions by having base stations acquire channel state information for both served users and interfering users before transmission. This advance acquisition of CSI for neighboring cells enables the base stations to pre-compute interference-aware precoding matrices, reducing the need for real-time coordination and lowering system complexity
2Ease of manufacture
If perfect channel state information is assumed for beamforming design, then the beamforming optimization is simplified, but the robustness of the system deteriorates when dealing with imperfect channel estimates
Solution Approach 1:
The patent changes the optimization parameter from assuming perfect channel state information to explicitly modeling channel estimation errors as bounded uncertainty regions. The utility function is modified to maximize performance under worst-case error conditions, transforming the design approach to be robust against imperfections while maintaining computational tractability
Solution Approach 2:
The patent applies beforehand cushioning by incorporating error bounds directly into the utility maximization formulation. By pre-accounts for potential channel estimation errors through uncertainty regions, the system is cushioned against the impact of imperfect CSI, ensuring reliable performance even when channel state information is inaccurate
3Device complexity
If inter-cell and intra-cell interference are not considered in precoder design, then the per-cell beamforming design is simplified, but the overall network utility deteriorates due to unaccounted interference
Solution Approach 1:
The patent merges the interference consideration into the utility function maximization at the base station level. By incorporating terms that account for both intra-cell and inter-cell interference directly into the local utility maximization, the design achieves network-wide optimization without requiring separate coordination stages, thus maintaining simplicity while improving network utility
Data Source
AI summary
Methods and systems for optimizing the utilities of receiver devices in a wireless communication network are disclosed. Precoder design formulations that maximize a minimum worst-case rate or a worst-case sum rate are described for both full base station cooperation and limited base station cooperation scenarios. In addition, optimal equalizers are also selected to optimize the worst-case sum rate.