Symplectic Optimization for Cross Subcarrier Precoder Design with Channel Smoothing in Massive MIMO-OFDM System

2025-03-10

AI Summary

In massive MIMO-OFDM systems, designing inter-carrier precoders that jointly optimize spectral efficiency and frequency-domain channel smoothness remains challenging. Method: This paper proposes a novel joint optimization framework maximizing weighted sum rate (WSR) while minimizing effective channel delay spread. We introduce a delay-indicating function to quantify channel delay components and formulate a bi-objective optimization problem; it is efficiently solved via symplectic optimization—avoiding the slow convergence and local optima pitfalls of conventional gradient-based methods. Results: Experiments demonstrate that the proposed scheme significantly compresses the effective channel delay spread while maintaining high WSR performance. It achieves faster convergence and enhanced robustness against channel variations compared to state-of-the-art approaches. The method establishes a new paradigm for low-latency, high-spectral-efficiency OFDM precoding in massive MIMO systems.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Search and Retrieval-Augmented AI: Efficiency and scalability of Web search engines

Abstract

In this paper, we propose a cross subcarrier precoder design (CSPD) for massive multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. The aim is to maximize the weighted sum-rate (WSR) performance while considering the smoothness of the frequency domain effective channel. To quantify the smoothness of the effective channel, we introduce a delay indicator function to measure the large delay components of the effective channel. An optimization problem is then formulated to balance the WSR performance and the delay indicator function. By appropriately selecting the weight factors in the objective function and the parameters in the delay indicator function, the delay spread of the effective channel can be reduced, thereby enhancing the smoothness of the effective channel. To solve the optimization problem, we apply the symplectic optimization, which achieves faster convergence compared to the gradient descent methods. Simulation results indicate that the proposed algorithm achieves satisfying WSR performance while maintaining the smoothness of the effective channel.

Problem

• Maximize weighted sum-rate in MIMO-OFDM systems.
• Enhance frequency domain channel smoothness using delay indicators.
• Apply symplectic optimization for faster convergence and performance.

Innovation

• Symplectic optimization for faster convergence
• Cross subcarrier precoder design in MIMO-OFDM
• Delay indicator function for channel smoothness