Performance Analysis of Zero-Forcing Beamforming Strategies for the Uplink of an MU-MIMO System with Multi-Antenna Users

2025-09-28

AI Summary

This paper addresses wireless resource management for multi-antenna users in OFDMA-based multi-user MIMO uplink systems. It systematically evaluates three zero-forcing beamforming (ZFBF) strategies—coordinated transmit-receive (CTR1), block diagonalization (BD), and coordinated transmit-receive with feedback (CTRF)—under practical constraints including modulation and coding schemes, power control, and fairness requirements. To enable efficient joint optimization across subcarriers and data streams within a full time slot, the authors propose a computationally scalable, greedy-search-based heuristic algorithm that ensures feasibility and fairness. Simulation results in rural macrocells show BD or CTR1 achieves performance comparable to the computationally intensive CTRF, while in urban macrocells, CTR1 closely approaches CTRF performance, demonstrating practical substitutability. Crucially, system parameters—including number of user antennas and channel correlation—significantly influence relative strategy performance, providing key design guidelines for real-world deployment.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Sampling/Simulation-based Search
• Multiagent Systems: Mechanism Design

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• User Modeling, Personalization and Recommendation: Federated recommendation systems and personalization
• Security and Privacy: Large-scale security measurements

Abstract

We conduct a comprehensive evaluation of the performance of the uplink of OFDMA-based MU-MIMO systems with multi-antenna users, for three Zero-Forcing (ZF) Beamforming (BF) strategies: Coordinated-Transmit-Receive-1 (CTR1), where only the strongest data stream is enabled per scheduled user; Block Diagonalization (BD), where all possible streams are enabled per scheduled user; Coordinated-Transmit-Receive-Flexible (CTRF), which allows a flexible stream allocation per user. The Radio Resource Management (RRM) of the uplink of all OFDMA-based systems must be done over an entire Time-Slot (TS) due to power management, making it challenging. To enable this study, we propose an efficient heuristic based on greedy-up searches for stream-sets that provides feasible solutions. It operates over the TS and considers fairness, practical Modulation and Coding Schemes and all RRM processes. The results show that, for Rural Macro scenarios, BD (resp. CTR1) could replace the more complex CTRF if the number of users is small (resp. large), while for Urban Macro scenarios, CTR1 emerges as an alternative to CTRF due to its similar performance. We also show that the system parameters can substantially impact the performance of the ZF strategies and that BD performance is more impaired with a simpler power management scheme than CTR1 and CTRF.

Problem

• Evaluating Zero-Forcing beamforming strategies for MU-MIMO uplink systems
• Addressing Radio Resource Management challenges in OFDMA-based uplink systems
• Comparing stream allocation flexibility and performance across different scenarios

Innovation

• Evaluated three Zero-Forcing beamforming strategies for MU-MIMO uplink
• Proposed efficient heuristic using greedy-up searches for stream-sets
• Analyzed performance under different scenarios and power management schemes