Spectral Efficiency Analysis of Massive MIMO-OFDM Systems with Double Quantization

2026-10-07

AI Summary

This study addresses the spectral efficiency degradation caused by dual quantization at both analog-to-digital converters (ADCs) and fronthaul links in massive MIMO systems, investigating the achievable uplink performance under channel estimation errors. A linear minimum mean square error (MMSE) channel estimator is derived for OFDM-based systems, and closed-form performance bounds are established using the use-and-then-forget bound. The core contribution lies in revealing that the two quantization resolutions exert comparable impacts on system performance, with the lower resolution serving as the dominant limiting factor. Furthermore, this work demonstrates that 6-bit quantization suffices to recover over 90% of the spectral efficiency achieved in ideal scenarios, thereby providing a theoretical foundation for practical hardware configuration in real-world systems.

Abstract

Massive multiple-input multiple-output (MIMO) achieves a high spectral efficiency (SE) by employing a large number of receive antennas in the uplink. Employing many receive antennas requires a large number of analog-to-digital converters (ADCs) and a high fronthaul data rate. Low-resolution ADCs can reduce power consumption and cost, while fronthaul quantization can reduce the required fronthaul data rate, at the expense of quantization distortion at both stages. In wideband orthogonal frequency-division multiplexing systems, ADC quantization is performed in the time domain, while fronthaul quantization may be applied after the discrete Fourier transform to transmit only active subcarriers. In this study, we investigate the achievable uplink SE over fronthaul links under double quantization and imperfect channel estimation. We derive a linear minimum mean-squared error channel estimator from the double-quantized pilot observations and obtain an achievable SE using the use-and-then-forget bound. Numerical results demonstrate that the ADC and fronthaul quantization resolutions have comparable impacts on the achievable SE. When the two resolutions differ, the lower resolution becomes the dominant factor limiting the SE. Furthermore, our numerical results show that six-bit ADC and fronthaul quantization achieve more than 90% of the SE attained in the ideal case.

Problem

• Massive MIMO
• OFDM
• Spectral Efficiency
• Double Quantization
• Fronthaul

Innovation

• Massive MIMO-OFDM
• Double Quantization
• Spectral Efficiency
• LMMSE Channel Estimation
• Fronthaul Quantization