On the design of an OFDMA-based software-defined modem: A CFO estimation perspective

Abstract

Carrier Frequency Offset (CFO) is critical to the decoder performance of an Orthogonal Frequency Division Multiple Access (OFDMA) system and the conventional research works have coped with this issue. On the other hand, excessive enhancement of the estimation accuracy causes redundant computational complexity, which is not desirable for SoftWare (SW) defined modems that solely conduct signal processing in a software environment. In this paper, we propose a design methodology of a two-step CFO estimator that controls a specific level of estimation accuracy and computational complexity in the SW defined modem. Based on a generalized numerical model of the estimation accuracy in a noisy environment, we provide how to design coarse and fine CFO estimators that meet the target level of estimation accuracy. To evaluate its validity, we constructed a SW defined modem testbed system that can estimate CFO in a real-time environment. The two-step CFO estimator suitable to a Long Term Evolution (LTE) Physical Broadcast CHannel (PBCH) decoder is implemented on the testbed based on the design methodology. The results show that the two-step CFO estimator is designed properly to operate in various Signal to Noise Ratio (SNR) regimes, maximizing the performance of the PBCH decoder. © 2023 The Author(s)