Abstract
Orthogonal frequency-division multiplexing (OFDM) systems over rapidly time varying channels may suffer from significant inter-carrier interference (ICI), which destroys the orthogonality between subcarriers and degrades the detection performance. Without sufficient ICI suppression, OFDM systems usually experience an error floor. According to the approximate matched filter bound (AMFB), the error floor in a coded OFDM system is not irreducible. In this work, we introduce novel multiple feedback matched filter (MBMF)-based ICI cancellation receivers. Based on the output of a novel MBMF scheme, the approach employs a multiple ICI cancellation strategy with or without signal-to-interference-plus-noise-ratio (SINR) ordering. The developed schemes can significantly improve the performance and remove the error floor with a negligible complexity increase. Given the multiple cancellation approach, we compare the SINR performance of the MBMF outputs with that employing single feedback and show that the SINR performance with multiple cancellation candidates is improved over that with a single one at practical SNR values. Additionally, for time-varying channels, we exploit partial fast Fourier transform (PFFT) by splitting one OFDM symbol into multiple segments; the channel state is separately estimated by least-squares (LS) methods without inserting more pilots. Simulation results demonstrate the superiority of the proposed methods over serial and block equalizers and the robustness to the Doppler effects compared to conventional single-segment method.
Highlights
Due to the Orthogonal frequency-division multiplexing (OFDM) system’s high spectral efficiency and simple equalization, it has been widely adopted by many digital communication standards, such as Long-term evolution (LTE), LTE-Advanced and Worldwide Interoperability for Microwave Access (WiMAX)
A simple frequency domain ZF equalizer using the banded channel structure has been proposed in [1]; recursive MMSE filters with decision feedback equalization and matched filter bound (MFB) [2,3] have been investigated, and the bound can be considered as the performance benchmark for inter-carrier interference (ICI) cancellation algorithms
We assume a scenario with the following settings: the carrier frequency fc = 650 MHz; the subcarrier spacing ∆f = 976.5 Hz; and the OFDM symbol period is TOFDM = 1/∆f ≈ 1 ms
Summary
Due to the OFDM system’s high spectral efficiency and simple equalization, it has been widely adopted by many digital communication standards, such as Long-term evolution (LTE), LTE-Advanced and Worldwide Interoperability for Microwave Access (WiMAX). In [4,5], the authors, using time-domain receiver windowing, further exploited the banded channel matrix in the frequency domain to design the serial and block equalizers with low complexity. Another method, based on the modified banded structure in the time or the frequency domain, estimates the symbols using a sequential least-square QR (LSQR) algorithm with selective parallel interference cancellation (PIC) [6]
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