Intercarrier Interference Cancellation with Frequency Diversity for OFDM Systems

The implementation of OFDM system suffers from the effect of phase noise (PHN) generated by local oscillator (LO), which disturbs the orthogonality among subcarriers and causes intercarrier interference (ICI). In frequency domain, the received signal can be formulated as the circular convolution of the transmitted signal and the ICI weighting function. In this paper, the symmetric conjugate property of the ICI weighting function is investigated. Based on that, the ICI self-cancellation of symmetric data-conjugate method is studied to suppress PHN. A new ICI cancelling demodulation (ICD) scheme with frequency diversity combining is proposed. Under flat fading channel, the carrier-to-interference ratio (CIR) improvement from this proposed method is larger than 22 dB, and can tolerate a phase noise with standard deviation of 7 deg when BER is 10^-3. In frequency selective fading channel, the proposed method is shown to be able to offer significant diversity gain

I. Introduction

Orthogonal frequency division multiplexing (ofdm) [1], though effective in avoiding intersymbol interference due to multipath delay, suffers from the front-end distortions such as carrier frequency offset (CFO) and phase noise (PHN), which destroy the orthogonality among subcarriers in one OFDM symbol and thus cause intercarrier interference (ICI) [2].