A symbol time compression for ICI reduction in high mobility OFDM systems

Conventional orthogonal frequency division multiplexing (OFDM) suffers from high mobility which leads to inter-carrier interference (ICI) and thus the system performance is degraded. In this paper, an OFDM symbol time compression (STC) in one half duration is proposed. The proposed STC scheme increases subcarrier spacing twice and thus the normalized Doppler frequency will be decreased by 50% and thus the bit error rate (BER) performance is improved compared to the conventional OFDM system. The proposed STC scheme is implemented by spreading and combining of input data streams. The proposed STC scheme is investigated in the digital video broadcasting terrestrial (DVB-T) system under AWGN and COST 207 typical multi-path fading channel for BPSK modulation scheme. The performance measures are the BER and the ICI power. The simulation results conform the theoretical ICI power and BER performance. The numerical results show the BER performance improvement compared to the conventional OFDM.

I. Introduction

The conventional OFDM combats multipath frequency selective fading channel [1]. The conventional OFDM system is sensitive to Doppler spread due to time varying channels which results ICI and degrades the BER performance of the system [2]. This paper discusses the prominent ICI reduction schemes. There are many categories to combat the ICI problem due to high mobility in OFDM systems. The first category is based on spatial diversity [3]–[6]. In [3], beamforming and Doppler compensation scheme were used to slow down the channel fluctuation due to high mobility.