OFDM impairment mitigation techniques

Abstract

OFDM is an attractive option for high speed wired/wireless data transmission due to its inherent resistance to inter symbol interference (ISI). However, lack of frequency diversity makes it vulnerable to frequency selective impairments such as narrowband interference, frequency selective fading, frequency dependent attenuations etc. In this work, we describe a novel Adaptive Weighting (AW) technique as an efficient method to improve the BER performance of grouped linear constellation preceding (GLCP) OFDM which is used to achieve frequency diversity. In this method during maximum likelihood sequence detection (MLSD), the distance of the possible constellation points from the received symbols are weighted according to the SNR of each subcarrier before the sequence with the minimum distance is chosen. The proposed technique is shown to outperform previous GLCP-OFDM and GLCP-ACS (Adaptive Subcarrier Selection) OFDM over all SNR ranges at the expense of slightly increased complexity.