Subcarrier Based Threshold Performance Enhancement In Constant Envelope Ofdm

Constant Envelope OFDM (CE-OFDM) addresses the major issue of a high peak-to-average power ratio (PAPR) in OFDM. However, since CE-OFDM is based on angle modulation, it suffers from the well known threshold effect which results in a large performance degradation at low carrier-to-noise ratios (CNRs). In this paper, we study the impact of the threshold effect induced phase cycle slips on the underlying phase modulated OFDM subcarriers in CE-OFDM. We study both the signal-to-noise ratio (SNR) as well as the bit error rate (BER) performance on a subcarrier basis and show that the performance degradation due to the threshold effect is much more significant at lower frequency subcarriers. Finally we develop a low complexity subcarrier based technique to mitigate the effect of the phase cycle slips for significant performance improvement.