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Multicarrier orthogonal frequency division multiplexing (OFDM) supports high data rate wireless communication using orthogonal frequency channel transmissions and offers excellent immunity against fading and intersymbol interference. However, it is characterized by a high peak-to-average power ratio (PAPR), which presents a major challenge for battery- driven terminals requiring efficient power amplification. Single carrier FDMA (SC-FDMA) is a variant of OFDM in which the data symbols are modulated in the time domain, which results in a more power efficient scheme. Continuous phase modulation (CPM) forms a class of single carrier constant amplitude waveforms which are known to be power efficient since the PAPR is always 0 dB. In this paper, we present a novel CPM-SC-FDMA modulation scheme which combines key characteristics of SC-FDMA and CPM to produce a constant envelope waveform which is transmitted over a set of OFDM subcarriers. Thus, this new scheme embodies the power efficiency of single-carrier CPM and the low implementation complexity of SC-FDMA. The basis of our approach is found in the observation that the discrete-time samples from the CPM waveform constitute a set of constant envelope time domain "symbols." When used with an interleaved FDMA (IFDMA) subcarrier mapping, the resulting waveform retains the constant envelope property of CPM. Simulations in AWGN and frequency selective channels indicate that by careful selection of the CPM- SC-FDMA parameters, that the bit error rate performance can improve upon that of conventional SC-FDMA.
Date of Conference: Nov. 30 2008-Dec. 4 2008