SC-FDMA Waveform Design, Performance, Power Dynamics and Evolution to MIMO

We study waveform design, performance and power dynamics of the localized form of the single-carrier frequency-division multiple access (SC-FDMA) considered for uplink in the 3GPP long-term evolution (LTE). A classical single-carrier scheme with root-raised-cosine filtering and two DFT-based schemes are considered, one with and another without a novel spectral expansion. It is shown how to design waveforms similar to the classical scheme by using this spectral expansion. The advantages are that now the transmitter and receiver can be fully specified in frequency domain and that any fraction of the total bandwidth can be assigned to a user. For constant-amplitude modulation (e.g. BPSK, QPSK), the power dynamics is reduced by 3 dB with spectral expansion. Of course, this is bought for 25% more bandwidth. The inherent power dynamics of complex QAM constellations covers part of this gain. Spectral expansion may sometimes be dispensable, e.g. for 16-QAM in the 3GPP LTE uplink. The evolution to MIMO follows directly from the receiver concept based on virtual antennas.