An Analysis of Ofdma, Precoded Ofdma and Sc-fdma for the Uplink in Cellular Systems

Orthogonal Frequency Division Multiple Access (OFDMA) appears today as a strong candidate in on-going standardization. Despite its attractive features, it has several drawbacks when employed in the uplink: The high peak-to-average power ratio (PAPR) inherited from Orthogonal Frequency Division Multiplexing (OFDM) and the inherent frequency diversity loss. The loss of frequency diversity can be combated by precoding. Variants of Precoded OFDMA include Spread Spectrum Multi-Carrier Multiple Access (SS-MCMA) and the frequency-domain implementation of single-carrier (SC) FDMA called DFT-Spread OFDM. The latter transforms OFDMA into a SC transmission system, avoiding the PAPR problem. SC-FDMA with uniformly spaced carriers can be also generated by time-domain processing, a technique known as Interleaved Frequency Division Multiple Access (IFDMA). This paper analyzes OFDMA, several variants of Precoded OFDMA as well as SCFDMA in its timeand frequency-domain implementations and compares them for uplink transmission. The spectrum and performance analysis confirm the benefits of SC-FDMA in terms of both high-power amplifier (HPA) output back-off and bit error rate (BER) performance on selective channels.