Comparison of OFDM and Ideal SC-DFE Achievable Rates and Performances Without Channel Knowledge at the Transmitter

Abstract

This paper provides an achievable rate and performance analysis between OFDM and cyclic prefixed SC-DFE when no channel knowledge is available at the transmitter. Through some algebraic manipulation of the OFDM and SC-DFE capacities and using the Jensen's inequality, we prove that the SC-DFE achievable rate is always superior to that of an OFDM scheme for 4- and 16-QAM for any given channel. For higher-order modulations, however, the advantage of the ideal SC-DFE is much smaller and also the results indicate that OFDM may surpass the ideal SC-DFE achievable rate by a small amount in some specific scenarios. Finally, we provide simulation results in order to assess, corroborate and illustrate the analytical results in terms of achievable rate and bit-error rate, where we conclude that a well designed OFDM system can be, in practical context, as effective as an ideal SC-DFE but with much smaller complexity when compared to a SC-DFE implementation with error-propagation mitigation.