A simple blind CFO estimate technique for a QO-STBC based MC-CDMA uplink system

We propose a simple technique for estimating the carrier frequency offset (CFO) of a quasi-orthogonal space–time block coding (QO-STBC) multicarrier code-division multiple-access (MC-CDMA) uplink system without the knowledge of channel state information in a multipath fading channel. Based on the intrinsic properties of the considered system, a useful multiply constrained minimum output energy (MCMOE) receiver is developed, and the CFO estimate is achieved by using a one-dimensional linear search, whose objective is to maximize the output power of the developed receiver. In addition, an alternative based on the Taylor series expansion technique is designed to avoid the exhaustive search. By feeding the CFO-compensated data back to the input of the MCMOE receiver, we use an iterative approach to further enhance the estimatorʼs performance. Numerical results have been conducted to demonstrate that the proposed CFO estimator provides an accurate estimate within a few times of iteration.