This letter presents a noise-robust sampling frequency offset (SFO) estimation scheme for OFDM-based WLAN systems. Mean square error of the proposed estimation scheme is derived and simulation results are provided to verify our analysis. The proposed SFO estimator has an improved performance over the existing schemes with a reduction of the estimation range.

Multiple access based on energy spreading transform (EST) in [1] has been shown to effectively separate multiuser signals in an iterative manner. In this paper, an optimum hard-decision detector for the EST-based multiple access is proposed. The proposed scheme employs minimum mean square error (MMSE) processing at each iteration to enhance the performance of the original scheme. Analysis and simulation results show the significant performance improvement of the proposed scheme over the original method.

A cyclic prefix reconstruction scheme is proposed for precoded single-carrier systems with frequency-domain equalization (SC-FDE) that employ insufficient length of cyclic prefix. For SC-FDE, cyclic prefix is employed to facilitate frequency-domain equalization at the receiver. Since inserting cyclic prefix incurs a loss in bandwidth-utilization efficiency, it is desirable to limit the length of cyclic prefix for SC-FDE. This paper designs the energy spreading transform (EST), a precoder that enables iterative reconstruction of missing cyclic prefix. The performance of the proposed scheme is shown to be close to that of SC-FDE with enough length of cyclic prefix.

In this letter, a new exact expression of the ergodic channel capacity for a Rician fading channel is provided that is written in terms of exponential integral and incomplete gamma function. Also, a good approximation of the Rician fading channel capacity is derived from the exact expression and its accuracy is numerically verified.

In a closed-loop scenario, the performance of transmit-diversity schemes for a multiple antenna system depends on the reliability of the channel state information (CSI). However, estimating the reliability of the instantaneous CSI at the transmitter is a challenging task. In this paper, we propose a robust transmit-diversity scheme for the case when the instantaneous CSI available at the transmitter is imperfect and its reliability is unknown to the transmitter. We show by simulation that our proposed scheme is efficient when the CSI reliability varies arbitrarily in every channel realization.