Sharif Digital Repository

This paper addresses the problem of frame detection in orthogonal frequency-division multiplexing (OFDM) systems. Using fourth-order statistics, a novel approach is presented for detection of a preamble composed of two identical parts in the time domain. First, it is demonstrated that sufficient statistics for detection of a periodic preamble do not exist, and conventional methods are not optimal. Next, looking at the detection of a preamble from the viewpoints of hypothesis testing and classification, a new method is presented based on the idea that fourth-order statistics can increase class separability (between-class distance) and consequently improve detection performance. It is proven... 

In this paper, the problem of coarse timing synchronization in orthogonal frequency-division multiplexing (OFDM) systems is investigated, and two new timing metrics with better performance are presented. The new metrics take advantage of two novel differential normalization functions that are based on the fourth-order statistics and are designed depending on the value of carrier frequency offset (CFO). The proposed timing metrics are theoretically evaluated using two different class separability criteria. It is shown that the new schemes considerably increase the difference between the correct and wrong timing points in comparison with previous methods. The computational complexity of the...