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Abstract:In this paper, a new time synchronization algorithm for OFDM systems with repetitive preamble is proposed. This algorithm makes use of coarse and fine time estimation; the fine time estimation is performed using a cross-correlation similar to previous proposals in the literature, whereas the coarse time estimation is made using a new metric and an iterative search of the last sample of the repetitive preamble. A complete analysis of the new metric is included, as well as a wide performance comparison, for multipath channel and carrier frequency offset, with the main time synchronization algorithms found in the literature. Finally, the complexity of the VLSI implementation of this proposal is discussed.

Ray Launching is a deterministic method for modeling radio wave propagation based in the Geometric Optic theory. This method is very efficient in three-dimensional and complex environments like inside buildings. But some problems appear implementing the reception algorithms, because the receptors are considered punctual and the rays haven't thickness. The Reception Sphere method is a popular technique used to fix this problem. An alternative method is to launch three-dimensional tubes, instead of rays. In this paper, both techniques are analyzed, showing the advantages and disadvantages of each one in efficiency and accuracy.