Abstract —This paper focuses on comb-type or scattered pilot arrangement in OFDM systems with a frequency guard band under the time-variant channel. If the maximum channel delay is large, there is a nearly singular matrix problem when a receiver adopts the Frequency Domain LS (FDLS) method to estimate the data subcarrier channel frequency response. This problem renders FDLS channel estimation more sensitive to noise. M. Yu and P. Sadeghi proposed a simply method to avoid the nearly singular matrix problem; however, they did not describe in detail how to select the important regularization parameter. Therefore, this study will discuss and analyze the regularization parameter, and propose a flow to select a suitable regularization parameter. From BER simulations, the proposed flow shows good performance.
 
Index Terms—OFDM, channel estimation, frequency domain LS channel estimation.