Cognitive radio is widely expected to be a promising technology to efficiently exploit underutilized spectrum. Regulatory committees in many countries are taking into account the spectrum policy of dynamic spectrum access using this technology. The TV band is under consideration as a first step to share the spectrum resource. As a result, many activities to specify a standard using this band have been shown. In this paper, an overview on the physical layer of Ecma-392 standard and IEEE 802.11af draft standard is presented together with software simulated performance results. Furthermore, the effect of the frequency diversity on different number of subcarriers and channel bandwidth is analyzed and discussed.