A system and method for estimating a channel in wireless communication systems using Orthogonal Frequency Division Multiplexing. Being able to examine the status of the environment existing upon the occurrence of the failure, including the condition of various processes and values facilitates resolution of the cause of the failure. The page is first displayed in its entirety. The first input includes a first group name for distributing a first electronic mail message. Software in the signal processing unit synchronizes the analog waveform and digital signals from the external digital source.