Broadband wireless access systems used in residential and business environments have to face hostile radio propagation environments, with multipath delay spread extending over tens or hundreds of bit interval. OFDM is multicarrier solution to the problem occurred by multipath effects. As we know that the most important feature of OFDM is frequency and time synchronization because they are the reason for the orthogonality between the subcarriers. In OFDM communication system there is synchronization error between transmitter and receiver local oscillator frequencies known as Carrier frequency offset cause ICI and destroy the orthogonality between subcarriers. In this book, we study how the CFO can effect SNR in an OFDM system basically in C-OFDM system, and calculate the amount of frequency offset and also we do the study of it in multipath environment.