this thesis consists of two separate topics involved with golay complementary sequences. in the first part, we present results of an experimental investigation where the distribution of peak-to-average power ratio (papr) in downlink mc-cdma systems is modeled by the generalized extreme value (gev) distribution. two orthogonal sets of sequences, walsh- hadamard and golay complementary sequences, are used in spreading processes in the system. then the parameters of the gev distribution are estimated for the papr distribution. through intensive numerical results, it is shown that the gev distribution is an accurate model of the papr distribution of mc-cdma systems. also, the statistically estimated gev distribution parameters for the papr reveal that when the number of subcarriers increases, the papr distributions converge to the gumbel distribution.