Wireless communications are one of the pillars of the development of the new generations of mobile communications. Each generation has used some multiple access technique to take advantage of the channel s resources. This dissertation presents an analysis of two orthogonal multiplexing techniques. Both techniques implement block transmission, where one is combined with the Code Division Multiple Access (CDMA) approach, while the other uses the multicarrier transmission technique Orthogonal Frequency Division Multiplexing (OFDM). The performance and spectral occupation of both techniques and their advantages are analyzed. Analytical expressions for the Power Spectral Density of the signals were obtained, which allowed establishing comparisons between both methods. The study of these multiplexing techniques is carried out in different propagation channels to evaluate the behavior of both systems in general. The three types of channels evaluated in this work are linear and time-invariant, linear and time-variant and, finally, non-linear and time-invariant. Each type of channel was modeled in matrix form for both systems independently. The simulations consider the Zero Forcing and Minimum Mean Squared Error equalizers, assuming a known channel.