Double rate OFDM system in time varying channel

This paper introduces a new way to increase the transmission rate of data in Orthogonal-Frequency-Division-Multiplexing (OFDM) system. The data rate is doubled by doubling the number of the subcarriers in the OFDM signal. The bandwidth of the OFDM signal and the OFDM-symbol rate are not changed. Complex Exponential Subcarriers (CESs) are used instead of Real Sinusoidal Subcarriers (RSSs). Two different complex symbols are transmitted simultaneously through each pair of conjugate symmetry subcarriers instead of one complex symbol in the conventional OFDM system. The modulation order on each subcarrier is reserved without any change. The time-domain samples of the proposed OFDM symbols are complex. The real and imaginary parts of these symbols are re-modulated with two orthogonal pulse-shapes. The used pulse-shapes are chosen to be Hilbert-transform pair. Different types of pulse-shapes are proposed for using with the proposed OFDM system.