Performances of the superimposition schemes for OFDM systems

To increase the spectral efficiency of orthogonal frequency division multiplexing (OFDM) systems, many techniques have been proposed. Recently, we proposed a superimposition scheme which is called the time domain superimposition of data (TDSD). In this paper, we compare the performance of TDSD with the conventional superimposition schemes such as the superimposed periodic pilot in the time domain (SPPT) and the added pilot semi-blind channel estimation (APSB) in terms of channel estimation, bit error rate (BER) performance, relative spectral efficiency, and complexity. The simulation results show that comparing to the conventional OFDM, TDSD can increase the spectral efficiency up to about 20% with the superimposition factor M = 16 while SPPT has the similar efficiency. APSB has the worst efficiency.