Approach to suppress out-of-band emission for dual pseudo noise padded time-domain synchronous-orthogonal frequency division multiplexing systems

The dual pseudo noise padded (DPNP) time-domain synchronous-orthogonal frequency division multiplexing (TDS-OFDM) which utilises the second pseudo noise (PN) sequence for channel estimation is able to reduce the complexity and improve the accuracy of channel estimation compared to the classical TDS-OFDM. However, because of the duplicate PN sequence, DPNP TDS-OFDM will suffer from severer out-of-band emission, which is a headache issue for the conventional TDS-OFDM. In this study, a novel out-of-band suppression approach based on a new PN design criterion as well as a windowing operation is proposed for the DPNP TDS-OFDM systems. The frame structure and system model are also modified to accommodate to the approach, while the overlap-and-add approach is adopted to guarantee the spectral efficiency. Both simulation and experimental results show that this approach could achieve satisfactory performance with much less complexity and no spectral efficiency loss compared to the classical DPNP TDS-OFDM system. In addition, an iterative channel estimation method is also proposed for the modified frame structure to combat against the long channel delay spread.