A multi-user uplink TDS-OFDM system based on dual PN sequence padding

The adoption of pseudo-noise (PN) sequence instead of cyclic prefix (CP) as guard interval (GI) enables time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) outperform Cyclic Prefixed- OFDM (CP-OFDM) by spectrum efficiency but at the expense of higher complexity. Up to now, TDS-OFDM is only used in unidirectional data transmission such as downlink broadcasting. The difficulty to eliminate the implicitly mixed interferences between different PN sequences and inverse discrete Fourier transform (IDFT) blocks caused by multiple users hinders the application of TDS-OFDM in multi-user uplink scenarios. To deal with this problem, this paper proposes a multi-user uplink TDS-OFDM system based on dual PN padding (DPNP) where the cancellation of mixed interference is avoid by joint cyclicity reconstruction for all users. In addition, joint channel estimation and separation is also proposed to restore the transmitted signal for each user. Theoretical analysis and computer simulation not only verify the feasibility of the proposed system, but also show that, compared with the conventional single-user TDS-ODFM system, it holds lower implementation complexity yet even better system performance in mobile environments.