A simple transmit diversity scheme based on cyclic-shift pseudo noise (PN) sequences for the time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) system is proposed and the corresponding channel estimation algorithms are also investigated. Simulation results are presented to verify the effectiveness of the proposed method.

A method to construct bit-interleaved coded modulation with iterative demapping and decoding (BICM-ID) is developed that approaches the Shannon limit very closely at high spectrum efficiency, where amplitude-phase shift keying (APSK) constellations are designed and chosen. For 1/2-rate 64APSK, the Es/N0 threshold derived through extrinsic information transfer (EXIT) charts is less than 0.55 dB away from the Shannon limit of the continuous-input additive white Gaussian noise (AWGN) channel, and exceeds the theoretical limit constrained by standard 64QAM-input.

A novel transmit diversity scheme with space-time-frequency coded training sequence is proposed to perform channel estimation flexibly over doubly selective channel, which offers a trade-off between maximum delay spread and maximum Doppler spread. Simulation results are presented to verify the effectiveness of the proposed flexible channel estimation method under different propagation conditions.

This paper proposes a novel system called the cyclic prefix reconstructable time domain synchronous orthogonal frequency division multiplexing ( CPR-TDS-OFDM ) system, which uses a new frame structure and restores the cyclicity of the received OFDM block with low complexity. Simulation results show that the CPR-TDS-OFDM system outperforms the conventional TDS-OFDM system in high-speed fading channels.

In this paper, estimation accuracy of channel frequency response (CFR) according to least squared (LS) criterion with two transmit antennas for the time domain synchronous-orthogonal frequency division multiplexing (TDS-OFDM) system is investigated. To minimize the estimation variance, the conditions to guide the pseudo-noise (PN) sequence design are discussed and three training sequence design schemes are proposed accordingly. Simulations show that the proposed PN sequence design scheme is effective, while the implementation complexity for the channel estimation is low.

Amplitude phase shift keying (APSK) constellation with Gray mapping was proposed recently. Inspired by the simplified soft demapping for regular Gray-QAM, a simplified soft demapping algorithm for Gray-APSK is proposed in this paper. Compared with conventional soft demapping schemes, its complexity is greatly reduced with only a little SNR loss, which is validated by the complexity analysis and FPGA compilation results.

In this paper, a novel pseudo-random noise complementary pair (PNCP) is proposed and adopted as the guard intervals in the time-domain synchronous OFDM (TDS-OFDM) system. The proposed PNCP has nearly ideal aperiodic auto-correlation property and inherits the differential property of the PN sequence. Simulations demonstrate the proposed TDS-OFDM system padded with PNCP could achieve better performance in both synchronization and channel estimation than the conventional TDS-OFDM system.

A BICM-ID system with 3-dimensional rotated BPSK constellation and signal space diversity (SSD) is proposed to combat the effect of Rayleigh fading. A new criterion based on mutual information is proposed to find the optimal rotation matrix, and the labeling that fits well with the outer code is presented. Simulation results show that at BER of 10-5 over a Rayleigh fading channel, with the code length of 192,000 bits and the iteration number of 100, the performance of the proposed system is only about 0.8 dB from the Gaussian-input Shannon limit and exceeds the limit constrained by the traditional QPSK input without rotation or SSD, at the spectrum efficiency of 1 bit/s/Hz.