Novel decision-directed channel estimation method for TDS-OFDM system

Time-domain synchronous orthogonal frequency division multiplexing system (TDS-OFDM) employs known pseudo-noise (PN) sequences as guard interval padding between adjacent OFDM symbols. Accurate estimation of channel impulse response (CIR) is difficult but very important to recover transmitted OFDM symbols by subtracting padded PN sequences. Conventional channel estimation methods only use PN sequences as the training sequences to obtain CIR. Actually, decision-directed channel estimation (DDCE) method which takes advantage of the fact that M-QAM modulated subcarriers in OFDM symbol also contain much valuable hidden-information due to regular constellation mapping and can be used to improve the accuracy of channel estimation. In this paper, the accuracy of channel estimation based on both PN sequence and OFDM symbol is investigated. Moreover, a novel DDCE method based on an accurate initial CIR obtained from two consecutive training sequence and partial decision results of OFDM subcarriers for TDS-OFDM system is proposed. Simulation results show that the proposed algorithm works well over the slow-varying frequency-selective fading channel.