Space-time trellis coded OFDM system with added pilot semi-blind iterative channel estimation

Various channel estimation methods for multiple-input multiple-output (MIMO) systems have been proposed. In most of these methods, channel estimation is performed at the preamble of a frame. In data transmission mode, decision-directed channel estimation (DDCE) is used for tracking the channel variations. However, DDCE can not track the channel variations in fast fading channels, and thus the performance degradation occurs. The added pilot semi-blind (APSB) channel estimation technique that does not consume additional bandwidth has been proposed for the scattered pilot assisted OFDM with a single transmit antenna. In this paper, to prevent the performance degradation for the space-time trellis coded OFDM (STTC-OFDM) system in fast fading channels, we propose the system that applies the APSB channel estimation to all the OFDM data symbols except the preamble of a frame. We also propose the simplified system that applies the APSB channel estimation to the last OFDM symbol of a frame. We show that the proposed systems can track the channel variations without additional bandwidth because of the use of the APSB channel estimation and improve the word error rate (WER) performances compared to the conventional system that uses only DDCE.