This paper proposes a minimum mean square error-frequency domain equalization (MMSE-FDE) method for training sequence inserted orthogonal frequency division multiplexing (TS-OFDM) signal under higher mobile environments. The salient features of proposed method are to enable the acquisition of frequency diversity gain by using an enhanced channel impulse response (CIR) matrix and to enable the reduction of complexity by using a fast algorithm for inverse matrix calculation. From the simulation results, this paper confirms that the proposed MMSE-FDE method can achieve better bit error rate (BER) performance than the conventional MMSE-FDE methods with keeping lower complexity under higher mobile environments.

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Recently the channel estimation method of using a time domain Training Signal (TS) for the Orthogonal Frequency Division Multiplexing (TS-OFDM) has been considered actively by many researchers as an alternative method of using pilot signals in the frequency domain. However most of them were investigated assuming the ideal symbol timing. This paper conducts the theoretical examinations for the effect of channel estimation method of using the TS method when the detected symbol timing has an offset from the ideal symbol timing. This paper also verifies the theoretical analysis by computer simulation results.

One significant problem of using discrete Fourier transform spreading-OFDM (DFTS-OFDM) is to produce the undesirable spectrum regrowth at the outside of allocated bandwidth due to the non-continuity between time domain symbols. To solve this problem, this paper proposes a simple spectrum regrowth reduction method for DFTS-OFDM by inserting interpolated samples for improving the continuity between symbols. This paper demonstrates the effectiveness of proposed method as comparing with conventional spectrum regrowth reduction methods by simulation results.