In current cellular networks, Spatial Modulation with Orthogonal Frequency Division Multiplexing (SM OFDM) is a newly designed transmission method that substitutes Multiple Input Multiple Output (MIMO) OFDM transmission. In practical frameworks, estimation of the channel is vital for recovering the transmitted data. In a conventional DFT-based channel estimation algorithm, impact of noise is reduced in the time domain. It retains the significant values with some sort of threshold value equal to the Cyclic Prefix (CP) length that differentiates the signal values and noise terms of Channel Impulse Response (CIR), thereby improving the performance in OFDM systems. Here we require information on CIR length in advance. But this results in performance degradation if the path delays are less for a channel. Hence this work proposes improved DFT-based channel estimation where the threshold value is set equal to the estimated CIR length using RMS delay spread approximation in SM OFDM systems. Symbol Error Rate (SER) and Mean Square Error (MSE) are the performance metrics considered in Rayleigh fading channel employing ITU-Vehicular A channel model for 16 QAM SM OFDM systems. Simulation output shows performance improvement of SER and MSE by the implementation of improved DFT-based channel estimation. At an SNR of 40 dB, the proposed method can enhance SER performance by about 2.8 dB and MSE performance about 4dB compared with conventional DFT estimation.

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An integration of Spatial Modulation with Orthogonal Frequency Division Multiplexing (SM OFDM) is a recently evolved transmission technique. In practical scenarios, channel estimation is significant for detecting transmitted data coherently. Impulse response based interpolation technique that provides channel frequency response estimate with reduction in noise error is proposed for comb type pilot based channel estimation of SM OFDM system along with 1D interpolation techniques under frequency selective channel. This scheme focus on carrying out smoothing and estimation in time domain and transforming output back to the frequency domain. BER performance is investigated for Rayleigh channel employing COST 207 project model on two test urban environments (Typical and Bad) for 4 and 16 QAM SM OFDM systems. Results show that the Least Square estimator with DFT interpolation performs finer compared to all one dimensional interpolation methods with less computational complexity by employing FFT algorithms.