Spatial Modulation Orthogonal Frequency Division Research Articles

Pilot-based channel estimation in spatial modulated OFDM systems for mobile wireless applications

Spatial modulation Orthogonal Frequency Division Multiplexing (SM OFDM) is a newly developed transmission technique that has been proposed as an alternative for multiple input multiple output (MIMO)-OFDM transmission. Channel estimation is important for coherent data detection in practical scenarios. This paper investigates estimate power, Mean Square Error (MSE) and Bit Error Rate (BER) parameter metrics with channel estimation algorithm for Additive White Gaussian Noise (AWGN) and Rayleigh fading channel on three test environments proposed by International Telecommunication Union (ITU) specified standard model. Simulation output shows that for an AWGN channel, an improvement of approximately 1 dB and 0.3 dB power is obtained with Minimum Mean Square Error (MMSE) estimate and Least Square (LS)-linear/Spline using DFT. Additionally, for various interpolations employed, MSE decreases as Signal to Noise Ratio (SNR) rises, and performance improvement in BER when compared to traditional LS/MMSE estimators also occurs. For Rayleigh fading channel also there arises an enhanced performance in the parameter metrics with MMSE-DFT compared to conventional estimators. In summary, simulation output shows that incorporating DFT algorithm can provide better estimate power, BER and MSE by eliminating the effect of noise externally the extreme channel delay length.

Optimal power allocation analysis for simulation system based on the N-continuous precoded SM-OFDM system with imperfect channel estimation

In this paper, we build the simulation system for the N-continuous (NC) precoded spatial modulation orthogonal frequency division multiplex (SM-OFDM) system with imperfect channel estimation exploiting MATLAB software. Additionally, we evaluate the optimal power allocation between pilot and data symbols in the system by minimizing the derived theoretical bit error rate (BER) upper bound operating with imperfect channel estimation when employs a pilot design approach which protects the pilot symbols from interference introduced by NC precoder. This is motivated by the fact that since the signals are subjected to the interference introduced by the precoding at each subcarrier in the considered system, the NC precoded SM-OFDM system can’t exploit the exiting optimal power allocation for SM-OFDM system straightly. Numerical simulations show that our pilot design approach outperform the existing pilot design approach,and employing the optimal power allocation achieves a significant gain on BER performance in the NC precoded SM-OFDM system compared to employing the equal power allocation.

Efficient Detection of Spatial Modulation OFDM Systems With Multiple Carrier Frequency Offsets

In this letter, an efficient detection scheme is proposed to mitigate the effect of the carrier frequency offset (CFO) in spatial modulation orthogonal frequency division multiplexing (SM-OFDM) systems. Specifically, the proposed scheme employs a novel symbol-by-symbol-aided iterative detector to the SM-OFDM systems with multiple CFOs, where the zero symbols are considered as constellation points. Simulation results demonstrate that the proposed scheme is capable of effectively mitigating the effect of multiple CFOs and of providing about considerable system performance improvement compared with the conventional parallel interference cancellation-aided maximum likelihood detector at a moderate complexity cost.

Pilot Symbol Aided Channel Estimation for Spatial Modulation-OFDM Systems and its Performance Analysis with Different Types of Interpolations

Spatial modulation orthogonal frequency division multiplexing (SM-OFDM) system has been recently proposed as an alternative for multiple-input multiple-output (MIMO)-OFDM systems to increase spectral efficiency by keeping a low-complexity implementation. In the literature, SM-OFDM systems assume a perfect channel state information (P-CSI) available at the receiver for coherent detection and the channel estimation problem is not considered. It is clear that the channel estimation is a critical issue on the performance of SM-OFDM systems. In this paper, a frame structure where pilot symbols are typically interspersed with data symbols among the sub-carriers to aid the channel estimation is considered. Then the pilot symbol aided channel estimation (PSA-CE) technique with different interpolations is proposed for the SM-OFDM systems. It is shown that in the proposed PSA-CE, equidistantly spaced pilot symbols allow to reconstruct the channel response by means of interpolation if the spacing of the pilots is sufficiently close to satisfy the sampling theorem. Linear, nearest neighbor, piecewise cubic Hermite and the low-pass interpolations are investigated to explore trade-off between complexity and performances. We show that the low pass interpolator yields better performance than the other interpolation techniques for selected cases such as higher order modulations. The results validate the potential of the proposed PSA-CE estimation applying to SM-OFDM systems.

Optimal power allocation for SM-OFDM systems with imperfect channel estimation

This paper analyses the bit error rate (BER) of the spatial modulation orthogonal frequency division multiplex (SM-OFDM) system and derives the optimal power allocation between the data and the pilot symbols by minimizing the upper bound for the BER operating with imperfect channel estimation. Furthermore, we prove the proposed optimal power allocation scheme applies to all generalized linear interpolation techniques with the minimum mean square error (MMSE) channel estimation . Simulation results show that employing the proposed optimal power allocation provides a substantial gain in terms of the average BER performance for the SM-OFDM system compared to its equal-power-allocation counterpart.