Spatial OFDM 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.

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

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

Analysis of Motion Blur on Spatial OFDM Based Pixelated Optical Communication Systems

Analysis of Motion Blur on Spatial OFDM Based Pixelated Optical Communication Systems

A Novel Optical Spatial Modulation OFDM Based on Complex Constellation Mapping with Hartley Transform

A Novel Optical Spatial Modulation OFDM Based on Complex Constellation Mapping with Hartley Transform

An Efficient Performance Analysis of Rake Receiver in Spatial Modulation OFDM on a LTE Channel

An Efficient Performance Analysis of Rake Receiver in Spatial Modulation OFDM on a LTE Channel

Hybrid Visible Light and Power Line Communication for Indoor Multiuser Downlink

Visible light communication (VLC) turns indoor light-emitting diode (LED)-based illumination devices into high-speed network portals that, for example, operate in tandem with existing Wi-Fi networks. Since in this scenario, multiple VLC-equipped luminaires would serve overlapping service areas, we suggest the use of power line communication (PLC) to coordinate and provide data to the VLC transmitters. In particular, in this paper, we propose a hybrid VLC-PLC (HVP) system architecture for the indoor downlink transmission and present the analytical framework for the data rate analysis of the HVP system. In our solution, spatial optical OFDM (SO-OFDM) is applied across multiple luminaires, for which we propose several subcarrier allocation schemes to exploit the frequency selectivity of the VLC and PLC channels. Different possible and meaningful variations of the HVP system, including the choice of optical OFDM transmission, relay, and multiple access schemes, are investigated and compared. The numerical results establish achievable rates for relevant communication scenarios and highlight the advantages of the proposed subcarrier allocation scheme in terms of rate and reduced peak power of optical OFDM signals.

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.

Impact of spatial sampling frequency offset and motion blur on optical wireless systems using spatial OFDM

Pixelated communication systems can convey high-speed data over optical wireless channels by using spatial orthogonal frequency division multiplexing (spatial OFDM) modulation. Two forms of spatial OFDM, spatial asymmetrically clipped optical OFDM (SACO-OFDM) and spatial dc-biased optical OFDM (SDCO-OFDM), have been considered in the literature of pixelated communication. This paper mathematically describes the SACO-OFDM signal and then proposes a power-efficient derivative of SACO-OFDM termed as noise-cancelled spatial OFDM (NCS-OFDM). However, NCS-OFDM and other spatial OFDM systems can be impaired by spatial sampling frequency offset (SSFO) defined as the difference in the number of transmitted and received pixels and by coexisting defocus and motion blur forming an asymmetric point spread function (APSF). In this paper, for the first time, the effects of SSFO and APSF on a spatial OFDM based pixelated system are investigated. Simulation results show that both SSFO and APSF cause phase distortions and attenuation of the data-carrying spatial-subcarriers resulting in bit error rate (BER) degradation. Simulation results also indicate that in the presence of several channel impairments including SSFO and APSF, NCS-OFDM outperforms SACO-OFDM and SDCO-OFDM in terms of power efficiency.

Performance analysis of spatial OFDM for pixelated optical wireless systems

AbstractPixelated optical wireless systems can transmit at high speed by encoding data in transmitted images using spatial orthogonal frequency division multiplexing (spatial OFDM) but are susceptible to a number of limiting factors including defocus, linear fractional misalignment (LFM) and vignetting. This paper investigates the effects of these impairments on the performance of both forms of spatial OFDM: spatial DC‐biased optical OFDM (SDCO‐OFDM) and spatial asymmetrically clipped optical OFDM (SACO‐OFDM). The novelty of this paper is in the theoretical analysis of the effect of defocus on a spatial OFDM based pixelated system. The theoretical results for defocus are found to be in agreement with the simulation results reported in the literature. Furthermore, the joint effects of defocus, LFM and vignetting are mathematically described. Analytical and simulation results show that these three factors are largely independent of each other. Simulation results indicate that these impairments and their associated mitigation techniques influence the optimum choice of DC bias for SDCO‐OFDM. Finally, it is shown that for the case of the joint impairments and for a given data rate, the bit error rate performance of SDCO‐OFDM with the optimum bias is slightly better than that of SACO‐OFDM. Copyright © 2015 John Wiley & Sons, Ltd.