We propose an efficient partial transmit sequence technique based on genetic algorithm and peak-value optimization algorithm (GAPOA) to reduce high peak-to-average power ratio (PAPR) in visible light communication systems based on orthogonal frequency division multiplexing (VLC-OFDM). By analysis of hill-climbing algorithm’s pros and cons, we propose the POA with excellent local search ability to further process the signals whose PAPR is still over the threshold after processed by genetic algorithm (GA). To verify the effectiveness of the proposed technique and algorithm, we evaluate the PAPR performance and the bit error rate (BER) performance and compare them with partial transmit sequence (PTS) technique based on GA (GA-PTS), PTS technique based on genetic and hill-climbing algorithm (GH-PTS), and PTS based on shuffled frog leaping algorithm and hill-climbing algorithm (SFLAHC-PTS). The results show that our technique and algorithm have not only better PAPR performance but also lower computational complexity and BER than GA-PTS, GH-PTS, and SFLAHC-PTS technique.
KEYWORDS: Associative arrays, Compressed sensing, Orthogonal frequency division multiplexing, Telecommunications, Visible radiation, Reconstruction algorithms, Modulation, Systems modeling, Signal to noise ratio, Signal attenuation
In order to mitigate bandwidth attenuation of diffusion link visible light communication systems caused by multipath effects, we present an optical orthogonal frequency division multiplexing channel estimation scheme based on compressed sensing (CS) and estimation of signal parameters via rotational invariance techniques (ESPRIT). First, we derived a parametric channel model. Then, we used ESPRIT to obtain multipath channel parameters. After that, we built a dynamic over-complete dictionary that can be used in CS processing. Finally, we reconstructed the channel response by using a basis pursuit denoising algorithm to equalize the received signal in frequency domain. Compared with traditional schemes, the proposed scheme can improve channel estimation accuracy without increasing dictionary size. A set of computer simulations demonstrated the effectiveness of the proposed scheme.
The problem of optics orthogonal frequency division multiplexing (optical-OFDM) communication lies in the peak to average power ratio (PAPR), which seriously affects the quality of communication systems. A composite technique, which combines the Hartley transform and KC companding technique to reduce the PAPR of an optical-OFDM system, is proposed. The proposed technique can obtain the same quality of OFDM signals and offer an improved bit error rate performance by using Hartley transform instead of the traditional Fourier transform, while the computational complexity is almost halved. Theoretical analysis and simulation results show that the proposed technique has a superior performance for reducing the PAPR when compared to the traditional technique.
The orthogonal frequency division multiplexing (OFDM) modulation technique has been used widely in visible light communications (VLC) systems to combat intersymbol interference. At the same time, the inherent drawback of OFDM with a high peak-to-average power ratio (PAPR) is brought into OFDM visible light communications (VLC-OFDM). Furthermore, considering the limited dynamic range characteristics of light-emitting diodes, the performance degradation caused by a high PAPR is more serious in VLC-OFDM. In this paper, we propose a partial transmit sequence (PTS) technique based on the combination of a genetic algorithm (GA) and a hill-climbing algorithm (GH-PTS) to solve the problem of high PAPR. GH-PTS is a modified PTS technique based on GA-PTS. Essentially, GH-PTS is a local optimization of GA-PTS. Simulation results show that the optimized technique is able to reduce PAPR more effectively without any loss of bit error rate performance than the GA-PTS technique in VLC-OFDM system.
We present a scheme based on precoding carrier allocation and independent component analysis (ICA) for indoor multiple-input-multiple-output (MIMO) visible light communication (VLC). In order to improve the reliability of the ICA algorithm for the mixed signal separation, at the sending end, frequency doubled-carriers are employed to module the parallel data which ensure that the modulated signals are independent of each other. The ICA algorithm is applied to separate the mixed signal at the receiving end directly without the requirement of the channel information. Simulation results show that this indoor MIMO VLC scheme can achieve excellent performance. When the signal-to-noise ratio is equal to 14 dB, the bit error ratio (BER) reaches the level of 10 −5 . So, the communication performance is superior to that of the commonly used schemes based on the channel estimation.
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