Abstract
This paper proposes a cyclic shifted layer asymmetrically clipped optical orthogonal frequency division multiplexing system (CS-LACO-OFDM) for optical wireless communications. The transmitted signal in CS-LACO-OFDM is generated by combining the signal of the first layer and signals of the remaining $L$ -1 layers with cyclic shift equivalents, where $L$ is the number of the CS-LACO-OFDM layers. In particular, the sets of cyclic shift value in CS-LACO-OFDM are modulated on the odd subcarriers of the first layer with complex-valued symbols. Information on cyclic shift sets can be easily detected with the help of modulated symbols conveyed in the first layer without increasing the receiver complexity. Simulation results show that the CS-LACO-OFDM has a similar peak-to-average power ratio performance as LACO-OFDM with separate selective mapping scheme when the number of candidate signals is the same but at remarkably low computational complexity. Furthermore, the average bit error rate of CS-LACO-OFDM over all layers is minimized by the proposed optimal optical power allocation.
Highlights
Compared with conventional radio frequency wireless communication system, orthogonal frequency division multiplexing (OFDM) based optical wireless communication (OWC) system is perceived as a promising technology that has numerous advantages, such as no electromagnetic interference, license-free spectrum, and high privacy protection [1]
SIMULATION RESULTS This section evaluates the performance of the CS-LACOOFDM system in terms of the average BER and complementary cumulative distribution function (CCDF) of peak-to-average power ratio (PAPR) by simulations
We consider the 6-Layer ACO-OFDM with 128 subcarriers (N = 128 and L = 6), where the symbols are modulated with 16-QAM in all layers and the optical power allocation for each layer is obtained from equation (29)
Summary
Compared with conventional radio frequency wireless communication system, orthogonal frequency division multiplexing (OFDM) based optical wireless communication (OWC) system is perceived as a promising technology that has numerous advantages, such as no electromagnetic interference, license-free spectrum, and high privacy protection [1]. The transmitted signals of OWC have to be real and unipolar owing to the inherent nature of an optical light emitting diode (LED) transmitter To meet this criterion, pulse amplitude modulated discrete multitone (PAM-DMT), asymmetrically clipped optical OFDM (ACO-OFDM), flip OFDM, direct current-biased optical OFDM (DCO-OFDM) have been extensively discussed in the literature [2]–[6]. L=2 where 0 ≤ v ≤ V − 1, ρ(l) is the optical power allocation factor to the lth layer and τv(l) is the cyclic shift in the Layer l ACO-OFDM of the vth transmitted signal. In a CS-LACO-OFDM system, the V cyclic shift sets have to be modulated to complex-valued symbols based on the selected constellation and assigned thereafter on the odd subcarriers of the first layer.
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