Spectral characterisation of variable weight MPPM modulation technique

Abstract

Asymmetric Hydrogenation of N-Alkyl Ketimines with Phosphine-Free, Chiral, Cationic Ru-MsDPEN Catalysts. -A wide range of N-alkyl imines is efficiently hydrogenated under mild conditions using a chiral Ru catalyst in the presence of Boc2O to give the corresponding N-Boc-protected amines in excellent enantioselectivity (up to 98% e.e.). The reaction can be carried out under environmentally friendly solvent--free conditions, although with slightly lower enantioselectivities. The synthesis of enantiopure N-Boc-protected sertraline (XI) is smoothly achieved using this method. - (CHEN, F.; WANG, T.; HE, Y.; DING, Z.; LI, Z.; XU, L.; FAN*, Q.-H.; Chem. Eur.

Advantages of solitonic shape pulses for full-optical wireless communication links

“…To show the superiority of the proposed pulse, we analyze the performance of rectangular, Gaussian and solitonic pulses shapes in terms of the peak-to-average optical power ratio (PAOPR) and bit error rate (BER). Note that the PAOPR is a favorable characteristic in intensity-modulation and direct-detection (IM/DD) infrared links that has been analytically corroborated in this letter, due to the inherent features of an IM and the average power constraints previously mentioned [5,6] . The better behavior of soliton pulses versus Gaussian and rectangular pulses in terms of BER as a direct consequence of having a higher PAOPR justifies its use in wireless optical links.…”

“…Particularly, the transmitted pulse shape can be adjusted to the channel conditions, keeping the average optical power transmitted at a constant level as a basic design criterion, due to strict ocular safety international regulations. Based on this idea, the authors proposed transmission schemes with Gaussian pulse shapes with reduced duty cycle to improve the performance of traditional schemes based on rectangular pulses [5,6] . In this letter, we propose the use of an optical pulse based on the power pulse shape of the optical soliton [7] for AOC systems.…”

Closed-form BER analysis of variable weight MPPM coding under gamma-gamma scintillation for atmospheric optical communications

“…Recently, the multiple PPM (MPPM) technique has been used in wireless optical systems to reduce the average transmitted optical power [6]. In addition, and for indoor infrared transmission conditions, a novel rateadaptive transmission technique using MPPM block coding of variable Hamming weight was presented in [9], where code words with different Hamming weights are allowed, including the all-zero one. The superiority in performance of this proposal with respect to others based on OOK schemes with memory is discussed in [9] because of its inherent higher peak-to-average ratio (PAOPR) parameter; i.e., a modulation technique that increases the PAOPR parameter is preferred as it provides better performance.…”

“…Here, the rate-adaptive transmission scheme using the variable weight MPPM (vw-MPPM) coding technique presented in [9] is employed for AOC systems to maximize the link performance, achieving a high rate adaptability by simply changing the coding translation matrix. Thus, the bit error rate (BER) performance of the vw-MPPM coding method, assuming maximum likelihood detection, is analyzed under free-space transmission conditions, obtaining a closed-form expression validated with Monte Carlo simulation results.…”

“…In Table 1, the hyperexponential fitting parameters for most relevant vw-MPPM code rates [9] are shown. Such a table has been obtained by using a least-squares fitting method over results of BER achieved by Monte Carlo simulations, having assumed absence of turbulent processes, and for several SNR values at the receiver.…”